Summary

In 1999, a resident of Vieques asked (that is, petitioned) the Agency for Toxic Substances and Disease Registry (ATSDR) to determine whether the Navy's operations on Vieques expose residents to unhealthy levels of environmental contaminants. For the last 2 years, ATSDR has studied this issue extensively. The results of those studies appear in a series of reports known as public health assessments (PHAs). This PHA evaluates the soils of Vieques and addresses the public health implications of exposure to them. ATSDR's findings and the reasons supporting them are documented throughout this report, but the main conclusions are identified below.

Soil Characteristics

ATSDR evaluated the general soil characteristics of Vieques to identify:

1. Whether the soils of Vieques have elevated levels of metals or other chemicals.
2. Whether the soils of Vieques show evidence of contamination by Navy training activities.

To answer these questions, ATSDR evaluated the general soil characteristics of Vieques in several ways.

• Soil sample analyses were grouped based upon their underlying parent material (the geologic units or rock formations), and the general chemical characteristics of those soils throughout the island were compared and contrasted. ATSDR concludes that the composition of the soils of Vieques including their constituent metal content is strongly influenced by the parent material (underlying geologic units) from which those soils are derived.
• The quality of the soil on Vieques was compared with sediment on the mainland of Puerto Rico and with the soil of the United States. ATSDR concludes that even though the maximum level of some of the metals detected in Vieques soil is moderately elevated in comparison to soil elsewhere (Puerto Rico and the United States), the levels are not inconsistent with what one would expect from soils also underlain by igneous or volcanic rocks.
• The levels of metals in the soils of the Live Impact Area (LIA) were examined to determine if they had been affected by Navy training activities. To do this, ATSDR utilized two different approaches: (1) to compare concentrations of chemicals detected at the LIA to the remainder of Vieques and (2) to compare concentrations of chemicals detected at the LIA to background (naturally occurring) soil samples in the former Naval Ammunition Support Detachment (NASD). ATSDR concludes that it appears that the soils of the LIA have been influenced by Navy training activities and do contain elevated levels of heavy metals. However, the concentrations of the chemicals in the soil are not at levels that pose an adverse health threat (see the Public Health Evaluation section).
• The soil analyses were examined for spatial trends (i.e. progressive trends or gradients from east to west) that might reflect contaminant migration from the LIA into the residential area. ATSDR concludes that the analyses do not detect spatial trends and thus do not supply supporting evidence for airborne transportation and deposition of contaminants into the residential area.

Public Health Evaluation

ATSDR identified two potential pathways of human exposure to chemicals in the soil of Vieques:

1. Residents and visitors of Vieques can contact the soil in the residential portion of the island.
2. Individuals can contact the soil when they enter the LIA.

ATSDR evaluated whether incidental ingestion or dermal contact with the soil would result in harmful health effects from either exposure pathway.

• ATSDR concludes that the residents of Vieques are not being exposed to harmful levels of chemicals in the soil on Vieques. The levels of metals and other chemicals detected on Vieques are too low to be of health concern for both adults and children.
• ATSDR concludes that the protestors who occupied portions of the LIA from April 1999 to May 2000 were not exposed to harmful levels of chemicals in the soil. The levels of metals and other chemicals detected at the protestor camps on the LIA were too low to be of health concern for both adults and children.

Overall Conclusions

Based upon a thorough evaluation of the soils of Vieques, including the soils of the residential area as well as the LIA, ATSDR concludes that Navy training activities have elevated the levels of some metals in soil at the LIA, however, residents and visitors of Vieques are not being exposed to harmful levels of contamination in those soils.

I. Introduction

In May 1999, a resident of Isla de Vieques (Vieques), Puerto Rico, requested (petitioned, see text box for definition) the Agency for Toxic Substances and Disease Registry (ATSDR) to determine whether hazardous substances from the detonation of munitions at the United States Navy (Navy) bombing range on the island pose a public health threat. In August 1999, ATSDR conducted an initial site visit to Vieques to meet with the petitioner, tour the island and bombing range, and gather available environmental data. As a result of this site visit, ATSDR accepted the petition and since then has been investigating public health concerns related to the Navy's training activities on Vieques.

ATSDR is responding to this petition in a series of documents known as public health assessments (PHAs). PHAs examine chemicals that enter the environment, how they move through the environment, and the levels that residents might encounter. ATSDR then uses this information to determine whether residents or visitors are exposed to levels of contamination that might cause health problems.

This PHA addresses the public health implications of exposure to soil contaminants through incidental ingestion or dermal contact. More details about the soil pathway can be found in Section IV. Evaluation of the Soil Exposure Pathway. The issue of heavy metal uptake in plants and livestock from Vieques is addressed in Section V. Community Health Concerns.

Although this report focuses on soil quality issues, ATSDR has committed to evaluate other ways chemicals from the bombing range might affect public health. ATSDR has already addressed, or plans to address, the following public health issues:

• In October 2001, ATSDR released the PHA addressing contamination in drinking water supplies and groundwater (ATSDR 2001b). This report concluded that the public drinking water supply on Vieques poses no public health hazard. However, high nitrates and nitrites, most likely resulting from agricultural pollution, in one private drinking water well indicate a health concern for children and pregnant women if they drank water from that well. The report evaluates these health issues in greater detail. Copies are available by contacting ATSDR (1-888-42-ATSDR), on ATSDR's Web site (http://www.atsdr.cdc.gov/HAC/PHA/vieques/vie_toc.html), and from records repositories on Vieques. The repositories are located at Biblioteca Publica (Calle Carlos Lebrum, Vieques), the Vieques Conservation and Historical Trust (Flamboyan Street, Vieques), and at the University of Puerto Rico's School of Public Health (San Juan, Puerto Rico).
• In July 2001, ATSDR, the Ponce School of Medicine, and the Centers for Disease Control and Prevention sponsored an expert panel review to address whether an association existed between place of residence (Vieques or Ponce Playa) and morphological cardiovascular changes among fishermen. The report summarizing the expert panel review was released in October 2001 (ATSDR and PSM 2001). Copies are available by contacting ATSDR (1-888-42-ATSDR) and on ATSDR's Web site (http://www.atsdr.cdc.gov/NEWS/viequesheartreport.html).
• In September 2002, ATSDR released the PHA addressing contamination in locally caught fish and shellfish from Vieques for public comment. In this report, ATSDR documented the results of the July 2001 sampling event and determined that consumption of fish and shellfish from Vieques represents no apparent public health hazard. While several metals were detected in some of the fish and shellfish, the concentrations that were present were too low to be of health concern. The report evaluates these issues in greater detail. Copies are available by contacting ATSDR (1-888-42-ATSDR), on ATSDR's Web site (http://www.atsdr.cdc.gov/HAC/PHA/vieques/vie_toc.html), and from records repositories on Vieques.
• In September 2002, ATSDR released the PHA addressing public health implications of exposure to air contaminants that could have been released from the Live Impact Area (LIA). In this report, ATSDR determined that the air exposure pathway at Vieques presents no apparent public health hazard. ATSDR found that the residents of Vieques have been exposed to contaminants released during the Navy's military training exercises, but these exposures are far lower than levels known to be associated with adverse health effects.

An important aspect of the public health assessment process is defining and addressing health concerns of community members. Throughout the process ATSDR has been, and will continue to work with the community to define specific health issues of concern (see Section II.G). Discussion with community members has also helped define ways in which ATSDR can provide educational materials and information to protect the public health of Vieques residents.

II. Background

Vieques is the largest offshore island in the Commonwealth of Puerto Rico. Vieques is 20 miles long, 4.5 miles at its widest point, and about 33,000 acres (or 51 square miles) in area. Figure 1 shows the location of Vieques and surrounding islands. As the figure illustrates, the nearest island to Vieques is the main island of Puerto Rico, approximately 7 miles to the west. The island of Culebra is roughly 9 miles north. St. Thomas, St. John, St. Croix, and other U.S. Virgin Islands are all at least 20 miles northeast and southeast from Vieques.

The highest point on the western half of Vieques is Monte Pirata (987 feet above sea level) and the highest point on the eastern half is Cerro Matias (450 feet above sea level). Other than these peaks, the Vieques terrain includes low rounded hills and an east-west ridge running through the center of the island. The average elevation of Vieques is approximately 246 feet above sea level (Cherry and Ramos 1995; Torres-Gonzalez 1989).

A. Land Use

The detailed map in Figure 2 illustrates land use in Vieques. The figure depicts the island in three separate sections, each of which is described in greater detail below:

• Former NASD. Figure 2 identifies the western portion of Vieques as the "Former NASD." Prior to May 2001, the Navy owned the 8,200-acre Naval Ammunition Support Detachment (NASD). Most of the NASD is undeveloped and was used for limited Navy operations, including ammunition storage, a rock quarry, communication facilities, and Navy support buildings (IT Corporation 2000). Some NASD areas were leased to local farmers for cattle grazing and other agricultural purposes. In May 2001, the Navy transferred most of the NASD to la Isla de Vieques, the Puerto Rico Conservation Trust, and the U.S. Department of the Interior. The Navy retained about 100 acres for radar and communication facilities (Navy 2001a).
• Residential Area. Figure 2 identifies the central portion of Vieques as the "Residential Area." This part of Vieques includes approximately 7,000 acres and currently borders Navy property only on the east. This section of the island houses the entire residential population of Vieques, mostly in the towns of Isabel Segunda and Esperanza. Section II.B of this assessment describes the demographics of Vieques in greater detail.

  Vieques land uses include residential, agricultural, commercial, and industrial. In the past, sugarcane was the principal crop. Other crops have included coconuts, grains, sweet potatoes, avocados, bananas, and papayas. In the 1960s and 1970s manufacturing was important for the economy, beginning with the 1969 construction of the General Electric plant (Bermudez 1998). But currently, only minimal manufacturing takes place on the island. Isabel Segunda and Esperanza, however, are home to commercial fishing fleets, and recently tourism has been increasing in economic importance.

• Current Navy Property.
  
  The Navy currently owns roughly the eastern half of Vieques. As Figure 2 shows, these lands are further divided into two sections: the Eastern Maneuver Area (EMA) and the Atlantic Fleet Weapons Training Facility (AFWTF). The EMA includes approximately 11,000 acres located immediately east of the residential area. The Navy uses the EMA periodically for various combat training activities, such as conducting shore landing exercises and small arms training (CH2MHILL and Baker 1999; IT Corporation 2000). Camp Garcia, where Marine Corps and Naval personnel are temporarily stationed on Vieques, is within the EMA. Typically, no more than 100 military personnel reside at Camp Garcia, but this number increases during training exercises. Some EMA areas are leased to local farmers for cattle grazing and agriculture.

East of the EMA is the AFWTF (3,600 acres), which as Figure 2 shows, is further divided into three smaller sections of land:

• The western part of AFWTF was formerly known as the Surface Impact Area. Prior to 1978, the area was used as an impact area for artillery. It is heavily vegetated and almost completely undeveloped, except for dirt roads, a few observation posts and towers, and the main observation post (OP-1), located on Cerro Matias.
• The middle portion of AFWTF is the LIA, also commonly referred to as the bombing range. This roughly 900-acre tract contains the targets for aerial and naval bombardment. The LIA is sparsely vegetated, and contains no structures--only surplus equipment (e.g., tanks, small airplanes, and trailers) the Navy uses as targets. Section II.F of this report includes more detailed information about the Navy's training activities on Vieques.
• The eastern tip of AFWTF is the Punta Este Conservation Zone. To preserve the unique upland forest scrub and evergreen scrub habitats, no Navy operations take place on this small piece of land. A variety of animals, including roseate terns and sea turtles, visit and nest there.

B. Demographics

ATSDR examines demographic data (i.e., population information) to determine the number of people potentially exposed to environmental chemicals, and to determine the presence of any sensitive populations, such as women of childbearing age, children, and the elderly. Demographic data also provide details on population mobility which, in turn, helps ATSDR evaluate how long residents might have been exposed to environmental chemicals.

Table 1 summarizes the 2000 US Census Bureau demographic data for Vieques. As the table shows, the 2000 Census reported that 9,106 people live on Vieques. This figure includes residents on both the residential area and Navy property. Table 1 also specifies the number of residents in three potentially sensitive populations: women of childbearing age, children, and the elderly. According to several anecdotal accounts, the population of Vieques is not highly mobile; many are lifelong residents of the island.

As noted previously, most of the residents of Vieques live in the two largest towns on the island, Isabel Segunda and Esperanza. Although these towns are located relatively close to the Navy property, they are several miles removed from the LIA. Approximately 7.9 miles (12.7 kilometers) of Navy owned land provides a buffer zone between the LIA and populated areas of Vieques.

C. Climate

Vieques lies in the path of the easterly trade winds (i.e., winds blowing from east to west). The climate is tropical-marine, with temperatures averaging about 79 Fahrenheit (26.3 Celsius). Annually, the temperature ranges from an average of 76 Fahrenheit (24.6 Celsius) in February to 82 Fahrenheit (28 Celsius) in August. The average amount of precipitation is about 45 inches a year. The western part of the island receives a higher amount of rainfall (about 50 inches a year) than the eastern section (about 25 inches a year). The rainy season is from August through November while the remainder of the year is drier. Tropical storms are common from June to November (NCDC 1985-1994; Torres-Gonzalez 1989).

African Dust Storms

Through the natural occurrence of African dust storms, Vieques, together with the mainland of Puerto Rico and the southeastern United States, receive in the summer an increase of airborne dust particles. Each year, large quantities of dust from the Sahara Desert and Sahel region in Africa are transported at high altitudes to the Caribbean Sea (USGS 2000). These dust storms can transport minerals, chemicals, bacteria, fungus spores--and possibly viruses and insects. African dust is comprised mainly of quartz, but also of other minerals, that are common in soil (Prospero 1999). Lead, iron, mercury, and beryllium have been detected in samples of African dust taken from the Virgin Islands, Barbados, Miami (Florida), and the Azores. Pesticides associated with pesticide spraying in the Sahel region have also been detected in the dust (Ballingrud 2000).

D. Geology

Vieques was formed from volcanic and other igneous rock. The island bedrock is mostly granodiorite, quartz diorite, and some lavas. Figure 3 is a generalized geologic map of Vieques identifying the island's geologic units (rock formations). On most of the western half as well as the central portion of the eastern half of the island, the bedrock is exposed and weathered. Because of the weathering of the bedrock, gravel, sands, and finer particles wash downhill during storms. Over the years this material has gathered in valleys near the ocean, forming alluvial deposits (see text box for definition). The alluvial sedimentary deposits generally consist of a mixture of gravel, sand, silt, and clay. Other portions of Vieques have ancient marine deposits from a time when the island was submerged. Today these deposits reveal areas with some limestone, sandstone, siltstone, and other sedimentary rocks at the surface.

Soil

Soils often form from the weathering and breakdown of the underlying rock or "parent material." Soils may be formed by the buildup of wind- or water-borne particles or by the addition of new minerals by naturally occurring chemical processes within the soil. There are many differing types of soil that form in different climates and on differing underlying parent materials. Five parameters, known as soil forming factors, contribute to the type of soil that can be found in an area: parent material (i.e., the geology that is present), relief (i.e., topography), organisms/microorganisms, climate, and time (Jenny and Hans 1941).

The natural soil on Vieques is a direct product of the island's bedrock, which as indicated above, is mostly granodiorite, quartz diorite, some volcanic lavas, and marine sedimentary deposits such as limestone. Soil type can vary according to topography or location. For example, because of differing soil-moisture conditions--which lead to differing rates and kinds of chemical and physical weathering and soil forming reactions--soil found on the top of a hill would be slightly different from that found in a valley. Organisms and microorganisms living in the soil participate in the soil formation process by extracting some chemicals, which they use as nutrients, and depositing others. Climate also affects the type of soil present. Soil found in a tropical-marine climate, such as Vieques, is different from soil in an arid climate. Soil is also a function of time, or how long the processes (e.g., erosion, deposition, weathering, and clay formation) have been at work.

Rocks are a natural source of the chemicals that are found in soil. Most rocks are formed from elements such as oxygen, silicon, aluminum, iron, magnesium, calcium, potassium, and sodium (USGS 1997). Chemical and physical processes break down the rocks and form minerals that are characteristic of the parent material. But human influences, such as agricultural processes and Navy training exercises at the LIA can also contribute to the chemicals found in the soil. Determining whether a chemical is present as a result of natural or human sources is sometimes difficult because frequently, it can be a combination of both.

Ninety-two elements occur naturally in our environment (USGS 2001a). Some of these elements are essential for life, such as iron and magnesium. Others are nonessential and can even be harmful if present in high enough concentrations (e.g., arsenic, cadmium, lead, and mercury). Some elements are required for life at certain levels, but can be harmful in concentrations that are too high (e.g., fluorine, copper, selenium, and molybdenum) (USGS 2001b).

E. Hydrogeology

All the groundwater on Vieques comes from rain that falls on the island. The rain runs downhill as intermittent stream runoff or it seeps into the soil and underlying deposits. Water is found in two main areas: (1) the upper portion of the bedrock and sedimentary rocks, and (2) the alluvial deposits. Water in pore space, cracks, and fractures in the bedrock eventually flows to the ocean or into alluvial deposits. Esperanza valley is the largest alluvial valley in Vieques and holds the most water.

Water Use

Most of the residents of Vieques currently receive their drinking water supply from the mainland of Puerto Rico through an underwater pipeline. The water is collected and treated on the main island of Puerto Rico, then piped into the distribution system through an underwater pipeline. This water originates in the mountains of the main island of Puerto Rico and is not affected by activities at the bombing range on Vieques. In addition, private groundwater wells and rainfall collection systems may still be used today to augment water supplies in some households and businesses.

F. Navy Operational History

The Navy has occupied portions of Vieques since 1941. In 1960, the Navy established targets on Vieques and began bombing practice (Navy 1990). The use of the LIA for air to ground and ship to shore training increased after the closing of the Culebra Island range in the mid-1970s. Currently, the Navy owns roughly the eastern half of the island--the EMA and AFWTF (see Figure 2). The Navy facilities are under the command of the Roosevelt Roads Naval Station on the mainland of Puerto Rico.

Ordnance Type and Use

Range utilization statistics data from 1983 to 1999 indicate that the Navy and other parties conducted exercises on Vieques between 159 and 228 days per year, with the total number of days not varying considerably from one year to the next. Generally, Navy training exercises were most frequent in February and August with fewer exercises in April, May, November, and December. The range utilization statistics suggest that, on average, 1,862 tons of ordnance were used at Vieques annually between 1983 and 1998. This ordnance, on average, contained 353 tons of high explosives (Navy 1999).

Live ordnance have not been used on Vieques since April 19, 1999, when two 500-pound bombs were accidentally dropped near OP-1, killing a civilian guard. In January 2000, the decision was made that the Navy could resume training on Vieques. The training is limited to 90 training days per year and the use of nonexplosive ordnance only. In May 2000, the Navy resumed training.

To varying degrees metals and metallic compounds are present in the munitions used on Vieques (see text box on the following page for descriptions of ordnance types). Rockets contain metals and metallic compounds in the initiator, igniter, propellant, and motor. A projectiles' body assembly and nose fuze are made of metals and metallic compounds. Both live and practice bombs contain metals and metallic compounds in the bomb body, base plug, suspension lug, fins, tail, fuze, and signal cartridge. The decoy, parachute, and simulator flares used on Vieques contain metals and metallic compounds in the ignition, first fire, flare slurry, friction material, and flare.

Certain pyrotechnic devices, such as illuminating flares and white phosphorous mortar rounds, are also used on Vieques for smoke generation. The flares contain sodium nitrate and magnesium, which when ignited produce magnesium oxide (magnesium hydroxide when wet), sodium oxide, nitrogen, carbon dioxide, carbon monoxide, and water. Upon contacting air, white phosphorous burns immediately, producing phosphorus pentoxide, which becomes phosphoric acid when wet (Young 1978).

Two types of explosives (see text box for definition), described below, were commonly used at Vieques, each with a different set of byproducts from the explosion reaction (Young 1978):

• One explosive is made from organic nitrated compounds (i.e., only carbon, hydrogen, oxygen, and nitrogen). Examples include TNT, RDX, HMX, tetryl, Explosive D, Composition B (RDX and TNT), Octol (HMX and TNT), and Composition A-3 (RDX and wax). Carbon dioxide (35%), nitrogen (27%), and carbon monoxide (16%; which rapidly oxidizes to carbon dioxide) are the primary byproducts resulting from this type of explosive. Water (8%), ethane (5%), carbon (6%), and propane (2%) are other minor byproducts. Trace amounts (less than 1%) of ammonia, hydrogen, hydrogen cyanide, methane, methyl alcohol, and formaldehyde are also formed (Young 1978).
• The other explosive contains aluminum in addition to organic nitrated compounds. Examples include Tritonal (TNT and aluminum), H-6 (TNT, RDX, and aluminum), and Torpex (TNT, RDX, and aluminum). The byproducts from a bomb made with this explosive include all the chemicals listed for the first type of explosive as well as acetylene, ethylene, phosphine, and aluminum oxide. The primary byproducts are aluminum oxide (38%), carbon monoxide (24%, which rapidly oxidizes to carbon dioxide), nitrogen (18%), and carbon (13%). Ethane (3%), water (1%), hydrogen (1%), and less than 1% of the remaining byproducts (i.e., carbon dioxide, ammonia, propane, hydrogen cyanide, methane, methyl alcohol, formaldehyde, acetylene, ethylene, and phosphine) are also formed (Young 1978).

During a February 19, 1999 training exercise, depleted uranium ammunition was inadvertently loaded aboard two U.S. Marine Corps aircraft (NRC 2000). The pilots fired 263 rounds of ammunition armed with depleted uranium penetrator projectiles on the LIA. The Navy has committed to recover all detectable depleted uranium penetrators, and as of August 2002 reported to have recovered 116 equivalent units. During June 6-15, 2000, the Nuclear Regulatory Commission (NRC) conducted an inspection of Vieques to determine whether the depleted uranium rounds contaminated the environment, thus creating a potential source of radiation exposure for Vieques residents. The NRC concluded that depleted uranium had not spread to areas outside the LIA. Thus the public had not been exposed to depleted uranium contamination or other radiation above normal background (naturally occurring) levels (NRC 2000). ATSDR has reviewed the NRC report and concludes that the background levels of radiation detected on Vieques do not present a public health hazard.

G. ATSDR Involvement at Vieques

Since its 1999 receipt of the petition requesting an evaluation of public health issues on Vieques, ATSDR has worked extensively to characterize and to respond to community needs. The following is a summary of ATSDR's past Vieques involvement:

• Site visits. Since 1999, teams of ATSDR scientists and community involvement specialists have visited Vieques more than 10 times. These visits included site familiarization, identification of health concerns, and collection of fish and shellfish for analysis. During two of the site visits, ATSDR personnel extensively toured the former NASD, EMA, and AFWTF, which included a ground and aerial tour of the LIA.
• Community involvement. Defining community concerns is an essential step in the public health assessment process. To define specific environmental health issues of concern, ATSDR met several times with individuals, families, and many other residents of Vieques. ATSDR is also working with elected officials, physicians, nurses, school educators, fishermen, leaders of women's groups, pharmacists, and businessmen. Among other discussion topics, ATSDR inquired how the agency can most effectively provide public health information to the community. ATSDR plans to continue such community involvement activities at Vieques at least into calendar year 2002.
• Health education. Throughout the community involvement process, ATSDR has worked with physicians, nurses, and school officials to provide educational materials and to support the overall public health of Vieques residents. To date, the agency has hosted four physician workshops and one nurses' training workshop covering the various aspects of environmental health, including procedures for taking an exposure history. The agency has also facilitated community education sessions on cancer. ATSDR intends to provide additional education sessions that will address topics such as air quality and asthma, nutrition and wellness, and environmental health.

H. Summary of the Available Soil Sampling on Vieques

In 1972, personnel from US Geological Survey (USGS) and the Puerto Rico Department of Natural Resources (PRDNR) jointly surveyed surface soil across Vieques to evaluate the metallic resource potential of the island (see Figure 4 for soil sample locations) (Learned et al. 1973). A total of 420 soil samples were taken and analyzed semi-quantitatively for metals ⁽¹⁾. In 1992, USGS released a reconnaissance geochemical survey with analytical results for stream sediment and soil samples from the Puerto Rican mainland, Culebra, and Vieques (Marsh 1992). The source for the Vieques soil data was the 1972 USGS and PRDNR survey. The sediment data for the mainland of Puerto Rico was generated through a cooperative sampling effort between USGS and PRDNR that began in the 1970s. A total of 2,852 stream sediment samples were analyzed for metals ⁽²⁾ .

In May 1978, the Naval Surface Weapons Center obtained and analyzed soil samples for explosive compounds from two areas within the EMA and four areas within the LIA (Hoffsommer and Glover 1978). At the same time, soil collected from one area within the EMA and five areas within the LIA was analyzed for explosion combustion products (Lai 1978) ⁽³⁾.

In October 1998, to document existing environmental conditions at a section of the former NASD's buffer zone proposed for expansion of the Vieques Municipal Airport, a contractor for the Navy collected five soil samples (see Figure 4 for locations) (PMC 1998). These samples were analyzed for volatile organic compounds, semivolatile organic compounds, pesticides, polychlorinated biphenyls, and metals.

In August 1999, a contractor for the Navy collected and analyzed for explosive compounds 32 surface soil samples along EMA's western border (see Figure 4 for soil sample locations) (CH2MHILL and Baker 1999). Twenty-one of the samples were collected from storm drains (i.e., culverts that are normally dry and only contain water during rain events); the remaining 11 were from areas adjacent to the monitoring wells.

From May 1999 to April 2000, personnel from Servicios Científicos y Téchnicos, Inc. (Garcia et al. 2000) collected and analyzed soil and sediment samples from 55 Vieques locations for metals and other inorganic compounds (Garcia et al. 2000). Of these, 44 samples were collected from the LIA; specifically, areas of direct impact, targets areas, and nearby areas. Five were collected from the Punta Este Conservation Zone and six were taken from the residential area. But ATSDR does not have access to the entire sampling data set. Only the highest and second-highest concentrations were reported for a total of 25 sample locations within the LIA ⁽⁴⁾ (see Figures 4 and 5 for soil sample locations).

In June 2000, at ATSDR's request, a Navy contractor collected and analyzed 37 surface soil samples within the LIA (specifically, from targets and drainage features and low lying areas which would collect stormwater runoff) and within conservation zones immediately adjacent to the LIA (see Figures 4 and 5 for locations) (CH2MHILL 2000a). Five of the sites specifically represented areas where the protestors lived from April 1999 to May 2000. The samples were analyzed for metals and explosive compounds.

In December 2000, a Navy contractor conducted a background (naturally occurring) sampling program in support of the Navy's Installation Restoration Program at the former NASD (CH2MHILL 2001). Samples of surface and subsurface soils, groundwater, surface water, and sediment were collected at various locations in the former NASD thought to be unaffected by man's activities. A total of 26 surface soil samples were collected and analyzed for metals (see Figure 4). A draft report summarizing the results of that investigation was released June 15, 2001.

I. Quality Assurance and Quality Control

To prepare this PHA, ATSDR reviewed and evaluated information provided in the referenced documents. The environmental data are from reports produced by many parties, including USGS in cooperation with PRDNR, the Navy, and Servicios Científicos y Téchnicos, Inc. The limitations of these data have been identified in the associated reports, and are restated in this document, as appropriate. The sampling procedures, analytical methods, and detection limits established for those investigations were consistent with the studies' objectives. Quality assurance and quality control measures were not available for the older data (i.e., Learned et al. 1973; Hoffsommer and Glover 1978; and Lai 1978) and data collected by Servicios Científicos y Téchnicos, Inc. (Garcia et al. 2000). ATSDR determined that the quality of environmental data available in the Vieques site-related documents constitutes an adequate basis for public health decisions. All available soil sampling data was considered during the public health assessment process.

III. Soil Characteristics

A. Background

As noted in Section II.D Geology, soils often form from the weathering and breakdown of the underlying rock or "parent material." Chemical and physical processes break down the rocks and form minerals that are characteristic of the parent material. Therefore, the natural soil on Vieques is a direct product of the island's bedrock, which is mostly granodiorite, quartz diorite, some volcanic lavas, and marine sedimentary deposits such as limestone.

What are the chemical characteristics of soils of the different geologic units on Vieques?

To compare and contrast the soils of Vieques, the soil samples were differentiated based on the underlying parent material (i.e., the rock formations or geologic units) on which they developed. ATSDR compared the constituent metals detected in the soil that developed on one geologic unit to the metals in the soil in the other geologic units. Comparisons were considered statistically significant (i.e., different) if there was less than 5% probability that the difference occurred by chance (i.e., p <0.05). Figure 3 illustrates the location of the generalized geologic units on Vieques used for this phase of the analysis (modified from Torres-Gonzalez 1989).

• Undivided marine sedimentary rocks comprise most of the LIA, a small area near Mosquito Pier, and along the southern shore from Ensenada Sombre to Bahia Corcho. These rocks--largely soft limestone--are shown as the Tl geologic unit on Figure 3. The soil developed on the Tl geologic units have significantly higher concentrations of boron (Tl mean X = 15.8 ppm, sample size (n) = 19; non-Tl X = 11.3 ppm, n = 397) and calcium (Tl X = 153,000 ppm, n = 19; non-Tl X = 20,100 ppm, n = 401) than soil of other non-Tl geologic units.
• Most of AFWTF, the EMA, and the northeast corner of the residential area are comprised of a complex assemblage of deeply weathered sandstone, siltstone, conglomerate, lava, tuffs, and breccia, largely of marine origin. These rocks are shown in Figure 3 as the Kv geologic unit. The soil developed on the Kv geologic units is significantly different (higher) than the soil of other non-Kv geologic units for boron, chromium, cobalt, iron, lead, magnesium, manganese, nickel, scandium, titanium, vanadium, yttrium, zinc, and zirconium. See the Exhibit 1 for the differences between the Kv and non-Kv geological units.

• The bedrock of Vieques is plutonic rocks (deep-seated, igneous intrusive rock), largely granodiorite and quartz diorite, abundant throughout the former NASD, the residential section, and central sections of the EMA. These rocks are shown in Figure 3 as the KTd geologic unit. The soil developed on the KTd geologic units have significantly higher concentrations of barium (KTd X = 917 ppm, n = 212; non-KTd X = 328 ppm, n = 241), strontium (KTd X = 295 ppm, n = 212; non-KTd X = 199 ppm, n = 204), and tin (KTd X = 14.2 ppm, n = 212; non-KTd X = 11.8 ppm, n = 237) than soil of other non-KTd geologic units.
• Beach and dune deposits, which are comprised of sand-sized fragments of calcite, quartz and volcanic rocks, with local concentrations of magnetite grains, are found in small pockets near the southern shore in the former NASD, near the mouth of Puerto Mosquito, and in the AFWTF. These deposits are shown in Figure 3 as the Qb geologic unit. The soil developed on the Qb geologic units have significantly higher concentrations of calcium (Qb X = 74,300 ppm, n = 3; non-Qb X = 25,700 ppm, n = 417) than soil of other non-Qb geologic units.
• Sand, silt, clay, gravel flood plain, terrace deposits, and piedmont fan deposits make up the alluvial deposits located along the north and south coasts of the former NASD, the western half of the south coast of the residential section, and in pockets along the coast of the EMA. These deposits are shown in Figure 3 as the Qa geologic unit. No significant differences appeared between the soil developed on the Qa geologic units and those found on non-Qa geologic units.
• Swamp and marsh deposits, mostly organic muck and peat, are only present in the northwest corner of the former NASD. These deposits are shown in Figure 3 as the Qs geologic unit. Because only one sample was taken from this unit, a statistical comparison could not be completed for the soil of the Qs geologic units.

Using the data collected by USGS and PRDNR in 1972 (Learned et al. 1973), ATSDR compared the chemical characteristics of the KTd geologic unit to the Tl geologic unit. This comparison is necessary for establishing the inherent chemical differences between these two units and will be useful in the discussion of the second approach ATSDR used to determine whether the soils of the LIA contain elevated levels of heavy metals (Section III.C). As shown in Exhibit 2, several metals were statistically significantly different.

B. Comparison of Vieques to the Mainland of Puerto Rico and the United States

Can the soil of Vieques be compared to the mainland of Puerto Rico?

Based on available information, only a generalized comparison can be made. While soil data are available for Vieques, the only area-wide, chemical characterization data available for the mainland of Puerto Rico are stream sediment sampling collected by USGS and PRDNR (Marsh 1992). The stream sediment samples were collected from active stream channels in drainage basins ranging in size from less than 1 square kilometer to less than 10 square kilometers. The objective of this geochemical sampling program was to characterize the distribution of commonly occurring elements and metals throughout the mainland of Puerto Rico.

Sampled stream sediments are representative of the soil and their parent material (e.g., the geologic substrates of that drainage basin) as well as other factors (e.g., human activity, etc.) that could have affected that drainage basin. The stream sediments are comprised of granular material derived from erosion, stream transportation, and deposition of the soil and drainage-related geologic deposits. The physical and chemical process responsible for the erosion, transportation, and deposition of those sediments could introduce several changes to the overall composition of the sediments as compared to the soil from which they were derived.

Ideally, ATSDR would compare the soil on Vieques to soil on the Puerto Rico mainland. But because comparable area-wide data for the mainland are not available, ATSDR determined that comparing the soil on Vieques to the sediment on the mainland of Puerto Rico would still serve to point out generalized similarities or differences between the two areas. Given the inherent differences between the two media, the following can be noted: the soil of Vieques has higher concentrations of antimony, arsenic, cadmium, calcium, manganese, molybdenum, silver, strontium, and yttrium than the stream sediment samples collected throughout the mainland (see Table 2).

However, when ATSDR compared the background sediment samples collected in the former NASD (CH2MHILL 2001) to the sediment data collected on the mainland of Puerto Rico (Marsh 1992), the levels of metals from the former NASD are lower or at the lower end of the range than those detected on the mainland, with the exception of calcium and sodium (see Table 3). Note that a small number of background sediment samples at the former NASD (n = 6) are being compared to a much larger sample set from the mainland of Puerto Rico (n = 2,852). In addition, the samples were collected and analyzed using differing procedures and methods.

How does the soil on Vieques compare to the average soil concentrations in the United States?

Vieques soil is generally comparable to the soil across the United States, especially areas underlain by igneous or volcanic rocks. A statistical comparison between Vieques and the United States was not conducted. Instead, this information is referenced to provide additional insight into the metals and other chemical concentrations detected on Vieques. The United States data represent background soil concentrations taken from uncontaminated areas across the conterminous (i.e., contiguous) United States (Shacklette and Boerngen 1984). The average concentrations for several of the metals were higher on Vieques than the average on the United States. Nevertheless, only the maximum concentrations of copper, iron, lead, tin, and zinc detected on Vieques were outside the ranges found throughout the United States (see Table 2).

As noted in Section II.H Summary of the Available Soil Sampling on Vieques, the soil samples collected by USGS and PRDNR in 1972 (Learned et al. 1973) may be as much as 4-fold higher than the true values. Therefore, any apparently "elevated" levels in comparison to background levels in the United States may be a result of this high-bias in the USGS/PRDNR data (the only island-wide soil sampling available for Vieques), rather than being truly elevated.

Regardless, as noted in Section II.D Geology, soils contain chemicals that are characteristic of the underlying rock, and the metal concentrations observed in the soil of Vieques are consistent with those observed in areas of relatively low-level mineralization (natural mineral enrichment through a variety of geologic processes) in igneous or volcanic rock.

C. Comparison of the LIA to the Remainder of Vieques

Do the soils of the LIA contain elevated levels of heavy metals?

ATSDR attempted to answer this question using two different approaches: (1) by comparing concentrations of chemicals detected at the LIA to the remainder of Vieques and (2) by comparing concentrations of chemicals detected at the LIA to background soil samples in the NASD. Both approaches yielded useful but slightly differing conclusions and each may be based upon data (high-biased) or assumptions (correlations of geologic/soil types) that may result in conclusions that are not entirely accurate.

• The first approach was to statistically compare the levels of chemicals detected in the LIA to the remainder of Vieques (see Table 4). As shown in Table 4, the soil on the LIA had significantly higher concentrations of boron and calcium than the soil from the remainder of Vieques when the soil on the LIA was compared to all soil types on Vieques.

  The LIA, however, is comprised of two geologic units--undivided marine sedimentary rocks (Tl) and a deeply weathered assemblage of largely marine sandstone, siltstone, conglomerate, lava, tuffs, and breccia (Kv) (Torres-Gonzalez 1989). As noted in Section III.A Background, chemical concentrations in soils that develop on different geologic units are inherently different. Therefore, ATSDR also compared the soil on the Tl geologic units on the LIA to soil on the Tl geologic units on the remainder of Vieques, and found that only cobalt was significantly higher on the LIA (see Table 5). In a comparison of the soil on the Kv geologic units on the LIA to the soil on the Kv geologic units on the remainder of Vieques, only calcium was significantly higher on the LIA (see Table 6).

  It should be noted that statistical comparisons could not be conducted for metals that were not detected across the entire island. In fact, antimony, arsenic, cadmium, and mercury were not detected anywhere but on the LIA. This could be because the earlier sampling conducted on the rest of Vieques (Learned et al. 1973) was not sufficiently sensitive to detect the low levels of these metals. Arsenic, for example, was detected on the LIA during more recent sampling, but was not detected during the geologic evaluation in 1972 because the detection limits were not low enough.

  This approach is based largely on the data collected by USGS and PRDNR in 1972 (Learned et al. 1973) and as noted in Section II.H Summary of the Available Soil Sampling on Vieques, these soil samples may be as much as 4-fold higher than the true values. However, regardless of the uncertainty regarding the values reported in these data, it is reasonable to expect that there is internal consistency of analytical results within this data set (i.e., values from the LIA and from the remainder of Vieques are both high-biased) and thus, ATSDR expects little impact from using these data.

• The second approach was to compare the levels of metals detected at the LIA during the 2000 soil sampling (CH2MHILL 2000a) to the background soil samples gathered in the former NASD (CH2MHILL 2001). This approach eliminates any inherent differences based on analytic and sampling methods. However, the soil samples were collected on different geologic units; therefore, in an effort to determine if the background levels for the KTd could be useful in evaluating potential contamination of the LIA by Navy training exercises, ATSDR compared the chemical make-up of the soils of the KTd with that of the soils of the Tl (see Section III.A Background). Comparing and contrasting only the soils of those two units reveals that, with the exception of barium, cobalt, iron, manganese, strontium, titanium, and vanadium that are statistically significantly different, the metals composition of the soils of the KTd and the Tl are otherwise similar. Given the qualified similarity of the soils of these two geologic units, the background values established for the KTd in the former NASD may be generally applicable as background values for the Tl in the LIA.

That established, ATSDR compared the soil samples collected from the Tl geologic unit in the LIA to the soil samples collected from the KTd geologic unit in the former NASD (see Table 7). This comparison revealed that the average concentrations for most of the chemicals in the soil from the LIA are elevated above background by 1.4 to 2.9-fold. The average arsenic concentration, however, seems to be roughly 14 times higher in the LIA than in the former NASD.

Overall, it appears that the soils of the LIA have been influenced by Navy training activities and contain elevated levels of heavy metals. Given the potential problems associated with the data and assumptions used, additional background soil sampling in the LIA would be necessary to confirm the validity of this conclusion. Although, ATSDR realizes collecting background samples from the LIA may no longer be possible. The next section, Section IV. Evaluation of The Soil Exposure Pathway, describes the methods ATSDR used to determine that despite the apparent elevation in chemical concentrations at the LIA, residents and visitors of Vieques are not being exposed to harmful levels of chemicals in the soil.

Has the LIA become more contaminated with time?

ATSDR attempted to compare soil samples collected from the LIA in 1972 (Learned et al. 1973) to soil samples collected from the LIA in 2000 (CH2MHILL 2000a), to determine if this 28-year interval of Navy training had significantly increased the level of contamination at the LIA. However, given that the data collected by USGS and PRDNR in 1972 appears to be elevated by as much as 4-fold higher than the true values (as described in Section II.H), this comparison became invalid.

D. Movement of Contamination from the LIA to the Residential Area

Is there a spatial pattern that indicates that metals are moving from the LIA to the residential area?

No. The available data do not indicate a pattern of high to low concentrations from east to west. Thus, this data set does not provide evidence indicating airborne transport of metals from the LIA to the residential area. Further analysis of this issue is being conducted by ATSDR using computer air transport models and will be presented in a separate air pathway evaluation (see Sections I and VIII).

To answer this question, ATSDR plotted on a map the locations of metal concentrations detected on Vieques. All of the studies, except the 1978 investigations (Hoffsommer and Glover 1978 and Lai 1978), identified their sampling locations either by latitude and longitude or on a figure. But only the reconnaissance geochemical survey conducted by USGS and PRDNR (Learned et al. 1973) collected samples from across the entire island. Therefore, most of the interpretations from this analysis are based on these data. As noted previously, it is reasonable to assume that there is internal consistency within the 1973 data and thus, those data are suitable for use in an evaluation of the relative spatial distribution of detected levels.

ATSDR generated chemical-specific maps for the metals that are found in munitions. None of the spatial maps showed a pattern beginning with high concentrations in the LIA and decreasing concentrations tapering off to the west of the island. Spatial maps were not generated for explosive compounds because the only detections were located at the LIA. Sampling for explosives was, however, conducted along the western border of the EMA in 1999, and none were detected (CH2MHILL and Baker 1999).

Although a spatial pattern describing a progressive east to west trend is not shown in the chemical-specific maps, other patterns are shown. For example, a western concentration of the highest levels of strontium detected is shown in Figure 6. Barium shows a similar western concentration and both chemicals seem to show an association with the areas underlain by granodiorite and quartz diorite (the KTd geologic unit).

A geologic association between the areas underlain by the undivided sedimentary rocks (the Tl geologic unit) and the occurrence of the highest detections of calcium is illustrated in Figure 7. Both vanadium and zinc show a geologic association with areas underlain by the marine sandstones and lavas (the Kv geologic unit), although the association is not a clearly developed as the calcium-Tl association.

Examination of the distribution of detected levels of the other metals does not show any clear pattern, trend, or association. This random distribution of detected levels is illustrated in Figure 8 for chromium. A similar random distribution is also exhibited by the spatial distribution of the detected levels of cobalt, copper, iron, magnesium, manganese, nickel, lead, titanium, yttrium, and zirconium.

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1. When ATSDR compared the metal concentrations in soil samples collected from the former NASD during this effort to background (naturally occurring) soil samples recently collected from the former NASD (CH2MHILL 2001), the data collected by USGS and PRDNR was found to be higher, sometimes by 4-fold. Barium and calcium differ from this pattern for unknown reasons. Since sampling locations from both events were from areas unaffected by the Navy training activities, it would appear that the older data is artificially elevated (i.e., higher than the true values). Another indication is that for those metals analyzed and detected in all samples, the minimum values obtained during the USGS/PRDNR study are higher that the minimum values obtained during the recent background study, even though the minimum detection levels were higher than those used when the background analyses were performed. If there were no high-bias in the data reported in 1973 then several of the samples collected should have been reported as not detected. These differences are probably due, in part, to differing analytic or sampling methods. However, regardless of the reason(s) for the apparent differences, the higher values were used by ATSDR to evaluate potential health effects.
2. Please see the discussion "Can the soil of Vieques be compared to the mainland of Puerto Rico?" in Section III.B for an explanation of ATSDR's use of sediment data.
3. The laboratory that analyzed the samples noted that "a completely positive identification was not possible due to the extremely low concentrations found" (Hoffsommer and Glover 1978). They further note "if these explosives are present, the concentrations do not exceed the values reported here." ATSDR evaluated the chemical concentrations as reported to be most protective of human health; however, this should not be interpreted as validation of the laboratory study's results.
4. ATSDR utilized the available data with certain limitations. In a statistical comparison of this data to the other data collected on the LIA (Learned et al. 1973; CH2MHILL 2000a), nine of the 20 chemicals were significantly different (higher, p <0.05): ammonia, barium, cadmium, copper, lead, mercury, nickel, nitrate/nitrite, and zinc. This does not imply anything is amiss with the data; it simply means that using only the highest and second highest detections rather than the complete data set would skew any results. Therefore, these data could not be used in the statistical analyses. They were, however, used to form conclusions during the public health evaluations.

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IV. Evaluation of the Soil Exposure Pathway

A. Introduction

What is meant by exposure?

ATSDR's PHAs are driven by exposure or contact. Chemicals released into the environment have the potential to cause harmful health effects. Nevertheless, a release does not always result in exposure. People can only be exposed to a chemical if they come in contact with that chemical. If no one comes into contact with a chemical, then no exposure occurs, thus no health effects could occur. Often the general public does not have access to the source area of the environmental release; this lack of access becomes important in determining whether the chemicals are moving through the environment to locations where people could come into contact with them.

The route of a chemical's movement is the pathway. ATSDR identifies and evaluates exposure pathways by considering how people might come into contact with a chemical. An exposure pathway could involve air, surface water, groundwater, soil, dust, or even plants and animals. Exposure can occur by breathing, eating, drinking, or by skin contact with a substance containing the chemical.

Exposure does not always result in harmful health effects. The sections below describe the conditions under which harmful effects might be expected to occur.

How does ATSDR determine which exposure situations to evaluate?

ATSDR scientists evaluate site-specific conditions to determine whether people are being exposed to site-related contaminants. When evaluating exposure pathways, ATSDR identifies whether exposure to contaminated media (soil, water, air, waste, or biota) is occurring through ingestion, dermal (skin) contact, or inhalation. Figure 9 describes ATSDR's exposure evaluation process.

If exposure is possible, ATSDR scientists then consider whether contamination is present at levels that might affect public health. ATSDR scientists select chemicals for further evaluation by comparing them against health-based comparison values. Comparison values are developed by ATSDR from available scientific literature concerning exposure and health effects. Comparison values are derived for each of the media and reflect an estimated chemical concentration that is not expected to cause harmful health effects for a given chemical, assuming a standard daily contact rate (e.g., amount of water or soil consumed or amount of air breathed) and body weight.

Comparison values are not thresholds for harmful health effects. ATSDR comparison values represent chemical concentrations many times lower than levels at which no effects were observed in experimental animal or human epidemiologic studies. If chemical concentrations are above comparison values, ATSDR further analyzes exposure variables (e.g., duration and frequency) for health effects, including the toxicology of the chemical, other epidemiology studies, and the weight of evidence.

Some comparison values used by ATSDR scientists include ATSDR's environmental media evaluation guides (EMEG), reference dose media evaluation guides (RMEG), and cancer risk evaluation guides (CREG). EMEGs, RMEGs, and CREGs are non-enforceable, health-based comparison values developed by ATSDR for screening environmental contamination for further evaluation. Risk-based concentrations (RBCs) and soil screening levels (SSLs) are health-based comparison values developed by EPA Region III to screen sites not yet on the National Priorities List (NPL), respond rapidly to citizens inquiries, and spot-check formal baseline risk assessments. Appendix A describes the comparison values used in this PHA.

More information about the ATSDR evaluation process can be found in ATSDR's Public Health Assessment Guidance Manual at http://www.atsdr.cdc.gov/HAC/HAGM or by contacting ATSDR at 1-888-42-ATSDR. Appendix B defines some of the technical terms used in this health assessment.

If someone is exposed, will they get sick?

Exposure does not always result in harmful health effects. The type and severity of health effects that occur in an individual as the result of contact with a chemical depend on the exposure concentration (how much), the frequency and duration of exposure (how long), the route or pathway of exposure (breathing, eating, drinking, or skin contact), and the multiplicity of exposure (combination of chemicals). Once exposure occurs, characteristics such as age, sex, nutritional status, genetics, lifestyle, and health status of the exposed individual influence how that individual absorbs, distributes, metabolizes, and excretes the chemical. Taken together, these factors and characteristics determine the health effects that can occur as a result of exposure to a chemical in the environment.

Considerable uncertainty exists regarding the true level of exposure to environmental contamination. To account for that uncertainty and to protect public health, ATSDR scientists typically use high-end, worst-case exposure level estimates to determine whether harmful health effects are possible. ATSDR used the following conservative approaches throughout this public health evaluation:

• As noted in Section II.H Summary of the Available Soil Sampling on Vieques, the soil samples collected by USGS and PRDNR in 1972 (Learned et al. 1973) may be as much as 4-fold higher than the true values (possibly due to differences in analytic procedures). However, regardless of the reason(s) for this apparent high-bias, these higher values were used by ATSDR to evaluate potential health effects.
• 
  ATSDR did not adjust the exposure doses to account for the low bioavailability (see text box for definition) of some of the metals in soil (e.g, arsenic, chromium, iron, lead, manganese, mercury, vanadium, and cadmium under certain circumstances), which leads to overly conservative estimated exposure doses. For example, laboratory studies have demonstrated that when arsenic-contaminated soil is ingested, only one-half to one-tenth of the arsenic in the soil is actually absorbed (Freeman et al. 1993; Freeman et al. 1995; Groen et al. 1994; Casteel et al. 1997b; and Rodriguez et al. 1999 as cited in Battelle and Exponent 2000). If one were to adjust for the low bioavailability of arsenic, for example, the exposure dose would be reduced by 0.1 to 0.5.
• Averages were calculated using detected concentrations only and do not take into account nondetected values. Even though this tends to overestimate the true average values, ATSDR chose to base our health evaluations on the more conservative averages to be more protective of public health.

Therefore, the estimated exposure levels are usually much higher than the levels to which people are really exposed. If the exposure levels indicate harmful health effects are possible, a more detailed review of exposure, combined with scientific information from the toxicological and epidemiologic literature about the health effects from exposure to hazardous substances, is performed.

What exposure situations were evaluated in this PHA?

ATSDR evaluated two scenarios that describe the potential pathways of human exposure to the soil of Vieques (see Table 8). Those potential pathways are:

1. The residents and visitors of Vieques (the receptor population) can come in contact with the constituent chemicals of the soil (environmental media) in the residential portion of the island. Chemicals from the LIA (the source) could potentially be carried to the residential area of Vieques (point of exposure) through the air since the prevailing winds are from east to west. Human exposure to the soil in the residential area could result in exposure not only to the natural constituents of the soil, but also to any additional chemicals that may have been carried by the wind from the LIA.
2. Individuals (the receptor population) can come into contact with the chemicals of the soil (environmental media) when they enter the LIA (the source). The longest exposure to this potential source of contamination occurred when protestors occupied the LIA from April 1999 to May 2000.

During typical behavior patterns, people incidentally (i.e., accidentally) ingest soil (route of exposure) when they eat food with their hands, smoke a cigarette, or put their fingers in their mouths because soil or dust particles can adhere to food, cigarettes, and hands. As a result of a normal phase of childhood in which they display hand-to-mouth behavior, children are particularly sensitive because they are more likely to ingest more soil than adults. Dermal exposure (route of exposure) to the soil can also occur through a variety of activities such as gardening, outdoor recreation, or construction. Because of this likely exposure to the soil, ATSDR evaluated potential health effects resulting from incidental ingestion and dermal contact.

This PHA, the Soil Pathway Evaluation, evaluates only those pathways related to exposure via incidental ingestion and dermal contact with potentially contaminated soil on Vieques, both in the residential area and on the LIA. Other pathways, such as exposure to the groundwater, air, and fish are not assessed in this PHA. They are being addressed by ATSDR in separate pathway evaluations (see Sections I and VIII for more details).

B. Methods Used to Evaluate Public Health

Overview

To evaluate exposures to soil at Vieques, ATSDR examined available data to determine whether chemicals were above ATSDR's comparison values. For those that did exceed comparison values, ATSDR derived exposure doses (see text box for definition) and compared them against health-based guidelines. ATSDR also reviewed relevant toxicological data to obtain information about the toxicity of chemicals of interest. As stated previously, exposure to a certain chemical does not always result in harmful health effects. The type and severity of health effects expected to occur depend on the exposure concentration, the frequency and duration of exposure, the route or pathway of exposure, and the multiplicity of exposure.

Comparing Data to ATSDR's Comparison Values

Comparison values are derived using conservative exposure assumptions, reflecting concentrations much lower than those observed to cause harmful health effects. Thus, comparison values are protective of public health in essentially all exposure situations. As a result, concentrations detected at or below ATSDR's comparison values do not warrant health concern. While a concentration at or below the relevant comparison value could reasonably be considered safe, it does not necessarily follow that any environmental concentration exceeding a comparison value would produce harmful health effects. It cannot be emphasized too strongly that comparison values are not thresholds of toxicity. The likelihood that harmful health outcomes will actually occur depends on site-specific conditions and individual lifestyle, as well as genetic factors affecting the route, magnitude, and duration of actual exposure--not an environmental concentration alone.

The majority of chemicals detected in the soil on Vieques were at or below comparison values and not further evaluated (see Table 9). Chemicals above comparison values were considered for further evaluation, prompting ATSDR to estimate exposure doses using site-specific exposure assumptions.

Deriving Exposure Doses

ATSDR derived exposure doses for those chemicals detected above ATSDR's comparison values. Exposure doses are expressed in milligrams per kilogram per day (mg/kg/day). When estimating exposure doses, health assessors evaluate chemical concentrations to which people could have been exposed, together with the length of time and the frequency of exposure. Collectively, these factors influence an individual's physiological response to chemical exposure and potential outcomes. Where possible, ATSDR used site-specific information regarding the frequency and duration of exposures. When site-specific information was not available, ATSDR employed several conservative exposure assumptions to estimate exposures.

The following equation estimates incidental ingestion of chemicals in soil:

Where:

Conc.:	Concentration of chemical in parts per million (ppm, which is also mg/kg)
IR:	Ingestion rate: adult = 100 milligrams (mg) of soil per day; child = 200 mg of soil per day*
EF:	Exposure frequency, or number of exposure events per year of exposure: 365 days/year
ED:	Exposure duration: adult = 70 years; child = 6 years
BW:	Body weight: adult = 70 kilograms (kg); child = 10 kg
AT:	Averaging time, or the period over which cumulative exposures are averaged (6 years or 70 years x 365 days/year)

* According to EPA's Exposure Factors Handbook (1997) the recommended mean values for soil ingestion are 100 mg of soil per day for children and 50 mg of soil per day for adults, but "200 mg/day for children may be used as a conservative estimate of the mean." ATSDR used more conservative ingestion rates to account for situations where people may incidentally consume more soil than under typical conditions (Calabrese et al. 1990 and Van Wijnen et al. 1990 as cited in EPA 1997).

Using Exposure Doses to Evaluate Potential Health Hazards

ATSDR analyzes weight of evidence to determine whether exposures might be associated with harmful health effects (noncancer and cancer). As part of this process, ATSDR examines relevant toxicologic, medical, and epidemiologic data to determine whether estimated doses are likely to result in harmful health effects. As a first step in evaluating noncancer effects, ATSDR compares estimated exposure doses (calculated using maximum concentrations) to conservative health guideline values, including ATSDR's minimal risk levels (MRLs) and EPA's reference doses (RfDs). The MRLs and RfDs are estimates of daily human exposure to a substance that are unlikely to result in noncancer effects over a specified duration. Estimated exposure doses that are less than these values are not considered to be of health concern. To maximize human health protection, MRLs and RfDs have built in uncertainty or safety factors, making these values considerably lower than levels at which health effects have been observed. The result is that even if an exposure dose is higher than the MRL or RfD, it does not necessarily follow that harmful health effects will occur.

But if health guideline values are exceeded, ATSDR examines the health effects levels discussed in the scientific literature and more fully reviews exposure potential. ATSDR reviews available human studies as well as experimental animal studies. This information is used to describe the disease-causing potential of a particular chemical and to compare site-specific dose estimates with doses shown in applicable studies to result in illness (known as the margin of exposure). For cancer effects, ATSDR compares an estimated lifetime exposure dose to available cancer effects levels (CELs), which are doses that produce significant increases in the incidence of cancer or tumors, and reviews genotoxicity studies to understand further the extent to which a chemical might be associated with cancer outcomes. This process enables ATSDR to weigh the available evidence in light of uncertainties and offer perspective on the plausibility of harmful health outcomes under site-specific conditions.

When comparing to actual health effects levels in the scientific literature, ATSDR tries to estimate more realistic exposure scenarios to use for comparison. In this level of the evaluation, an average concentration ⁽⁵⁾ is used to calculate exposure doses to estimate a more probable exposure. It is highly unlikely that anyone would incidentally ingest the maximum concentration on a daily basis and for an extended period of time because not all the soil contains the maximum concentration of any given chemical. Therefore, it is more likely that soil containing a range of concentrations would be ingested over time.

Using Other Methods to Evaluate Potential Health Hazards

When dealing with exposure to lead ATSDR uses, in addition to the traditional methodologies described above, a second approach. A substantial part of human health effects data are expressed in terms of blood lead level rather than exposure dose. Thus, ATSDR developed this secondary approach to utilize regression analysis with media-specific uptake parameters to estimate what cumulative blood lead level might result from exposure to a given level of contamination. This is accomplished by multiplying the detected concentration by a media-specific slope factor, which is 0.0068 ± 3*(0.00097) micrograms per deciliter (µg/dl) per ppm in soil (ATSDR 1999c). The Centers for Disease Control and Prevention (CDC) have determined that health effects are more likely to be observed if actual exposures are at or above 10 µg/dl. This second approach is a screening tool for evaluating expected blood lead levels--it is not used in lieu of a toxicological exposure dose evaluation.

Sources for Health-based Guidelines

By Congressional mandate, ATSDR prepares toxicological profiles for hazardous substances found at contaminated sites. These toxicological profiles were used to evaluate potential health effects from exposure to soil on Vieques. ATSDR's toxicological profiles are available on the Internet at http://www.atsdr.cdc.gov/toxpro2.html or by contacting the National Technical Information Service (NTIS) at 1-800-553-6847. For more information about the toxicological profiles, please call ATSDR at 1-888-42-ATSDR. EPA also develops health effects guidelines, and in some cases, ATSDR relied on EPA's guidelines to evaluate potential health effects from exposure to soil. These guidelines are found in EPA's Integrated Risk Information System (IRIS)--a database of human health effects that could result from exposure to various substances found in the environment. IRIS is available on the Internet at http://www.epa.gov/iris. For more information about IRIS, please call EPA's IRIS hotline at1-301-345-2870 or e-mail at Hotline.IRIS@epamail.epa.gov.

Chemicals Without Health-based Guidelines

Essential nutrients (e.g., calcium, magnesium, phosphorous, potassium, and sodium) are important minerals that maintain basic life functions; therefore, certain doses are recommended on a daily basis. Because these chemicals are necessary for life, MRLs and RfDs do not exist for them. They are found in many foods, such as milk, bananas, and table salt. Exposure to these essential nutrients in the soil will not result in harmful health effects.

Health-based comparison values also do not exist for a few other chemicals detected in soil on Vieques. For these chemicals, ATSDR looks more closely at the chemicals' prevalence, at other scientific literature, and at natural levels found in the soil. Bismuth, gold, lanthanum, tungsten, and ammonium perchlorate were detected in less than 3% of the samples. These chemicals are not prevalent on the island; thus the potential for people to come in contact with them is limited. Scandium, yttrium, and zirconium were detected much more frequently. But these elements are present at concentrations within the ranges in which they naturally occur in United States soil (see Table 2). The fact that no scientific literature exists on the health effects of these elements could suggest no one has determined that exposure to these chemicals is harmful. Therefore, given the limited exposure to some of the chemicals and the apparent lack of a health-exposure relationship with the others, these chemicals are not evaluated further within this PHA.

C. Public Health Evaluation

Question 1: Are the residents of Vieques being exposed to harmful levels of chemicals in the soil on Vieques?

No. The levels of metals and other chemicals detected on Vieques are too low to be of health concern for both adults and children through incidental ingestion or dermal contact with the soil. Of the metals detected in the soil across Vieques, only seven (arsenic, cadmium, chromium, iron, manganese, lead, and vanadium) were detected above comparison values (see Table 9). After detailed evaluations of these seven metals, as well as mercury, ATSDR concluded that all the chemicals detected in the soil on Vieques were at concentrations too low to be of health concern for anyone incidentally ingesting or touching the soil.

Exposure from Incidental Ingestion of Soil on Vieques

For exposure through incidental ingestion, ATSDR derived conservative exposure doses for the metals detected above comparison values by using the maximum concentrations in the equation listed in the Methods Used to Evaluated Public Health section (IV.B) and by comparing the estimated exposure doses to standard health guideline values (MRLs and RfDs). See Figure 10 for the locations of the maximum detections of these metals. The following exhibit contains the expected doses for six of the seven metals detected above comparison values (see Table 9). Lead was not included in the exhibit because an oral health guideline is not available for lead.

Exhibit 3. Estimated Exposure Doses Compared to Health Guidelines

Metal	Maximum Detected Concentration(ppm)	Estimated Exposure Dose (mg/kg/day)		Oral Health Guideline(mg/kg/day)	Basis for Health Guideline
		Adult	Child
Arsenic	36	0.000051	0.00072*	0.0003	chronic MRL/RfD
Cadmium	31.3	0.000045	0.00063*	0.0002	chronic MRL
Chromium	700	0.001	0.014*	0.003	chronic RfD(Chromium VI)
Iron	150,000	0.21	3.0*	0.3	chronic RfD
Manganese	5,000	0.0071	0.10*	0.02	chronic RfD
Vanadium	500	0.00071	0.01*	0.003	intermediate MRL

* Estimated exposure exceeds health guideline; however, an exposure dose that is higher than the MRL or RfD does not necessarily result in harmful health effects. These metals are further evaluated in this section of the PHA.

Using the maximum detected concentration, the resulting exposure doses for all of the metals were below the conservative health guidelines for oral exposure for adults--indicating that all of the chemicals detected on Vieques are at concentrations too low to be of health concern for adults. The exposure doses for children were above health guidelines for all of the metals. However, calculated exposure doses higher than the health guidelines do not automatically mean harmful health effects will occur. Rather, they are an indication that ATSDR should further examine the harmful effect levels reported in the scientific literature and more fully review exposure potential.

The following discussions detail ATSDR's evaluations of exposure from incidental ingestion of arsenic, cadmium, chromium, iron, lead, manganese, and vanadium--all found in the soil on Vieques. Even though mercury does not have a comparison value or health guideline, toxicological and epidemiological information is available. Therefore, mercury was also evaluated in further detail using information from its toxicological profile.

Are residents being exposed to harmful levels of arsenic in the soil?

No. Adult exposure from incidentally ingesting arsenic in soil on Vieques is not expected to result in harmful health effects; the estimated exposure dose is below the conservative health guideline. Similarly, because the estimated exposure dose is below levels of health effects documented in the toxicological literature, childhood exposure is not expected to result in harmful health effects. Childhood exposure is evaluated further in this section following a brief description of the different forms of arsenic, their uses, fate and transport in the body, and potential health effects.

Arsenic occurs naturally in soil and in many kinds of rocks; it is widely distributed in the Earth's crust. Most arsenic compounds have no smell or distinctive taste. In the environment arsenic is usually combined with other elements such as oxygen, chlorine, and sulfur. When combined with these elements arsenic is called inorganic arsenic. When combined with carbon and hydrogen it is called organic arsenic. The organic forms of arsenic are usually less harmful than the inorganic forms (ATSDR 2000a). To be protective of public health during the evaluation, all of the arsenic detected on Vieques was assumed to be in the more harmful inorganic form. Therefore, all of the effects levels reported from the literature are for exposure to inorganic arsenic.

Currently, about 90% of all commercially produced arsenic is used to pressure-treat wood. Arsenic is also a component of some munitions. In the past, arsenic was widely used as a pesticide; in fact, some organic arsenic compounds are still used in pesticides. Other important arsenic uses are in lead-acid car batteries, semiconductors, and light-emitting diodes.

Incidental ingestion of arsenic-contaminated soil is one way arsenic can enter the body. Once in the body, the liver changes some of the arsenic into a less harmful organic form. Both inorganic and organic forms of arsenic leave the body in urine. Studies have shown that 45-85% of the arsenic is eliminated within one to three days (Buchet et al. 1981a; Crecelius 1977; Mappes 1977; Tam et al. 1979b as cited in ATSDR 2000a); however, some will remain for several months or longer.

Inorganic arsenic is a poison that can cause death if ingested in large doses (e.g., 2 to 121 mg/kg/day). Ingesting lower levels can cause stomach and intestine irritation or decreased production of red and white blood cells. Long-term oral exposure to (i.e., ingestion of) inorganic arsenic can result in darkening of the skin and appearance of small corns or warts on the palms, soles of the feet, and torso. The health effects expected to result from exposure to high concentrations of organic arsenic are uncertain, but could include nerve injury or stomach irritation. The U.S. Department of Health and Human Services (DHHS), the International Agency for Research on Cancer (IARC), the National Toxicology Program (NTP), and EPA have all independently determined that arsenic is carcinogenic to humans.

Daily exposure to the maximum concentration of arsenic for 70 years is not expected to cause any harmful health effects for adults living on Vieques because the resulting exposure dose is too low to be of health concern (i.e., below conservative health guidelines, see Exhibit 3). Lifetime exposure to the maximum concentration of arsenic in soil on Vieques would also not result in an increase in cancer because the expected lifetime dose (0.000051 mg/kg/day) from exposure to the maximum concentration of arsenic is lower than the most conservative cancer effects level (CEL; that is, lung cancer resulting from exposure to 0.0011 mg/kg/day of arsenic in water).

Childhood exposure to arsenic was further evaluated using a more realistic exposure scenario--an average concentration to calculate an exposure dose. By using an average concentration, ATSDR can estimate a more probable exposure. Using the same equation and assumptions used above in the health guideline comparison, but substituting the average arsenic concentration (8.91 ppm) for the maximum concentration, the calculated exposure dose for children is 0.00018 mg/kg/day. ATSDR then compared this potential exposure to actual health effects levels in the toxicological and epidemiological literature (ATSDR 2000a).

The oral health guideline is based on a study in which humans were exposed to arsenic at a dose of 0.0008 mg/kg/day for more than 45 years. No adverse health effects were noted. Some of the other studies describe less serious health effects (e.g., fatigue, headache, dizziness, insomnia, nightmare, and numbness) resulting from exposure to 0.005 mg/kg/day of arsenic, and serious health effects (e.g., increased prevalence of cerebrovascular disease and cerebral infarction) resulting from long-term exposure to 0.002 mg/kg/day of arsenic. All of these exposure levels, including the no observed adverse effects level (NOAEL) of 0.0008 mg/kg/day, are higher than the levels expected to result from childhood exposure to concentrations of arsenic detected in soil on Vieques.

A majority of available data focuses on exposure to arsenic in adults, but children are sometimes more susceptible than adults to health effects. Some information suggests that arsenic metabolism in children is less efficient than in adults; so children might not convert as much inorganic arsenic into the less harmful organic form (Concha et al. 1998b as cited in ATSDR 2000a). See the Child Health Initiative section of this PHA for a brief discussion concerning the greater susceptibility children could have from exposure to arsenic.

Note that exposure to arsenic is based on levels detected in the soil at the LIA and near the Vieques Municipal Airport. Sampling conducted in the residential area was not sufficiently sensitive to detect the low levels of arsenic possibly existing on Vieques. The maximum and average soil concentrations used to calculate exposure doses are based on sampling conducted in areas where residents and visitors are restricted and are, therefore, not exposed to such arsenic levels on a daily basis. The majority of the data (39 of 41 detections) are from the LIA, and as noted in Section III.C, the soils of the LIA have been influenced by Navy training activities and contain elevated levels of arsenic. Therefore, by incorporating these conservative assumptions, the exposure doses that were calculated were based on a possible worst-case scenario.

In addition, most of the available information on arsenic comes from epidemiologic studies in which humans drank contaminated water. When present in water, arsenic is readily absorbed by the body and is assumed to have a 100% bioavailability; but the bioavailability of arsenic in soil is much lower (estimated 3% to 50%; Rodriguez et al. 1999; Ruby et al. 1996, 1999 as cited in ATSDR 2000a). Therefore, only a portion of the arsenic in soil is expected to be readily absorbed into the human body. That said, however, all of ATSDR's evaluations assumed 100% bioavailability of arsenic from soil.

Based on the foregoing, ATSDR concludes that arsenic levels found in the soil would not result in harmful health effects for any adults or children who might incidentally ingest soil while living on Vieques.

Are residents being exposed to harmful levels of cadmium in the soil?

No. Because the estimated exposure dose is below the conservative health guideline, adult exposure from incidentally ingesting cadmium in soil on Vieques is not expected to result in harmful health effects. Similarly, because the estimated exposure dose for children is below levels of health effects documented in the toxicological literature, childhood exposure is also not expected to result in harmful health effects. Childhood exposure is evaluated further in this section following a brief description of cadmium and its uses, its fate and transport in the body, and potential health effects.

Cadmium is an element found naturally in soil and rocks throughout the earth's crust. It has no recognizable odor or taste. Although in its pure form it is a soft, silver-white metal, it is usually found as a mineral combined with other elements such as oxygen, chlorine, or sulfur. Cadmium is widely used in industrial and consumer products, including batteries, pigments, metal coatings, plastics, and some metal alloys. Munitions, fertilizers, and cigarettes also contain cadmium.

Generally, the main sources of cadmium exposure are through smoking cigarettes and, to a lesser extent, eating foods contaminated with cadmium. Incidental ingestion of soil containing cadmium can also lead to cadmium entering the body. But only about 5 to 10% of ingested cadmium is actually absorbed by the body; the majority is passed out of the body in feces (McLellan et al. 1978; Rahola et al. 1973 as cited in ATSDR 1999b). Cadmium that is absorbed goes to the kidneys and liver. Because only small portions of cadmium slowly leave the body, once it is absorbed, it tends to remain in the body for years. The body changes most of the cadmium into a form that is not harmful, but if too much cadmium is absorbed, the liver and kidneys cannot convert all of it into the harmless form (Goyer et al. 1989; Kotsonis and Klaassen 1978; Sendelbach and Klaassen 1988 as cited in ATSDR 1999b).

Most of the available research on the health effects from exposure to cadmium are from animal studies. Very few people are actually exposed to high levels of cadmium, and long-term exposure to low levels is difficult to determine given the many other factors that come into play in human exposure. The available research has shown that ingesting high levels of cadmium severely irritates the stomach. Ingesting lower levels of cadmium over a long time can lead to cadmium buildup in the kidneys, thus damaging the kidneys and possibly causing bones to become fragile.

Studies of cadmium in humans and animals have not found an increase in cancer, however, more research is needed before a definitive conclusion can be reached regarding whether cadmium does or does not cause cancer. As a conservative approach, IARC has determined that cadmium is carcinogenic to humans. DHHS reasonably anticipates that cadmium is a carcinogen. EPA has determined that when inhaled, cadmium is a probable human carcinogen.

As shown in Exhibit 3, because the resulting exposure dose is below conservative health guidelines, daily exposure to the maximum concentration of cadmium for 70 years is not expected to cause any harmful health effects for adults living on Vieques. Lifetime exposure to the maximum concentration of cadmium on Vieques is also not expected to result in an increase in cancer because the expected lifetime dose (0.000045 mg/kg/day) is lower than the CEL (increased rates of prostatic adenomas resulted in rats from exposure to 3.5 mg/kg/day of cadmium in food).

Childhood exposure to cadmium was further evaluated using an average concentration, which better represents actual exposures, to calculate an exposure dose. Using the same equation and assumptions described previously, with the average cadmium concentration (1.6 ppm) in place of the maximum concentration, the calculated exposure dose for children is 0.000032 mg/kg/day. ATSDR then compared this potential exposure to actual health effects levels in the toxicological and epidemiological literature (ATSDR 1999b).

The oral health guideline is based on a study in which no adverse health effects were reported for people who were exposed to 0.0021 mg/kg/day of cadmium in their food over their lifetime. Another study involving humans describes serious health effects (renal tubule interstitial lesions) occurring from exposure to 0.0078 mg/kg/day of environmental cadmium for more than 25 years. The reported levels of exposure, including the NOAEL of 0.0021 mg/kg/day, are two orders of magnitude higher than levels expected to result from childhood exposure to concentrations of cadmium detected in the soil on Vieques.

Little good information is available to document human health effects from exposure to cadmium, and virtually none focuses on exposures in children. Children are sometimes more susceptible than adults to health effects. The available animal research indicates that younger animals absorb more cadmium than adults and are more susceptible to a loss of bone and decreased bone strength than adults. See the Child Health Initiative section of this PHA for a brief discussion concerning the greater susceptibility that children may have from exposure to cadmium.

Note that exposure to cadmium is based on levels detected in the soil on the LIA. Sampling conducted in the residential area was not sensitive enough to detect the low levels of cadmium that might be present on Vieques. The maximum and average soil concentrations used to calculate exposure doses are based on sampling conducted in an area where residents and visitors are restricted and are, therefore, not exposed to these cadmium levels on a daily basis. Also as noted in Section III.C, the soils of the LIA have been influenced by Navy training activities and contain elevated levels of cadmium. Therefore, by incorporating these conservative assumptions, the exposure doses that were calculated were based on a possible worst-case scenario. In addition, it should also be noted that only two out of 28 cadmium detections were above ATSDR's comparison value (see Table 9). This indicates that the majority of the concentrations were detected at levels not warranting health concern.

Therefore, ATSDR does not expect that exposure to cadmium levels found in soil would result in harmful health effects for either adults or children who could incidentally ingest soil while living on Vieques.

Are residents being exposed to harmful levels of chromium in the soil?

No. Adult exposure resulting from incidental ingestion of chromium in soil on Vieques is not expected to result in harmful health effects; the estimated exposure dose is below the conservative health guideline. Childhood exposure is also not expected to result in harmful health effects because the estimated exposure dose is below levels of health effects documented in the toxicological literature. Childhood exposure is evaluated further in this section following a brief description of the different forms of chromium, their uses, fate and transport in the body, and potential health effects.

Chromium occurs naturally in rocks, soil, volcanic dust, animals, and plants. It is present in three main forms: chromium 0, chromium III (trivalent chromium), and chromium VI (hexavalent chromium). Chromium III occurs naturally in the environment and is an essential nutrient required by the body to promote sugar, protein, and fat usage. It is also used in the brick lining for high-temperature industrial furnaces, for making metals and alloys, and for chemical compounds. Chromium VI and chromium 0 are the result of industrial processes. Chromium 0 is a steel-gray solid used mainly to make steel and other alloys. Mixtures of chromium III and VI are used for chrome plating, dye and pigment manufacturing, leather tanning, wood preserving, drilling muds, rust and corrosion inhibitors, textiles, and toner for copiers. Chromium is also a component of some munitions. Chromium compounds have no detectable taste or odor.

Incidental ingestion of soil containing chromium can lead to chromium entering the body. Chromium VI is more easily absorbed than chromium III, but once inside the body, chromium VI is converted into chromium III. Most of the chromium ingested will exit the body in feces within a few days and never enter the bloodstream. Only a very small amount (0.4 to 2.1%) can pass through the walls of the intestine and enter the bloodstream (Anderson et al. 1983; Anderson 1986; Donaldson and Barreras 1966 as cited in ATSDR 2000b).

Chromium VI is more harmful than chromium III, an essential nutrient required by the body. The National Research Council recommends that adults ingest 50-200 µg of chromium III every day and has established safe and adequate daily dietary intakes of 10-80 µg for children (NRC 1989 as cited in ATSDR 2000b). Ingesting small amounts of chromium III and VI is not expected to cause harmful health effects; ingesting large amounts, however, has been shown to cause upset stomachs, ulcers, convulsions, liver and kidney damage, or even death (resulting from a one-time ingestion of 7.5 or 29 mg/kg/day of chromium VI).

When inhaled, Chromium VI is a known human carcinogen; exposure to chromium VI in the air has been linked to an increase in lung cancer. DHHS has determined that certain chromium VI compounds are known human carcinogens. IARC has determined that chromium VI is carcinogenic to humans and chromium 0 and chromium III are not classifiable as to their carcinogenicity. EPA has determined that chromium VI in air is a human carcinogen but insufficient evidence exists to determine whether chromium VI and chromium III in food and water are human carcinogens.

Although some or all of the chromium detected on Vieques could be chromium III, an essential nutrient; as a conservative approach to the health evaluation, ATSDR assumed that all of the chromium was the more harmful chromium VI. Therefore, all of the health effects levels reported from the literature are for exposure to chromium VI.

As shown in Exhibit 3, because the resulting exposure dose is below conservative health guidelines, daily exposure to the maximum concentration of chromium for 70 years is not expected to cause harmful health effects for adults living on Vieques. Exposure from incidental ingestion of soil contaminated with chromium is also not expected to result in an increase in cancer; the scientific evidence available suggests that oral exposure to chromium would not result in cancer. Animal studies involving chromium ingestion have found no evidence of carcinogenicity.

Childhood exposure to chromium was further evaluated using an average concentration, which better represents actual exposures, to calculate an exposure dose. Using the same equation and assumptions described previously, with the average chromium concentration (58.2 ppm) in place of the maximum concentration, the calculated exposure dose for children is 0.0012 mg/kg/day. ATSDR then compared this potential exposure to actual health effects levels in the toxicological and epidemiological literature (ATSDR 2000b).

The oral health guideline is based on a study in which no adverse health effects were reported in animals exposed to 2.5 mg/kg/day of chromium VI in their drinking water. The only long-term human study documented in the literature reported less serious health effects (oral ulcer, diarrhea, abdominal pain, indigestion, vomiting, leukocytosis, and immature neutrophils) from exposure to chromium VI in the environment at an exposure dose of 0.57 mg/kg/day. These levels of exposure are two and three orders of magnitude higher than doses expected to result from childhood exposure to concentrations of chromium detected in the soil on Vieques.

A limited amount of information is available on the toxicity of chromium in children, and most of these data involve cases in which children ingested lethal doses of chromium VI. Children are sometimes more susceptible to health effects than adults, but whether this is true for chromium is unknown. One animal study reported that more chromium III entered the bodies of newborns than adults (Sullivan et al. 1984 as cited in ATSDR 2000b). While children need small amounts of chromium III for normal growth and development, whether this is true for chromium VI is unknown.

Note that only 10 times out of 463 detections was chromium detected above ATSDR's comparison value (see Table 9). This indicates that the vast majority of the concentrations were detected at levels not warranting health concern.

ATSDR concludes that exposure to chromium levels found in residential soil would not result in harmful health effects for either adults or children who might incidentally ingest soil while living on Vieques.

Are residents being exposed to harmful levels of iron in the soil?

No. Adult exposure resulting from incidental ingestion of iron in soil on Vieques is not expected to result in harmful health effects; the estimated exposure dose is below the conservative health guideline. Similarly, childhood exposure is also not expected to result in harmful health effects because the estimated daily consumption is below levels known to result in childhood poisoning. Childhood exposure is evaluated further in this section following a brief description of iron, its uses by the body, and recommended intakes.

Iron is a naturally occurring element in the environment. In fact, by weight it is the fourth most abundant element in the earth's crust (LANL 2001). The most common iron ore is hematite, which frequently can be seen as black sand along beaches and stream banks. As a pure metal, iron is very reactive chemically and will rapidly corrode, especially in moist air or at high temperatures. It is hard and brittle, and is usually combined with other metals to form alloys, including steel. Iron is a component of some munitions.

Iron is also an important mineral, assisting in the maintenance of basic life functions. It combines with protein and copper to make hemoglobin, which transports oxygen in the blood from the lungs to other parts of the body, including the heart. It also aids in the formation of myoglobin, which supplies oxygen to muscle tissues (ANR 2000). Without sufficient iron, the body cannot produce enough hemoglobin or myoglobin to sustain life. Iron deficiency anemia is a condition occurring when the body does not receive enough iron. The National Academy of Sciences' Recommended Dietary Allowance is 10 mg/day for children, adult men, and adults over the age of 50; 15 mg/day for women under the age of 50; and 30 mg/day for pregnant women (FDA 1997). The U.S. Food and Drug Administration's (FDA) Reference Daily Intake for iron is 18 mg/day (Kurtzweil 1993).

As shown in Exhibit 3, because the resulting exposure dose is below conservative health guidelines, daily exposure to the maximum concentration of iron for 70 years is not expected to cause harmful health effects for adults living on Vieques.

Acute iron poisoning has been reported in children under 6 years of age who have accidentally overdosed on iron-containing supplements for adults. According to the FDA, doses greater than 200 mg per event could poison or kill a child (FDA 1997). Doses of this magnitude are generally the result of children ingesting iron pills and not from incidentally ingesting iron in soil.

Generally, iron is not considered to cause harmful health effects except when swallowed in extremely large doses, such as in the case of accidental drug ingestion. Therefore, toxicological and epidemiological literature is limited. For comparison, ATSDR calculated a daily consumption from exposure to the average concentration of iron in soil (45,600 ppm) using a modification of the dose equation described in the Methods Used to Evaluate Public Health section (IV.B) (Dose = Conc. x IR). Exposure to iron in the soil would increase a child's daily consumption of iron by 4.56 mg/day. The median daily intake of dietary iron is roughly 11-13 mg/day for children 1 to 8 years old and 13-20 mg/day for adolescents 9 to 18 years (NAS 2001). Therefore, the daily increases in consumption (from incidentally ingesting soil from Vieques) are not likely to cause a person's daily dose to exceed levels known to induce poisoning (e.g., >200 mg/event). Further, the body uses a homeostatic mechanism to keep iron burdens at a constant level despite variations in the diet (Eisenstein and Blemings 1998).

Therefore, based on the foregoing, ATSDR concludes that exposure to iron levels found in the residential soil would not result in harmful health effects for either adults or children who might incidentally ingest soil while living on Vieques.

Are residents being exposed to harmful levels of lead in the soil?

No. Adult and child exposures from incidentally ingesting lead are not expected to result in harmful health effects; the estimated exposure doses are below levels of health effects documented in the toxicological literature, and the calculated blood lead level is below CDC's health guideline. These exposures are evaluated further in this section following a brief description of lead and its uses, its fate and transport in the body, and potential health effects.

Lead is a bluish-gray metal naturally found in small amounts in the Earth's crust. Detection of large amounts is usually the result of human activities. Lead has no distinguishable taste or smell. It can exist in a metallic form or combine with other chemicals to form lead compounds or salts. Lead is used in the production of batteries, ammunition, metal products, and in ceramic glazes and paints. It is also used in a variety of medical (e.g., radiation shields to protect against X-rays and in fetal monitors), scientific (e.g., electronic circuitry), and military (e.g., jet turbine engine blades and military tracking systems) equipment. In the past, some lead compounds were used in gasoline to increase the octane rating. Their use was phased out in the 1980s and leaded gasoline was banned in 1996.

Incidental ingestion of lead will cause some lead to enter the body and bloodstream. The amount of lead that enters the body depends on how old you are and when your last meal was eaten. More lead will enter the blood in children than in adults (Alexander et al. 1974; Blake et al. 1983; James et al. 1985; Rabinowitz et al. 1980; Ziegler et al. 1978 as cited in ATSDR 1999c). When soil was incidentally ingested by people who had recently eaten, 2.5% of the lead was absorbed. On the other hand, about 26% of the lead entered the bloodstream in people with empty stomachs (Maddaloni et al. 1998 as cited in ATSDR 1999c). Within a few weeks, 99% of the amount of lead absorbed by adults will exit in urine and feces (Rabinowitz et al. 1977 as cited in ATSDR 1999c), whereas only about 68% of the lead taken into children will leave their bodies (Ziegler et al. 1978 as cited in ATSDR 1999c). Once in the body, lead will travel to soft tissues, such as the liver, kidneys, lungs, brain, spleen, muscles, and heart. After several weeks of continual exposure, most of the lead moves from the soft tissue into bones and teeth. In adults, about 94% of the total amount of lead in their bodies can be found in bones. In children, about 73% of lead in their bodies is stored in their bones (Barry 1975 as cited in ATSDR 1999c).

In both adults and children, lead primarily affects the nervous system, resulting in decreased performance or weakness in fingers, wrists, and ankles. Exposure to high levels of lead can severely damage the brain and kidneys and can cause miscarriages in pregnant women. No evidence exists that lead causes cancer in humans. Still, some animal testing has shown kidney tumors to develop if the animals are given large doses of lead (27-371 mg/kg/day). DHHS has determined that lead acetate and lead phosphate reasonably can be expected to cause cancer. EPA classifies lead as a probably human carcinogen.

Although a health guideline is not available for lead, toxicological and epidemiological information is available. Therefore, exposure to lead was evaluated in detail for both adults and children. The average lead concentration (17.1 ppm) together with the listed assumptions, were used in the equation described in the Methods Used to Evaluate Public Health section (IV.B). The calculated exposure doses are 0.000024 mg/kg/day for adults and 0.00034 mg/kg/day for children. ATSDR then compared these potential exposures to actual health effects levels reported in the toxicological and epidemiological literature (ATSDR 1999c).

In the few acute and intermediate studies in people, less serious health effects (decreased aminolevulinic acid dehydratase activity and increased red blood cell porphyrin) resulted from exposure to 0.01 to 0.03 mg/kg/day of lead in capsules. Health effects from chronic exposure to lead have not been documented in humans. No adverse effects were observed in animals chronically exposed to 0.57-27 mg/kg/day of lead. These reported health effects levels are several orders of magnitude higher than would be expected to result from exposure to concentrations of lead detected in soil on Vieques.

It should be noted that lead was only detected above EPA's soil screening level for play areas in 2 out of 463 detections (see Table 9). This indicates that the vast majority of the concentrations were detected at levels below those of health concern.

Also, to evaluate potential increases in cancer from exposure to lead, ATSDR compared the lifetime exposure dose for adults to the CELs reported in the literature. Three long-term studies in animals described renal tubular adenomas and carcinomas when animals consumed food or water with 27 to 371 mg/kg/day of lead. But because of the high doses of lead used, ATSDR cautions against using these animal studies to predict whether cancer will actually occur in humans. Still, these doses are much higher than the doses expected to result from lifetime exposure to the maximum concentration of lead in the soil on Vieques.

Children are more susceptible to lead poisoning than are adults. Because their bodies tend to absorb more lead than adults' bodies, children experience more severe health effects at lower doses than adults. To add an additional perspective about whether harmful health effects are expected to occur, ATSDR also determined the blood lead level expected to result from exposure to lead in soil on Vieques using the formula described in the Methods Used to Evaluate Public Health section (IV.B). Exposure to the average soil concentration is estimated to result in blood lead levels ranging from 0.067 to 0.17 µg/dl--well below CDC's level of concern (10 µg/dl).

For these reasons, ATSDR does not expect that exposure to lead levels found in the residential soil would result in harmful health effects for either adults or children who might incidentally ingest soil while living on Vieques.

Are residents being exposed to harmful levels of manganese in the soil?

No. Adult exposure resulting from incidental ingestion of manganese in soil on Vieques is not expected to result in harmful health effects; the estimated exposure dose is below the conservative health guideline. Childhood exposure is also not expected to result in harmful health effects because the estimated exposure dose is below levels of health effects documented in the toxicological literature. Childhood exposure is evaluated further in this section following a brief description of manganese and its uses, its fate and transport in the body, and potential health effects.

Manganese is naturally found in many types of rocks and comprises about 0.1% of the earth's crust (ATSDR 2000c). Pure manganese is a silver-colored metal; it does not, however, occur in the environment as a pure metal. It is usually combined with other elements (e.g., oxygen, sulfur, and chlorine) to form compounds and does not have a distinctive taste or smell. Manganese compounds are mined and used to produce manganese metal, which is combined with iron to make various types of steel. Some manganese compounds are used in the production of batteries, in dietary supplements, and as ingredients in ceramics, pesticides, and fertilizers. Manganese is also a component of some munitions. Additionally, manganese is present in many foods, including grains and cereals, and is found in high concentrations in tea.

Manganese is an essential trace element and is required by the body to break down amino acids and produce energy. Incidental ingestion of soil containing manganese can result in manganese entering the body. Most manganese, however, is excreted in feces. About 3 to 5% of manganese is absorbed by the body when ingested (Davidsson et al. 1988, 1989; Mena et al. 1969 as cited in ATSDR 2000c). Typically, people have small amounts of manganese in their bodies. Under normal circumstances, the amount is regulated so the body has neither too much nor too little (EPA 1984a as cited in ATSDR 2000c). For example, if large amounts of manganese are consumed, large amounts will be excreted. The total amount of manganese in the body tends to stay the same even when exposed to higher levels than usual. Still, if too much manganese is ingested, the body might not be able to adjust and eliminate the additional amount.

Consuming too much manganese can cause weakness, stiff muscles, trembling hands, or nerve disease. One study reported that people who drank water with high concentrations of manganese and other chemicals experienced symptoms similar to those associated with the condition referred to as manganism (mental and emotional disturbances, and body movements that are slow and clumsy). Manganism, however, is typically the result of inhaling high levels of manganese dust in the air. It is not certain whether eating or drinking too much manganese can cause symptoms of manganism.

As shown in Exhibit 3, because the resulting exposure dose is below conservative health guidelines, daily exposure to the maximum concentration of manganese for 70 years is not expected to cause any harmful health effects for adults living on Vieques.

Children have typically not been studied for health effects from exposure to manganese. The existing data indicate that children experience similar toxicity effects as adults. Yet no studies were identified that determined whether children are more or less susceptible to manganese than adults. Although animal studies indicate that infant animals take in and retain more manganese than adults, the level of manganese children need to stay healthy is unknown (ATSDR 2000c).

Childhood exposure to manganese was further evaluated using an average concentration--which better represents actual exposures--to calculate an exposure dose. Using the same equation and assumptions described previously, with the average manganese concentration (1,220 ppm) in place of the maximum concentration, the calculated exposure dose for children is 0.024 mg/kg/day.

The Food and Nutrition Board of the National Research Council determined that 2-5 mg of manganese/day for adults is an "estimated safe and adequate daily dietary intake" (NRC 1989 as cited in EPA 1998). The World Health Organization (WHO) concluded that 2-3 mg/day is adequate for adults and 8-9 mg/day is "perfectly safe" (WHO 1973 as cited in EPA 1998). Based on these studies, EPA has determined that an appropriate reference dose for manganese in food is 10 mg/day, which EPA calculated to a NOAEL of 0.14 mg/kg/day. Therefore, the NOAEL is higher than the levels expected to result from childhood exposure to concentrations of manganese detected in the soil on Vieques.

In addition, the daily consumption from exposure to the average concentration of manganese in soil was calculated using a modification of the dose equation described in the Methods Used to Evaluate Public Health section (IV.B) (Dose = Conc. x IR). Exposure to manganese in the soil would increase a child's normal daily consumption of manganese through food by 0.24 mg/day. This relatively small daily increase in manganese consumption is not likely to increase a child's daily dose above the levels considered safe by WHO and the Food and Nutrition Board of the National Research Council. But this depends entirely on each child's normal dietary intake of manganese.

Note also that manganese was only detected once out of 463 detections above the comparison value (see Table 9). This indicates that the vast majority of the concentrations were detected at levels not warranting health concern.

Based on the foregoing, ATSDR concludes that exposure to manganese levels found in the residential soil would not result in harmful health effects for either adults or children who might incidentally ingest soil while living on Vieques.

Are residents being exposed to harmful levels of mercury in the soil?

No. Adult and child exposures from incidental ingestion of mercury are not expected to result in harmful health effects; the estimated exposure doses are below levels of health effects documented in the toxicological literature. These exposures are evaluated further in this section following a brief description of the forms of mercury, their uses, fate and transport in the body, and potential health effects.

Mercury exists naturally in the environment in several different forms: metallic mercury (also known as elemental mercury), inorganic mercury, and organic mercury. Metallic mercury is the pure form of mercury; it is a shiny, silver-white metal, liquid at room temperature. Inorganic mercury is formed when metallic mercury combines with elements such as chlorine, sulfur, or oxygen. Most inorganic mercury compounds are white powders or crystals, with the exception of mercuric sulfide, which is red (but turns black after exposure to light). When mercury combines with carbon, organic mercury compounds are formed. The most common organic mercury is methylmercury, which when pure is a white crystalline solid. Microorganisms (bacteria and fungi) and natural processes can change mercury from one form to another. The most common organic mercury compound generated through these processes is methylmercury.

Metallic mercury is used in thermometers, fluorescent bulbs, barometers, batteries, and some electrical switches. Silver-colored (amalgam) dental fillings typically contain about 50% metallic mercury. Some people who practice Espiritismo, Voodoo, Palo Mayombe, or Santeria, use metallic mercury (sold as azogue in botanicas) in their religious or ethnic rituals. Various fungicides, topical antiseptics, antibacterials, and red-colored dyes contain inorganic mercury compounds. Some organic mercury compounds have been used as antifungal agents in paints and on seed grains. Mercury is also a component of some munitions.

The different forms of mercury are absorbed and distributed differently in the body.

• When small amounts of metallic mercury are incidentally ingested, only about 0.01% of the mercury will enter the body through the stomach or intestines (Sue 1994; Wright et al. 1980 as cited in ATSDR 1999a). More can be absorbed if one suffers from a gastrointestinal tract disease. The small amount of metallic mercury that enters the body will accumulate in the kidneys and the brain, where it is readily turned into inorganic mercury. It can stay in the body for weeks or months, but most is eventually excreted through urine, feces, and exhaled breath.
• Typically, less than 10% of inorganic mercury is absorbed through the stomach and intestines. But it has been reported that up to 40% can be absorbed in the intestinal tract (Clarkson 1971; Morcillo and Santamaria 1995; Nielson and Anderson 1990, 1992; Piotrowski et al. 1992 as cited in ATSDR 1999a). Once in the body, a small amount of the inorganic mercury can be converted into metallic mercury, which will be excreted or stored as described above. Inorganic mercury enters the bloodstream and moves to many different tissues, but will mostly accumulate in the kidneys. Inorganic mercury does not easily enter the brain. It can remain in the body for several weeks or months and is excreted through urine, feces, and exhaled breath.
• Methylmercury is the most studied organic mercury compound. It is readily absorbed in the gastrointestinal tract (about 95% absorbed) and can easily enter the bloodstream (Aberg et al 1969; Al-Shahristani et al. 1976; Miettinen 1973 as cited in ATSDR 1999a). It moves rapidly to various tissues and the brain, where methylmercury can be turned into inorganic mercury, which can remain in the brain for long periods. Slowly, over months, methylmercury will leave the body, mostly as inorganic mercury in the feces.

Permanent damage to the nervous system, brain, or kidneys can result from exposure to mercury. The different forms of mercury, however, have different effects in the body. Ingesting organic mercury, such as methylmercury, will affect areas of the brain and can result in personality changes, tremors, changes in vision, deafness, muscle incoordination, loss of sensation, and difficulties with memory. On the other hand, inorganic mercury does not readily enter the brain and is not expected to cause neurological damage. Still, swallowing large amounts of inorganic mercury will damage the stomach and intestines and result in nausea, diarrhea, or ulcers. The kidneys are sensitive to damage from all forms of mercury, but if damage is minimal, the kidneys tend to recover once the mercury is expelled from the body. Because it is not readily absorbed in the gastrointestinal tract, ingesting metallic mercury is not likely to result in any severe harmful health effects.

Only limited animal studies and no human data are available to determine whether mercury is a carcinogen. IARC and DHHS have not classified mercury as to its human carcinogenicity. EPA has determined that mercury chloride (an inorganic mercury compound) and methylmercury (an organic mercury compound) are possible human carcinogens.

Neither a comparison value or a health guideline is available for mercury. Still, toxicological and epidemiological information are available. Accordingly, exposure to mercury was evaluated in detail for both adults and children. The average mercury concentration (0.028 ppm) together with the listed assumptions were used in the equation described in the Methods Used to Evaluate Public Health section (IV.B). The calculated exposure doses are 0.00000004 mg/kg/day for adults and 0.00000055 mg/kg/day for children. ATSDR then compared these potential exposures to actual health effects levels in the toxicological and epidemiological literature (ATSDR 1999a). Because organic mercury compounds are more readily absorbed when ingested than metallic or inorganic mercury, health effects would occur at a lower exposure dose to organic mercury than to metallic or inorganic mercury. Therefore, as a conservative approach, ATSDR assumed that all of the mercury detected on Vieques was organic mercury and based this review on exposure to organic mercury compounds.

In three studies, people had been chronically exposed to 0.0005 to 0.0013 mg/kg/day of methylmercury in their food and experienced no adverse health effects. When they were exposed to 0.0012 mg/kg/day of methylmercuric chloride in their food, they experienced less serious health effects (delaying walking and abnormal motor scores in children). These effects levels reported in the literature, including the NOAELs of 0.0005-0.0013 mg/kg/day, are several orders of magnitude higher than the exposure expected to result from adults and children incidentally ingesting soil on Vieques.

Despite the fact that the carcinogenicity of mercury is still uncertain, ATSDR compared the lifetime exposure dose for adults to the CELs reported in the literature. Four long-term studies described increases in renal adenomas and carcinomas when animals consumed food or water containing 0.69 to 4.2 mg/kg/day of mercury. These doses are several orders of magnitude higher than the doses expected to result from lifetime exposure to the maximum concentration of mercury in the soil on Vieques.

Information concerning systemic health effects in children from exposure to various forms of mercury have been well documented in the literature. Children tend to experience similar toxicological health effects as seen in adults. During critical periods of development, however, children are more susceptible to effects from exposure to metallic mercury and methylmercury. See the Child Health Initiative section of this PHA for a brief discussion concerning the greater susceptibility that children could have from mercury exposure.

Note that exposure to mercury is based on levels detected in soil at the LIA. Mercury analyses have not been conducted in the residential area of Vieques. The maximum and average soil concentrations used to calculate adult and child exposure doses are based on sampling conducted in an area to which residents and visitors are restricted. Therefore, people are not being exposed to these mercury levels on a daily basis. Also, as noted in Section III.C, the soils of the LIA have been influenced by Navy training activities and contain elevated levels of mercury. Therefore, by incorporating these conservative assumptions, the exposure doses that were calculated were based on a possible worst-case scenario.

In conclusion, ATSDR does not expect that exposure to mercury levels found in the soil would result in harmful health effects for either adults or children who could incidentally ingest soil while living on Vieques.

Are residents being exposed to harmful levels of vanadium in the soil?

No. Because the estimated exposure dose is below the conservative health guideline, adult exposure from incidentally ingesting vanadium in soil on Vieques is not expected to result in harmful health effects. Childhood exposure is also not expected to result in harmful health effects because the estimated exposure dose is below levels of health effects documented in the toxicological literature. Childhood exposure is evaluated further in this section following a brief description of vanadium together with its uses, its fate and transport in the body, and potential health effects.

Vanadium is a white to gray metal that is often found as crystals. It occurs naturally in fuel oils and coal and is usually combined with other elements such as oxygen, sodium, sulfur, or chloride. Vanadium compounds are used to make steel, rubber, plastics, and ceramics. Vanadium is also a component of some munitions.

Most of the vanadium that is ingested by humans is not absorbed (only 0.1% to 2.6% is absorbed, Conklin et al. 1982; Roshchin et al. 1980 as cited in ATSDR 1992b), rather most passes through the body unchanged and is excreted in feces. Small amounts, however, can enter the bloodstream after being swallowed. Once in the body, vanadium is quickly excreted in urine.

Very few studies have investigated any adverse health effects from exposure to vanadium. Most of the available information is the result of animal testing. Although animal testing is a useful way for scientists to learn how a chemical is absorbed, used, and released, some uncertainty remains concerning the application of these test results to humans. That said, less serious developmental and systemic health effects were reported from oral exposure to vanadium. When female rats drank water contaminated with vanadium, some minor birth defects occurred. Information is not available on the carcinogenicity of vanadium. In studies that investigated health effects other than cancer, however, no increase in tumors was observed in animals exposed to vanadium in their drinking water.

As shown in Exhibit 3, daily exposure to the maximum concentration of vanadium for 70 years is not expected to cause any harmful health effects for adults living on Vieques because the resulting exposure dose is below conservative health guidelines.

Childhood exposure to vanadium was further evaluated, using an average concentration, which better represents actual exposures, to calculate an exposure dose. Using the same equation and assumptions described previously, with the average vanadium concentration (162 ppm) in place of the maximum concentration, the calculated exposure dose for children is 0.0032 mg/kg/day. Note that the calculated exposure for children is only slightly above the health guideline (0.003 mg/kg/day). Because health guidelines have built-in uncertainty factors, exposure doses slightly above the health guideline are not expected to result in harmful health effects. Regardless, however, of this generality, ATSDR compared the potential childhood exposure to the available health effects levels in the toxicological and epidemiological literature (ATSDR 1992b).

The oral health guideline is based on a study in which no adverse health effects were observed when animals were given 0.3 mg/kg/day of vanadium in their water. Several other animal studies reported no adverse health effects from oral exposure to vanadium in doses ranging from 0.54 to 17 mg/kg/day. The only study conducted on humans reported exposures to vanadium in capsules containing a dose of 1.3 mg/kg/day did not result in any adverse health effects. The lowest dose shown to cause less serious health effects (hemorrhagic foci and vascular infiltration) in animals is 0.57 mg/kg/day. Long-term exposure to vanadium in water resulted in less serious health effects (altered lung collagen) from exposure to 2.8 mg/kg/day. Serious health effects (hemorrhagic foci effects increased) resulted from animals exposed to 2.87 mg/kg/day of vanadium in their drinking water. The reported health effects levels, including the NOAELs of 0.3 to 17 mg/kg/day, are higher than the levels expected to result from childhood exposure to concentrations of vanadium detected in soil on Vieques.

Therefore, ATSDR concludes that exposure to vanadium levels found in the residential soil would result in harmful health effects for either adults or children who might incidentally ingest soil while living on Vieques.

Exposure from Dermal Contact with Soil on Vieques

Dermal exposure to chemicals detected below comparison values should not cause harmful health effects. In essentially all exposure situations, including dermal contact, comparison values are derived using conservative exposure assumptions that are protective of public health. Therefore, only those metals detected above comparison values (arsenic, cadmium, chromium, iron, manganese, lead, and vanadium) were evaluated for exposure through dermal contact (see Table 9). Mercury does not have a comparison value; because, however, toxicologic information is available, this metal was also further evaluated.

Unlike the evaluation for incidental ingestion, dermal contact is not evaluated quantitatively through deriving exposure doses. Rather, this evaluation is a qualitative discussion of the metal's potential to be absorbed into the body through the skin. Considerable uncertainty exists for quantitatively estimating dermal exposure, especially for contact with soil because there is very little chemical-specific data available and the predictive techniques have not been well validated (EPA 1992a).

In general, metals are not readily absorbed through the skin. Exposure to metals through dermal contact results in a much lower dose than the previously discussed incidental ingestion pathway. The following paragraphs outline the absorption potential for each of the seven metals detected above comparison values, as well as mercury.

• Dermal exposure to arsenic is usually not of concern because only a small amount will pass through skin and into the body (4.5% of inorganic arsenic in soil, Wester et al. 1993 as cited in ATSDR 2000a). Direct skin contact with inorganic arsenic could cause some irritation or swelling, but skin contact is not likely to result in any serious internal effects.
• Dermal exposure to cadmium is not known to affect human health because under normal conditions, virtually no cadmium can enter the body through the skin (less than 0.2% from soil, Wester et al. 1992 as cited in ATSDR 1999b).
• Unless the skin is damaged, very little chromium will enter the body through contact with the skin. Nevertheless, some people are allergic to chromium and will develop rashes, redness, or swelling when in contact with chromium (ATSDR 2000b).
• No specific studies regarding dermal exposure to iron are available; but metals such as iron are not readily absorbed through the skin. EPA uses an absorption factor of 1% for metals when chemical-specific data are lacking (EPA 1995). This absorption factor would result in a minimal amount of iron entering the body.
• Only a small amount of lead is absorbed by the body through the skin (0.3%, Moore et al. 1980 as cited in ATSDR 1999c). What is absorbed represents a much smaller amount than that absorbed via ingestion (EPA 1986a as cited in ATSDR 1999c). Leaded gasoline does contain a lead compound that can be quickly absorbed. Leaded gasoline, however, is no longer sold; thus it is unlikely that people will contact the form of lead that can enter the body through skin.
• Very little inorganic manganese will enter the skin if one contacts contaminated soil. Still, animal research has shown that organic manganese compounds can be absorbed through dermal contact. One compound, potassium permanganate, has been reported to damage the skin. Two pesticides that contain manganese (maneb and mancozeb) can cause skin reactions in people who have allergies to these pesticides or work with large quantities of them (ATSDR 2000c). Dermal exposure to organic manganese compounds in the soil on Vieques can lead to an increase in overall dose. If it is conservatively assumed that the dose expected to result from dermal exposure is equal to the dose from incidental ingestion of manganese, one arrives at a cumulative exposure dose below EPA's NOAEL.
• Small amounts of inorganic mercury and an organic form of mercury, methylmercury, can enter the body through skin contact. But this represents a much smaller amount than that absorbed via ingestion. Other organic mercury compounds, such as dimethylmercury, are readily absorbed through the skin (ATSDR 1999a). Dermal exposure to mercury in the soil on Vieques could lead to an increase in overall dose if organic mercury compounds are present. Even if we conservatively assume that the dermal dose is equal to the ingested dose, it would still result in an exposure at least an order of magnitude lower than the reported NOAELs.
• No specific studies regarding dermal exposure to vanadium are available. However, because of its low solubility, it is not considered to be readily absorbed through the skin (ATSDR 1992b). In addition, EPA uses a conservative absorption factor of 1% when chemical-specific information is not available. This would also indicate only a very small amount of vanadium entering the body.

In conclusion, ATSDR does not expect that dermal contact with soil on Vieques will result in harmful health effects. In the rare instance when a person is allergic to a specific metal (e.g., chromium and manganese), skin irritation could develop. The overall internal dose, however, is not likely to be large enough to add substantially to the expected exposure resulting from incidental ingestion of the soil.

Exposure to Multiple Chemicals

Several studies, including those conducted by the National Toxicology Program in the United States and the TNO Nutrition and Food Research Institute in the Netherlands, among others, generally support the conclusion that if each individual chemical is at a concentration not likely to produce harmful health effects (as is the case on Vieques), exposures to multiple chemicals are also not expected to be of health concern (for reviews, see Seed et al. 1995; Feron et al. 1993).

Question 2: Were the protestors who occupied portions of the LIA from April 1999 to May 2000 exposed to harmful levels of chemicals in the soil?

No. Both adult and child protestors were not exposed to harmful levels of chemicals present in the soil on the LIA. Of the chemicals detected in the soil on the LIA, only two (arsenic and iron) were detected above comparison values. These two metals are evaluated in greater detail below. All other chemicals were at concentrations too low to be of health concern for anyone incidentally ingesting or touching the soil.

In June 2000, a Navy contractor collected and analyzed five surface soil samples from sites specifically representing areas where protestors lived from April 1999 to May 2000 (see Figure 5) (CH2MHILL 2000a). The samples were analyzed for metals and explosive compounds. In addition, from May 1999 to April 2000, personnel from Servicios Científicos y Téchnicos, Inc. collected and analyzed soil and sediment samples for metals and other inorganic compounds (Garcia et al. 2000). Some of the highest and next highest detections were in areas of the LIA occupied by protestors. Table 10 summarizes the chemicals detected in these areas.

Of the chemicals detected in the areas on the LIA occupied by protestors, only concentrations of arsenic and iron were detected at levels above comparison values (see Table 10). All other chemicals were detected at concentrations too low to be of health concern. A comparison value is not available for mercury. As with the previous evaluation for residents of Vieques, ATSDR derived conservative exposure doses for arsenic, iron, and mercury and compared the estimated doses to standard health guideline values (MRLs and RfDs). The maximum concentrations and an exposure duration of 1 year were used in the equation referenced in the Methods Used to Evaluate Public Health section (IV.B) to determine the exposure dose for those who lived at the LIA for a year.

Were the protestors exposed to harmful levels of arsenic?

No. The estimated exposure doses for both adults and children are below the conservative health guideline for arsenic; therefore, exposure is not expected to result in harmful health effects.

ATSDR calculated exposure doses for those who could have incidentally ingested arsenic while living on the LIA for a year to be 0.0000096 mg/kg/day for adults and 0.00013 mg/kg/day for children. Both doses are below the health guideline ATSDR and EPA have determined is unlikely to result in noncancer effects (0.0003 mg/kg/day). This exposure is also not expected to result in an increase in cancer; the dose expected to result from exposure to the maximum concentration (0.00000013 mg/kg/day) is orders of magnitude lower than the most conservative CEL (0.0011 mg/kg/day). In addition, as stated above, only a small amount of arsenic can pass through the skin and be absorbed.Therefore, protestors who incidentally ingested or dermally contacted arsenic in the soil at the LIA were not exposed to harmful levels--the concentrations detected were too low to be of health concern for both adults and children.

Were the protestors exposed to harmful levels of iron?

No. Adult exposure to iron is not expected to result in harmful health effects because the estimated exposure dose is below the conservative health guideline. Similarly, childhood exposure is not expected to result in harmful health effects because the estimated daily consumption is below levels known to result in childhood poisoning.

For the protestors who lived on the LIA for a year, ATSDR calculated exposure doses from incidentally ingesting iron to be 0.097 mg/kg/day for adults and 1.3 mg/kg/day for children. The adult exposure to iron was below ATSDR's oral health guideline (0.3 mg/kg/day)--indicating that iron was detected at concentrations too low to be of health concern for adults. Childhood exposure was further evaluated by calculating a daily consumption from exposure to iron in soil using a modification of the dose equation (Dose = Conc. x IR). Exposure to the maximum concentration of iron in the soil would increase a child's daily consumption of iron by 6.79 mg/day. Since the median daily intake of dietary iron is roughly 11-13 mg/day for children 1 to 8 years old and 13-20 mg/day for adolescents 9 to 18 years (NAS 2001), this relatively small daily increase in consumption is not likely to cause a child's daily dose to be above the levels known to induce poisoning (>200 mg/event). In addition, the National Academy of Sciences and FDA recommend that people ingest a certain amount of iron (10 to 30 mg/day depending on age and gender) because iron is an important mineral essential for basic life functions. Further, the body uses a homeostatic mechanism to keep iron burdens at a constant level despite variations in the diet (Eisenstein and Blemings 1998). Finally, as stated above, only a minimal amount of iron could potentially enter the body through dermal absorption. Therefore, the protestors who lived on the LIA for a year and who might have incidentally ingested or contacted the soil were not exposed to harmful levels of iron.

Were the protestors exposed to harmful levels of mercury?

No. The estimated exposure doses for both adults and children are below the conservative health guideline for mercury; therefore, exposure is not expected to result in harmful health effects.

ATSDR calculated exposure doses from incidental ingestion of mercury in soil on the LIA to be 0.000000024 mg/kg/day for adults and 0.00000034 mg/kg/day for children. Both doses are orders of magnitude below the NOAELs of 0.0005-0.0013 mg/kg/day. This exposure is also not expected to result in an increase in cancer; the dose expected to result from exposure to the maximum concentration (0.0000000003 mg/kg/day) is several orders of magnitude lower than the reported CELs (0.69-4.2 mg/kg/day). In addition, if we assume that some mercury is dermally absorbed, the combined exposure is still orders of magnitude lower than the reported health effects levels. Therefore, both adults and children who might have incidentally ingested or dermally contacted mercury in the soil while living on the LIA for a year were not exposed to harmful levels--the concentrations detected were too low to be of health concern.

In conclusion, ATSDR does not expect that the protestors who occupied portions of the LIA from April 1999 to May 2000 were exposed to harmful levels of chemicals.

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5. Averages were calculated using detected concentrations only and do not take into account nondetected values. Even though this tends to overestimate the true average values, we chose to base our health evaluations on the more conservative averages to be more protective of public health.

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V. Community Health Concerns

An integral part of the public health assessment process is addressing community concerns related to environmental health. ATSDR has been working with, and will continue to work with, the community to define specific health issues of concern. On multiple trips to the island, ATSDR has met with a variety of individuals and organizations, including local officials, physicians, nurses, pharmacists, leaders of women's groups, school educators, fishermen, and business people. ATSDR has also met with individual families. Meeting with a broad spectrum of community members is critical to determine health issues of concern and to assess the environmental health issues on Vieques.

General issues of health concern related to exposure to the soil on Vieques have been assessed in this PHA. In addition, ATSDR released a meeting summary report of an expert review panel who discussed the issue of whether an association existed between place of residence and morphological cardiovascular changes among fishermen (ATSDR and PSM 2001) and a PHA addressing Vieques groundwater and public water supply systems (ATSDR 2001b). Copies of these documents are available by contacting ATSDR (1-888-42-ATSDR) and from records repositories on Vieques. Public health issues related to exposure to chemicals in the air and in fish and shellfish were also evaluated by ATSDR. PHAs addressing these exposure pathways were released for public comment in October 2002.

This section of the PHA addresses additional community concerns relating to heavy metal uptake in plants and animals around Vieques and the state of the science of hair analysis.

1. Concern: Heavy Metal Contamination in Plants

Community members are concerned that heavy metals associated with the Navy's training activities are accumulating in agricultural plants and thereby, reaching the residents of Vieques through the food chain pathway.

In February and March 2000, researchers from Casa Pueblo and Recinto Universitario de Mayaguez (RUM), University of Puerto Rico, sampled the prevailing vegetation in the LIA (specifically Carrucho Beach, Monte David, and Gato and Icacos Lagoons) for heavy metals (Massol Deyá and Díaz 2000b). Reference populations of the same species were also collected in Bosque Seco de Guánica and RUM Alzamora Ranch. In addition, researchers from Casa Pueblo and University of Puerto Rico randomly collected agricultural and common vegetation from three sites within the residential section of Vieques: an agricultural area in Monte Carmelo, a section of Monte Carmelo that borders Camp Garcia, and an agricultural farm in Barrio Monte Santo, Gobeo sector (Massol Deyá and Díaz 2001). The authors reported that several species contained "excessive or toxic" levels of heavy metals and that these contaminants were moving through the food chain.

ATSDR determined through independent review with an agronomist with the US Department of Agriculture (USDA) that the studies provide insufficient evidence that heavy metals are accumulating in plants at a level that would cause harm to people.

First, many of the samples that were analyzed are not species that are eaten. In addition, when species that are eaten were sampled, the edible parts (e.g., pepper fruits, pumpkins, and seeds of pigeon peas) were not sampled, rather the stems and leaves were analyzed. Human exposures from locally grown foods can only be estimated from the edible portions of the food source (USDA 2002). In general, the edible portions of plants (e.g., fruits and berries) are less likely to accumulate metals from soil because of normal plant processes (e.g., physiological barriers that prevent contaminants from getting to the tops of plants) (ATSDR 2001a).

Second, without quality assurance samples, it is likely that errors occurred in the analysis process (USDA 2002). The reports lack the use of standard reference materials (e.g., orchard leaves available from the National Institute of Standards and Technology) to demonstrate that the results are accurate and background corrections for lead, cobalt, nickel, and cadmium to eliminate the effect of light scattering by non-element materials in the samples.

Third, research has shown that small soil particles can become embedded in the surface waxy layer of leaves and are difficult to remove (USDA 2002). Even with a thorough washing, soil particles will adhere to the plant materials. This adhered soil can actually carry more contaminants than what is taken up by the plant from the soil (ATSDR 2001a). When elements are present in plant samples as soil particles, they are often of low bioavailability and while the external contamination may also be ingested, the chemicals bound to soil are not usually in a form that can be absorbed by the body (USDA 2002). While there are methods to determine how much of a chemical concentration is adhered as soil and how much is in the plant tissue, these were not utilized by the researchers.

Because of these factors, ATSDR could not quantify exposures from these reports nor draw any health conclusions about whether consuming plants grown in Vieques would result in harmful health effects.

2. Concern: Heavy Metal Contamination in Livestock

Community members expressed concern over the possibility that livestock are accumulating heavy metals by grazing on contaminated plants. In support, a study by Casa Pueblo de Adjuntas reports that heavy metals were found in the hair of goats. To address this concern, the Puerto Rico Department of Agriculture in cooperation with the Farmers Association of Puerto Rico (AAPR) sampled grass, fruit-bearing trees, and bovine livestock from Monte Carmelo, Martineau, Monte Santo, Esperanza, Lujan, Gubeo, and western Vieques for cadmium, cobalt, copper, lead, manganese, and nickel. They concluded that the agricultural products from Vieques are suitable for consumption and do not contain toxic levels of these contaminants (El Nuevo Día 2001).

To date, ATSDR has not been able to obtain the original data or report that support these findings. Once the information becomes available, ATSDR will also evaluate whether eating agricultural products grown on Vieques could lead to any potential health effects.

3. Concern: Hair Analysis

Community members expressed concern that they were being exposed to unhealthy levels of metals, as shown by hair analysis. However, the medical literature recommends that physicians not rely solely on hair analysis to diagnose or treat heavy metal toxicity (Frisch and Schwartz 2002).

In June 2001, ATSDR convened an expert panel to discuss the state of the science relating to analyzing hair for environmental exposure (ATSDR 2001c). The panel consisted of individuals who represented state and federal government agencies, academia, and private practice and whose expertise, interests, and experience covered a wide range of related technical disciplines.

The panelists agreed that "for most substances, insufficient data currently exist that would allow the prediction of a health effect from the concentration of the substance in hair. The presence of a substance in hair may indicate exposure (both internal and external), but does not necessarily indicate the source of exposure." They noted that a relationship between contaminant concentrations in hair and any kind of measurable outcome have only been established for methylmercury and to a limited extent for arsenic, provided external contamination can be ruled out.

The expert panel recognized that laboratory methods exist to measure the levels of some environmental contaminants in hair, but commented that procedures need to be standardized to help ensure more accurate and reliable results. They also identified several factors that limit the interpretation of even the most accurate, reliable, and reproducible laboratory results: (1) the lack of reference (or background) ranges in which to frame the interpretation of results, (2) difficulties in distinguishing internal from external contamination in hair, (3) a lack of understanding of how and to what extent environmental contaminants are incorporated into the hair, (4) the lack of correlation between levels in hair and blood and other target tissues, as well as the lack of epidemiologic data linking substance-specific hair levels with adverse health effects, and (5) little information is available pertinent to the study of environmentally relevant organic compounds in hair.

Copies of the meeting summary report are available by contacting ATSDR (1-888-42-ATSDR) and on ATSDR's Web site (http://www.atsdr.cdc.gov/HAC/hair_analysis/).

Community members can direct additional health concerns to:

Program Evaluation and Records Information Services Branch
ATSDR, Division of Health Assessment and Consultation
Attn: Isla de Vieques, Puerto Rico
1600 Clifton Road, NE (E-56)
Atlanta, Georgia 30333

Community members can also telephone the ATSDR regional representatives in New York, New York at (212) 637-4307 or call the toll-free telephone number, 1-888-42-ATSDR.

VI. ATSDR Child Health Initiative

ATSDR recognizes that in communities faced with contamination of their water, soil, air, or food, infants and children can be more sensitive to environmental exposure than adults. This sensitivity is a result of the several factors, including (1) because they play outdoors, children are more likely to be exposed to certain media (e.g., soil); (2) children are shorter than adults, which means they can breathe dust, soil, and vapors close to the ground; and (3) children are smaller than adults, therefore childhood exposure results in higher doses of chemical exposure per body weight. To account for this greater susceptibility, ATSDR assumes a higher ingestion rate for children than adults. Because children can sustain permanent damage if these factors lead to toxic exposure during critical growth stages, ATSDR as part of its Child Health Initiative is committed to evaluating their special interests at sites such as Vieques.

Based on a thorough review of the available data, ATSDR concludes that children are not being exposed to harmful levels of chemicals in the soil on Vieques. As described in the Public Health Evaluation section (IV.C), most of the chemicals detected on Vieques are below conservative comparison values and; therefore, are not at levels of health concern. Childhood exposures were further evaluated for the seven metals (arsenic, cadmium, chromium, iron, lead, manganese, and vanadium) detected above comparison values, plus mercury. According to the toxicological and epidemiological literature, children can be more susceptible to arsenic, cadmium, iron, lead, and mercury exposures than adults. But whether children are more susceptible to chromium, manganese, and vanadium than are adults has not been established.

• Children can experience health effects from lower arsenic doses (due to less inorganic arsenic being converted into organic arsenic) than those reported in the literature for adults. Nevertheless, the health effects levels are an order of magnitude higher than the exposure dose expected to result from children who incidentally ingest soil on Vieques. Furthermore, a 50% reduction in health effects levels to compensate for the greater susceptibility in children would still result in higher effects levels than the expected exposure for children contacting arsenic in the soil on Vieques.
• Although children can experience health effects from a lower cadmium dose (due to the possibility that children can absorb more cadmium) than that reported for adults in the literature, the effects levels are still two orders of magnitude higher than the exposure dose expected to result from children incidentally ingesting soil on Vieques. Furthermore, a 50% reduction in effects levels to account for the greater susceptibility in children, would still result in health effects levels much higher than the exposure expected for children contacting cadmium in the soil on Vieques.
• 
  Children are more susceptible to accidentally poisoning themselves with iron-containing supplements than are adults. ATSDR specifically addressed childhood exposures in comparison to health effect levels of iron in the Public Health Evaluation section (IV.C) of this PHA, concluding that the dose expected to result from children incidentally ingesting soil on Vieques is well below documented health effects levels.
• Children are more susceptible to health effects from exposure to lead than are adults. The health effects levels reported in the literature, however, are two orders of magnitude higher than the exposure dose expected for children incidentally ingesting soil on Vieques. In addition, the blood lead level expected to result from exposure to lead in the soil is below CDC's level of health concern for children.
• During critical periods of development, children are more susceptible than adults to metallic mercury and methylmercury exposure. The health effects levels reported in the literature, however, are several orders of magnitude higher than the exposure dose expected to result from children incidentally ingesting soil on Vieques. Furthermore, a 50% reduction in effects levels to account for the greater susceptibility in children would still result in health effects levels several orders of magnitude higher than the exposure expected for children contacting mercury in the soil.

VII. Conclusions

Soil Characteristics

• After evaluating the soil geologically to identify any chemical trends between geologic units (e.g., rock formations) on Vieques, ATSDR concluded that significant differences existed in the metal composition of soils developed on the different geologic units. The soil developed on a complex assemblage of marine sandstones, siltstones, conglomenates, lava, and tuff. The tuff (the Kv formation) is the most dissimilar geologic unit, with significantly different concentrations of 14 metals. The soil developed on the alluvial sands, silts, and gravels (the Qa formation) is similar to the soil developed on other geologic units, with no significantly different metals. This indicates that the soils of Vieques are strongly influenced by the constituent chemicals of their parent materials.
• ATSDR compared the quality of the soil on Vieques with the sediment of the Puerto Rican mainland. After acknowledging the inherit differences between the two media, ATSDR noted that the soil of Vieques has higher concentrations of antimony, arsenic, cadmium, calcium, manganese, molybdenum, silver, strontium, and yttrium than the stream sediment samples collected throughout the mainland of Puerto Rico. However, when ATSDR compared the background sediment samples collected in the former NASD to the sediment data collected on the mainland of Puerto Rico, the levels of metals from the former NASD are lower or in the low end of the range.
• ATSDR also compared the quality of the soil on Vieques with background soil concentrations within the United States. A statistical comparison was not conducted, but the average concentrations for several of the metals were noted to be higher on Vieques than the averages on the United States. The maximum concentrations of copper, iron, lead, tin, and zinc detected on Vieques were outside the ranges found throughout the United States. However, the levels detected on Vieques are not inconsistent with what one would expect from soils also underlain by igneous or volcanic rocks.
• ATSDR evaluated whether Navy training activities have elevated the levels of metals in the soils of the LIA. To do this, ATSDR (1) compared concentrations of chemicals detected at the LIA to the remainder of Vieques and (2) compared concentrations of chemicals detected at the LIA to background soil samples in the former NASD. The results of the evaluations indicate that the soils of the LIA have been influenced by Navy training activities and contain elevated levels of heavy metals. However, the concentrations of the chemicals in the soil are not at levels that pose an adverse health threat (see the Public Health Evaluation section).
• ATSDR evaluated general spatial trends for specific metals to identify whether a spatial pattern indicated chemicals are moving from the LIA to the residential area. The available data do not indicate a pattern of high to low concentrations from east to west. Thus, this data set does not provide evidence for airborne transport of metals from the LIA to the residential area.

Public Health Evaluation

ATSDR concludes that the levels of the metals found in the soil on Vieques would not result in harmful health effects for either adults or children who might incidentally ingest or come in contact with the soil while living on Vieques or while living on the LIA for a year. ATSDR has categorized this site as having no apparent public health hazard from exposure to soil on Vieques (definitions of public health categories are included in the glossary in Appendix B).

• ATSDR compared the chemicals detected in the soil on Vieques to conservative comparison values. Only seven metals (arsenic, cadmium, chromium, iron, manganese, lead, and vanadium) were detected above comparison values. All other chemicals were detected at concentrations too low to be of health concern for anyone (adults and children) incidentally ingesting or contacting the soil. After evaluating in greater detail the seven metals detected above comparison values, as well as mercury, ATSDR reached the following conclusions:
• Exposure to arsenic in soil on Vieques is not expected to result in harmful health effects because (1) the estimated exposure doses from incidental ingestion for adults and children are below the conservative health guideline for adults and below levels of health effects documented in the toxicological literature for children and (2) the small amount of arsenic that can be absorbed through the skin is not likely to result in any serious internal effects.
• Exposure to cadmium in soil on Vieques is not expected to result in harmful health effects because (1) the estimated exposure doses from incidental ingestion for adults and children are below the conservative health guideline for adults and below levels of health effects documented in the toxicological literature for children and (2) virtually no cadmium can enter the body through the skin.
• Exposure to chromium in soil on Vieques is not expected to result in harmful health effects because (1) the estimated exposure doses from incidental ingestion for adults and children are below the conservative health guideline for adults and below levels of health effects documented in the toxicological literature for children and (2) very little chromium will enter the body through contact with the skin.
• Exposure to iron in soil on Vieques is not expected to result in harmful health effects because (1) the estimated exposure dose from incidental ingestion for adults is below the conservative health guideline, (2) a child's estimated daily consumption is below levels known to result in childhood poisoning, and (3) only a minimal amount of iron is assumed to enter the body through the skin.
• Exposure to lead in the soil on Vieques is not expected to result in harmful health effects because (1) the estimated exposure doses from incidental ingestion for both adults and children are below levels of health effects documented in the toxicological literature, (2) the resulting child blood lead level is below CDC's health guideline, and (3) only small quantities of lead can be absorbed by the body through the skin, and what is absorbed represents a much smaller amount than that absorbed via ingestion.
• Exposure to manganese in soil on Vieques is not expected to result in harmful health effects because (1) the estimated exposure doses from incidental ingestion for adults and children are below the conservative health guideline for adults and below levels of health effects documented in the toxicological literature for children and (2) the increased exposure expected to result from dermal contact is below the NOAELs documented in the literature.
• Exposure to mercury in soil on Vieques is not expected to result in harmful health effects because (1) the estimated exposure doses from incidental ingestion for both adults and children are below levels of health concern documented in the toxicological literature and (2) the increased exposure expected to result from dermal contact is at least an order of magnitude lower than the reported NOAELs documented in the literature.
• Exposure to vanadium in soil on Vieques is not expected to result in harmful health effects because (1) the estimated exposure doses from incidental ingestion for adults and children are below the conservative health guideline for adults and below levels of health effects documented in the toxicological literature for children and (2) due to its low solubility, vanadium is not considered to be readily absorbable through the skin.
• ATSDR also conducted a public health evaluation specific to the protestors, who from April 1999 to May 2000 lived on the LIA. ATSDR compared the chemicals detected in the soil on Vieques to conservative comparison values. Only two metals (arsenic and iron) were detected above comparison values. All other chemicals were detected at concentrations too low to be of health concern for anyone (adults and children) incidentally ingesting or contacting the soil. After evaluating in greater detail the two metals detected above comparison values, as well as mercury, ATSDR reached the following conclusions:
• Exposure to arsenic in soil on Vieques is not expected to result in harmful health effects because (1) the estimated exposure doses from incidental ingestion for adults and children are below the conservative health guideline for adults and children and (2) the small amount of arsenic that can be absorbed through the skin is not likely to result in any serious internal effects.
• Exposure to iron in soil on Vieques is not expected to result in harmful health effects because (1) the estimated exposure dose from incidental ingestion for adults is below the conservative health guideline, (2) a child's estimated daily consumption is below levels known to result in childhood poisoning, and (3) only a minimal amount of iron is assumed to enter the body through the skin.
• Exposure to mercury in soil on Vieques is not expected to result in harmful health effects because (1) the estimated exposure doses from incidental ingestion for both adults and children are below levels of health concern documented in the toxicological literature and (2) the increased exposure expected to result from dermal contact is at least an order of magnitude lower than the reported NOAELs documented in the literature.

VIII. Public Health Action Plan

The Public Health Action Plan for Vieques contains a description of actions taken and those to be taken by ATSDR, the Navy, EPA, USGS, the Puerto Rico Environmental Quality Board (PREQB), and the Puerto Rico Department of Health (PRDOH). The purpose of the Public Health Action Plan is to ensure that this PHA not only identifies public health hazards, but also provides a plan of action to mitigate and prevent harmful human health effects that may be resulting from exposure to hazardous substances in the environment. The public health actions that are completed or ongoing are as follows:

Actions Completed:

• Various organizations sampled soil, including USGS and PRDNR, the Naval Surface Weapons Center, contractors for the Navy, and Servicios Científicos y Téchnicos, Inc.
• In August 1999, ATSDR conducted an initial site visit to Vieques to meet with the petitioner, tour the island and bombing range, and gather environmental data. As a result of this site visit, ATSDR accepted the resident's petition and initiated the public health assessment process.
• In September 2000, ATSDR met with various agencies, including PRDOH, PREQB, EPA, USGS, and the Navy, to gather data and to discuss the scope and nature of ATSDR investigations. ATSDR also met with the petitioner to tour various sites on Vieques and to update the petitioner on our efforts.
• In June and October 2000, ATSDR discussed with local health care providers their public health concerns and provided training regarding how to medically assess environmental exposures. During these visits ATSDR met with numerous residents of the island to discuss health concerns.
• In February 2001, ATSDR released the public comment version of the Public Health Assessment for the Drinking Water Supplies and Groundwater Pathway Evaluation.
• In March 2001, ATSDR held a public availability session to meet individually with community members regarding the findings of the evaluation of drinking water and groundwater on Vieques.
• In April 2001, ATSDR toured Vieques both by land and by air with the principal purpose of identifying suitable areas to sample fish and shellfish off the coast of Vieques.
• In June 2001, the Navy, ATSDR, and contractors for both collected air samples on Vieques to characterize levels of air contamination during air-to-ground bombing exercises. ATSDR's air exposure pathway PHA will document the sampling results.
• In July 2001, ATSDR, the Ponce School of Medicine, and CDC sponsored an expert review panel to address whether an association existed between place of residence (Vieques or Ponce Playa) and morphological cardiovascular changes among fishermen.
• In July 2001, EPA's Environmental Response Team--in cooperation with ATSDR--sampled fish and shellfish in the coastal waters off Vieques. A PHA will document the sampling results. ATSDR also met with the petitioner to provide an update on ATSDR efforts.
• In September 2001, ATSDR conducted additional community involvement activities to inform participants of the scope of ATSDR investigations and seek additional community input. Continuing education and public health training was held for the nurses of Vieques and environmental health instruction was given to area parents and high school students.
• In October 2001, ATSDR released the Public Health Assessment for the Drinking Water Supplies and Groundwater Pathway Evaluation.
• In October 2001, ATSDR released a report summarizing the expert panel review addressing whether an association existed between place of residence (Vieques or Ponce Playa) and morphological cardiovascular changes among fishermen.
• In October 2002, ATSDR released the public comment version of the Public Health Assessment for the Fish and Shellfish Evaluation.
• In October 2002, ATSDR released the public comment version of the Public Health Assessment for the Air Pathway Evaluation.

Actions Ongoing:

• ATSDR is continuing to meet with various community members and organizations to receive concerns and exchange information. This effort will continue throughout the public health assessment process.
• ATSDR will continue to meet with local health care providers to discuss health concerns for the community and to provide educational materials for addressing the community's health needs.
• PRDOH is working on Vieques and in Puerto Rico generally to gather information regarding the incidence of cancer in Puerto Rico and on Vieques. That information will be added to the current cancer registry information.
• ATSDR will review cancer registry information and data gathered by PRDOH. The information will be evaluated as it relates to potential pathways of environmental exposure.

Preparers of Report

Jeffrey Kellam, M.S.
Geologist
Federal Facilities Assessment Branch
Division of Health Assessment and Consultation

W. Mark Weber, Ph.D.
Geologist
Federal Facilities Assessment Branch
Division of Health Assessment and Consultation

Gary Campbell, Ph.D.
Environmental Health Scientist, Section Chief
Federal Facilities Assessment Branch
Division of Health Assessment and Consultation

Michelle Arbogast, M.S.
Environmental Scientist
Eastern Research Group

Dana Abouelnasr, Ph.D.
Senior Scientist
Office of Federal Programs

Paul Calame
Geographic Information Specialist
Electronic Data Systems

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Appendices

Appendix A:

Comparison Values

CREG:	Cancer Risk Evaluation Guide, a highly conservative value that would be expected to cause no more than one excess cancer in a million persons exposed over time.
EMEG:	Environmental Media Evaluation Guide, a media-specific comparison value that is used to select contaminants of concern. Levels below the EMEG are not expected to cause adverse noncarcinogenic health effects.
RBC:	Risk-based Concentration, a contaminant concentration that is not expected to cause adverse health effects over long-term exposure.
RMEG:	Reference Dose Media Evaluation Guide, a lifetime exposure level at which adverse, noncarcinogenic health effects would not be expected to occur.
SSL:	Soil Screening Level, an estimate of a contaminant concentration not expected to result in noncarcinogenic health effects during a specified duration of exposure, or to be associated with no more than an estimated one excess cancer in a million (10-6) persons exposed during a 70-year life span.

Appendix B: ATSDR Glossary of Environmental Health Terms

Absorption:

How a chemical enters a person's blood after the chemical has been swallowed, has come into contact with the skin, or has been breathed in.

Acute Exposure:

Contact with a chemical that happens once or only for a limited period of time. ATSDR defines acute exposures as those that might last up to 14 days.

Adverse Health Effect:

A change in body function or the structures of cells that can lead to disease or health problems.

ATSDR:

The Agency for Toxic Substances and Disease Registry. ATSDR is a federal health agency in Atlanta, Georgia that deals with hazardous substance and waste site issues. ATSDR gives people information about harmful chemicals in their environment and tells people how to protect themselves from coming into contact with chemicals.

Background Level:

An average or expected amount of a chemical in a specific environment. Or, amounts of chemicals that occur naturally in a specific environment.

Biota:

Used in public health, things that humans would eat - including animals, fish and plants.

Cancer:

A group of diseases which occur when cells in the body become abnormal and grow, or multiply, out of control

Carcinogen:

Any substance shown to cause tumors or cancer in experimental studies.

Chronic Exposure:

A contact with a substance or chemical that happens over a long period of time. ATSDR considers exposures of more than one year to be chronic.

Completed Exposure Pathway:

See Exposure Pathway.

Comparison Value:

Concentrations or the amount of substances in air, water, food, and soil that are unlikely, upon exposure, to cause adverse health effects. Comparison values are used by health assessors to select which substances and environmental media (air, water, food and soil) need additional evaluation while health concerns or effects are investigated.

Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA):

CERCLA was put into place in 1980. It is also known as Superfund. This act concerns releases of hazardous substances into the environment, and the cleanup of these substances and hazardous waste sites. ATSDR was created by this act and is responsible for looking into the health issues related to hazardous waste sites.

Concern:

A belief or worry that chemicals in the environment might cause harm to people.

Concentration:

How much or the amount of a substance present in a certain amount of soil, water, air, or food.

Contaminant:

See Environmental Contaminant.

Dermal Contact:

A chemical getting onto your skin. (see Route of Exposure).

Dose:

The amount of a substance to which a person may be exposed, usually on a daily basis. Dose is often explained as "amount of substance(s) per body weight per day".

Dose / Response:

The relationship between the amount of exposure (dose) and the change in body function or health that result.

Duration:

The amount of time (days, months, years) that a person is exposed to a chemical.

Environmental Contaminant:

A substance (chemical) that gets into a system (person, animal, or the environment) in amounts higher than that found in Background Level, or what would be expected.

Environmental Media:

Usually refers to the air, water, and soil in which chemical of interest are found. Sometimes refers to the plants and animals that are eaten by humans. Environmental Media is the second part of an Exposure Pathway.

U.S. Environmental Protection Agency (EPA):

The federal agency that develops and enforces environmental laws to protect the environment and the public's health.

Epidemiology:

The study of the different factors that determine how often, in how many people, and in which people will disease occur.

Exposure:

Coming into contact with a chemical substance.(For the three ways people can come in contact with substances, see Route of Exposure.)

Exposure Assessment:

The process of finding the ways people come in contact with chemicals, how often and how long they come in contact with chemicals, and the amounts of chemicals with which they come in contact.

Exposure Pathway:

A description of the way that a chemical moves from its source (where it began) to where and how people can come into contact with (or get exposed to) the chemical.

ATSDR defines an exposure pathway as having 5 parts:

1. Source of Contamination,
2. 
   
3. Environmental Media and Transport Mechanism,
4. 
   
5. Point of Exposure,
6. 
   
7. Route of Exposure; and,
8. 
   
9. Receptor Population.
   
   

When all 5 parts of an exposure pathway are present, it is called a Completed Exposure Pathway. Each of these 5 terms is defined in this Glossary.

Frequency:

How often a person is exposed to a chemical over time; for example, every day, once a week, twice a month.

Hazardous Waste:

Substances that have been released or thrown away into the environment and, under certain conditions, could be harmful to people who come into contact with them.

Health Effect:

ATSDR deals only with Adverse Health Effects (see definition in this Glossary).

Indeterminate Public Health Hazard:

The category is used in Public Health Assessment documents for sites where important information is lacking (missing or has not yet been gathered) about site-related chemical exposures.

Ingestion:

Swallowing something, as in eating or drinking. It is a way a chemical can enter your body (See Route of Exposure).

Inhalation:

Breathing. It is a way a chemical can enter your body (See Route of Exposure).

MRL:

Minimal Risk Level. An estimate of daily human exposure - by a specified route and length of time -- to a dose of chemical that is likely to be without a measurable risk of adverse, noncancerous effects. An MRL should not be used as a predictor of adverse health effects.

NPL:

The National Priorities List. (Which is part of Superfund.) A list kept by the U.S. Environmental Protection Agency (EPA) of the most serious, uncontrolled or abandoned hazardous waste sites in the country. An NPL site needs to be cleaned up or is being looked at to see if people can be exposed to chemicals from the site.

NOAEL:

No Observed Adverse Effect Level. The highest dose of a chemical in a study, or group of studies, that did not cause harmful health effects in people or animals.

No Apparent Public Health Hazard:

The category is used in ATSDR's Public Health Assessment documents for sites where exposure to site-related chemicals may have occurred in the past or is still occurring but the exposures are not at levels expected to cause adverse health effects.

No Public Health Hazard:

The category is used in ATSDR's Public Health Assessment documents for sites where there is evidence of an absence of exposure to site-related chemicals.

PHA:

Public Health Assessment. A report or document that looks at chemicals at a hazardous waste site and tells if people could be harmed from coming into contact with those chemicals. The PHA also tells if possible further public health actions are needed.

Point of Exposure:

The place where someone can come into contact with a contaminated environmental medium (air, water, food or soil). For examples:
the area of a playground that has contaminated dirt, a contaminated spring used for drinking water, the location where fruits or vegetables are grown in contaminated soil, or the backyard area where someone might breathe contaminated air.

Population:

A group of people living in a certain area; or the number of people in a certain area.

Public Health Assessment(s):

See PHA.

Public Health Hazard:

The category is used in PHAs for sites that have certain physical features or evidence of chronic, site-related chemical exposure that could result in adverse health effects.

Public Health Hazard Criteria:

PHA categories given to a site which tell whether people could be harmed by conditions present at the site. Each are defined in the Glossary. The categories are:

1. Urgent Public Health Hazard
2. 
   
3. Public Health Hazard
4. 
   
5. Indeterminate Public Health Hazard
6. 
   
7. No Apparent Public Health Hazard
8. 
   
9. No Public Health Hazard

Receptor Population:

People who live or work in the path of one or more chemicals, and who could come into contact with them (See Exposure Pathway).

Recommended Dietary Allowance:

A set of estimated nutrient allowances established by the National Academy of Sciences. It is updated periodically to reflect current scientific knowledge.

Reference Daily Intake:

A set of dietary references base don the Recommended Dietary Allowances for essential vitamins and minerals and, in selected groups, protein. This term replaces the use of "Daily Reference Value."

Reference Dose (RfD):

An estimate, with safety factors (see safety factor) built in, of the daily, life-time exposure of human populations to a possible hazard that is not likely to cause harm to the person.

Route of Exposure:

The way a chemical can get into a person's body. There are three exposure routes:

- breathing (also called inhalation),
- eating or drinking (also called ingestion), and
- or getting something on the skin (also called dermal contact).

Safety Factor:

Also called Uncertainty Factor. When scientists don't have enough information to decide if an exposure will cause harm to people, they use "safety factors" and formulas in place of the information that is not known. These factors and formulas can help determine the amount of a chemical that is not likely to cause harm to people.

Source (of Contamination):

The place where a chemical comes from, such as a landfill, pond, creek, incinerator, tank, or drum. Contaminant source is the first part of an Exposure Pathway.

Statistics:

A branch of the math process of collecting, looking at, and summarizing data or information.

Toxic:

Harmful. Any substance or chemical can be toxic at a certain dose (amount). The dose is what determines the potential harm of a chemical and whether it would cause someone to get sick.

Toxicology:

The study of the harmful effects of chemicals on humans or animals.

Tumor:

Abnormal growth of tissue or cells that have formed a lump or mass.

Uncertainty Factor:

See Safety Factor.

Urgent Public Health Hazard:

This category is used in ATSDR's Public Health Assessment documents for sites that have certain physical features or evidence of short-term (less than 1 year), site-related chemical exposure that could result in adverse health effects and require quick intervention to stop people from being exposed.

Appendix C:

Sampled Chemicals: Metals

Metals	CH2MHILL 2001	CH2MHILL2000a	Garcia et al. 2000	CH2MHILL and Baker 1999	PMC 1998	Hoffsommer and Glover 1978	Lai 1978	Learned et al. 1973
Aluminum	X	X	X		X
Antimony	X	X			X			X
Arsenic	X	X	X		X			X
Barium	X	X	X		X			X
Beryllium	X	X			X			X
Bismuth								X
Boron								X
Cadmium	X	X	X		X			X
Chromium	X	X	X		X			X
Cobalt	X	X	X		X			X
Copper	X	X	X		X			X
Gold								X
Iron	X	X	X		X			X
Lanthanum								X
Lead	X	X	X		X			X
Manganese	X	X	X		X			X
Mercury	X	X	X
Molybdenum								X
Nickel	X	X	X		X			X
Niobium								X
Scandium								X
Selenium	X	X	X		X
Silver	X	X	X		X			X
Strontium								X
Thallium	X	X			X
Thorium								X
Tin		X	X					X
Titanium								X
Tungsten								X
Vanadium	X	X	X		X			X
Yttrium								X
Zinc	X	X	X		X			X
Zirconium								X

Appendix C:

Sampled Chemicals: Inorganics

Inorganics	CH2MHILL 2001	CH2MHILL2000a	Garcia et al. 2000	CH2MHILL and Baker 1999	PMC 1998	Hoffsommer and Glover 1978	Lai 1978	Learned et al. 1973
Ammonia			X				X
Ammonium perchlorate		X
Calcium	X				X			X
Cyanide							X
Magnesium	X				X			X
Nitrate and nitrite			X				X
Perchlorate							X
Phosphorus			X
Potassium	X				X
Sodium	X				X
White phosphorous							X

Appendix C:

Sampled Chemicals: Explosives

Explosives	CH2MHILL 2001	CH2MHILL2000a	Garcia et al. 2000	CH2MHILL and Baker 1999	PMC 1998	Hoffsommer and Glover 1978	Lai 1978	Learned et al. 1973
Cyclotetramethylene tetranitramine (HMX)		X		X
Cyclotrimethylene trinitramine (RDX)		X		X		X
1,3-Dinitrobenzene		X		X
2,4-Dinitrotoluene		X		X
2,6-Dinitrotoluene		X		X
2-amino-4,6-Dinitrotoluene		X		X
4-amino-2,6-Dinitrotoluene		X		X
Methyl-2,4,6-trinitrophenylnitramine (tetryl)		X		X		X
2-Nitrotoluene		X		X
3-Nitrotoluene		X		X
4-Nitrotoluene		X		X
Nitrobenzene		X		X
Nitroglycerin		X		X
Pentaerythritol tetranitrate		X		X
1,3,5-Trinitrobenzene		X		X
2,4,6-Trinitrotoluene (TNT)		X		X		X

PMC 1998 also sampled for volatile organic compounds, semivolatile organic compounds, pesticides, and polychlorinated biphenyls in the NASD near the Vieques Municipal Airport.

Appendix D: Responses to Public Comments

The Agency for Toxic Substances and Disease Registry (ATSDR) received the following comments during the public comment period (October 23 to December 31, 2001) for the Soil Pathway Evaluation for the Isla de Vieques Bombing Range Public Health Assessment (PHA) (October 2001). For comments that questioned the validity of statements made in the PHA, ATSDR verified or corrected the statements. The list of comments does not include editorial comments, such as word spelling or sentence syntax.

General

1. Comment: It is important that the available data relating to public health in Vieques be analyzed rigorously.

2. Response: ATSDR's exposure evaluation process carefully and thoroughly evaluates whether people are being exposed to hazardous substances and, if so, whether that exposure is harmful and should be stopped or reduced. As the first step in the process, ATSDR scientists review site environmental data to determine the types of contamination present, their quantity and location, and how people could come into contact with them. If the environmental data shows that people have or could come into contact with hazardous substances at the site, ATSDR scientists rigorously analyze the weight of evidence of existing scientific information, including the results of medical, toxicologic, and epidemiologic studies to determine if exposures are likely to result in harmful health effects.

3. Comment: Reading the PHA required a significant investment of time (56 hours). Is the PHA a document intended for broad public consumption or the product of an effort to compile and analyze data in a "scientific" manner?

4. Response: ATSDR relies on technical and scientific information to arrive at its health conclusions. This information is incorporated in the PHA, which is written for the general public rather than the scientific or regulatory communities. However, a PHA of this length is necessary in order to provide an evaluation of all available information.

5. Comment: ATSDR's concern with possible exposure pathways involving soil on the residential portions of Vieques is legitimate. However, exposure pathways involving trespassing onto the property of the federal government should be considered in a different light because there is no valid reason for people to trespass.

6. Response: While it is illegal to trespass onto the Navy's property, a health concern existed for those people who occupied portions of the Live Impact Area (LIA) from April 1999 to May 2000. ATSDR would have been remiss not to evaluate this exposure situation despite the illegal nature of the occupation.

7. Comment: It is absurd that ATSDR failed to find a problem with the soil on Vieques, given that many Vieques residents face serious health problems. The conclusions of the PHA are rejected and it is apparent that ATSDR is operating under the undue influence of the US Navy. ATSDR should cease its work on PHAs at Vieques.

8. Response: ATSDR is mandated by law [Comprehensive Environmental Response, Compensation, and Liability Act, (CERCLA)] to assess public health implications at sites on the National Priorities List (NPL). In addition, ATSDR can conduct public health assessments at the request of concerned individuals (i.e., through a petition). This PHA and related ATSDR public health actions currently underway in Vieques result from a petition submitted by a Vieques resident. It is under this mandate that ATSDR is conducting its investigation on Vieques.

9. Comment: Thank you for the time and effort spent developing PHAs at Vieques. Nevertheless, it is dubious that the PHA will dispel the controversy surrounding Naval activities at Vieques, since the root of the controversy relates to "economic development and not contaminant levels."

10. Response: Thank you for the comment.

11. Comment: The PHA's discussions of soil types and geology were very helpful in explaining the processes of natural soil formation and distribution in Vieques.

12. Response: Thank you for the comment.

ATSDR's Activities at Vieques

7. Comment: The PHA is in error where it claims that ATSDR held a "public availability session" in Vieques in March 2001, because the people of Vieques protested this meeting and thus, it cannot be said to have taken place.

8. Response: ATSDR's public availability sessions are typically good forums for community members to define specific health issues of concern that they would like ATSDR to address. They also provide a good opportunity for people to ask specific questions about ATSDR's health evaluation process and conclusions. Therefore, ATSDR commiserates with the commentator that the unfortunate protest by a few activists prevented the people of Vieques from having free access and exchange with ATSDR about their health concerns and questions during the public availability session held in March 2001.

9. Comment: ATSDR's conclusions were based on a biased sampling of pre-existing data rather than the collection of new data.

10. Response: The quality and extent of the existing information about the soil on Vieques is sufficient to support the public health decisions discussed in the document. ATSDR reviews all existing environmental data and exposure information that is available when drawing its conclusions and making its recommendations about public health.

11. Comment: If the relevant data are in some way less than adequate, ATSDR should simply state its data needs and speak no further.

12. Response: When evaluating public health hazards, ATSDR prefers to use as much information as possible when assessing environmental exposures. However, sometimes data are limited, particularly for past exposure scenarios. With limited data, ATSDR uses the available information about site conditions and the best professional judgement of ATSDR's scientists to draw conclusions and make appropriate recommendations. Following this approach, there was sufficient information to address the central question of whether residents of Vieques are being exposed to harmful levels of chemicals present in the soil.

13. Comment: ATSDR's provisions for public comment were imperfect. The comment form ATSDR provided with the PHA was restrictive in terms of the questions it asks and the amount of space it allots to answering them. In addition, a public comment period for December is when many people are preoccupied with holiday activities.

14. Response: In the letter accompanying the PHA, ATSDR solicited written comments about the PHA in addition to requesting that the reader complete the enclosed questionnaire (i.e., the Reader Evaluation form). Public comments that ATSDR receives are not limited to the Reader Evaluation form and are typically much more detailed. The public comment period (October 23 to December 31, 2001) was extended beyond the usual 30 days to account for holiday activities.

15. Comment: Hopefully ATSDR will respond to public comments on the soil PHA as successfully as they had responded to public comments on the previous drinking water PHA.

16. Response: Thank you for the comment.

17. Comment: The data presented in the PHA do not convincingly substantiate the PHA's conclusions about the past, current, and future health effects of the soil on Vieques. It would be inappropriate for ATSDR to produce further PHAs having to do with Vieques before correcting the errors in the soil PHA and the errors alleged to persist in the previous drinking water PHA. These PHAs are so rife with error that only two explanations seem plausible: either ATSDR is intentionally seeking to obscure public health risks in Vieques or ATSDR staff are not competent to evaluate public health risks in Vieques.

18. Response: Thank you for the comment. ATSDR appreciates objective comments and criticisms that can be used to contribute to the PHA. Before being released, the PHA was reviewed by qualified scientists from other federal agencies (e.g., USGS) that are not connected to ATSDR.

Soil Geology

13. Comment: Further consider the differences between the soils in the LIA and the soils elsewhere on Vieques. It is acceptable, based on the data presented in the PHA, that the composition of the two kinds of soils were different, but what is the scientific basis upon which the difference could be considered "slight" (and thus implicitly disregarded)? The PHA contains no statistical analysis of the difference between LIA and non-LIA soils. This omission is striking in light of the PHA's admission that there are indeed differences between soils from the two areas. Table 4 (Table 3 in the Public Comment PHA) should be subdivided into additional tables, each comparing samples of a particular soil type from within and outside the LIA.

14. Response: ATSDR concluded that the soil on the LIA differed slightly from the soil on the rest of Vieques after statistically comparing the chemical concentrations detected in each area. Comparisons were considered statistically significant (i.e., different) if there was less than 5% probability that the difference occurred by chance (i.e., p<0.05). Out of the 26 chemicals that were detected in both areas, only two chemicals (boron and calcium) showed any significant differences (see Table 4). Tables 5 and 6 have been added to the final release of the PHA to provide clarification to ATSDR's comparison of the Tl and Kv geologic units on the LIA to those on the rest of the island.

15. Comment: The PHA did not present sufficient evidence to support its conclusion that the metal concentrations observed in the soil of Vieques are consistent with ordinary expectations for soil associated with underlying igneous rock. This conclusion has limited application on Vieques, since some parts of the island are not associated with underlying igneous rock.

16. Response: ATSDR geologists determined that the mineralogy of the soils on Vieques is similar to naturally occurring soils that come from igneous/volcanic sources (that underlie a significant portion of the island). The areas that are not associated with underlying igneous rock would be expected to have a lower metal content. ATSDR considered the lower metal levels when determining that the mineralogy of Vieques is similar to soils elsewhere with a similar underlying geology.

    Moreover, ATSDR evaluated all soil analysis data available based upon the underlying geologic rock type (i.e., soil parent material). ATSDR's Vieques team scientists are trained in the factors influencing soil formation and expected, based upon long-established scientific principles, to see differences in the chemical make-up of the soils reflecting, at least in part, the nature of those parent materials.

Comparisons Between Soils on Vieques Island, Sediments on Puerto Rico Island, and Soils in the United States

15. Comment: Can one meaningfully evaluate whether soil metal concentrations on Vieques are normal by comparing them to sediment metal concentrations in Puerto Rico? The comparison is "dubious" because stream sediments are affected by human activity, stream transportation, and stream deposition. All of ATSDR's conclusions that rely upon using soil/sediment comparisons are "erroneous." ATSDR asserted that soil data were not available for Puerto Rico, however, ATSDR analyzed soil samples in several PHAs in Puerto Rico (Vega Baja, Guayama, and Humacao).

16. Response: As noted in the Section II.B of the PHA, only a generalized comparison can be made between the soil of Vieques and sediment in the mainland of Puerto Rico. Sampled stream sediments are generally representative of the soil and their parent material, however, several factors could introduce changes to the overall composition of the sediments as compared to the soil from which they were derived. Notwithstanding, ATSDR determined that comparing the soil on Vieques to the sediment on the mainland of Puerto Rico would still serve to point out generalized similarities or differences between the two areas.

    Ideally, ATSDR would compare the soil on Vieques to soil on the mainland. While the soil data available in previous PHAs in Puerto Rico provides some information about specific locations in Puerto Rico, they do not provide the area-wide perspective available in the stream sediment sampling data collected by the United Stated Geological Survey (USGS) and the Puerto Rico Department of Natural Resources (PRDNR) (Learned et al. 1973).

17. Comment: Vieques soil samples do not reflect the actual severity of metal contamination. At a certain point in Vieques' history (mid-1970s), there was an intensification of bombing activity on the island. If values prior to the intensification were lower, they would trigger a downward bias in average values. Therefore, one risks under-estimating the severity of contemporary metal contamination.

18. Response: The use of the LIA for air to ground and ship to shore training increased after the closing of the Culebra Island range in the mid-1970s. USGS and PRDNR collected soil samples from Vieques in 1972, prior to this intensification of training activity (Learned et al. 1973). However, as described in Section II.H, these data appear to be elevated by as much as 4-fold. Therefore, instead of triggering a downward bias in average values, these earlier data are actually causing an overestimation of average soil contamination, by as much as 4-fold.

    In addition, ATSDR's investigation of potential health effects from exposure to the soil on Vieques is a conservative evaluation, for the following reasons:

    • When evaluating health effects, ATSDR relied on data collected recently as well as data collected before an intensification of bombing activities. Chemicals were selected for further consideration based on the maximum concentration detected in any of the data sets, regardless of location or date of sampling.
    • 
      
      
    • ATSDR calculated averages using detected concentrations only, which overestimates the true average value; therefore, health evaluations were based on conservative averages.
    • 
      
      
    • ATSDR relied on highly conservative assumptions (e.g., high incidental ingestion rates) to estimate exposure.
    • 
      
      
    • ATSDR did not adjust the exposure doses to account for the low bioavailability of some of the metals in soil, which leads to overly conservative estimated exposure doses.
    • 
      
      
19. Comment: In those instances where the PHA finds a substance at greater concentrations in Vieques soil than in Puerto Rican sediment or United States soil, it does not venture any explanation of whether the Navy's activities are responsible.

20. Response: It is difficult to determine the source of an "elevated" chemical concentration, especially when dealing with heavy metals in soil because natural geology plays a significant role on the composition of soil. The important consideration is that there are no apparent health hazards associated with exposures to the soil on Vieques, regardless of the source.

Spatial and Chronological Patterns in Metal Levels

18. Comment: The PHA fails to furnish evidence which would allow the reader to independently arrive at the PHA's conclusion that there are no spatial patterns in the distribution of contaminants. The following are examples of information that would provide this evidence:
19. 
    
    
    • An explanation of the analytical methods ATSDR used to evaluate whether or not patterns exist.
    • 
      
      
    • A complete map and corresponding descriptive chart showing the spatial distribution of all sampling activities considered in the PHA.
    • 
      
      
    • Individual maps for each metal that show the spatial distribution of soil sampling results for that metal.
    • 
      
      

    Response: To provide further clarification to the spatial analyses, ATSDR included three figures (Figures 6-8) in the final release of the PHA that indicate the three types of patterns observed--western concentration, geologic association, and random distribution. As noted in Section III.D, none of the spatial maps depicted a progressive east to west trend. Thus, these analyses do not provide evidence of airborne transport of metals from the LIA to the residential area. Further analysis of this issue is being conducted by ATSDR using computer air transport models and will be presented in a separate air pathway evaluation (see Sections I and VIII).

20. Comment: Contrary to the PHA's conclusions, Figure 10 (Figure 5 in the Public Comment PHA) indicates that there is a spatial pattern of metal levels on the island of Vieques. The maximum levels of iron, vanadium, manganese, and chromium occur west of the LIA and the highest levels of lead, mercury, cadmium, and arsenic are located in the eastern end of the island, near or in the LIA, which is indicative of a spatial pattern in the distribution of metal levels. In addition, a report cited in the PHA (SCI 2000) mentions the existence of a spatial pattern in the distribution of metals.

21. Response: A spatial distribution of high chemical concentrations in the LIA (i.e., the presumed source) with decreasing concentrations tapering off to the west of the island for each chemical would have provided some indication that heavy metals from the LIA were migrating through the air towards the residential area. However, the distribution of each of the chemical concentrations do not illustrate such a pattern. Figures 6 to 8 show the spatial patterns (western concentration, geologic association, and random distribution) for the chemicals evaluated. For example, a western concentration of the highest levels of strontium detected is shown in Figure 6. Please see Section III.D for additional information about the trends that were observed. Further analysis of this issue is being conducted by ATSDR in a separate air pathway evaluation (see Sections I and VIII).

22. Comment: Explain how the current soil sampling data might relate to soil contamination present during past (or future) periods of live bombing.

23. Response: Soil sampling data collected during past periods of live bombing might differ from current sampling data in the level of explosive compounds detected since live munitions contains high explosives and practice munitions contain inert materials. However, high explosive compounds are designed to react during impact leaving only extremely small quantity of explosive compounds after detonation. ATSDR evaluated soil sampling data collected during periods of live bombing (e.g., Learned et al. 1973; Marsh 1992; Hoffsommer and Glover 1978; Lai 1978; and PMC 1998) and data that were collected up to 14 months after the cessation of live bombing (e.g., CH2MHILL and Baker 1999; Garcia et al. 2000; and CH2MHILL 2000a). At this time, ATSDR is unaware of any planned future activities involving the use of live ordnance.

24. Comment: A chronological link between Naval activities and contaminant concentrations is so much to be expected that ATSDR's failure to find such a link should raise suspicions about the PHA's methodology. ATSDR is not adequately motivated to review the quality of its own work in the face of surprising results.

25. Response: ATSDR objectively evaluated the data using accepted scientific methods. A chronological link is not something that can be assumed, but must be substantiated by relevant data. Scientific objectivity does not allow for any preconceived opinions to interfere with the evaluation. In non-laboratory sciences the theory of multiple working hypotheses must prevail. Induction and deduction lead the scientist by continual testing of ideas (hypotheses) to a conclusion. That conclusion will be subject to testing against new data, if and/or when it is developed and available.

26. Comment: Is it possible to determine whether or not there was a chronological pattern in certain metal levels (such as arsenic levels), given that earlier samples were made with instruments less sensitive than current instruments?

27. Response: Subsequent to the release of the public comment version of the PHA, ATSDR obtained a draft report that characterized the background levels of metals in the surface soils of the former NASD (CH2MHILL 2001). Given this new data, ATSDR compared the mean background soil concentrations from the former NASD (CH2MHILL 2001) to the mean soil concentrations for a subset (from the former NASD) of the earlier data (Learned et al. 1973), and found that the older data were 1.2 to 4 times higher than the background levels. Barium and calcium differ from this pattern for unknown reasons. In addition, the minimum values obtained during the earlier study were higher that the minimum values obtained during the recent background study, even though the minimum detection levels were higher than those used when the background analyses were performed. If there were no high-bias in the data reported in 1973 then several of the samples collected should have been reported as not detected.

    Since sampling locations from both events were from areas unaffected by the Navy training activities, it would appear that the older data is artificially elevated (i.e., higher than the true values), by as much as 4-fold. Therefore, in light of the newly acquired background data, the chronological evaluation became invalid and ATSDR revised this discussion in the final release of the PHA (see Section III.C).

28. Comment: The metal results obtained by Learned et. al (1973) were compared to those obtained by CH2MHILL (2000). The PHA found no significant difference between the 1972 and 2000 data with the exception of chromium, however, no data were presented to allow the reader to evaluate the values.

29. Response: In the public comment version of the PHA, ATSDR attempted to compare soil samples collected from the LIA in 1972 (Learned et al. 1973) to soil samples collected from the LIA in 2000 (CH2MHILL 2000a), to determine if this 28-year interval of Navy training had significantly increased the level of contamination at the LIA. However, new data (CH2MHILL 2001) received after the release of the public comment PHA indicated that the data collected in 1972 may be elevated by as much as 4-fold higher than the true values (as described in Section II.H). Therefore, this comparison became invalid and ATSDR revised this discussion in the final release of the PHA (see Section III.C).

30. Comment: Was the comparison between the soils of the United States and Vieques based on the entire United States or some other approach?

31. Response: Vieques soil samples were compared to soil samples taken from uncontaminated areas across the entire conterminous (i.e., contiguous) United States.

Soil Sampling

25. Comment: The 37 soil samples collected by CH2MHILL (for its June 2000 report) were too limited in scope and might have missed important areas of contamination. It is curious that only three of the 37 samples were taken in actual shooting target areas, while seven samples were taken in a conservation area where one would not expect pollutants to aggregate. In addition, the action of surface water might have organized metals into small, easily-missed pockets of contamination. This sampling pattern reflects a deliberate intent to avoid finding metal contamination.

26. Response: One of the goals of the sampling was to assess whether explosive compounds were present in the surface soil at the LIA (CH2MHILL 2000a). To meet this goal, CH2MHILL collected soil from 37 locations, including specific samples from drainage features and low lying areas which would collect stormwater runoff (19 samples), from within targets (7 samples), from known, protestor beach camps (4 samples), and from conservation zones upwind and downwind of the LIA (7 samples). Figure 5, which shows the sample locations, has been included in the final release of the PHA.

27. Comment: The PHA should have addressed the ways in which variation in soil sampling methodologies might affect comparisons between soil data from different reports.

28. Response: When variations in soil sampling methodologies affected a conclusion ATSDR noted this in the PHA. For example, the health evaluation for arsenic notes that exposure to arsenic is based on levels detected in the soil at the LIA and near the Vieques Municipal Airport because sampling conducted in the residential area was not sufficiently sensitive to detect the low levels of arsenic possibly existing in the residential area (see Section IV.C). Also, ATSDR noted in the final release of the PHA that the data collected by USGS and PRDNR (Learned et al. 1973) appears to be elevated above true values by up to 4-fold (see Section II.H); and described how this affected any evaluations, where appropriate (for example, see Section III.B).

29. Comment: ATSDR should reconcile its claim about the absence of harmful heavy metal concentrations in the soil with the facts stated in the US Navy/US Environmental Protection Agency (EPA) surface water discharge violation reports.

30. Response: EPA is a regulatory agency, whereas ATSDR is primarily an advisory agency. It is not unreasonable, in some cases, that a chemical concentration may be in violation of a regulatory level according to EPA, but may not be at a harmful level according to ATSDR. ATSDR's PHAs are driven by exposure, or contact. Even though chemicals may have been released into the environment, a release does not always result in exposure. People can only be exposed to a chemical if they come in contact with that chemical. If no one comes into contact with a chemical, then no exposure occurs, thus no health effects could occur.

    In addition, ATSDR considers the level of exposure. Exposure does not always result in harmful health effects. The type and severity of health effects that occur in an individual as the result of contact with a chemical depend on a number of factors, including the exposure concentration as well as the frequency and duration of exposure. ATSDR analyzes the weight of evidence of available toxicologic, medical, and epidemiologic data to determine whether exposures might be associated with harmful health effects. Taken together, these factors help determine if health effects could occur as a result of exposure to a chemical in the environment.

Explosives and Ordnance

28. Comment: The PHA's statement that the majority (82%) of the ammunition used in Vieques was non-explosive is erroneous. A July 15, 1999, Navy report provides contrary information--specifically, that only 39.64% of the ammunition was non-explosive.

29. Response: Thank you for the information. Since the PHA was written, ATSDR has acquired additional usage data. Section II.F Ordnance Type and Use has been updated in the final release of the PHA.

30. Comment: The PHA did not pay adequate attention to evaluating health risks associated with skin-permeable explosive chemicals (such as TNT, RDX, and tetryl). The very reports used by ATSDR in the PHA show significant levels of explosives in the Vieques environment. These compounds decompose relatively quickly in the environment, so the mere presence of the compounds indicates that they are being released on a continual basis.

31. Response: While five explosive compounds were detected in the soil on Vieques, all of them were detected at levels too low to be of health concern. As shown in Table 9, all concentrations of explosive compounds were below their respective health-based comparison values. Comparison values are derived using conservative exposure assumptions and reflect concentrations much lower than those known to cause harmful health effects. Thus, concentrations detected at or below these values do not warrant health concern. Furthermore, comparison values are protective of public health in all exposure situations, including dermal contact.

32. Comment: The PHA does not pay adequate attention to the presence of hazardous bombing debris and unexploded ordnance in the LIA.

33. Response: ATSDR's PHAs are driven by exposure. If no one can contact the hazard, then no exposures occur, and no harmful health effects can occur. Because the LIA is a restricted area, residents and visitors of Vieques who are engaged in legal activities are not being exposed to unexploded ordnance or bombing debris. ATSDR does agree that the people who willingly choose to illegally trespass onto Navy property are taking a risk because despite the Navy's efforts to locate unexploded ordnance, removal efforts tend to only be 75% effective (Wilcox 1997).

Comparison Values

31. Comment: The PHA did not adequately justify and explain its choice of comparison values. The PHA uses five different kinds of comparison values: Cancer Evaluation Guides (CREGs), Environmental Medical Evaluation Guides (EMEGs), Reference Dose Media Evaluation Guides (RMEGs), Risk Based Concentrations (RBCs), and Soil Screening Levels (SSLs). CREGs, EMEGs, and RMEGs were developed by ATSDR, but who developed the RBC and SSL values?

32. Response: Comparison values are developed by ATSDR and EPA from available scientific literature concerning exposure and health effects. Comparison values are media-specific and reflect an estimated chemical concentration that is not expected to cause harmful health effects for a given chemical. Thus, comparison values are protective of public health in essentially all exposure situations. CREGs, EMEGs, and RMEGs are non-enforceable, health-based comparison values developed by ATSDR for screening environmental contamination for further evaluation. RBCs and SSLs are non-enforceable, risk-based comparison values developed by EPA Region III to screen sites not yet on the NPL, respond rapidly to citizens inquiries, and spot-check formal baseline risk assessments. Definitions for these comparison values are provided in Appendix A.

33. Comment: What action would ATSDR recommend for those places (described in the PHA) where substances in the soil were found at levels above their comparison values?

34. Response: While concentrations at or below comparison values may reasonably be considered safe, it does not automatically follow that any environmental concentration that exceeds a comparison value would be expected to produce adverse health effects. It cannot be emphasized strongly enough that comparison values are not thresholds of toxicity. They represent chemical concentrations many times lower than levels at which no adverse effects were observed in experimental animal or human epidemiologic studies. The likelihood that harmful health effects will actually occur depends on site-specific exposure conditions, not an environmental concentration alone.

    Before recommending actions, ATSDR first examines potential exposures to the contaminants in the soil by following the process described in Section IV. Evaluation of the Soil Exposure Pathway. This process enables ATSDR to weigh the available evidence in light of uncertainties and offer perspective on the plausibility of harmful health outcomes under site-specific conditions. Using this process, ATSDR determined that no harmful health effects are expected to occur from exposure to the soil on Vieques. If ATSDR's exposure evaluation process would have identified a situation that could result in harmful health effects, ATSDR would have issued a public health advisory warning of the danger and urged regulators to take actions to prevent adverse human health effects resulting from exposure to hazardous substances in the soil.

Public Health Conclusions

33. Comment: How can ATSDR conclude that adults and children were not exposed to dangerous levels of chemical substances found in the soil of the LIA, since the PHA reported that concentrations of several chemical substances exceeded comparison values?

34. Response: As stated in our response to the previous comment, comparison values are derived using conservative exposure assumptions and reflect concentrations much lower than those observed to cause harmful health effects. While a concentration at or below the relevant comparison value could reasonably be considered safe, it does not necessarily follow that any environmental concentration exceeding a comparison value would produce harmful health effects. It cannot be emphasized too strongly that comparison values are not thresholds of toxicity. The likelihood that harmful health outcomes will actually occur depends on site-specific conditions and individual lifestyle, as well as factors affecting the route, magnitude, and duration of actual exposure--not an environmental concentration alone. Chemicals detected above comparison values are evaluated further by estimating exposure doses using site-specific exposure assumptions. ATSDR examines relevant toxicologic, medical, and epidemiologic data to determine whether these estimated doses are likely to result in harmful health effects. Although the concentrations of seven chemicals exceeded comparison values (see Table 9), after evaluating potential exposure doses, ATSDR determined that none of the chemicals are present at levels of health concern.

35. Comment: There is a discrepancy between the arsenic comparison values in Table 9 (Table 5 in the Public Comment PHA) and the health guidelines in Exhibit 3 (Exhibit 2 in the Public Comment PHA). The average arsenic concentration (8.91 ppm) is above the adult CREG (0.5 ppm), but below the child's EMEG (20 ppm) in Table 9. However, in Exhibit 3 the estimated exposure dose is below the minimal risk level (MRL) and reference dose (RfD) for adults, but above for children.

36. Response: No discrepancy exists between the values presented in Table 9 and Exhibit 3. The observation noted in the comment can be explained by further describing the distinction between cancer and noncancer screening values (e.g., comparison values and health guidelines) used by ATSDR in its public health assessment process.

    Comparison values represent concentrations of a substance (in this case arsenic in soil) to which humans may be exposed during a specified period of time without experiencing adverse health effects. Separate guidelines are available for cancer and noncancer effects. ATSDR typically compares the maximum detected concentration with the most conservative (i.e., protective) comparison value available for that chemical. This process enables ATSDR to quickly identify concentrations that are not of public health concern (i.e., those below comparison values) and those that might require further evaluation (i.e., those above comparison values).

    As shown in Table 9, ATSDR considered the CREG for cancer effects (i.e., the overall most conservative comparison value) and the child EMEG (i.e., the most conservative comparison value for noncancer effects) when evaluating health effects from exposure to the soil on Vieques. Even though only the child EMEG is reported in Table 9, an adult EMEG (200 ppm) also exists to evaluate noncancer health effects for adults. The maximum detected concentration of arsenic (36 ppm) exceeds the CREG (0.5 ppm) and the child EMEG (20 ppm), but not the adult EMEG; which is parallel to the comparison shown in Exhibit 3 (see next paragraph).

    The next step in the health evaluation process is to look more closely at those substances that exceed comparison values. In doing so, ATSDR estimates exposure doses for adults and children based on site-specific considerations and compares those doses with available health guideline values. Health guideline values for noncancer effects include MRLs and RfDs, as shown in Exhibit 3. Consistent with Table 9, the child dose (based on the maximum concentration) exceeds the MRL/RfD, but the adult dose does not.

    Exhibit 3 does not consider cancer effects because no health guideline value is available to evaluate cancer effects for arsenic, as there is for noncancer effects. Exceeding the CREG; therefore, has no bearing on the comparison of doses with MRLs. ATSDR addressed cancer health effects on a more qualitative basis in the arsenic evaluation in the PHA (see Section IV.C).

37. Comment: The PHA erroneously used a lineal equation to evaluate exposure doses because all such equations are questionable for use in live beings.

38. Response: An exposure dose is an estimate of how much of a substance a person may contact based on their actions and habits. Estimating an exposure dose requires identifying how much, how often, and how long a person may come in contact with a substance. The exposure dose equation described in Section IV.B of the PHA calculates a total dose accumulated over time, which is a useful number for health assessments (EPA 1992b). The standard equation that was used to estimate exposure doses in humans is an appropriate and conservative approach, consistent with ATSDR's Public Health Assessment Guidance Manual (ATSDR 1992a) and EPA's Superfund Risk Assessment Guidance (EPA 1989).

39. Comment: It is unrealistic to assume that a 6 year old child weighs 10 kilograms (kg), as 20 kg seems a more realistic weight.

40. Response: ATSDR based the calculations for childhood exposure on highly conservative assumptions. Even though a lower body weight tends to overestimate exposure, using 10 kg for a child's body weight is justified for very young children, who are more apt to ingest soil than older children. According to the National Health and Nutrition Examination Survey (NHANES), the average body weight for children 6 to 11 months old is 9.1 kg (NCHS 1987 as cited in EPA 1997).

41. Comment: When trying to reconstruct a dose calculation performed in the PHA the resulting answer differed from the PHA's by six orders of magnitude:

42. 

    The PHA reported 0.000720 mg/kg/day. Why is there a difference in the units and the value of the result?

    Response: The discrepancy between the two calculations appears to be due to unit conversions. Below is a detailed account of the unit conversions necessary to complete the dose calculation. As the equations show, the units below all cancel, thus ensuring that the calculation is correct. ATSDR clarified this calculation in the final release of the PHA.

    First calculate the soil concentration into units consistent with those for the other parameters:

    36 ppm of arsenic in soil	=	36 mg of arsenic 1 kg of soil	=	36 mg of arsenic 1,000,000 mg of soil

    (since ppm = mg/kg and 1 kg = 1,000,000 mg)

    Second, calculate the estimated exposure dose for arsenic using the equation and assumptions provided in the text of the PHA:

    

    

    The units cancel as shown below:

    

    Which results in an estimated dose of 0.00072 mg of arsenic / kg of body weight / day.

43. Comment: Clarify whether the PHA assumed an adult ingestion rate of 100 mg/day or 50 mg/day. If ATSDR is indeed using an ingestion rate of 100 mg/day, it is making a highly conservative (i.e., protective) assumption and should make note of that.

44. Response: ATSDR conservatively used an adult ingestion rate of 100 mg/day to evaluate exposures rather than EPA's recommended value of 50 mg/day. This ingestion rate is supported by a tracer study that found that adults ingested from 30 to 100 mg of soil a day (Calabrese et al. 1990 as cited in EPA 1997). ATSDR noted this in Section IV.B of the final release of the PHA.

45. Comment: The PHA's assumption that the primary mode of exposure to soil contaminants is through soil consumption is doubtful. It is absurd to assume that people are continually eating soil around Vieques, particularly in areas formerly occupied by the Navy.

46. Response: While it may seem doubtful, scientific evidence exists to support the ingestion rates of soil in adults and children (EPA 1997). ATSDR is not assuming that the people of Vieques are literally "eating" soil, rather people are incidentally (i.e., accidentally) ingesting soil when they eat food with their hands, smoke a cigarette, or put their fingers in their mouths. Soil or dust particles can adhere to food, cigarettes, and hands and result in incidental ingestion. Children are particularly sensitive to this phenomena and are more likely to ingest more soil than adults. Furthermore, during a normal phase of childhood, children display hand-to-mouth behavior which inadvertently results in consumption of soil.

47. Comment: The PHA should address the possibility of synergistic effects arising from the interaction of several low-level chemical exposures and the possibility of significant cumulative exposures occurring through several different contaminated media (e.g., soil, air, water, and foods).

48. Response: Most of the literature on the effects of chemical mixtures focus on relatively high exposures that may produce results such as synergism, additivity, and non-competitive inhibition. However, concentrations far in excess of typical environmental concentrations are generally required to produce such effects.

    Several studies, including those conducted by the National Toxicology Program (NTP) in the United States and the TNO Nutrition and Food Research Institute in the Netherlands, among others, generally support the conclusion that exposure to a mixture of chemicals is unlikely to produce any adverse health effects as long as the components of that mixture are present at levels well below their respective no observed adverse effects levels (NOAELs) (i.e., at concentrations that would have produced no adverse effects in animals treated individually with each component chemical; for reviews, see Seed et al. 1995; Feron et al. 1993). This observation appears to hold true whether the individual chemicals affect the same or different target organ(s) via different mechanisms and different exposure pathways (i.e., the situations that generally pertain to typical environmental mixtures). Even chemicals with the same or similar modes of action do not appear to exhibit either synergism or additivity, as long as the levels of exposure are well below the respective NOAELs of the individual chemicals; which is what was found for chemicals in the soil on Vieques.

    The entire public health assessment process is lengthy, especially when addressing complex environmental issues. ATSDR is evaluating each exposure pathway separately to be most responsive to the petitioner and the people of Vieques. After all the individual PHAs are completed, ATSDR will prepare a short summary of all the health issues evaluated at Vieques. This summary will present the results of ATSDR's media-specific PHAs and will also consider whether overall exposures to environmental chemicals pose a public health hazard.

49. Comment: The limitations of the sampling methodologies employed in the PHA also limit the applicability of the dose estimates reported. It would be far more helpful to directly assess health risks by taking hair and blood samples from residents of Vieques.

50. Response: ATSDR was prepared to take hair, blood, and urine samples from the residents of Vieques in 2001. To successfully complete the project ATSDR solicited the support and assistance of several Vieques physicians. However, the physicians have expressed reservation about whether the results will be reflective of actual exposures and have been unwilling to proceed. While the offer to collect hair, blood, and urine samples is still available, the project has been indefinitely postponed until the physicians are willing to assist.

    In June 2001, at ATSDR's invitation, seven experts in the fields of hair analysis, toxicology, and medicine met to discuss the utility of hair analysis in evaluating exposures and health effects at hazardous waste sites. The experts agreed that "for most substances, insufficient data currently exist that would allow the prediction of a health effect from the concentration of the substance in hair. The presence of a substance in hair may indicate exposure (both internal and external), but does not necessarily indicate the source of exposure" (ATSDR 2001b). For more details, a discussion of hair analysis has been added to Section V. Community Health Concerns in the final release of the PHA.

51. Comment: The PHA speaks out of ignorance when it states that the protestors occupying the LIA from 1999 to May 2000 were not exposed to harmful levels of chemicals in the soil. Did ATSDR collect detailed information about the behavior patterns of the protestors (e.g., food preparation and consumption, daily hygiene, housing arrangements, daily forays throughout LIA)? It is not possible to arrive at an accurate exposure assessment without this data.

52. Response: While ATSDR did not collect detailed behavior information, the conservative assumptions that were used to evaluate exposures are expected to overestimate actual exposures under normal circumstances and more-accurately estimate exposures for the protestors who lived on the LIA for a year. ATSDR based the ingestion rates on the likelihood that the people occupying the LIA were incidentally ingesting a higher than normal amount of soil every day.

    EPA recommends using average ingestion rates of 100 mg/day for children and 50 mg/day for adults when calculating exposures, but notes that "200 mg/day for children may be used as a conservative estimate of the mean" (EPA 1997). In addition, ATSDR consulted the literature and found one study that estimated soil ingestion rates for children who were expected to have higher soil intake rates than normal (i.e., children vacationing at campgrounds). An average soil intake rate of 174 mg/day was reported (Van Wijnen et al. 1990 as cited in EPA 1997). Therefore, by using ingestion rates of 200 mg/day for children and 100 mg/day for adults, ATSDR took into consideration situations where people may incidentally consume more soil than under typical conditions (e.g., when the protestors lived on the LIA).

Additional Data

43. Comment: ATSDR does not compare the levels found in the soil of Vieques with background levels reported in "Draft Soil, Groundwater, Surface Water, and Sediment Background Investigation Report for U.S. Naval Ammunition Support Detachment, Vieques Island, Puerto Rico," that was published by CH2MHILL in June 2001. The data provided in the following table are consistent with the theory that the concentrations of heavy metals in the soil of Vieques have been enriched above natural levels by the activities of the U.S. Navy.
44. 
    
    

    Metal	Stated Background Concentration (CH2MHILL June 2001) units in ppm	Stated Average Soil Concentration (PHA) units in ppm	Stated Maximum Soil Concentration (PHA) units in ppm
    Arsenic	2.2	8.91	36
    Barium	364.5614	594	3,000
    Cadmium	0.04	1.6	31.3
    Chromium	74	58.2	700
    Copper	68	72.6	1,500
    Iron	9,360	45,600	150,000
    Lead	4.19	17.1	1,000
    Manganese	1,167.178	1,200	5,000
    Zinc	65.09994	78.5	3,000
    Mercury	0.04564024	0.0275	4.21
    Vanadium	183.6659	162	500

    Response: Thank you for bringing these data to ATSDR's attention. ATSDR was not aware of the report cited as it is in draft form and not yet available for release. Based upon an evaluation of this new data, ATSDR agrees with the commentator--the concentrations of metals at the LIA are indeed higher than background concentrations within the former Naval Ammunition Storage Detachment (NASD). ATSDR has revised Section III.C in the final release of the PHA to reflect this conclusion. It is important to note that even though the heavy metal concentrations are higher in the LIA than the former NASD, none of the levels are of health concern (see Section IV).

45. Comment: Additional soil sampling data (collected by the Navy in 2000) is available for non-range areas of the Eastern Maneuver Area (EMA)/Camp Garcia. An additional report published by C2HMHILL in October 2000 shows elevated metal concentrations in soil samples taken from western Vieques.

46. Response: ATSDR contacted the Navy and confirmed that all currently available data in the non-range areas of the EMA/Camp Garcia have already been incorporated into the PHA.

    The "Final Expanded Preliminary Assessment/Site Investigation, US Naval Ammunition Storage Detachment, Vieques, Puerto Rico" (CH2MHILL 2000b) investigated contamination at several solid waste management units (SWMUs) in the former NASD. Surface soil samples were collected and analyzed for organic compounds, metals, pesticides, polychlorinated biphenyls, and explosives. Contamination at these SWMUs is not associated with the Navy's bombing activities at the LIA, rather local sources at the former NASD (e.g., disposal sites and underground storage tanks) contributed to the contamination. Using the same procedures and methodologies described in the Evaluation of the Soil Exposure Pathway (Section IV) discussion of the PHA, ATSDR reviewed the surface soil data and determined that none of the SWMUs pose a public health hazard. The concentrations of chemicals at the SWMUs are not at levels of health concern for anyone exposed to the soil at these sites.

47. Comment: Because soil sampling was restricted to just the first six inches of soil, deeper samples should be taken before an assessment is made.

48. Response: ATSDR's PHAs are driven by exposure. People can only be exposed to a chemical if they come in contact with that chemical. If no one comes into contact with a chemical, then no exposures occur, thus no health effects could occur. When evaluating exposures to soil, ATSDR is most concerned with the top 6 inches of the soil because that is the layer that people can easily contact. Deeper soils are inaccessible and; therefore, no exposures of harmful health effects could occur from any chemicals present.

49. Comment: The PHA cannot justify its conclusions that there are no explosives contamination in the residential soil of Vieques and that there is no spatial pattern of explosives contamination on Vieques, given that it admits to lacking sampling data for the residential and western regions of Vieques.

50. Response: ATSDR carefully considered the possibility that explosive compounds might transport in the air and deposit on soils in downwind areas. First, ATSDR notes that explosive compounds in the bombs dropped on Vieques are largely destroyed upon impact. That is, explosive compounds react during impact, releasing large amounts of energy, and only a small quantity of the explosive compounds remain after detonation.

    Second, if long-range transport of explosive compounds occurred in appreciable amounts, then one would expect to find soils throughout the downwind areas with explosives contamination. However, the soil sampling data collected on the eastern edge of the residential area of Vieques found no evidence of explosive compounds. Specifically, explosives were not detected in 32 samples collected from storm drains along the border that receives runoff from the Navy's land (CH2MHILL and Baker 1999). It is unlikely that explosive compounds would be detected further downwind from this sampling area (e.g., in the soils of the residential area) if explosive compounds were not detected along this boundary zone between the residential area and the EMA. ATSDR's PHA on the air exposure pathway presents further information on atmospheric transport of contaminants from the LIA (see Sections I and VIII).

51. Comment: The PHA should consider soil samples collected near Open Burning/Open Detonation (OB/OD) areas and other Naval waste management areas. Elevated levels of metallic and organic contaminants have been recorded near these sites.

52. Response: ATSDR contacted the Navy and confirmed that all currently available data near OB/OD areas within the LIA have already been incorporated into the PHA; with the exception of data that were analyzed according to Toxicity Characteristic Leachate Procedure (TCLP) (personal communication with Atlantic Division Naval Facility Engineering Command personnel, March 2002). Samples are analyzed using TCLP to help regulators determine whether the soil qualifies as and should be disposed of as hazardous waste. Data analyzed according to TCLP confirm the potential presence of certain chemicals in the soil and their potential to leach, however, the results do not provide any indication as to the concentrations present. Remember that the presence of a chemical will not automatically result in harmful health effects. The type and severity of health effects that occur in an individual as the result of contact with a chemical depend on the exposure concentration (how much) and the frequency and duration of exposure (how long). Therefore, data that do not provide the concentration of the chemical in the soil do not provide useful information for an evaluation of public health exposures.

    This PHA is focused on addressing the petitioner's concerns about Naval bombing activities at the LIA. As noted in Comment 44, the Navy investigated contamination at several SWMUs in the former NASD, including one inactive OB/OD area (CH2MHILL 2000b). Surface soil samples were collected and analyzed for organic compounds, metals, pesticides, polychlorinated biphenyls, and explosives. Even though contamination at these SWMUs is not associated with the Navy's bombing activities at the LIA, ATSDR reviewed the surface soil data and determined that none of the SWMUs pose a public health hazard.

53. Comment: With the exception of 32 surface samples collected in August 1999 along the EMA's western boundary, none of the sample results cited in the PHA have been reviewed (by the commentator). Therefore, it is difficult to evaluate the PHA's conclusions.

54. Response: ATSDR evaluated the technical and scientific data in the referenced documents and summarized the essential information in the PHA for the general public. The full references are provided in the PHA for those wishing to evaluate the original studies themselves.

55. Comment: ATSDR misrepresented the extent of the data that is available for the EMA. The PHA claims that Hoffsommer and Glover only analyzed two areas in the EMA and four in the LIA, however, Hoffsommer and Glover actually found pollutants in fifteen areas in the EMA, eleven areas in western Vieques, and two drinking water samples. This discrepancy is indicative of a broader program (on the part of ATSDR) to deliberately misread its source materials.

56. Response: In May 1978, the Naval Surface Weapons Center obtained and analyzed soil samples for explosive compounds from two areas within the EMA (described as "soil near Bahia de la Chiva, Maneuver Area, Camp Garcia" and "soil near brackish water at Bahia Tapon") and four areas within the LIA (described as "soil sample between craters A and B," "soil from small lagoon," "soil from dry lagoon," and "soil from crater B Demolition Range #6") (Hoffsommer and Glover 1978). They also took water samples from 11 areas outside the LIA and from 15 areas within the LIA. These data were appropriately included in ATSDR's evaluation of the drinking water supplies and groundwater on Vieques (ATSDR 2001a). This PHA, the Soil Pathway Evaluation, evaluates only those pathways involving exposure to potentially contaminated soil on Vieques and; therefore, presented and analyzed all available soil data.

57. Comment: ATSDR's evaluation omits important independent work by experts such as Dr. Neftali Garcia and Jorge Fernández, whose findings contradict ATSDR's.

58. Response: Data collected by Neftalí Garcia was included in the PHA. The reference is:

    Servicios Científicos y Técnicos, Inc. (SCI). 2000. Environmental impact of Navy activities in Vieques. Dr. Neftalí Garcia, Ana M. López, Mariela Soto, Shereeza Rosado, and Brenda Berríos. July 11, 2000.

    At this time, ATSDR is not aware of any soil data collected by Dr. Jorge Fernández. ATSDR welcomes any additional information to support our ongoing efforts on Vieques. Please send additional information to:

    Program Evaluation and Records Information Services Branch
    ATSDR, Division of Health Assessment and Consultation
    Attn: Isla de Vieques, Puerto Rico
    1600 Clifton Road, NE (E-56)
    Atlanta, Georgia 30333

59. Comment: The PHA should include a map showing the locations of the 420 samples evaluated in the assessment to help the reader independently verify that the data samples were of adequate quality.

60. Response: Figure 4, which shows all the sample locations, has been included in the final release of the PHA.

Other Exposure Pathways

52. Comment: There are potential health risks associated with consuming contaminated plants and animals around Vieques. Locally grown crops might be bioaccumulating metals. A study conducted by Dr. Massol in 2001, reported high concentrations of the following metals in local crops: lead, cadmium, manganese, cobalt, nickel, and copper. In addition, ATSDR should consider the effect of wastewater treatment plants on nearby marine life.

53. Response: Community concerns about heavy metal accumulation in plants and animals around Vieques have been included in the final release of this PHA (see Section V. Community Health Concerns). To address the concern about marine life, ATSDR contracted EPA to collect and analyze fish and shellfish in the coastal waters and near shore areas of Vieques in July 2001. ATSDR's fish and shellfish evaluation documents the results of the sampling and public health evaluation (see Sections I and VIII).

54. Comment: The PHA having to do with drinking water was an excellent overview of the island's water supply and hydrogeology, however here is some additional information. USMC Well #6 and Navy Well #14 at Camp Garcia were installed after 1967. Before 1967, an underground pipeline provided water to Camp Garcia. Camp Garcia's sanitary water system involved salt water pumped from the lagoon to a holding pond.

55. Response: Thank you for the information.

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