PUBLIC HEALTH ASSESSMENT
NAVAL AIR STATION FALLON
(a/k/a FALLON NAVAL AIR STATION)
FALLON, CHURCHILL COUNTY, NEVADA
The Nevada State Health Division (NSHD) has been investigating a childhood leukemia cluster in the Fallon area since late summer 2000. To assist the investigation, NSHD requested technical assistance from the Agency for Toxic Substances and Disease Registry (ATSDR) to identify possible chemical releases, evaluate environmental data, and conduct an exposure pathway analysis. An exposure pathway is the way by which humans come in contact with materials in the environment. ATSDR prepared this public health assessment (PHA) to evaluate exposure pathways and to respond to community concerns about past, current, and potential future exposures to contaminants originating at the Naval Air Station in Fallon (NASF), Nevada.
This PHA evaluates the likelihood that any contaminants identified at NASF may be a public health concern. The ATSDR public health assessment process is exposure, or contact, driven. People may or may not be exposed to chemicals in the environment, through contact with soil, air or water. If people are exposed, it is important to determine whether the exposure is to amounts, and in a manner, that could result in adverse health effects. ATSDR uses environmental and toxicological evaluations to determine whether it is possible for such adverse health effects to occur. The process ATSDR uses in its evaluation is detailed in this document. ATSDR conducted a comprehensive evaluation of NASF, including evaluating chemicals that are not associated with leukemia.
NASF is an active station located in Churchill County, Nevada, approximately 6 miles southeast of the city of Fallon. The main station covers 7,982 acres and contains airfield, maintenance, public works, and housing facilities. An additional 14 parcels totaling 148,000 acres are used for flight training exercises and are located in the general vicinity of the main station. The main station is fenced and all entrances are gated.
Most of the hazardous wastes generated or disposed of at NASF is associated with the maintenance of aircraft and ground vehicles. Other significant sources of waste contamination include jet fuel spills or leaks (JP-5 and JP-8) from aircraft fueling and refueling operations and fuel disposal activities. In addition to fuel-related contamination, solvents, oils, and other wastes associated with aircraft operations and maintenance activities at NASF have resulted in the release of substances into the soil, surface water and sediment, air, and groundwater.
NASF, in accordance with the Department of Defense's Installation Restoration Program, has conducted investigations to characterize the nature and extent of contamination at NASF. Most contamination at NASF has been detected in on-site groundwater and to a lesser extent in soil. NASF has conducted a remedial investigation and an intrinsic remediation assessment to identify the most appropriate methods of cleaning up contaminated soil and groundwater plumes at NASF.
ATSDR conducted site visits to NASF in April and August 2001. During these site visits, ATSDR met with NASF's Commanding Officer and other NASF personnel and was briefed on specific concerns pertaining to environmental releases at NASF. ATSDR also met with representatives from NASF's environmental office and toured the base. During the course of these site visits, ATSDR collected relevant information about the day-to-day operations of NASF, noted any past environmental issues or concerns, and gathered data from reports and documents generated from prior investigations. Based on all the information gathered, ATSDR reached the following conclusions:
Groundwater:As long as the groundwater is not used for drinking, exposure to on-site groundwater at NASF poses no past, current, or future public health hazard. ATSDR reviewed available on-site groundwater data. Low levels of contaminants have been detected in groundwater on-site. However, the contaminant plume does not extend past NASF boundaries. Some chemicals were detected in on-site monitoring wells at levels above ATSDR's health-based comparison values (CVs). These chemicals include: total petroleum hydrocarbons (TPHs), volatile organic compounds (VOCs) (e.g., trichloroethylene, benzene, and cis1,2-dichloro- ethylene), and metals (e.g., boron and arsenic, which are often naturally occurring in groundwater). Although fuel and some solvents released to the environment have resulted in areas of groundwater contamination at NASF, groundwater beneath the station has never been used as a source of drinking water. According to NASF representatives, there are no current or future plans to use groundwater at NASF for drinking water or other domestic purposes (e.g., showering or cooking).
Drinking Water: ATSDR concludes that the drinking water supply for NASF and the city of Fallon has not been impacted by site-related contaminants. Although high levels of naturally occurring arsenic is a health concern, a water treatment plant is being constructed to reduce levels of arsenic in the drinking water to meet EPA's safe drinking water standards. Drinking water for NASF and most city of Fallon residents is obtained from off-site wells that get water from a deep aquifer referred to as the Fallon basalt aquifer. These wells have not been impacted by site-related chemicals because they are at least 2 miles northwest of any NASF source areas, are upgradient from NASF, and the depth to the basalt aquifer is more than 500 feet below ground surface. All past monitoring results have met state and federal safe drinking water standards for VOCs, semi-volatile organic compounds, and pesticides. The only inorganic substance that has not met state and federal safe drinking water standards is arsenic. Arsenic, which is naturally occurring in the Fallon area, has been detected at levels that exceed EPA's maximum contaminant level.
Private Drinking Water Wells: On the basis of currently available data, ATSDR concludes that exposure to site-related chemicals in private drinking water wells poses no past, current, or future public health hazards. Groundwater investigations at NASF have indicated that contamination is confined to the shallow aquifer beneath NASF. Generally, private wells in the area surrounding NASF draw water from the intermediate aquifer and are not be impacted by contamination in the shallow aquifer. Since monitoring wells in all aquifers studied around NASF's boundary have not contained site-related chemicals at levels above ATSDR's CVs, it is not expected that private wells have been impacted by site-related chemicals.
Surface Water, Sediment and Drainage Canals: ATSDR concludes that exposure to surface water and sediment at NASF or to chemicals in drainage canals flowing from the base to off-site locations poses no past, current, or future public health hazard. Permanent surface water features at NASF are limited to irrigation ditches and drainage canals. Fuel-related chemicals and some metals have been detected at levels below health concern in drainage canals on site. The irrigation ditches and drainage canals have not been used for recreational purposes (e.g., swimming, fishing, boating) on site. In addition, any potential exposures to on-site surface water or sediment would be very infrequent, of short duration, and not of public health concern. Outside NASF, levels would be as low or lower as a result of dilution, so that individuals who may come in contact with drainage canal waters flowing from the base to off-site locations would not be exposed at levels that would be of public health concern.
Soil: ATSDR concludes that exposure to soil contamination at NASF poses no past, current, or future public health hazard. ATSDR concludes that there is no off-site soil contamination from activities at NASF. ATSDR reviewed available on-site soil data. TPHs and some VOCs were detected in surface soil above their CVs at some sites within NASF. Access to NASF, however, is restricted and there is no evidence that on-site personnel or their families living in family housing have been in contact with these areas. Since some of the installation restoration sites that contain contaminated soil are not fenced, ATSDR cannot rule out the possibility that some residents of the station and on-site personnel could be exposed. However, any exposures to soil contaminants would likely be infrequent and of short duration. Generally, these sites do not contain NASF-related contaminants in soil that exceed ATSDR's CVs. Therefore, soil contaminants from NASF are not expected to be transported off site at levels that would be of health concern.
Air: ATSDR concludes that exposure to air contaminants from stationary sources at NASF pose no past, current, or future public health hazard. ATSDR evaluated possible exposures to air contaminants from stationary sources such as boilers, generators, and painting operations at NASF. NASF's air quality analysis results showed that the predicted concentrations of EPA criteria pollutants (i.e., CO, NO2, PM10, SO2) from stationary sources at the station do not exceed corresponding national ambient air quality standards. Meteorological data shows that prevailing winds are from the west, from the direction of the city of Fallon toward NASF and therefore generally serve to blow any contaminants away from the town. Recent air monitoring data in the Fallon area from EPA's Aerometric Information Retrieval System database showed that PM10 concentrations were well below EPA's national ambient air quality standards.
Jet Fuel and Engine Emission Byproducts: ATSDR concludes that exposure to air contaminants related to jet fuel and engine emission byproducts at NASF pose no past, current, or future public health hazard. As mentioned above, meteorological data shows that prevailing winds are from the west, from the direction of the city of Fallon toward NASF and therefore would generally serve to blow any airborne contaminants away from the town. An extensive literature search was conducted for information on the nature of military jet engine emissions. ATSDR researched the most current aircraft emissions data available from EPA, FAA, and the Navy. We used these data sets to develop realistic emissions estimates for the aircraft engines at NASF. Using this information, a screening model for dispersion of emissions was conducted. Using the most representative data available, we found that estimated ambient air concentrations for all pollutants considered were either below health-based comparison values or reasonably consistent with levels routinely measured in small communities and suburban locations across the United States. The sampling conducted by the Centers for Disease Control and Prevention (CDC) did not detect levels of chemicals that might be components of jet fuel or jet engine emission byproducts in either biological and environmental samples in case families or control families. ATSDR therefore can not link the potential exposure of members of the Fallon community to jet fuel and emission byproducts to non-cancer public health effects. Additionally, extensive literature search was conducted on existing toxicologic research on jet fuel and emission byproducts. Based on these data searches, a toxicological evaluation was conducted. The toxicological evaluation also supports the finding that aircraft emissions from NAS Fallon can not be linked with either the leukemia cases in the nearby community nor are exposures likely that would result in non-cancer public health effects.
Several members of the community in the vicinity of NAS Fallon have expressed concern over the possibility that fuel jettisoned from Naval aircraft might be a potential cause of illnesses in the community. According to U.S. Navy operations guidelines, fuel jettisoning typically only occurs when an emergency landing is required. The fuel is released in order to decrease the potential for an explosion or fire during an urgent or emergency landing. The community concern regarding the jettisoning of fuel by Navy aircraft is extensively discussed in the Community Health Concerns section. Based on information provided by NASF, ATSDR concludes that jettisoning at NASF does not pose a past, current or future public health hazard.
Naval Air Station Fallon (NASF) is an active station located in Churchill County, Nevada, approximately 6 miles southeast of the city of Fallon (Figure 1). The main station covers 7,982 acres and contains airfield, maintenance, public works, and housing facilities. The main station is fenced and all entrances are gated, allowing only authorized personnel access. An additional 14 parcels used for flight training exercises totaling 148,000 acres are located in the general vicinity of the main station. The station is bounded on the west by U.S. Route 95 and on the north and east by U.S. Route 50. Carson Lake Pasture, which is a series of ditches and small marshes, is approximately 3 miles to the south of the station. There is very little developed land in between NASF and the Carson Lake Pasture (ORNL 1994).
NASF was originally established as a military facility in 1942 under the Civil Aviation Administration and Army Air Corps. Initially, four airfields were constructed as part of the Western Defense Program. In 1943, the Navy assumed control of the air fields and, in June 1944, Naval Air Auxiliary Station (NAAS) Fallon was commissioned (ORNL 1994). Over the years, the station has undergone several operational changes. NAAS Fallon originally provided training, servicing, and support to air groups sent to the station for combat training. From 1945 to 1975, the Air Force also used part of the station as part of an early warning radar network.
Training operations at NAAS Fallon peaked between April and September 1945. After a brief period of inactivity during the late 1940s and early 1950s, NAAS Fallon was reestablished in October 1953. In January 1972, NAAS Fallon expanded its operations and officially became known as NASF. NASF currently serves primarily as an aircraft weapons delivery and tactical air combat training facility (ORNL 1994).
In addition to the main station, nine other major parcels used by NASF include:
- Range B-16 (21,120 acres)
- Range B-17 (21,400 acres)
- Range B-19 (17,332 acres)
- Range B-20 (41,030 acres)
- Electric Warfare Range (34, 380 acres)
- Shoal Sites, which consists of two parcels (4,620 acres total)
- Army Electronics Command (AEC) Site (2,560 acres)
- Helicopter Training Range (5,760 acres)
Most of the hazardous wastes generated or disposed of at NASF were from: (1) spent products, off specification products, and expired products associated with the maintenance of aircraft and ground vehicles; (2) jet fuel spills or leaks (JP-5 and JP-8) from aircraft fueling and refueling operations and fuel disposal activities; (3) the discharge and disposal of solvents, oils, jet fuels, antifreeze, and hydraulic fluid used in vehicle and air station maintenance activities and fire training exercises; and (4) the disposal of other wastes associated with activities at NASF, including pesticides and herbicides, detergents, paints, and industrial and municipal garbage (ORNL 1994). These practices have resulted in the release of contaminants into the soil, surface water and sediment, air, and groundwater.
In August 1986, the Nevada Department of Environmental Protection (NDEP) issued a Finding of Alleged Violation and an Order to Comply resulting from the discovery of jet fuel contamination in soils and in groundwater at NASF's New Fuel Farm (Site 2). These actions were issued in accordance with Nevada Revised Statutes (NRS) 445.221, which prohibit the unlawful discharge of pollutants without a permit. The Order to Comply required that NASF submit information on the extent of contamination and implement an approved plan to clean up the site (ORNL 1994). Other actions by NDEP included issuing a notice of violation in March 1989 due to a malfunction of the fuel farm oil/water separator and, in February 1990, an investigation concerning an alleged fuel spill during February 1988 (ORNL 1994). In addition to these incidents, NDEP's Bureau of Corrective Actions has generated a total of eight other case files documenting incidents (e.g., small fuel spills) resulting from NASF activities on site.
Based on initial information from historical records, aerial photographs, agency contacts, field inspection, and personnel interviews, a total of 27 potentially contaminated sites were identified at NASF (Dames & Moore 1988). In accordance with the Department of Defense's Installation Restoration Program (IRP) managed under the authority of the Navy, a preliminary assessment/site inspection (PA/SI) was conducted at NASF in September 1987. As a result of the PA/SI, 21 of the 27 potentially contaminated sites initially identified were found to warrant further investigation (Figure 2). The other six sites were not considered to be significant sources of contamination. Seventeen of these 21 sites were divided into four groups, while four of the sites remained alone. As of this writing, nine of the 27 potentially contaminated sites (5, 7, 8, 13, 15, 19, 25, 26, and 27) have been closed by NDEP and do not require any additional cleanup. The groups and the sites, including the six "no action" sites, are listed below and a description of each of the 21 "action" sites is provided in Table 1:
- Four Individual Sites located in different areas of the station:
- Crash Crew Training Area (Site 1);
- Hangar 300 Area (Site 3);
- Checkerboard Landfill (Site 20); and
- Road Oiling Area (Site 24).
- New Fuel Farm (Site 2); and
- Transportation Yard (Site 4).
- Defuel Disposal Area (Site 6);
- Napalm Burn Pit (Site 7);
- Receiver Site Landfill (Site 21); and
- Northeast Runway Landfill (Site 22).
- Wastewater Treatment Plant (Site 9); and
- Southeast Runway Landfill (Site 18).
- Ground to Air Transmitting and Receiving (GATAR) Compound (Site 10);
- Paint Shop (Site 11);
- Pest Control Shop (Site 12);
- Boiler Plant Tanks (Site 13);
- Old Vehicle Maintenance Shop (Site 14);
- Old Fuel Farm (Site 16);
- Hangar 5 (Site 17);
- Post World War II Burial Site (Site 19); and
- Shipping and Receiving Disposal (Site 23).
- Ordnance Area (Site 5);
- Bore Site Gunbutt (Site 8);
- Old Navy Exchange Gas Station (Site 15);
- New Runway Rubble Disposal Area (Site 25);
- Off-site Rubble Disposal Area (Site 26); and
- Diesel Fuel Spill Site (Site 27).
The Nevada State Health Division (NSHD) has been investigating contributing factors that may be associated with a leukemia cluster in the Fallon area that has primarily affected young children. As part of this investigation, NSHD has requested technical assistance from ATSDR in order to identify possible contaminant releases, evaluate environmental data, and conduct appropriate pathway analyses that will help address community concerns related to any possible associations between environmental contaminants and leukemia.
ATSDR conducted a site visit to NASF on April 18, 2001. This site visit was part of a larger ATSDR effort to investigate whether potential exposures from environmental contaminants might be associated with a clustering of leukemia in children living in the Fallon, Nevada, area. During this site visit, ATSDR met with NASF's commander and other NASF personnel and was briefed on specific concerns pertaining to environmental releases at NASF. ATSDR also met with representatives from NASF's environmental office and received a tour of each of the IRP sites. During the course of the site visit, ATSDR collected information about the day to day operations of NASF, noted any past environmental issues or concerns, and gathered data from reports and documents generated from prior investigations.
In August 2001, ATSDR attended a briefing by the new commander at NASF and met with several members from NASF's environmental office. A tour of the station was provided for ATSDR staff who were visiting for the first time. The site visit to NASF was part of a larger effort by ATSDR and other state and federal agencies to gather information and conduct public availability sessions within the community.
ATSDR has been gathering information about environmental releases of contaminants occurring not only at NASF, but throughout all of Churchill County, Nevada. However, this public health assessment (PHA) addresses only those environmental releases that are a result of activities or operations at NASF. The focus of this PHA is to evaluate any contaminants identified at NASF that may pose a potential public health hazard, not just those that may be associated with leukemia. The scope of this evaluation only includes NASF activities that have resulted in contamination at the main station. If warranted, other Navy or Navy-related operations that take place off-site of the main station in the Fallon area are addressed within the community concerns section of this document.
The climate and prevailing wind patterns of a given location affect how contaminants move through the air. Annual climatological summaries for the Fallon area from 1997 to 2001, provided by the National Climatic Data Center (NCDC), indicate that the annual temperatures ranged from a low of 4 degrees Fahrenheit (ºF) to 104ºF. Annual mean minimums for 1997 to 2001 were 37-38ºF. Annual mean highs were 68-70ºF. Annual mean average temperature in the Fallon ranged from 53 to 54ºF. For the same period, annual precipitation ranged from 3.5 to 6.7 inches.
Figure 3 is a wind rose generated from data collected at NAS Fallon's onsite meteorological station between 1991 and 1995. Prevailing wind patterns are clearly from west to east (i.e., the winds blow away from the community toward NASF). Winds rarely blew from NAS Fallon to the community; specifically, southeasterly winds were observed only 3% of the time.
ATSDR examines demographic information to identify the presence of sensitive populations, such as young children and the elderly, in the vicinity of a site. Demographics also provide details on residential history in a particular area, information that helps ATSDR assess time frames of potential human exposure to contaminants. Demographic information for the site and residential areas surrounding NASF is presented in this section.
According to the most recent statistics released by NASF in March 2001, a total of 3,077 people were employed at NASF; including 1,038 active duty military personnel, 1,250 contractors, 542 civil service personnel, and 247 other employees. According to NASF personnel, the average length of assignment of military staff at the station is approximately 36 months. An average of 40,000 total military personnel pass through the various training courses at NASF every year and the average length of stay for these individuals is 14 days (NASF official website October 2001; NASF housing office, Personal Correspondence, May 11, 2001).
There are currently about 50 on-site housing units at NASF that are designated for families. These housing units are in the southern portion of NASF and are referred to as the Fairview Housing area. An additional 213 permanent housing units and 1,148 transient housing units are designated for single (i.e., not married) personnel. These housing units are located in several different parts of the station (NASF housing office, Personal Correspondence, May 11, 2001). There are also approximately 328 military personnel who live in off-site military housing (Desert Winds, Blue Sky, Mountain View, and Sagebrush housing areas) directly west of and adjacent to NASF. As of March 2001, there were 84 children under the age of 18 living on site and 307 children under the age of 18 living in off-site military housing. There is one daycare facility on navy property for use by NASF personnel. Located just west of the NASF Main Gate, the facility accommodates approximately 124 children under the age of 18 (NASF housing office, Personal Correspondence, May 11, 2001).
The city of Fallon is the largest population center in the area, with approximately 7,500 people. Approximately 23, 980 people live in the surrounding unincorporated parts of Churchill County (US Census Bureau 2000). The Fallon Shoshone-Paiute tribe, with approximately 1,300 members, maintains over 8,200 acres of land in the area. The population for both the city of Fallon and the county has been slowly increasing over the last several years (USGS 2001). A small number of residences are located within a one mile radius of NASF, however, the area immediately adjacent to NASF is mostly undeveloped or used for agriculture. During ATSDR's site visit, NASF representatives noted one residence directly east of the station's boundary. Additional information provided by the Navy confirms a total of five residences east of the NASF boundary (Cottle 2002).
NASF Fallon is located in the Lahontan Valley, which is part of the Carson Desert. The Lahontan Valley serves as a sink for surface water runoff from the surrounding mountains and the Carson River. The station is situated in an undeveloped area, midway between the city of Fallon to the northwest, Stillwater Point Reservoir to the northeast, and Carson Lake to the south (Ecology and Environment 1989).
The Carson Desert covers approximately 2,000 square miles and includes a large basin, which is approximately 4,000 feet above sea level, surrounded by mountains. The Stillwater Range and the Lahontan Mountains border the basin on the east; the West Humboldt Range on the north; the Hot Springs and Dead Camel Mountains on the west; and the Desert, White Throne, Blow Sand, Cocoon, and Bunejug Mountains on the south. The mountains range from 4,400 feet to 8,800 feet above sea level (Battelle 2001).
The soil beneath NASF is primarily fine-grained (e.g., clay or silty clay) with lesser amounts of coarser-grained materials (e.g., silty sands, sandy loam). Beneath the top soils are approximately 2,000 feet of sedimentary deposits of various origin. Basalts are present beneath the sedimentary deposits (Dames & Moore 1988). Most of the land surrounding NASF is either open brush or irrigated farmland. Alfalfa is the main irrigated crop in the Lahontan Valley. Non-irrigated land is sparsely vegetated with greasewood, rabbit brush, salt grass, and marsh grasses (USGS 2001). Much of the area immediately surrounding the station is irrigated, and there are several irrigation ditches used to deliver water and drainage canals to remove excess water (ORNL 1992).
Approximately half of all the land area at the main station is leased out for non-military uses. The safety buffer zone surrounding the airfield is leased out to ranchers as part of the Navy's Agricultural Outlease Program. There are 11 parcels of land leased out and some of the lessees grow alfalfa, rye, barley, and corn. Most of the leased land is used for irrigated pasture for cattle. These agricultural parcels, totaling about 3,900 acres, are located in the northwest, northeast, and southeast corners of the station, and off the west end of runway # 7 (Dames & Moore 1988; Cottle 2002).
Surface water enters the Carson Desert from the west via Carson River and the Truckee Canal. Both of these surface water bodies flow into the Lahontan Reservoir (also referred to as Lake Lahontan), a man-made feature that was built as part of the Newlands Irrigation Project in the early 1900s to provide irrigation water to the Carson Desert (Battelle 2000). Water from the Lahontan Reservoir is channeled through a network of irrigation ditches and open drainage canals (drains) that flow toward Carson Sink and Carson Lake, which are the lowest points in the Carson Desert. Carson Sink is a flat salt-encrusted basin, located in the northeastern portion of the desert, that covers approximately 400 square miles. Carson Lake is located in the southeastern part of Carson Desert and occupies approximately 25,000 acres. Approximately 340 miles of man-made ditches provide irrigation water to an estimated 1,500 farm head gates. Approximately 350 miles of drainage ditches route irrigation return flow and shallow groundwater seepage to the Carson Lake and Stillwater Wildlife Management Area (Battelle 2000).
Four primary surface water distribution systems are located at NASF: 1) the L-Line Canal; 2) the Lower Diagonal No. 1 (LD # 1) Drain; 3) the Lower Diagonal (LD) Drain; and 4) the New River Drain north of Wildes Road. All four of these surface water systems converge approximately 2 miles from the station boundary and feed into the Stillwater Point Diversion Drain, eventually draining into the Stillwater National Wildlife Refuge and the Stillwater Reservoir (Ecology & Environment 1989; Cottle 2002).
Some fishing and hunting of waterfowl, game birds, rabbits, coyotes, and deer occurs off site in the Valley, however, fishing and hunting do not occur at NASF. The only on-site surface water features are the irrigation ditches and drainage canals, which become very shallow after the irrigation season. The majority of fish species in the drains are not typically consumed and usually do not survive through the year because of fluctuating water levels.
In preparing this PHA, ATSDR reviewed and evaluated information provided in the referenced documents. Documents prepared for Resource Conservation and Recovery Act (RCRA) and Comprehensive Environmental Response and Liability Act (CERCLA) programs must meet specific standards for adequate quality assurance and quality control measures for chain-of-custody procedures, laboratory procedures, and data reporting. The environmental data presented in this PHA are largely from site characterization, remedial investigation, and groundwater monitoring reports prepared by the U.S. Navy under CERCLA's Installation Restoration Program. Additional reports and information have been provided by USGS and NDEP. The validity of the analyses and conclusions drawn in this document are dependent on the availability and reliability of the referenced information.
ATSDR reviews data from site-related reports and evaluates whether detection limits are set at levels that are protective of public health. ATSDR also notes any inconsistencies or problems with data collection or reporting and evaluates whether the information is adequate to be used for making public health decisions. Based on our evaluation, ATSDR determined that the quality of environmental data available from the site-related documents for NASF is adequate to make public health decisions.
In this section, ATSDR evaluates whether community members have been (past), are (current), or will be (future) exposed to harmful levels of chemicals. Figure 5 describes the conservative exposure evaluation process used by ATSDR.
If exposure was or is possible, ATSDR then considers whether chemicals were or are present at concentrations that might be harmful to people. ATSDR does this by screening the concentrations of contaminants in environmental media (e.g., groundwater or soil) against health-based comparison values (CVs) (Appendix A). CVs are chemical concentrations that health scientists have determined are not likely to cause adverse effects, even when assuming very conservative/worst case exposure scenarios. Because CVs are not thresholds of toxicity, environmental levels that exceed CVs would not necessarily produce adverse health effects. If a chemical is found in the environment at levels exceeding its corresponding CV, ATSDR examines potential exposure variables and the contaminant toxicology. ATSDR emphasizes that a public health hazard exists only if contact with harmful levels of contaminated media occurs with sufficient frequency and duration for harmful effects to occur.
Following the strategy outlined above, ATSDR examined whether human exposure to harmful levels of contaminants via these pathways existed in the past, exists now, or could potentially exist in the future. ATSDR summarizes its evaluation of these exposure pathways in Table 2 and describes it in more detail in the discussion that follows. To acquaint readers with terminology used in this report, a glossary is included in Appendix B.
ATSDR reviewed the environmental data generated from initial environmental assessments and remedial investigations (RIs) of the IRP sites at NASF to determine if there are any associated past, current, or future public health hazards. ATSDR also evaluated other environmental data such as drinking water monitoring data. ATSDR's exposure pathway evaluation will focus on groundwater, surface water and sediment, soil, and air contaminants (Table 2).
- ATSDR concludes that exposures to on-site groundwater at NASF pose no past, current, or future public health hazard. Although fuel-related releases and some solvents have resulted in areas of groundwater contamination at NASF, groundwater beneath the station has never been used as a source of drinking water. According to NASF representatives, there are no current or future plans to use groundwater beneath NASF for drinking water or other domestic (e.g., showering or cooking) purposes.
- ATSDR concludes that exposures to off-site groundwater near NASF pose no past, current, or future public health hazard. The NASF drinking water wells, which are screened in the Fallon basalt aquifer, have not been impacted by site-related contaminants. Since the potable wells are at least two miles northwest of any NASF source areas, are upgradient from NASF, and the depth to the basalt aquifer is more than 500 feet below ground surface, they are not likely to be impacted by contaminated groundwater from NASF.
Groundwater from the shallow alluvial aquifer around NASF is not widely used as a source of potable water due to its high levels of naturally occurring dissolved solids and metals. There are some private wells to the east and south of the station boundary that are screened in the intermediate aquifer and a very small number of private wells to the south of NASF that are screened in the shallow aquifer. These wells are primarily used for irrigation and for livestock. Groundwater samples collected from monitoring wells near the station boundary have not contained any site-related contaminants at levels of health concern.
The Lahontan Valley is part of the Basin and Range geological province. It is a sink for surface water runoff from surrounding mountains and the Carson River. The area is arid and, on average, only receives about 5 inches of rain per year. In order to address the water needs for the Carson Desert area, the U.S. Department of the Interior funded the Newlands Irrigation Project. This project was designed to irrigate crop land in western Nevada using the combined waters of the Truckee and Carson Rivers. Although water is diverted from both the Truckee and Carson Rivers, the large majority of the water is taken from the Carson River. Most of the irrigated water is Water for the Newlands Irrigation Project is diverted from the Truckee River into the Truckee Canal for irrigation (ORNL 1992).
Groundwater in Lahontan Valley is primarily found in four principal aquifer systems: 1) a shallow alluvial aquifer; 2) an intermediate alluvial aquifer; 3) a deep alluvial aquifer; and 4) the Fallon basalt aquifer. The deep alluvial aquifer is not a source of potable water and will not be discussed further. A brief description of each of the three productive aquifers is provided below.
Shallow Alluvial Aquifer: The shallow alluvial aquifer is an unconfined aquifer with the water table forming the upper surface. This aquifer extends approximately 50 feet below ground surface (bgs). Groundwater levels in the shallow alluvial aquifer beneath NASF range between 10 feet bgs in the northwestern portion of the station to 3 feet bgs in the southeastern portion of the station. The groundwater flow in the shallow aquifer is southeastward in the NASF area. Recharge to the shallow aquifer is primarily from infiltration of irrigated water used on fields and leakage of unlined irrigation ditches (Dames & Moore 1988).
Intermediate Alluvial Aquifers: This is a confined aquifer that lies beneath the shallow alluvial aquifer. The intermediate alluvial aquifer begins around 50 feet bgs and extends down to between 500 and 1,000 feet. The strata within this aquifer consist of interbedded deposits of clay, silt, and sand, with occasional stringers of gravel. These deposits are found at depths greater than 50 feet bgs. Groundwater flow direction in the upper part of the aquifer is approximately east-southeasterly (Dames & Moore 1988).
Fallon Basalt Aquifer: The Fallon basalt aquifer consists of buried basalt deposited by volcanic activity from about 1 to 2.5 million years ago. The aquifer is an asymmetrical, mushroom-shaped body that is about 4 miles wide and about 10 miles long from southwest to northeast. The aquifer is surrounded by sediments of the shallow, intermediate, and deep aquifers and is confined over much of its extent, limiting the amount of recharge from the surrounding aquifers and surface water runoff. USGS studies of the Fallon basalt aquifer suggest that at depths greater than 1,000 feet bgs, the basalt aquifer narrows and becomes a very thin column. The Fallon basalt aquifer is surrounded by, and in contact with, all three alluvial aquifers (Dames & Moore 1988;USGS 2001).
Most of the potable drinking water for the Fallon area comes either from the shallow or intermediate alluvial aquifer or the Fallon basalt aquifer. The Fallon basalt aquifer is the sole source of drinking water for NASF and also provides potable water to the city of Fallon and the Fallon Paiute-Shoshone reservation, which is approximately 10 miles northeast of NASF. Most private residences within Churchill County, but outside the Fallon service area, rely on shallow and intermediate alluvial aquifer wells for drinking water. Most wells in the intermediate aquifer are completed at depths of 90 to 120 feet bgs. Water obtained from the shallow aquifer in much of the Lahontan Valley is often not potable due to high levels of naturally occurring dissolved solids and metals (NASF 1994). Surface water is not used as a source of drinking water at NASF or for off-site residential areas (USGS 2001).
On-site Drinking Water Wells: There are no drinking water wells on NASF property and the groundwater underneath the station is not used for any other domestic (e.g., cooking or showering) purposes.
Off-site NASF Wells: NASF obtains its potable water from three drinking water supply wells located off site, approximately 1 mile from the NASF northern boundary and 2.5 miles north of any NASF sources of contamination, near an area referred to as Rattlesnake Hill (Figure 4). The wells are approximately 540 feet deep and are completed in the Fallon basalt aquifer. The three wells combined are capable of yielding between 1,000 and 2,100 gallons per minute. There is one storage tank with a capacity of 1.2 million gallons. The primary water treatment at NASF is chlorination. Additionally, NASF utilizes reverse osmosis filtration units and Glacier dispensing units at some locations on the station to filter metals (e.g., arsenic)(Dames & Moore 1988; NAS-Fallon 1994; Bud Ford, NASF Environmental Office, Personal Communication, October 22, 2001; Clifton Beck, NASF, Comments on Public Comment PHA for NASF, March 20, 2003).
Off-site Public (Municipal) Wells: The city of Fallon maintains four wells that supply water to most of the residents. The groundwater is drawn from wells in the Fallon basalt aquifer that are approximately 600 feet deep. The municipal wells are located near the NASF supply wells. The city has two storage tanks with a combined capacity of 2.8 million gallons. Fallon does not currently have a water treatment plant and the only treatment currently required is chlorination for bacteria. In 1990, the city entered into a Compliance Schedule Agreement with the Nevada State Board of Health to design and implement a treatment system to remove arsenic from the drinking water (Larry White, City of Fallon Water Department, Personal Communication, October 30, 2001).
Off-site Private Wells: The outlying areas in the region are supplied by individual wells which usually tap the shallow or intermediate alluvial aquifers. The closest drinking water wells are approximately 0.2 mile to the east of Site 6 (Defuel Disposal Area), which are downgradient of the shallow aquifer plume. There are five dwellings that each have a private well that has been used for drinking water. In addition to the five private wells to the east of NASF, several domestic wells that draw from the shallow alluvial aquifer are located downgradient of NASF. The closest domestic well is approximately 0.5 mile southeast of the station. These wells are not used for drinking water because of high levels of naturally occurring dissolved solids and mineral content and are used primarily for irrigation and livestock watering (Dames & Moore 1988; Ecology & Environment 1989). Since contaminants have not been detected in samples collected from monitoring wells near the NASF boundary, it is unlikely that the domestic wells used for irrigation or livestock would contain site-related contaminants.
Nature and Extent of Contamination
On-site Groundwater Contamination
Groundwater in the shallow alluvial aquifer beneath NASF has been impacted by releases of chemicals, resulting in several plumes. The main plumes are associated with six contaminated source areas (Figure 6). Groundwater monitoring is routinely conducted at these six primary source areas. Additional monitoring wells have also been installed on site in areas where leaking underground or above ground storage tanks (USTs or ASTs) have been identified or in other locations where groundwater contamination was suspected mostly as a result of small fuel spills. Previous groundwater investigations at NASF (e.g., assessment of intrinsic remediation) indicate that the intermediate aquifer is not impacted by shallow aquifer contamination because there is an upward hydraulic gradient from the intermediate aquifer to the shallow aquifer preventing the downward migration of contaminants (Battelle 2001). The nature and extent of contamination at these six primary areas are described below.
- Crash Crew Training Area (Site 1) -- This area, located in the southern portion of NASF, has been contaminated as a result of fire training activities conducted at the site between the mid 1950s and April 1988. Waste products from the fuel farms and aircraft and vehicle maintenance areas were burned routinely in an earthen pit. The waste liquids were usually stored in two ASTs and transported to the pit via pipes beneath the ground (Battelle 2001). Groundwater at Site 1 is monitored with 28 wells and 9 piezometers. The primary contaminants in the groundwater at this site are volatile organic compounds (VOCs) and total petroleum hydrocarbons (TPHs). Trichloroethylene (TCE) (840 ppb) and benzene (800 ppb) were among the VOCs detected above ATSDR's CVs (Table 3).
- New Fuel Farm (Site 2) -- Site 2 is located in the west-central portion of NASF. The New Fuel Farm was constructed in 1957 to replace the Old Fuel Farm, which was taken out of service in 1963. Site 2 is used to store jet fuel, diesel fuel, and gasoline. As a result of known spills and fuel handling practices (e.g., daily draining of fuel trucks and routine disposal of residual liquids at the bottom of storage tanks), free-phase petroleum has contaminated the soil and groundwater. This site contains a large number of monitoring wells (at least 40), product recovery wells, and piezometers. The first wells were installed in 1986 and wells have been installed as recently as 1995 for the purpose of delineating the extent of contamination and recovering free product.
- Hangar 300 Area (Site 3) -- Site 3 is located in the west-central portion of the station and includes several small former disposal areas in the vicinity of the Hangar 1 facility. The site includes two groundwater plumes: one area is located north of Hangar 1, referred to as the northern plume, and the other area is located south of Hangar 1, referred to as the southern plume. The southern plume is the primary area of focus since the northern plume does not contain significant contamination. Groundwater in the southern plume became contaminated as a result of discarding aircraft and vehicle maintenance wastes onto unpaved ground in three areas: (1) the south disposal area; (2) the ground-support equipment area; and (3) the wells air start area. These areas were used from the 1960s through the 1980s. Some of the wastes that were discarded include jet fuel, hydraulic fluids, lube oil, and solvents (e.g., carbon tetrachloride and TCE).
- Defuel Disposal Area (Site 6) -- Site 6 is located along the eastern boundary of the station, midway between the northern and southern station boundaries. The site was used to dispose fuel which did not meet military specifications and was removed from aircrafts during maintenance operations. Approximately 70,000 gallons of waste fuel are believed to have been disposed directly onto unpaved ground between 1966 and 1972. Twenty monitoring wells and 10 piezometers have been installed at Site 6. One of the wells was installed for the purposes of recovering free product. The most recent groundwater samples were analyzed for VOCs and TPH. Samples collected from previous investigations were also analyzed for metals.
- Old Vehicle Maintenance Shop (Site 14) -- Two separate groundwater plumes have been identified at Site 14. The first plume, referred to as the "northern plume," is located north of E Street near the Old Vehicle Maintenance Shop. Groundwater contamination has resulted from leaks and spills, primarily from two lube pits and two USTs. The lube pits have been filled with soil and the USTs have been removed. A total of 25 monitoring wells and seven piezometers have been installed to characterize the southern plume. The groundwater is primarily contaminated with fuel-derived compounds (e.g., TPHs)(Table 3). Beginning in 1994, NASF began removing free product from two wells (MW-18 and MW-52) (Battelle 2001).
- Old Fuel Farm (Site 16)-- Site 16 is located in the southern portion of the station and served as the main fuel storage and dispensing area from 1943 to 1962. The area is contaminated with various fuels (e.g., jet fuel, diesel, and gasoline) that were used for operations at NASF. These fuels were stored in four large concrete USTs located at the northern end of the site. In 1992, the USTs were destroyed and partially removed. A total of 35 monitoring wells and 10 piezometers have been installed at Site 16. One of the wells primarily serves to recover free product. VOCs, including benzene (130 ppb), 1,2-dichloroethane (54 ppb), and TCE (42 ppb) were detected above ATSDR's CVs (Table 3).
Free-phase product (primarily petroleum with low concentrations of solvents) accumulated on the surface of the water table about 200 feet to the southwest of the former fire training pit. Approximately 880 gallons of free product was removed from the site using a bioslurper system containing 30 extraction wells. The bioslurper system was installed in 1996 and is not currently active due to very low production rates. The wells continue to be monitored and if increased levels of free product are identified, the system may be reactivated (Battelle 2001; ORNL 2001; Brown 2002). Since the completion of the RI, cis-1,2-dichloroethylene (1,2-DCE) (2,500 ppb), a break down product of TCE, has been detected above ATSDR's CV in samples collected from Site 1 (The Environmental Co., Inc. 2001).
Groundwater is routinely analyzed for VOCs and TPHs. Other than benzene (290 ppb), which was detected above ATSDR's CV, and TPHs quantified as diesel (TPH-D), very few fuel constituents were detected in groundwater at the site. Several remedial actions have been implemented at this site to remove free-phase contamination from the subsurface, including: (1) installation of a bioslurper system installed in 1993 until its operation was discontinued in November 2001; (2) periodic removal of product from recovery wells installed in March 1992; and (3) operation of three recovery trenches installed in 1996 (Battelle 2001).
A total of 15 monitoring wells have been installed to characterize the extent of contamination in the southern plume. The most recent samples were analyzed for VOCs and TPH. Samples collected from previous investigations were also analyzed for metals. In April 1999, as part of the intrinsic remediation assessment, TCE (22 ppb) and cis 1,2-DCE (28 ppb) were detected in groundwater above ATSDR's CVs. TCE was detected in monitoring wells as high as 160 ppb in April 1991 (Table 3) (Battelle 2001).
The RI for Site 6 did not recommend remedial action for groundwater. However, because of the proximity to the eastern station boundary, the Navy decided to include the site in the intrinsic remediation assessment (e.g., natural attenuation), which is designed to determine whether intrinsic remediation is suitable to address groundwater contamination (Battelle 2001).
The second plume, referred to as the "southern plume," is located south of E Street, near the Seabee Yard. Fuel-related constituents and some organic solvents (e.g., 1,2-DCA and benzene) have been detected in the groundwater. The primary source of the fuel contamination is likely the Old Vehicle Maintenance Shop (Site 14) and possibly the Old Fuel Farm (Site 16). A total of 17 monitoring wells were installed to characterize the southern plume. There are no current sources of contamination in the area. Soil sampling conducted during the intrinsic remediation assessment did not identify elevated soil contaminants that would result in additional groundwater contamination (Battelle 2001).
Contamination close to the NASF boundary is primarily limited to low concentrations of TPHs. Although most boundary or near-boundary monitoring wells do not contain any contaminants above ATSDR's CVs, TPHs have been detected at two monitoring wells near the eastern and southern boundary of the station. The highest concentration of TPH (86 ppb) identified along the eastern boundary was detected in monitoring well (MW) 46 and the highest concentration of TPH (60 ppb) identified near the southern boundary was detected in MW 31. Recent analyses of selected monitoring wells have not detected VOCs or TPHs (JBR 2000; JBR 2001). Screening values are not available for TPHs, however, the individual components that make up TPHs (e.g., benzene, ethylbenzene, toluene, xylene) are routinely tested for at NASF. None of these contaminants exceeded ATSDR's CVs in the monitoring wells closest to the NASF boundary. Some metals, such as arsenic (3,500 ppb), boron (60,000 ppb), molybdenum (420 ppb), and vanadium (1,300 ppb), were detected above ATSDR's CVs in monitoring wells near the NASF boundary (ORNL 1994; NASF 2001). These metals are naturally occurring and the concentrations are consistent with levels that have been detected in drainage canals and in the shallow aquifer in the Fallon area (USGS 1994; USGS 1997).
Off-site Groundwater Contamination
There are three off-site wells that are used to supply drinking water to NASF. These wells are approximately one mile northwest of the NASF boundary and upgradient of all the contaminant plumes on site. The NASF drinking water wells, which are screened in the Fallon basalt aquifer, have not been impacted by site-related contaminants. It is very unlikely that site-related contaminants could impact these basalt aquifer wells because they are upgradient from NASF and the depth to the basalt aquifer is more than 500 feet (Dames & Moore 1988). Arsenic occurs naturally in the Fallon basalt aquifer and samples collected from the drinking water wells typically exceed EPA's MCL. In January 2001, EPA established a new MCL (10 ppb) for arsenic in drinking water replacing the old standard of 50 ppb. Recent sampling conducted in January 2000 detected arsenic at 140 ppb from one of NASF's supply wells (NASF 2001). There are also four off-site wells used by the city of Fallon to supply water to most residents. These wells are located in close proximity to the NASF wells and are also screened in the basalt aquifer. Recent monitoring tests have not detected any site-related contaminants in these wells.
Evaluation of Potential Public Health Hazards
Groundwater beneath NASF has never been used as a source of drinking water and no plans exist to use the groundwater in the future. The Navy is currently conducting a pilot study to evaluate different groundwater remediation methods. The study includes evaluation of: 1) enhanced in-situ anaerobic bioremediation for treating groundwater contaminated with dissolved chloroethenes (solvents); 2) enhanced in-situ aerobic bioremediation for treating groundwater contaminated with dissolved fuel hydrocarbons; 3) air sparging for removing dissolved chloroethenes and fuel hydrocarbons; and 4) aboveground treatment of pumped groundwater containing dissolved chloroethenes and/or fuel hydrocarbons using air stripping technology. The studies are being conducted at Sites 1, Crash Crew Training Area and Site 14, Old Vehicle Maintenance Shop (southern plume). Construction on the individual treatment systems is complete and studies are anticipated to continue through the end of the year. According to NASF representatives, a planned bioreactor (groundwater treatment facility) study has been moved from the field (full scale) to the laboratory (bench scale). A report on the pilot study is due out late next year (Brown 2002).
Assuming that groundwater is not used in the future, ATSDR concludes that on-site groundwater contamination at NASF do not pose a past, current or future public health hazard.
NASF and city of Fallon drinking water supply -- The public health impact of naturally occurring arsenic will be addressed in future ATSDR public health assessment documents. ATSDR concludes that off-site NASF and city of Fallon municipal wells have not been impacted by site-related contamination and does not pose a past, current of future public health hazard. NASF and the city of Fallon obtain their drinking water from supply wells that are screened in the Fallon basalt aquifer, which is located one mile northwest and upgradient of the station's northern boundary. These are deep wells that are at least 2 miles from any of the known sources of contamination. Groundwater at NASF flows towards the south and southeast, in the opposite direction of the drinking water supply wells.
Based on reviews of drinking water monitoring reports for NASF, containing information dating back to 1996, (March 2001) and the city of Fallon, containing information dating back to 1981, (February 2000), ATSDR did not identify any contaminants, other than naturally occurring arsenic, of potential public health concern. All monitoring results have met state and federal safe drinking water standards for VOCs, semi-volatile organic compounds (SVOCs), and pesticides. The only inorganic compound that has not met state and federal safe drinking water standards is arsenic. Arsenic, which is a naturally occurring contaminant in the Fallon area, has been detected at levels that exceed its CV. A treatment plant designed to remove arsenic is being constructed for the city of Fallon, NASF, and the Fallon Paiute-Shoshone Tribe. It is expected to be in operation by the beginning of 2004. The new treatment plant will sufficiently reduce the levels of arsenic in the drinking water to comply with the new EPA arsenic standard of 10 ppb.
Private drinking water wells -- There are private wells to the east of the station boundary that are screened in the intermediate aquifer. Groundwater from the shallow alluvial aquifer is not generally used as a source of potable water due to high levels of naturally occurring dissolved solids and metals. Since groundwater flows southeast, towards the station's boundary near Site 6, it is possible that contaminants in groundwater could migrate off site in this area in the future. However, NASF has been routinely sampling monitoring wells that are located near the eastern and southern station boundary. So far, only very low levels of TPHs have been detected in the past in these monitoring wells and it does not appear that any site-related contaminants have migrated off site. On-site groundwater plumes on the eastern and southern portions of the station have the potential to migrate off site. However, monitoring wells near the station boundary have not contained any site-related contaminants above ATSDR's CVs. In addition, the on-site groundwater plumes are only in the shallow aquifer and private wells in the area are generally screened in the intermediate aquifer. Groundwater remediation activities are ongoing to reduce on-site contamination at NASF and contaminated groundwater from NASF plumes is not expected to migrate off site at levels that would result in harmful exposures. ATSDR concludes that off-site private wells have not been impacted by site-related contamination at NASF and, therefore, does not pose a past, current or future public health hazard.
- Other than the manmade irrigation ditches and drainage canals, there are no permanent surface water bodies at NASF. No VOCs, SVOCs, polychlorinated biphenyls (PCBs), or pesticides were detected above ATSDR's CVs in samples collected from the drainage canals. Since concentrations of TPHs and metals detected in surface water and sediment within the drainage canals were not at levels of health concern and the potential for human contact with the drainage canals is very limited, ATSDR concludes that exposures to on-site surface water and sediment pose no past, current, or future public health hazard.
The irrigation ditches and drainage canals are the only permanent surface water features at NASF. The L-Line Canal supplies irrigation water to the agricultural fields that are leased out by NASF. The two main drains running through NASF are the LD #1 and the LD Drain. The LD # 1 Drain is about 12 feet wide and 12 feet deep with an average water depth of about 1 foot during low flow in the winter. The LD Drain is about 25 feet wide and 12 feet deep with an average water depth of 2 feet during low flow. In addition to the two main drains, there are several small, unnamed lateral drains. The L-Line Canal, which supplies irrigation water to the station, has not been sampled by NASF because all the water is transported from off site locations. The two main drains running through the station are potential pathways for migration of contaminated groundwater since both of the drainage canals can accumulate water from the shallow alluvial aquifer at certain times of the year. The LD drain is located south (downgradient) of some sources of contamination at NASF. However, groundwater flow is generally to the southeast away from the city of Fallon. The LD #1 drain is located upgradient (north) of any NASF sites that have been identified and would not likely be impacted by site-related contaminants.
According to NASF representatives, surface water samples from NASF are collected on an annual basis and submitted to a NDEP-certified laboratory (Krishnamoorthy 2002). During the RI, investigators evaluating water quality in the two drains, LD #1 Drain and LD Drain, determined that groundwater in the vicinity of the contaminated groundwater plume alternately discharges to and is recharged by the surface water in the LD #1 Drain. In addition, a fuel spill in February 1991 caused extensive contamination in the LD #1 Drain. The spill was cleaned up in March 1991.
Nature and Extent of Contamination
On-Site Surface Water and Sediment Contamination
During the RI, surface water samples were collected from eight locations, four from each drain. The irrigation ditches were not sampled because the water from these ditches is being transported from off site locations onto NASF property. These samples were collected every two weeks from early September through early October 1989. Sediment samples were collected in August 1989 near the center of flow from the drain bottom at each surface water sampling location. Water and bottom sediment samples were analyzed for VOCs, SVOCs, PCBs, metals, pesticides, and TPHs. In addition to the samples collected during the RI, NASF has collected surface water samples annually from five sampling locations along the drainage canals. ATSDR has reviewed the annual surface water sampling data from 1993 through 2001 (Oak Ridge 1994).
The results of surface water analyses during the RI did not show detectable levels of VOCs or SVOCs in any of the samples. Arsenic (268 ppb), boron (7,470 ppb), selenium (60 ppb), and lead (30 ppb) were the only metals that exceeded ATSDR's CVs for drinking water (Table 4). Selenium was only detected in one of the samples and lead was detected in two of the eight surface water samples collected. TPHs were also identified in most of the surface water samples, ranging from 1 to 5 ppm. Specific jet fuel contaminants such as benzene, naphthalene, toluene, ethylene, and xylene were not evaluated during the RI sampling. The routine monitoring results reviewed from 1993 through 2001 showed that all TPHs were below the reported detection limits. The VOCs, bromoform (40 ppb), bromodichloromethane (8.9 ppb), and dibromochloromethane (30 ppb) were detected above ATSDR's CVs.
The results of sediment analyses did not show detectable levels of PCBs or pesticides in sediment. No VOCs or SVOCs were detected above ATSDR's CVs. One jet fuel contaminant, naphthalene (2.1 ppm), was detected at one sampling location, however, it is well below ATSDR's health-based CV. TPHs were detected in all the sediment samples, however, none exceeded NDEP's action level of 100 ppm. Some of the same metals that were elevated in the surface water were also elevated in sediment.
Off-Site Surface Water and Sediment Contamination
The water from the drainage canals eventually flows to either the Stillwater Reservoir and Wildlife Preserve to the northeast or Carson Lake and wetlands area to the south. No samples were collected during NASF investigations in irrigation ditches or drainage canals off site.
Evaluation of Potential Public Health Hazards
Surface water -- Permanent surface water features at NASF are limited to the irrigation ditches and drainage canals. According to NASF representatives, these ditches and canals have not been used for recreational purposes (e.g., swimming, fishing, boating) on site. Access to the drainage canals is restricted to on-site personnel. Any potential exposures to on-site surface water or sediments would have been very infrequent and of short duration. There are no current of future plans to use the drainage canals for recreational activities or to allow access to non-authorized personnel. Low levels of TPHs were identified in the water and sediment samples collected in the drainage canals during the 1994 RI. Since concentrations of TPHs detected in surface water and sediment were low and the potential for human contact with the drainage canals was very limited, ATSDR concludes that exposures to on-site surface water and sediment do not pose a past, current or future public health hazard.
Surface water and sediment-- Some low levels of fuel-related contaminants and metals have been detected in drainage canals on site. Off-site migration of site-related contaminants from the drainage canals in the future will depend, in part, on the successful completion of ongoing remedial activities to reduce groundwater contamination underneath NASF. There are no current plans by NASF to evaluate the potential for pesticides and other contaminants in surface water to migrate off site. In the unlikely event that an individual came in contact with surface water flowing off site, these levels would not be expected to pose a health concern. ATSDR concludes that past, current, and future exposures to off-site surface water and sediment from the base do not pose a public health hazard.
- Soil contamination is limited to a small number of source areas on site. Some source areas are accessible (e.g., not fenced ) to on-site personnel and are a relatively short distance from the family housing area. Therefore, potential exposure pathways cannot be ruled out. However, access to these and other working areas at NASF is restricted and any exposures to soil contaminants by visitors, workers, or on-site personnel would likely be infrequent and of short duration. During a site visit, ATSDR observed that security personnel diligently investigated unauthorized persons and did not allow access working areas without clearance. It is unlikely that children or other unauthorized persons would wander into working areas of NASF without being noticed. As long as current installation access controls and restrictions exist, ATSDR concludes that exposure to soil contaminants at NASF poses no apparent public health hazard.
Surface or subsurface soil samples were collected at each of the IRP site areas. Soil contamination at most of the sites consists of petroleum-hydrocarbon-related compounds (e.g., TPHs) and to a lesser extent solvents. Samples were also analyzed for PCBs at Site 23 where transformers were formerly stored. The nature and extent of soil contamination detected at each of the IRP sites and any corrective measures taken by NASF are summarized in the discussion that follows.
Nature and Extent of Contamination
On-site Soil Contamination
Below is a review of surface soil contamination detected at NASF sites. Refer to Table 1 for a description of each of the IRP site areas.
- Four individual sites
- Crash Crew Training Area (Site 1): The most significant surface soil contamination at this site occurs at the fire pit, which was used to burn flammable liquids. The concentrations of TPH (5,300 ppm) in soil samples collected from the fire pit has exceeded the NDEP action level of 100 ppm in soils. VOCs and SVOCs were detected at concentrations below ATSDR's CVs. The only other soil contamination discovered outside the fire pit area is associated with the contaminated groundwater plume associated with Site 1.
- Hangar 300 Area (Site 3): Soil contamination at this site is mainly confined to small areas and consists of petroleum-hydrocarbon-related compounds and low concentrations of solvents, which were below ATSDR's CVs. None of the soil samples collected contained TPH levels exceeding the NDEP action level of 100 ppm.
- Checkerboard Landfill (Site 20): No site-related contaminants were detected in soil above ATSDR's CVs.
- Road Oiling Area (Site 24): No site-related contaminants were detected in soil above ATSDR's CVs.
The primary soil remediation effort at Site 1 consists of the "biopile." NASF has selected to reduce the levels of TPH and VOC contamination within this biopile through a process of biodegradation remediation. NASF adopted this method shortly after the Navy's contractor tested the effectiveness of the technology. In July 1999, contaminated soil from the fire training pit was collected and placed in a designated area within Site 1. The average TPH and total chlorinated solvent concentrations at the time the "biopile" was formed were approximately 3,200 ppm and 25 ppm respectively. For the first 4 months, samples were collected on a monthly basis. However, since contaminant concentrations have not decreased very rapidly, the sample collection period has been reduced to every 6 months.
The most recent samples (at the time this document was generated) were collected in November 2001 and TPH levels were approximately 600 ppm. This level continues to be above the regulatory goal of 100 ppm set by NDEP. Most of the chlorinated solvents were removed from the pile during the first few months of operation, and were not detected in the October 1999 sampling event. In July 2002, a fence was placed around the biopile and a contract has been approved to remove, treat, and dispose of the contaminated soil at an off site regulated disposal facility (Brown 2002; Chuck Deverin, NASF Environmental Office, Personal Correspondence, January 25, 2002).
- Group I sites
- New Fuel Farm (Site 2): Most of the soil samples have been collected in the northern portion of Site 2. Low levels of TPH contamination were identified and only one soil sample exceeded NDEP's action level of 100 ppm. This was a sample from the weed control area near the fence line that separates Site 1 and Site 2. Low concentrations of pesticides below ATSDR's CVs were also detected in this area.
- Transportation Yard (Site 4): Soil samples were mostly collected around Building 378, which contained a floor drain where vehicle fluids, coolants, and paint wastes were flushed into subsoils beneath the building. TPHs were not detected in these soil samples and no other contaminants were detected above ATSDR's CVs.
- Group II sites (includes the Defuel Disposal Area [Site 6]; Napalm Burn Pit [Site 7]; Receiver Site Landfill [Site 21]; and the Northeast Runway Landfill [Site 22])
- Group III sites (includes the Wastewater Treatment Plant [Site 9] and Southeast Runway Landfill [Site 18])
- Group IV sites
- Gator Compound (Site 10): No site-related soil contamination was detected during the RI.
- Paint Shop (Site 11): No site-related soil contamination was detected during the RI.
- Pest Control Shop (Site 12): Low levels of DDT (0.82 ppm), DDE (0.14 ppm), and DDD (0.13 ppm) were detected in some soil samples. The levels of DDT, DDE, and DDD in all of the soil samples collected were below ATSDR's health-based CVs. One sample was analyzed for petroleum hydrocarbons, but none were detected.
- Boiler Plant Tanks (Site 13): Soil contamination was identified at Site 13 during the removal of the boiler plant USTs. TPHs detected in soil exceeded NDEP's action level of 100 ppm.
- Old Vehicle Maintenance Shop (Site 14): One sample collected during the installation of a monitoring well (MW 18) contained TPHs and VOCs. Benzene (41 ppm) was detected above its CV.
- Old Fuel Farm (Site 16): Some of the soil samples collected from boreholes around the USTs contained petroleum hydrocarbons that exceeded NDEP's action level of 100 ppm. Additional samples collected from excavation pits during the removal of USTs contained TPHs as high as 4,500 ppm. All samples with detectable contamination were collected from subsurface soil. VOCs, SVOCs, and metals were not detected above ATSDR's CVs.
- Hangar 5 (Site 17): No site-related soil contamination was detected at Site 17 above ATSDR's CVs.
- Post-World War II Burial Site (Site 19): Very low levels of petroleum hydrocarbons were detected in one of the soil samples near MW 29. No other site-related contaminants were detected at this site.
- Shipping and Receiving Disposal (Site 23): Although transformers were formerly stored at this location, PCBs were not detected in any of the soil samples. Very low concentrations of DDT (0.10 ppm), DDD (0.02 ppm), and DDE (0.09 ppm) were detected, however, they were below ATSDR's CVs.
No site-related contamination was detected in soil samples collected from the Group II Sites. The Phase II RI could not confirm the presence of the Napalm Burn Pit, which was reportedly located within the Receiver Site Landfill (Site 21). This site was recommended for "no further action" after the RI was completed.
TPH was detected in one soil sample above NDEP's action level of 100 ppm. Other than this one sample, no site-related contaminants were detected in soil. This site was recommended for "no further action" after the RI was completed.
Off-site Soil Contamination
NASF has not collected soil samples in any off site locations.
Evaluation of Potential Public Health Hazards
Soil contamination --NASF is fenced and public access to the station has always been restricted. Generally, source areas (i.e., contaminated soil or disposal areas) contain very low levels of contamination that do not exceed ATSDR's CVs. Most of the soil contamination at NASF comes from jet fuel related spills or leaks from USTs and ASTs. Most source areas are not in close proximity to base residential areas. An exception is the biopile located within Site 1, that contains TPHs and VOCs. However, the biopile was fenced off in July 2002 and is not a public health concern. Any past contact with the biopile or any other source areas and soil contaminants by unauthorized personnel would likely be of short duration. For these reasons, ATSDR concludes that exposure to contaminated soil does not pose a past, current or future public health hazard.
NASF has not collected any soil samples off site. Most IRP areas on site do not contain site-related contaminants that exceed ATSDR's conservative health-based CVs. Therefore, site-related soil contaminants are not expected to be transported off site at levels that would be of health concern. ATSDR concludes that off-site soil contamination from NASF does not pose a public health hazard. Specific issues of soil contamination in the Fallon area will be addressed in future ATSDR evaluations not related to NASF.
- ATSDR evaluated specific air quality issues related to stationary sources at NASF. We started by accessing meteorological data to identify the directions in which emissions most frequently blow. Figure 3 shows the prevailing wind directions measured over a 5-year period at NASF. The figure indicates that winds in this area blow most commonly out of the west, the north, and the south. It is important to note that winds rarely blew from the southeast to the northwest; therefore, emissions from NASF only infrequently blow directly toward the community.
- ATSDR evaluated potential sources of air emissions from stationary sources (e.g., boilers, generators, and painting operations) at NASF. In December 2000, NASF conducted an air quality analysis to evaluate the impacts of most EPA criteria pollutants in the vicinity of the station (i.e., nitrogen oxides [NOx], carbon monoxide [CO], particulate matter [PM]10, and sulfur dioxide [SO2]). The results of NASF's analysis indicated that the criteria pollutants listed above do not exceed national ambient air quality standards (NAAQS). Therefore, ATSDR concludes that exposure to air contaminants from stationary sources at NASF poses no public health hazard.
Some of the stationary emission sources operated by NASF require permitting under Nevada Administrative Code (NAC) regulations. Sources of regulated air pollutants at NASF include boilers, generators, and painting operations. In order to comply with the NAC regulations, NASF is required to complete an environmental evaluation, which includes providing maximum concentration estimates of EPA's criteria pollutants. In order to comply with this requirement, NASF conducted a dispersion modeling analysis for NASF's stationary emission sources (URS 2000). There are no stationary emission sources (e.g., incinerators or open burning/open detonation activities) that result in significant heavy metal or other toxic releases at NASF. Most emissions sources at NASF are non-stationary (e.g., aircraft and military vehicles).
Nature and Extent of Air Contamination
On-site Air Monitoring
According to NASF representatives, ambient or point source air monitoring has not been conducted at NASF in the past and there are no plans to institute a monitoring program in the future. NASF conducted air dispersion modeling to evaluate the impacts of most EPA criteria pollutants (i.e., NO2, CO, PM10, and SO2) released in the NASF area. The modeling was conducted using the U.S. EPA Industrial Source Complex Short Term model, standard EPA methodologies, and a modeling protocol that was reviewed by NDEP's Bureau of Air Quality. NASF's analysis was limited to estimating emissions from on-site stationary sources (e.g., boilers, heaters, generators, painting operations). The dispersion model also included the contribution from ambient background concentrations (URS 2000). The results of the dispersion modeling analysis estimated that none of the EPA criteria pollutants evaluated exceeded the NAAQS.
Off-site Air Monitoring
ATSDR reviewed air monitoring data from EPA's Aerometric Information Retrieval System (AIRS). ATSDR identified limited ambient air monitoring for the Fallon area between 1972 and 2001. Data were available for two air monitoring stations in Fallon, Nevada. One station, located at South Maine Street, operated from 1972 through 1987 and collected data for 24-hour average total suspended particulates (TSP). The other station, located at South Russell Street, operated for 5 months in 1998. Sampling data were collected for 24-hour average PM10 concentrations.
From 1972 through 1987, 24-hour average concentrations of TSP exceeded EPA's NAAQS (260 µg/m3) on four occasions. A total of 743 samples were collected over this period and the maximum TSP concentration was 385 µg/m3 measured in May 1975. During the short time period that PM10 monitoring occurred, none of the samples exceeded EPA's NAAQS. There were a total of 25 samples collected and analyzed for PM10 with the maximum detected value of 71 µg/m3.
Evaluation of Potential Public Health Hazards
On-site and off-site
NASF's air quality analysis results showed that the predicted concentrations of criteria pollutants (i.e., CO, NO2, PM10, SO2) from stationary sources at NASF do not exceed the NAAQS. The model combines both emissions from NASF as well as background concentrations and compares the total with NAAQS. Since the emissions from stationary sources at NASF have not changed significantly since the station began operation, it is very unlikely that air contaminants from these sources would have exceeded EPA's NAAQS in the past. There are no other significant sources of air contaminants at NASF. TSP concentrations exceeded the NAAQS on four occasions during the 15-year monitoring period (1982-1987), however, the TSP concentrations for most of the monitoring period were below EPA's standard. Limited air monitoring data in the Fallon area from EPA's AIRS database showed that PM10 concentrations were well below EPA's regulatory standard.
According to NASF representatives, site-related activities at NASF are not expected to change in the future. There are no plans to construct any facilities on site that would significantly increase the levels of air contaminants emitted from stationary sources. Based on the available information, ATSDR concludes that exposure to air contaminants from stationary sources at NASF do not pose a past, current or future public health hazard.
- ATSDR evaluated the potential for adverse public health effects from exposure to jet fuel and jet engine emission byproducts. As a part of this evaluation, ATSDR examined specific air quality issues related to jet fuel and jet engine emission by-products at NASF. We started by accessing meteorological data to identify the directions in which emissions would most frequently blow. Figure 3 shows the prevailing wind directions measured over a 5-year period at NASF. The figure indicates that winds in this area blow most commonly out of the west, the north, and the south. It is important to note that winds rarely blew from the southeast to the northwest; therefore, emissions from NASF only infrequently blow directly toward the community.
- Screening model analyses of emissions from NASF aircraft found that estimated ambient air concentrations for all pollutants considered were either below health-based comparison values or reasonably consistent with levels routinely measured in small communities and suburban locations across the United States.
- CDC collected biological samples from families of ALL victims and from control families in Fallon. Environmental samples were also collected from the houses of ALL victims and control families in Fallon. Analysis of these samples did not detect levels of volatile organic compounds or semivolatile organic compounds, including jet fuel and emission byproducts components at levels that could represent a public health hazard.
- A toxicological evaluation of jet fuel and emissions byproducts, also suggests that exposure to emissions from airplanes (commercial and military) in the Fallon, NV area is not likely to be responsible for the leukemia reported in the community. The potential exposure of members of the Fallon community to jet fuel and emission byproducts is not expected to be sufficient to result in non-cancer public health effects.
Jet fuels are one of the primary fuels for turbine engines worldwide and are the most widely available aviation fuels. Commercial illuminating kerosene was the fuel chosen for early jet engines because of its availability compared to gasoline during wartime. As a result, the development of commercial jet aircraft following WWII centered primarily on the use of kerosene-type fuels. Thus, many commercial jet fuels today have basically the same composition as kerosene, but are under more stringent specifications than those for kerosene (Irwin 1997). Jet Propulsion Fuel 8 (JP-8) is basically the same as jet fuel used by the commercial airline industry (i.e. Jet A), except for performance enhancing additives. JP-8 has been used by the militaries of some North Atlantic Treaty Organization (NATO) countries since 1972 and since 1992-1996 by the US Air Force, the US Army and the Japanese Self-Defense Forces.
Approximately 60 billion gallons of JP-8 (F-34 international designation) and the commercial jet equivalents Jet A (domestic flights) and Jet A-1 (international flights) are used internationally on an annual basis, with approximately half being used in the US (Ritchie et al. 2001a).
Jet fuel (e.g., JP-8 and Jet A) is mixture of many chemicals, with the primary component being kerosene (>98%). Most petroleum products are made from crude oil. Crude oil contains primarily hydrocarbon compounds linked in chains of different carbon lengths. Gasoline is a blend of compounds with shorter carbon chains. Kerosene is a blend of the middle distillate or medium carbon chain compounds. Diesel fuel and home heating fuel contain longer carbon chain compounds. Gasoline typically contains more benzene and benzene-containing compounds than kerosene and diesel fuel. Kerosene normally has a boiling range well above the boiling-point of benzene; accordingly, the benzene content of JP-8 is usually below 0.02%. In the United States, gasoline typically contains less than 1% benzene by volume, but in other countries the benzene concentration may be as high as 5% (ATSDR 2000).
Nature and Extent of Contamination
Exposure Considerations - Jet Engine Emissions
A critical first step in this evaluation is to determine the likelihood that exposures are or can occur to sufficient amounts of the contaminants to present a possible public health hazard. IN this case, airborne contaminants must be reaching the community of Fallon for a possible hazard to exist. Figure 3 is a wind rose generated from data collected at NAS Fallon's onsite meteorological station between 1991 and 1995. Prevailing wind patterns are clearly from west to east (i.e., the winds blow away from the community toward NASF). Winds rarely blew from NAS Fallon to the community; specifically, southeasterly winds were observed only 3% of the time. Based on this information, it is apparent that airborne contaminants would only seldom be able to reach the community.
The second step in ATSDR's evaluation was to conduct a screening model to in order to understand the possible extent of emissions for aircraft at NASF, ATSDR conducted a screening analysis of inhalation exposures to contaminants in aircraft emissions from NASF. The analysis was based on modeling of emissions and dispersion. The analysis was also based largely on data from aircraft engine testing conducted by the Navy's Aircraft Environmental Support Office. These data were found to be generally consistent with emission factors adopted by the Federal Aviation Administration (FAA) and used in ATSDR's previous evaluation of aircraft emissions from Kelly Air Force Base.
In cases such as this where actual data do not exist, models are the only tools available to evaluate the nature and extent of contamination. ATSDR emphasizes that models are only capable of estimating exposure concentrations, based on a scientific understanding of how chemicals move in the environment. All models, however, have assumptions and uncertainties and may or may not accurately represent actual conditions.
Aircraft emissions from an airport or military base are determined by many factors, such as the amount of aircraft operations, the aircraft engine types, the fuel burned, and the durations that aircraft operate in different engine modes. Multiple approaches have been used to estimate aircraft emissions for different scenarios. These approaches all focus on characterizing the aircraft emissions that occur while aircraft operate on the ground and during takeoff and landing; they do not characterize emissions while aircraft operate aloft. Appendix C provides a brief summary of the approaches used.
Aircraft activity and the resulting ground level emissions are defined by the landing and takeoff cycle (LTO). The LTO cycle operation modes are defined by standard power settings for aircraft. An LTO cycle is comprised of five components: approach, taxi/idle-in, taxi/idle-out, takeoff, and climb out (EPA, 1999). Generally, volatile organic compound emissions rates are highest when engines are operating at low power, such as when idling or taxiing. Taxi/idle time depends on airport specific operational procedures, and would generally be less at a military airbase.
In a U.S. Navy report (2000), hazardous pollutants from aircraft engine test cells were estimated. It was reported that approximately 94% of the total hazardous air pollutants emitted during a typical LTO were formed during engine idle modes, which represented approximately 10% of the total fuel used during the engine test, but this mode accounted for most of the time in the LTO cycle.
Because aircraft emissions are highly dependent on the number of aircraft operations, types of aircrafts, and fuels used, ATSDR reviewed available information on aircraft activity at NASF. (Rogers, 2001). The number of sorties at NASF ranged from 38,500 in 1998 to 41,200 in 2001. The number of aircraft operations for the same time period ranged from 202,000 to 244,000. NASF considers the following different activities as individual "operations": landing, takeoff, and entering into restricted air space. A "sortie," on the other hand, is essentially every time an aircraft leaves and returns to the base. Therefore, a plane that takes off from NAS Fallon, enters restricted air spaces three separate times, and lands at NAS Fallon is considered a single sortie, with five operations. Emissions estimates are based on the number of sorties, which best reflect the activities that contribute to overall emissions.(1) Specifically, emissions are calculated assuming 41,200 sorties occur per year--the highest aircraft activity rate from the available data. According to base personnel, data on the number of sorties from years prior to 1998 are not available (Rogers, 2001).
Base personnel also communicated the percentage of aircraft types found at NAS Fallon (Rogers, 2001). The number of sorties per aircraft type was estimated by multiplying the percent of total aircraft by the total number of sorties per year. According to this approach, the estimated numbers of sorties per aircraft type shows that the largest number were by F/A18, with 18,450 sorties, followed F-14s, with 6,180 sorties and F-5s with 4,120. Appendix C provides detailed information on the number of sorties by aircraft type as well as a detailed explanation of the modeling procedures used.
Table 5 presents the estimates of the highest annual average air concentrations that result from aircraft emissions at NASF. Estimates were made for the 11 hazardous air pollutants most frequently detected in aircraft emissions, and are based entirely on emissions data for F/A-18 aircraft operating on JP-8 fuel. This aircraft type accounts for the largest number of aircraft at the base. Multiple data analyses show that the aircraft emissions are dominated by contributions from aircraft idling.
A crucial step in the assessment methodology is evaluating the public health implications of exposure to any contaminants identified as requiring further evaluation. For these contaminants, ATSDR puts the public health implications of exposure into perspective by considering site-specific exposure conditions and interpreting toxicologic and epidemiologic studies published in the scientific literature. Thus, this step is a state-of-the-science review of what the exposure levels mean in a public health context.
Of the 11 chemicals considered, only acrolein, benzene, and formaldehyde had estimated air concentrations higher than health-based comparison values, but by relatively small margins (a factor of 5 or less). It is important to note that ambient (i.e., nationwide air concentrations of these three chemicals are consistently higher than the most conservative health-based comparison values at locations throughout the United States, and the predicted levels for NASF fall within the range, or below the range, of levels routinely measured in small communities around the country. Two studies were conducted a commercial airports that provide a perspective on the levels of emissions and the potential public health effects for these emissions.
A 1993 EPA study of the cancer risks attributed to air pollution in Southwest Chicago reported that Chicago's Midway Airport (approximately 800,000 LTO/year) was in the top five pollutant source contributors. Road vehicle emissions were the number one contributor, with emissions from Chicago's Midway Airport ranking number five. In general, this means that in combination, cars, trucks, buses and trains are the major contributors of carcinogens in Southwest Chicago (approximately 25% of the estimated cancer risk). Chicago's Midway Airport represented approximately 10% of the estimated cancer risk with road vehicles representing 25% (EPA, 1993).
The Illinois EPA (IEPA, 2002) recently reported that emissions from Chicago O'Hare International Airport (one of the world's busiest airports) have an impact on air quality in adjacent communities, but that the impact did not result in levels higher than those found in a typical urban environment (IEPA, 2002).
Most of the published hypothetical cancer risks associated with airports have been based on extrapolated probabilities for exposure to known carcinogens emitted (measured or estimated) from airplanes. Two studies investigated the cancer incidence of communities near airports. The Illinois Department of Pubic Health (2001) examined actual cancer incidence observed in communities near Chicago's O'Hare and Midway airports, and the Washington State Department of Health (1999) similarly investigated Seattle's SeaTac airport. Both studies found no evidence to substantiate a clear and observable elevation of cancer cases among communities residing close to airports.
One would expect air concentrations of airplane and vehicle emissions to be greater near these airports as compared to the Fallon, NV area. The results of these epidemiologic studies suggest that leukemia and other cancer rates associated with airplane emissions would not be elevated in the areas adjacent to the NASF.
CDC Biological and Environmental Sampling Analyses
According to information forwarded to ATSDR from CDC's National Center for Environmental Health, environmental samples were collected from the homes of both the families of the leukemia victims and from control families living in the Fallon area. Environmental media sampled included; indoor air, indoor dust, water from taps, and outdoor surface soil. CDC also collected blood samples from the families of leukemia victims and the control families. According to the preliminary results made available by CDC, these samples did not detect levels of VOCs or SVOCs that would indicate the presence of jet fuel constituents or emission byproducts at levels that would pose a public health hazard (CDC 2002a, 2002b). These results provide further evidence that jet fuel and jet engine emissions are not the likely cause of the leukemia cluster.
Toxicological Evaluation Considerations - Jet Fuel
The general population can be exposed to jet fuel (JP-8 and Jet A) vapors and emissions in the air. EPA has conducted air quality studies near several commercial airports and in certain cities. The EPA (1993) reported that aircraft engines are major source contributors for several volatile organic compounds (1,3-butadiene, formaldehyde, and benzene) and polycyclic organic compounds/particulate matter.
People living near airports or military air bases may also be exposed to higher levels of jet fuel vapors than the general population. People are exposed to many of the same jet fuel chemicals at gasoline stations, in their garage, while using lawn mowers and other gasoline-powered tools, and near areas with vehicle traffic. Additionally, some people use kerosene heaters during cold weather seasons, which would also result in exposure to the same chemicals present in jet fuel chemicals. People working in military and commercial jet fuel industries, where jet fuels are used, may be exposed to higher levels than the general population.
A chemical comparison of jet fuels and gasoline indicates that gasoline has a much higher benzene content (see Table 1 of Appendix D). Additionally, the difference between military and commercial jet fuel is in the performance enhancing additives. Some of the additives are formulated with hydrocarbons found in fuel (e.g., ethylbenzene and xylene), but none of the additives are considered leukemogenic (i.e., capable of causing leukemia). In general, it appears that as a source of air pollution in urban areas, motor vehicle emissions contribute more volatile organic compounds (including benzene, 1,3-butadiene and formaldehyde) than jet engine emissions. Exposure to benzene occurs during vehicle refueling. However, the exposure level can vary greatly depending on the environmental conditions and filling procedure. Exposure concentrations for benzene during vehicle refueling have been reported to range from approximately 1.5 ppb to 1.3 ppm (Smith, 1999).
Ambient concentrations of benzene in air in the United States range from 2 to 19 ug/m3, with higher levels in urban areas (Wallace, 1996). Because approximately 85% of atmospheric benzene is from mobile sources, such as motor vehicles or airplanes, higher concentrations are often detected inside motor vehicles and adjacent to major roadways (Egeghy, 2000). Egeghy et al. (2000) indicated that benzene concentrations can be 3-8 times higher inside vehicles than in ambient air and that the mean concentration of benzene in breath before refueling was 8.6 ug/m3. The mean level of benzene in breath immediately after refueling was 160 ug/m3. Interestingly, the reported background levels of benzene in breath of nonsmokers ranged from 0.8 to 5.3 ug/m3. Based on the screening model used for this evaluation, ATSDR is estimating a level, for the nearest offsite receptor, of benzene of 0.222 ug/m3. This level is not excessive when compared with the levels noted above.
Emissions from vehicles and airplanes contain volatile organic compounds, including 1,3-butadiene and formaldehyde. The DHHS has determined that 1,3-butadiene is a human carcinogen and formaldehyde is a probable human carcinogen. Studies in animals, as low as 6.25 ppm, have shown that 1,3-butadiene is carcinogenic in mice and rats at multiple organ sites (EPA 1998). Human epidemiologic studies have reported an association between 1,3-butadiene exposure and lymphatic leukemia in styrene-butadiene rubber workers. It's important to note that there is a lack of quantitative exposure data in the monomer plant workers and the polymer plant workers exposure data is limited but suggest that concentrations greater than 1 ppm for years are necessary to increase the risk of cancer in workers. Ambient air levels of 1,3-butadiene in urban and suburban locations ranged from 0.10 to 0.46 ppb while levels in smoke-filled bars ranged from 1.2 to 8.4 ppb (EPA 1998). The modeled annual average air concentration for 1,3-butadiene from aircraft emissions at Naval Air Station Fallon was estimated to be 0.3 ppb (see Table 5 of Appendix C). Formaldehyde has been shown to cause nasal cancer in animals. Excess mortality from leukemia and brain cancer was generally not seen among industrial workers, which suggests that the excess for these cancers among workers is due to something other than formaldehyde.
Evaluation of Potential Public Health Hazards
A principal part of the environmental pathways evaluation for jet fuel and engine emission byproducts involves a determination of how likely it would be for these contaminants to migrate via air from NASF to the community. Meteorological data for NASF indicates that predominant wind direction is from west to east, from the community toward NASF. Screening models predict that the levels of contamination generated are not sufficient to present a public health hazard, even if wind patterns were to allow contaminants to migrate from NASF to the community. CDC analysis of environmental and biological samples collected from the community do not indicate the presence of sufficient levels of jet fuel constituents or emission byproducts to present a likely public health hazard.
Finally the results of the toxicological evaluation do not suggest that jet fuel or emission byproducts are likely to present a public health hazard in Fallon. The majority of leukemia cases (15 of 16 cases) in Fallon, NV are the acute lymphocytic leukemia (ALL) type. Since benzene-related leukemia is predominantly of the acute myelogenous leukemia (AML) type, this would suggest that these leukemias resulted from something other than exposure to benzene. The most common leukemia associated with benzene exposure is AML rather than ALL. Modeled concentrations of benzene and 1,3-butadiene from NASF in the Fallon area are below levels that increase the risk of cancer, including ALL. A review of the chemical composition of jet fuel (JP-8 and Jet A) found no other compounds, including additives, that have been shown to cause leukemia.
Based on our review, it appears that exposure to emissions from airplanes (commercial and military) in the Fallon, NV area is not likely responsible for the leukemia reported in the community. The potential exposure by members of the Fallon community to jet fuel and emission byproducts is not expected to be sufficient to result in non-cancer public health effects.
1 This approach essentially assumes that "touch-and-go" operations do not contribute to the overall emissions. ATSDR has no data on how many of these operations occur during a year. However, the idle mode of aircraft engines is associated with the largest portion of aircraft emissions. Since "touch-and-go" operations presumably do not involve idle engine modes, neglecting these operations is expected to have only marginal impacts on the estimated emission rates.