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HEALTH CONSULATION

Evaluation of Polychlorinated Biphenyl Residues in Residential Soils Along Evans Road

FORT MONMOUTH, EVANS AREA
(a/k/a FORT MONMOUTH-EVANS #1)
WALL TOWNSHIP, MONMOUTH COUNTY, NEW JERSEY


SUMMARY

Fort Monmouth is located in the central-eastern portion of New Jersey in Monmouth County. Fort Monmouth houses the headquarters of the Army Communications and Electronics Command. The installation includes the Main Post, Charles Wood area, and the Evans Area. The Evans Area was formerly used primarily for research and development, but is currently being closed under the Army Base Realignment and Closure (BRAC) Program. During Army operations at the Evans Area, polychlorinated biphenyls (PCB) used as insulating fluid in electrical equipment were spilled onto surface soils.

The Evans Area is surrounded by a mix of residential and commercial development. Inadequate storm water collection systems on the Evans Area resulted in runoff and flooding of neighboring residential properties along Evans Road. PCB residues bound to the soil particles were deposited in residential yards by the flooding.

Residents of Evans Road have expressed health concerns related to PCB exposure and are fearful for the health of their families. Some residents are afraid to use their yards for recreation and gardening, are concerned that PCBs may cause birth defects and wonder if cancers in the community could possibly be related to PCB contamination of their properties.

In August 2001, the Army Center for Health Promotion and Preventative Medicine (CHPPM) and the BRAC Environmental Coordinator (BEC) for Fort Monmouth requested ATSDR's assistance in evaluating the health impacts of PCB contaminated soil that migrated from Camp Evans onto residential areas along Evans Road.

As an independent federal public health agency, the purpose of ATSDR's involvement is to determine if and how people may be exposed to PCB from contaminated soil, what the public health impact of any exposure might be and what actions are appropriate to protect public health. ATSDR has toured the Fort Monmouth Evans Area, observed impacted residential lots along Evans Road and reviewed environmental sampling data. ATSDR provided input to the Army on soil sampling locations and dust monitoring and control measures. Additionally, ATSDR attended public meetings and held an availability session to collect and respond to community health concerns surrounding soil contamination along Evans Road.

ATSDR evaluated how people might come into contact with contaminated soil and estimated potential PCB exposure. ATSDR concluded that contaminated soils in residential properties along Evans Road do not present a health hazard to adults or children. Exposures are infrequent and, even under worst-case conditions, too low to result in adverse health effects.

Contaminated soil has been removed on Army property adjacent to the fence line and several residential properties. The Army is currently planning to remediate contaminated soils at an additional six residential properties. The Army took additional soil samples along Evans Road, Diana Road, Squirrel Road and Shore Drive. Preliminary sampling results indicate no PCB concentrations exceed soil standards beyond the Evans Road area. ATSDR will review additional soil sampling data when they become available.


BACKGROUND AND STATEMENT OF ISSUES

Site location and description

Fort Monmouth is located in the central-eastern portion of New Jersey in Monmouth County, approximately 45 miles south of New York City and 70 miles northeast of Philadelphia (Figure 1). The Evans Area (also referred to as Camp Evans) is approximately 10 miles south of the main post, in Wall Township, Monmouth County, New Jersey. Camp Evans includes approximately 219 acres divided into two adjacent areas.

Fort Monmouth houses the headquarters of the Army Communications and Electronics Command. The installation includes the Main Post, Charles Wood Area, and the Evans Area. Camp Evans was used primarily for research and development, but is currently being closed under the Army Base Realignment and Closure (BRAC) Program. In July 1993, the BRAC Commission recommended the realignment and closure of the Evans Area. The realignment involves closing the entire Evans Area (219 acres). Fort Monmouth has been divided into 10 parcels of land to accelerate the realignment and closure process (1, 4) .

Environmental studies identified 37 sites in the Main Post, Charles Wood, and Evans Areas. The prominent site types include landfills, underground storage tanks (UST), hazardous waste storage areas, polychlorinated biphenyl (PCB) spill areas, asbestos areas, and radiological storage and spill areas. Primary contaminants released to groundwater and soil include petroleum hydrocarbons, PCB and heavy metals. All PCB and PCB-contaminated electrical equipment has been removed from the Evans Area (2).

Surrounding community

The Evans Area is surrounded by a mix of residential and commercial development. To the northeast, the installation borders the Shark River. The area of Wall Township adjacent to the Evans Area is characterized by older residential development on relatively small lots. These sixteen residential lots along Evans Road are approximately 100' x 100'. Homes were constructed approximately in the late 1960s to 1970s. The backyards are around 30'- 40' from the dwellings to the fence line. The back yards are covered by grass with occasional areas of bare soil. Several have pools and gardens. Some have playground equipment and toys, indicating the presence of small children. An informal survey of the population along Evans Road reveals approximately 30 residents, ranging in age from young children to senior citizens. Some residents have lived along Evans Road for more than 30 years (3).

Surface drainage and contaminant transport off of the Evans Area

The topography of the Evans Area ranges from approximately 80 feet above mean sea level (MSL) in the southern portion of the site to 2 feet above MSL along Shark River. The central portion of the Evans Area is relatively flat with an average elevation ranging from 70 to 80 feet above MSL. Laurel Gully Brook divides the Evans subpost. There is a relatively steep grade behind the residential properties down to Shark River along the northeast boundary of the Evan Area (1).

Inadequate storm water collection systems on post resulted in runoff and flooding of neighboring residential properties along Evans Road. PCB residues bound to the soil particles were deposited in residential yards abutting the Evans Area property by the flooding. Additionally, contaminated soils were carried off site and deposited in depression areas where water accumulated and along the paths where water flows along Evans Road. The Army attempted to block the runoff by building a retaining wall along the eastern fence line, however this was inadequate to restrict flow so flooding of neighboring properties continued. The wall was extended and height increased. Modifications appear to be preventing flooding during heavy rainfall.

In the early 1990s, PCB-containing insulating fluid was sprayed onto the ground and adjacent residential property on Evans Road when electrical equipment in a substation along the eastern fence line failed (1).

Discovery of contamination beyond site boundaries

There have been several PCB cleanup projects undertaken at Evans Area. In Fall 2000 during a sewer removal project, the Army discovered PCB levels above the New Jersey Department of Environmental Protection (NJDEP) residential soil standards of 0.49 mg/kg near a building on Army property along the eastern fence line. The homeowner was contacted as a courtesy because the Army needed to expand their sampling efforts to the Army property that extended 4 feet beyond the fence line into the back yard of the homeowner. The Army sampled the government property and sampling results were reviewed by the NJDEP and U.S. Environmental Protection Agency (USEPA). Sampling revealed no PCB above the state residential soil standards beyond the fence line which seemed to indicate that contamination had not spread far beyond Evans Area. Therefore, the Army decided not to conduct further sampling on the homeowner's property (4).

Further on post soil sampling at two dozen electrical transformer pad sites in March 2001 revealed PCB levels above state residential standards near the Evans Area substation and at five other transformer pads. The Army contracted to have more extensive sampling done at those six sites, as well as two neighboring properties adjacent to the substation. That sampling began in July 2001 (1).

Soil sampling in residential lots along Evans Road

Results of sampling within the Evans Area received the end of July 2001 indicated that the substation contamination was more widespread than anticipated. Five additional homeowners along Evans Road affected by this discovery were notified and arrangements made to sample soil on their properties. Soil samples were taken at a depth of 0-6 inches below ground surface. The samples were analyzed by the Fort Monmouth Environmental Laboratory, which follows US Environmental Protection Agency-approved analytical methods and is certified by the New Jersey Department of Environmental Protection (Cert.# 13461) (1).

Between July 2001 and December 2002, the Army sampled a total of 16 residential properties along Evans Road. Overlying turf was removed and soil samples were taken at a depth of 0-6 inches, 2 feet and 3 feet below ground surface. Sampling areas were chosen to define the depth and extent of contamination to assist in developing a removal plan. Based upon ATSDR input, additional samples were taken in areas where people may come into contact with soil, such as areas of bare soil and under playground equipment.

PCB contamination appears primarily restricted to surface soils 0-6 inches in depth. The maximum detected concentration of 6.9 mg/kg was along the fence line of residential lot 4. The average concentration of PCB in the soil at each property was below 0.5 mg/kg. Soil sampling results from all residential properties along Evans Road are presented in Table 1.

Mg/Kg, or milligram per kilogram, is a unit of concentration.  For soil contaminated with PCB, mg/kg means milligrams of PCB per kilogram of soil.  A kilogram is approximately 2.2 pounds. One million milligrams equals one kilogram.  
Sometimes, mg/kg is expressed as a part per million, or ppm.  One ppm is analogous to one inch in 16 miles.The Army took additional soil samples along Evans Road, Diana Road, Squirrel Road and Shore Drive down gradient from the Evans Road properties. Preliminary sampling results indicate no PCB concentrations exceed NJDEP residential soil standards beyond the Evans Road Area. The Army plans to limit further soil sampling to investigating three lots on the East side of Evans Road (4). ATSDR will review additional soil sampling data when it becomes available.

Remedial action at residential properties along Evans Road

Since several sampling locations revealed PCB concentrations exceeding the NJDEP residential soil standard of 0.49 mg/kg, the Army is required to remove contaminated soil exceeding this standard. Contaminated soil on Army property adjacent to the fence line and several residential properties has been removed (Figure 2). The Army is currently planning to remediate contaminated soils at an additional six residential properties. A comprehensive Site Assessment Summary Report, Decision Document and Remedial Action Work plan is currently available for a 30-day public comment period (April 31st to May 30th). Once the NJDEP concurs with the work plan the remedial work will be contracted and completed.

Table 1. PCB concentrations in residential surface soils (0-6"depth).1

Residential Lot #

Detects/# of samples

Range of detected samples
(mg PCB/kg soil)

Average concentration2
(mg PCB/kg soil)

1 21/49 ND - 0.885 0.093
2 14/20 ND - 0.742 0.173
3 42/48 ND - 1.545 0.181
4 59/73 ND - 6.909 0.421
5 41/76 ND - 3.768 0.293
6 63/72 ND - 1.488 0.328
7 26/69 ND - 2.307 0.176
8 12/56 ND - 0.815 0.032
9 0/33 ND 0.011
10 9/39 ND - 0.760 0.080
11 24/62 ND - 2.992 0.149
12 11/44 ND - 0.287 0.040
14-16 8/37 ND - 0.282 0.038
17 0/11 ND 0.025
18 15/49 ND - 0.570 0.062
19 17/47 ND - 0.613 0.072

1. Data was compiled from individual property sampling reports and summary tables provided to ATSDR.
2. Non-detect (ND) values were included in calculating averages as ½ the detection limit.


DISCUSSION

What are PCBs?

 PCB exposure in the general environment: People can be exposed to PCBs from swallowing contaminated food or soil, breathing dust or air containing PCBs, drinking contaminated water or absorbing PCBs through the skin. - For most people who don't work with PCBs, exposure occurs primarily through ingesting fish, meats and milk containing tiny amounts of PCB residues. - Most people in industrialized countries have minute amounts of PCB stored in their adipose (fat) tissue.  These background levels of PCBs are harmless. Over time, our bodies slowly eliminate them. Since PCBs were banned in the late 1970s, levels in the environment, animal foods and human bodies have been slowly declining.PCBs are mixtures of up to 209 individual polychlorinated biphenyl compounds (called congeners). No natural sources of PCBs are known to exist. PCBs are either oily liquids or solids, colorless to light yellow in color, with no known smell or taste. Some PCBs can be present in the air as a vapor. Many commercial PCB mixtures are known in the United States by the trade name Aroclor. PCBs have been used as coolants and lubricants in transformers, capacitors, and other electrical equipment because they do not burn easily and are good insulators. These properties are the reason they were used widely in the electrical transformer manufacturing industry until PCBs were banned in 1977 (5).

Use of PCBs and disposal of PCB wastes lead to releases of PCBs in the environment, mostly to surface soils. The fate of PCBs in the environment depends on the environmental medium (e.g., air, soil, or water) that is contaminated. PCBs usually bind to soil and persist in the soil for many years. This is true for most PCB congeners that contain high amounts of chlorine such as the type released at the Evans Area. PCBs with lower amounts of chlorine can volatilize (evaporate) from contaminated soil into the air. Since the PCBs in soil at the Evans Area are weathered (old spill) most if not all of the volatile portion would be gone, and no one would be expected to be exposed from breathing PCB volatiles.

What are health concerns of exposure?

PCBs have been associated with several noncancerous health effects in animals, including liver, thyroid, dermal and ocular changes, immunological alterations, neurodevelopmental changes, reduced birth weight, and reproductive effects (5, 6-14). Typically, effects were seen at exposures much higher than would be expected from the concentrations in soil along Evans Road.

Studies attempting to show the same health effects in humans that have been observed in animals have generally been inconclusive. Studies of PCB-exposed workers are inherently the most valuable. Exposures to PCBs among workers in some occupations such as manufacture and testing of electrical equipment were very high, and some study populations contain workers with job-related exposures of 20 years or more. Both the magnitude and duration of exposure provides the best opportunity to clearly observe which kinds of effects might reasonably be attributable to PCBs. The exposures to workers in these studies are much higher than those that would be experienced by individuals exposed to PCBs in contaminated soils along Evans Road (see discussion below) .

Studies of PCB-exposed populations collectively suggest that the primary adverse health effect attributable to PCB exposure are dermal (skin): chloracne (a severe form of cystic acne), pigmentation changes and eye irritation (15). These dermal effects were also seen in populations that consumed PCB-contaminated rice oil (5, 15, 16). Although controversial, some human studies have found associations between PCB exposure and neurobehavioral effects in children, particularly in infants exposed during gestation in mothers who consumed contaminated fish (5). In spite of the variety of adverse effects seen in PCB-exposed laboratory animals, clearly demonstrable adverse effects appear to be generally absent in PCB-exposed humans.

ATSDR's chronic Minimal Risk Level (MRL) for PCBs (0.00002 mg/kg/day) is based on the lowest effect level identified in the scientific literature, i.e., a lowest observed effect level (LOAEL) of 0.005 mg/kg/day for decreased antibody levels in Rhesus monkeys treated daily for 55 months with Aroclor 1254 in a glycerol/corn oil mixture (5-7). This exposure regimen lead to PCB levels of about 5 ppm in adipose (fat) tissue of these monkeys. Similar doses for 37 months induced adverse skin effects in adult monkeys as well as their offspring (5, 8, 9). However, humans with adipose tissue levels up to 100 ppm who may have been occupationally exposed daily to 0.070- 0.140 mg/kg/day (14-28 times the Rhesus monkey LOAEL and 3500-7,000 times ATSDR's MRL) for months to years showed no evidence of impaired health (16). It would appear, therefore, that humans are less sensitive than subhuman primates are to various adverse effects of PCBs (16).

PCBs are known to cause cancer in animals (5). However, the evidence that PCBs cause cancer in humans is not as clear. The potential for PCBs to cause cancer in humans has been investigated through human studies that have examined both occupational and environmental exposures. Some studies investigating exposures to PCBs in the work place (usually at much higher levels than what is found in the environment) have been associated with liver, biliary tract, intestinal, and skin cancer while others have found no statistically significant increase in cancer mortality (15-26). Although some of these studies did report a positive association, the limitations in the design of these studies and the inconsistency of results from one population to another make it difficult to ascertain whether the observed effects were causally related to PCB exposure.

In contrast to human studies, there is stronger evidence that PCBs cause liver and thyroid cancer in animals (27-32). Based on sufficient evidence of carcinogenicity in animals, PCBs have been classified as reasonably anticipated to be a human carcinogen by the National Toxicology Program (NTP) and as a probable human carcinogen by the U.S. Environmental Protection Agency (EPA). Although the evidence from animal studies clearly show that PCB exposure at high doses cause liver and thyroid tumors, the weight of evidence from human studies does not support a causal association between PCBs and human cancer (16, 33).


EXPOSURE PATHWAY ANALYSIS

What is meant by exposure?

ATSDR's analyses are exposure, or contact, driven. Chemical contaminants disposed or released into the environment have the potential to cause adverse health effects. However, a release does not always result in exposure. People can only be exposed to a contaminant if they come in contact with that contaminant. Exposure may occur by breathing, eating, or drinking a substance containing the contaminant or by skin contact with a substance containing the contaminant.

How does ATSDR determine which exposure situations to evaluate?

ATSDR scientists evaluate site conditions to determine if people could have been (a past scenario), are (a current scenario), or could be (a future scenario) exposed to site-related contaminants. When evaluating exposure pathways, ATSDR identifies whether exposure to contaminated media (soil, water, air, waste, or biota) has occurred, is occurring, or will occur through ingestion, dermal (skin) contact, or inhalation.

If exposure occurred or could be possible, ATSDR scientists then consider whether contamination is present at levels that might affect public health. ATSDR scientists select contaminants for further evaluation by screening them against health-based comparison values. Comparison values represent concentrations of a substance (in water, soil, or air) to which humans may be exposed during a specified period of time without experiencing adverse health effects. Comparison values are developed by ATSDR from scientific literature available on exposure and health effects.

Comparison values are not thresholds for adverse health effects. ATSDR comparison values establish contaminant concentrations many times lower than levels at which no effects were observed in experimental animals or human epidemiologic studies. Although concentrations at or below the relevant comparison value may reasonably be considered safe, exceeding a comparison value does not imply that adverse health effects would be expected. If contaminant concentrations are above comparison values, ATSDR further analyzes exposure variables (for example, duration and frequency), the toxicology of the contaminant, other epidemiology studies, and the weight of evidence for health effects.

The purpose of conservative (i.e., protective) health-based guidelines are to enable health professionals to eliminate substances from further evaluation of potential health hazards. Since maximum concentrations of PCBs at all properties along Evans Road where PCBs were detected exceeded at least one ATSDR comparison value (Table 2), all 16 properties were evaluated further.

In preparing this analysis, ATSDR staff members have used established methodologies for determining how people might be exposed to PCBs and what harmful effects, if any, might result from such exposure. See Appendix A for a detailed discussion of data quality assurance considerations, human exposure pathways analyses, ATSDR's health comparison values, and the methods used to select contaminants of concern.

Table 2. ATSDR Comparison Values for PCBs in soil.

Comparison Value Type of Comparison Value # of residential properties with PCBs above the comparison value
0.06 ppm EMEG - pica child 15 of 16
0.40 ppm CREG 15 of 16
1.0 ppm EMEG - child 5 of 16
10.0 ppm EMEG - adult 0 of 16

EMEG - Environmental Media Evaluation Guideline
CREG - Cancer Risk Evaluation Guideline

If someone is exposed, will they get sick?

Remember, in order for adverse health effects to occur from site-specific contaminants: 1. Contact with contamination must occur., 2. Exposure must be of sufficient magnitude and duration to cause adverse health effects.Exposure does not always result in harmful health effects. The type and severity of health effects that occur in an individual from contact with a contaminant depend on the exposure concentration (how much), the frequency and/or duration of exposure (how long), the route or pathway of exposure (breathing, eating, drinking, or skin contact), and the multiplicity of exposure (combination of contaminants). Once exposure occurs, characteristics such as age, sex, nutritional status, genetics, lifestyle, and health status of the exposed individual influence how the individual absorbs, distributes, metabolizes, and excretes the contaminant. Together, these factors and characteristics determine the health effects that may occur as a result of exposure to a contaminant in the environment.

There is considerable uncertainty about the true level of exposure to environmental contamination. To account for the uncertainty inherent in estimating exposures and to be protective of public health, ATSDR scientists typically define a range of exposure from average to worst-case exposure level estimates as the basis for determining whether adverse health effects are possible. Because of conservative assumptions about how people may be exposed, estimated exposure levels usually are much higher than the levels that people are really exposed to. If the exposure levels indicate that adverse health effects are possible, then a more detailed review of exposure combined with scientific information from the toxicological and epidemiologic literature about the health effects from exposure to hazardous substances is performed.

How would someone be exposed to soil contamination in yards along Evans Road?

In this document, ATSDR evaluated multiple exposure routes to PCBs in residential soils, including incidental ingestion (unintentional consumption) of contaminated surface soil, dermal (skin) contact, and inhalation of fugitive dust. Compared to skin and inhalation contact, incidental ingestion is the predominant exposure pathway for residents along Evans Road to contaminated soil.

PCBs were detected in the surface soil of residential yards. Incidental ingestion of surface soil could take place during several different activities. For adults, these include primarily gardening and yard work. For children, these include playing in the dirt or ingesting outdoor dust tracked into the house. The potential for exposure to contaminants in soil via incidental ingestion is greater for children because they are more likely to ingest more soil than adults as a result of behavioral patterns present during childhood. Inadvertent soil ingestion among children may occur through the mouthing of objects or hands. Mouthing behavior is considered to be a normal phase of childhood development. Adults may also ingest soil or dust particles that adhere to food, cigarettes, or their hands.

Children and adults are not expected to come into contact with surface soils very often due to the grass cover that prevents contact with soil contamination beneath the turf. Subsurface soil contact would be even more infrequent. Concentrations of PCBs were lower in subsurface soil than surface soil and in most cases was not even detected. Since there are some areas of bare soil, to be conservative ATSDR assumed that contact was possible with all areas of surface soil contamination.

ATSDR evaluated other possible exposure pathways associated with contaminated soil, including dermal (skin) contact and inhalation of PCB adsorbed to fugitive dust particles. Relative to incidental ingestion, inhalation of PCB-contaminated soil particles and absorption of PCB from skin contact are small contributors to total exposure.

Another potential exposure pathway is ingestion of home-grown vegetables contaminated with PCBs. Vegetables grown in gardens with PCB-contaminated soil have shown negligible contamination with PCBs from uptake through the roots, or from PCBs that have been volatilized into the air from the soil and then deposited on the leaves (5). The main concern for PCBs and vegetables is the dirt found on the exterior of vegetables grown in contaminated soil. When home-grown fruit and vegetables are washed and peeled, the opportunity for exposure to contaminated soil is eliminated. The route of incidental ingestion of soil, examined in this document, accounts for this type of exposure.

Estimating exposure doses

Exposure activities and the concentration of the contaminant both play an important role in determining the amount of PCBs to which a person is exposed. However, a variety of other factors are involved in estimating an exposure dose and to evaluate what adverse health effects, if any, may occur from that exposure. These factors include:

  • duration of exposure: when the contamination occurred and how long residents have lived there.
  • frequency of exposure: how often the person has contact with the soil.
  • body weight: the amount the person weighs.
  • area of contamination: does the person come into contact with the highest level of PCBs all the time?
  • bioavailability (potential for absorption from the gastrointestinal tract).

These factors all have a part in determining an exposure dose, or the estimated average amount of PCBs ingested by a person on a daily basis (for more information on exposure doses and examples of calculations, see Appendix A).

The exposure assessment is designed to estimate the average daily amount of contact with PCB-contaminated soils over a longer period of time, typically months to years. To be protective ATSDR makes conservative assumptions about how someone would contact contamination that likely over predicts the amount of exposure that most people along Evans Road would experience in order. For example, ATSDR assumed that people would contact all areas of soil contamination throughout the year where in reality, snow and ice would limit contact with contaminated soil during Winter months. Over time, someone would likely come into contact with soils at many locations and not be limited to just contacting soil at one point. Therefore, using average surface soil concentrations of PCBs for the exposure assessment is reflective of the range of contamination that someone might contact. ATSDR also evaluated exposure to the maximum detected concentration found in any residential yard and estimated a maximally exposed worst-case scenario.

The levels of PCBs examined in this document represent current contamination levels. Past levels of PCBs are unknown. Because PCBs are persistent in the environment, the current levels are used in this document to represent past exposures. However, some degradation (including vaporization, migration with eroded soil or windblown dust) may have occurred; therefore, it is possible that PCB levels might have been higher in the past. This may result in somewhat higher exposure dose estimates than provided in this document, but given the large margin of exposure between site-specific exposure estimates and health-based guidelines (e.g. MRLs) the possibility of adverse health effects is very remote. Exposure dose estimates are presented in Tables 3-5 (1).

Public Health Implications of exposure to PCB in Evans Road residential lots

Contaminated soils in residential properties along Evans Road do not present a health hazard to adults or children.  Exposures are infrequent and the magnitude, even under worst-case conditions, too low to result in adverse health effects.  In many cases contaminated soils are below grass cover, reducing the potential for contact.

Exposure estimates reflect total combined exposures from ingestion, dermal and inhalation pathways. These estimated average daily dose levels for adult and child residents along Evans Road do not exceed the protective ATSDR minimal risk level for PCB exposure (Table 3). It is important to remember that sensitive populations are considered when MRLs and other health-based comparison values are developed. Safety factors are incorporated into the MRL to help ensure sensitive populations are amply protected. In addition, comparison values are developed to specifically account for children's exposures. Therefore, when comparison values are not exceeded, we can be confident that it is highly unlikely that even the most sensitive populations would be adversely affected.

If I ate the most contaminated soil every day over many years, how much soil would I need to eat to get close to the lowest dose level where effects were seen in long-term animal studies?: If we assume that a typical three-year old child ate the most contaminated soil found on any residential property (6.9 mg/kg), to approach the lowest dose where an effect was seen in animals, that child would need to eat about three teaspoons of soil per day! An adult would need to eat more than 14 teaspoons of soil every day, equivalent to about 1/4 cup of soil! In reality, no one eats that much soil, even children who exhibit pica behavior (deliberate soil consumption). The spot where the most contaminated soil was detected off-post is covered by grass and along the fence line, so it is highly unlikely that anyone would even come into casual contact with that soil.  There is evidence that humans are less sensitive than animals to PCB exposure, so estimating the amount of soil an adult would need to eat to get a dose even close to the estimated level where no health effects were seen in exposed workers, this person would have to consume almost 4 cups per day of the most contaminated soil!ATSDR estimated worst-case doses assuming a person was exposed exclusively to the maximum soil concentration, 350 days/year, 24 hours/day (Table 4). Figure 3 shows a comparison between worst case exposure estimates for Evans Road residents and dose ranges where cancer and non cancer effects have been observed in animals. Worst case exposure estimates are orders of magnitude below dose levels in animal and studies where effects have been observed.

As depicted in Table 4, worst case exposure estimates for a child and adult are 83 and 500 times, respectively, below the lowest observed adverse effect level seen in animal studies. These doses are 1166 and 7000 times, respectively, below the no observed effect level based upon a study involving occupationally-exposed workers. ATSDR calculated the margins of exposure in Table 4 by dividing the worst-case exposure estimate by the corresponding LOAEL, NOAEL and CEL values.

At this time the weight of evidence from human studies does not support a causal association between PCBs and human cancer, however PCBs are known to cause cancer in animals. The exposure dose for a theoretical maximally-exposed adult is 100,000 times lower than the lowest dose in animal studies where cancer was seen (Table 4). This animal dose level of 1 mg/kg/day is roughly equivalent to 70 mg/day for an average 140 pound adult. To get that dose from eating soil contaminated with the maximum concentration found along Evans Road (6.9 mg/kg), this person would need to eat more than 10 kilograms (22 pounds) of contaminated soil per day!

A description of ATSDR's use of quantitative cancer risk estimates and an example for the situation at Evans Road is included in Appendix B.

Studies involving populations living on or near areas of soil contamination in the absence of consuming contaminated fish have not found any signs of PCB-induced pathology nor any documented elevation in serum PCB. Poor skin and digestive system absorption of PCBs in soil and little or no direct contact may explain the lack of PCB uptake from contaminated soils.

Information in the scientific literature indicate that humans living in contaminated environments where food contamination is not an issue usually do not accumulate additional body burdens of PCBs (16). In a study investigating PCB exposure at waste sites, blood serum PCB levels were within background ranges in persons at highest risk of non-occupational exposure to PCBs at 10 different contaminated sites, even though environmental PCB levels were as high as 2.5 ppb in monitoring well water samples and 330,000 ppb in soil samples (34). At two other sites in this study, where average blood levels were elevated, it was subsequently determined that occupational exposures and consumption of PCB-contaminated fish had occurred. In Greater New Bedford, MA, high concentrations of PCBs were found in sediment, wildlife and fish. Serum specimens were obtained from 391 male and 449 female volunteers. These volunteers had resided in the area for at least 5 years. The prevalence of elevated PCB serum levels in this group was typical of an urban nonoccupationally exposed population (35).

ATSDR's Child Health Initiative

ATSDR recognizes that infants and children may be more sensitive than adults to environmental exposure in communities faced with contamination of their water, soil, air, or food. This sensitivity is a result of many factors, including the following: (1) due to their play activities, children are more likely to be exposed to certain media like soil when they play outdoors; (2) children are shorter than adults, and therefore may be more likely to breathe dust, soil, and vapors close to the ground; and (3) children are smaller than adults and therefore may receive a higher level of chemical exposure relative to their size and body weight. Children also can experience permanent damage if exposed to toxic substances during critical growth and development periods. As part of the Child Health Initiative, ATSDR is committed to evaluating children's unique vulnerabilities to environmental contaminants.

Pica is a rare behavior in young children, usually ages 1 to 3 years, involving deliberate ingestion of large amounts of soil during a short period of time. Pica is usually intermittent and a short-term activity in young children and appears more frequent severe in developmentally disabled children than in children in the general population (36).

To be protective of children, ATSDR evaluated pica exposure scenarios as part of the exposure assessment (Table 5). Furthermore, ATSDR considered site-specific factors relevant to how a child would be exposed to contaminated soils along Evans Road. In evaluating health implications of child exposure, ATSDR compared estimated exposures to MRLs which are by design protective of child health.

Table 3: Estimated average daily exposure to contaminated soils in residential properties.1

Lot # Adult dose
(mg/kg/day)
Child dose
(mg/kg/day)
Minimal Risk Level (MRL)
(mg/kg/day)
MRL exceeded?
1 1.32E-07 8.07E-07 2.0E-05 N
2 2.46E-07 1.50E-06 2.0E-05 N
3 2.57E-07 1.57E-06 2.0E-05 N
4 5.99E-07 3.65E-06 2.0E-05 N
5 4.17E-07 2.54E-06 2.0E-05 N
6 4.66E-07 2.85E-06 2.0E-05 N
7 2.50E-07 1.53E-06 2.0E-05 N
8 4.55E-08 2.78E-07 2.0E-05 N
9 1.56E-08 9.55E-08 2.0E-05 N
10 1.14E-07 6.95E-07 2.0E-05 N
11 2.12E-07 1.29E-06 2.0E-05 N
12 5.69E-08 3.47E-07 2.0E-05 N
14-16 5.40E-08 3.30E-07 2.0E-05 N
17 3.55E-08 2.17E-07 2.0E-05 N
18 8.82E-08 5.38E-07 2.0E-05 N
19 1.02E-07 6.25E-07 2.0E-05 N

1. Exposure estimate reflects total combined exposures from ingestion, dermal and inhalation pathways.

Table 4. Estimated average daily exposure using maximum detected soil concentration.1

  Dose (mg/kg/day) LOAEL/dose2 NOAEL/dose3 CEL/dose4
Child 0.00006 83 1166 16666
Adult 0.00001 500 7000 100000

1. Assumes exposure exclusively to point of maximum soil concentration, 350 days/year, 24 hours/day, and reflects total combined exposures from ingestion, dermal and inhalation pathways.
2. Chronic oral lowest observed adverse effect level (LOAEL) is equivalent to 0.005 mg/kg/day, which is the lowest observed adverse effect level identified in animal studies (6-7).
3. Human no observed adverse effect level (NOAEL) estimated from occupational studies 0.07-0.14 mg/kg/day (16).
4. Cancer effect level (CEL) is equivalent to 1.0 mg/kg/day, the lowest dose in animal studies where a statistically significant increase in tumors was observed (31).

Table 5. Pica child exposure estimate using highest average concentration in residential soil.

  Concentration (mg/kg) Dose (mg/kg/day) NOAEL/Dose1
Pica Child 0.421 0.00009 5555

1. Lowest NOAEL from acute (short term) animal study is equivalent to 0.5 mg/kg/day (37). Pica is an intermittent and short term phenomenon, therefore comparison with acute duration studies is appropriate.

Health concerns raised by Evans Road residents

Residents have expressed several health concerns surrounding the PCB contamination in residential properties. Additional concerns surrounding property values, real estate transactions and legal issues have been expressed. Though important, these issues are beyond the scope of this document and should be addressed by representatives of the U.S. Army, local government officials and legal professionals.

1. Would children playing in the backyard be exposed to harmful levels of PCB in soil?

No. Contaminated soils in residential properties along Evans Road do not present a health hazard to children. Exposures, even under worst-case conditions, are too low to result in adverse health effects. In many cases, contaminated soils are below grass cover, reducing the potential for contact.

2. Could the PCB contamination in soil harm a breastfeeding child or unborn baby?

No. Exposures were well below the ATSDR MRL for PCBs. The MRL is designed to be protective of both developmental and reproductive health effects and considers sensitive populations such as newborns and developing fetuses. Mothers along Evans Road should feel confident that the PCB contamination will not affect their reproductive health or harm an unborn child. ATSDR encourages individuals to discuss their concerns with their health care provider or if additional information is needed regarding the benefits of breastfeeding. The ATSDR has a variety of information available for health care providers regarding health effects from exposure to hazardous substances. Obtain information online at http://www.atsdr.cdc.gov or by contacting the information line toll free at 888-42-ATSDR.

3. Is the PCB contamination likely to cause cancer?

Exposure to PCBs in soil along Evans Road is not expected to cause cancer. At this time the weight of scientific evidence from human studies does not support a causal association between PCBs and human cancer. Hypothetical worst-case exposure levels at Evans Road were over 100,000 lower than the lowest level in animal studies where cancer was observed, and much lower than the exposure estimates where no harm to health was observed in studies involving exposed workers. As detailed in the hypothetical example in Appendix B, one "excess" cancer case over the background rate would require lifetime exposure to soil concentrations over 11,900 mg/kg, more than 1724 times the maximum soil PCB concentration reported (6.9 ppm) in residential soil along Evans Road.

4. Is it safe to use my garden?

Yes. Plants do not readily uptake PCBs from contaminated soil. The vast majority of the contamination would be located in the soil adhering to the vegetables which would be removed during washing and peeling. Gardening in contaminated soil may result in the potential for exposure via skin contact and incidental ingestion, however the exposure estimates even to the most contaminated soils indicate that the PCBs do not pose a health hazard from direct contact.

5. What about the threat of airborne PCB particles? All the sampling and clean up work already done on Evans near our backyards and the proposed sampling closer to our homes raises concerns that we may be inhaling dangerous substances "kicked up" by Army activities.

Due to community concerns surrounding fugitive dust, ATSDR prompted the Army to implement more stringent dust control and use sampling equipment to collect and monitor dust levels at the Evans Area fence line. ATSDR reviewed the sampling results and determined that the dust levels were too low to pose a health hazard.

The exposure dose estimates took into account the contribution from inhalation of fugitive dust. Dust inhalation contributed a tiny amount to the total exposure dose and would not be expected to be a health hazard. Dust is a nuisance however, and ATSDR is recommending that during remedial activities the Army continue to implement dust control and monitor fugitive dust levels.

6. Do I need to be relocated?

Typically, relocation is appropriate for urgent public health hazards involving the potential for short-term or immediate health effects from exposure to hazardous materials. In the case of soil contamination along Evans Road, there is not a health hazard.

ATSDR is sensitive to the fact that the soil contamination and remediation work is disruptive and interferes with enjoyment of residents' property. ATSDR indicated to the Army that heavy equipment used during remedial equipment could pose a physical danger to Evans Road residents and to be especially cautious when working at homes with small children. ATSDR has suggested that the Army work with individual homeowners on a case-by-case basis to determine whether temporary relocation is an option during remedial activity.

7. How can I protect my family from soil contamination?

Although PCB contamination in residential soil is not a health hazard it is good public health practice to minimize exposure. ATSDR advises that residents take simple, practical steps to minimize the potential for contact with PCBs. Effective ways to reduce exposure include:

  1. Wash hands before eating and after playing or working outside.
  2. Discourage children from eating soil and putting their dirty hands or fingers in their mouths.
  3. Change and launder clothes following outdoor activities.
  4. Leave shoes outside to reduce the potential for tracking soil into the home.
  5. Wash home-grown produce.
  6. Close windows when soil excavation work is in progress.
  7. Cover bare soils with turf or mulch to eliminate the potential for contact.

CONCLUSIONS

  1. Contaminated soil containing PCB has migrated from the Evans Area onto neighboring residential yards. It is not known for certain when PCB contamination migrated from the Evans Area. In many cases contaminated soil is below grass cover which reduces the potential for contact. Given that there are bare areas of soil and that remedial activities at the Evans Area generate fugitive dust, there is the potential for past, current and future exposure for residents living along Evans Road who contact contaminated soil.


  2. Contaminated soil in residential properties along Evans Road do not present a health hazard to adults or children. Exposures are infrequent and the magnitude, even under worst-case conditions, too low to result in adverse health effects.


  3. The Army took additional soil samples along Evans Road, Diana Road, Squirrel Road and Shore Drive down gradient from the Evans Road properties. Preliminary sampling results indicate no PCB concentrations exceed NJDEP residential soil standards beyond the Evans Road Area. ATSDR will review additional soil sampling data when it becomes available.

RECOMMENDATIONS

ATSDR makes the following recommendations:

  1. Given the potential for fugitive dust during remedial activities, ATSDR recommends that during remedial activities the Army continue to implement dust control measures and monitor downwind fugitive dust levels at the fence line and in residential lots when conducting remedial actions on private property.

ATSDR recommends a 24-hour average particulate concentration of 150 µg/m3 as an action level requiring notification of homeowners in the immediate vicinity and implementation of dust control measures. This action level is intended as a precaution to protect those with respiratory or heart disease, small children and elderly individuals who may be more sensitive to particulate exposures. As a general guideline, if this action level is exceeded (say for 5-10 min, because instruments do fluctuate), the action should be to slow down and possibly stop work until the dust source is identified and stopped.

  1. The Army should notify Evans Road homeowners in the vicinity of planned remedial actions prior to remedial work to allow residents to take steps to reduce the impact of nuisance dust (i.e. close windows).


  2. The Army should immediately establish a communication channel for residents to contact the Army in case of concerns regarding fugitive dust and other remedial activities.


  3. The Army should share soil sampling data taken beyond the Evans Road Area with ATSDR as soon as it becomes available. The need for further public health activities will be determined as additional data is reviewed.

PREPARERS OF REPORT

Report Author

Scott Sudweeks
Toxicologist, Federal Facilities Assessment Branch
Division of Health Assessment and Consultation


Reviewers

Diane Jackson
Section Chief, Federal Facilities Assessment Branch
Division of Health Assessment and Consultation

Sandy Isaacs
Branch Chief, Federal Facilities Assessment Branch
Division of Health Assessment and Consultation

Allan Susten
Assistant Director for Science
Division of Health Assessment and Consultation


REFERENCES

  1. Versar 2001. Substation Area Assessment, Remedial Action Work plan and Time Critical Removal Action Memorandum, Volume 1. United States Army, Fort Monmouth Evans Area, Wall Township, NJ. October 2001.


  2. Foster Wheeler 2001. Post Wide Environmental Decision Document. United States Army, Fort Monmouth Evans Area, Wall Township, NJ. September 2001.


  3. Personal communication with Charles Appleby, BRAC Environmental Coordinator, Fort Monmouth, August 2001.


  4. Personal communication with Charles Appleby, BRAC Environmental Coordinator, Fort Monmouth, May 2002.


  5. Agency for Toxic Substances and Disease Registry 2000. Toxicological profile for polychlorinated biphenyls (PCBs). Atlanta: U.S. Department of Health and Human Services; November 2000.


  6. Tryphonas H, Hayward S, O'Grady L, et al.1989. Immunotoxicity studies of PCB (Aroclor 1254) in the adult Rhesus (Macaca mulatta) monkey - Preliminary report. Int J Immunopharmacol,.11:199-206.


  7. Tryphonas H, Luster MI, White KL, et al. 1991. Effect of PCB (Aroclor 1254) on non-specific immune parameters in the Rhesus (Macaca mulatta) monkeys. Int J Immunopharmacol ;13:639-48.


  8. Arnold DL, Bryce F, Karpinski K, et al.1993. Toxicological consequences of Aroclor 1254 ingestion by female Rhesus (macaca mulatta) monkeys. Part 1B. Prebreeding phase: Clinical and analytical laboratory findings. Food Chem Toxicol.,31(11):811-24.


  9. Arnold DL, Bryce F, McGuire PF, et al. Toxicological consequences of Aroclor 1254 ingestion by female Rhesus (Macaca mulatta) monkeys. Part 2. Reproduction and infant findings. Food Chem Toxicol 1995;33:457-74.


  10. Rice DC. Effect of postnatal exposure to a PCB mixture in monkeys on multiple fixed interval-fixed ratio performance. Neurotoxicol Teratol 1997;19(6):429-34.


  11. Rice DC. Effects of postnatal exposure of monkeys to a PCB mixture on spatial discrimination reversal and DRL performance. Neurotoxicol Teratol 1998;20(4):391-400.


  12. Rice DC. Behavioral impairment produced by low-level postnatal PCB exposure in monkeys. Environ Res 1999;80:S113-21.


  13. Rice DC and Hayward S. Effects of postnatal exposure to a PCB mixture in monkeys on nonspatial discrimination reversal and delayed alternation performance. Neurotoxicology 1997;18(2):479-94.


  14. Rice DC and Hayward S. Effects of postnatal exposure of monkeys to a PCB mixture on concurrent random interval-random interval and progressive ration performance. Neurotoxicol Teratol 1999;21(1):47-58.


  15. James,R.C.; Busch,H.; Tamburro,C.H.; Roberts,S.M.; Schell,J.D.; Harbison,R.D. Polychlorinated biphenyl exposure and human disease. J.Occup.Med. 35(2):136-148. February 1993.


  16. Kimbrough RD. Polychlorinated biphenyls (PCBs) and human health: An update. Crit Rev Toxicol 1995;25:133-66.


  17. Brown DP. Mortality of workers exposed to polychlorinated biphenyls - An update. Arch Environ Health 1987;42(6):333-9.


  18. Brown DP and Jones M. Mortality and industrial hygiene study of workers exposed to polychlorinated biphenyls. Arch Environ Health 1981;36:120-9.


  19. Gustavsson P and Hogstedt C. A cohort study of Swedish capacitor manufacturing workers exposed to polychlorinated biphenyls (PCBs). Am J Ind Med 1997;32(3):234-9.


  20. Gustavsson P, Hogstedt C and Rappe C. Short-term mortality and cancer incidence in capacitor manufacturing workers exposed to polychlorinated biphenyls (PCBs). Am J Ind Med 1986;10:341-4.


  21. Bertazzi PA, Riboldi L, Pesatori A, et al. Cancer mortality of capacitor manufacturing workers. Am J Ind Med 1987;11:165-76.


  22. NIOSH. Health hazard evaluation report. Westinghouse Electric Corporation, Bloomington, Indiana. Cincinnati, OH: Hazard Evaluations and Technical Assistance Branch, National Institute for Occupational Safety and Health. 1991 HETA 89-116-2094.


  23. Kimbrough RD, Doemland ML and LeVois ME. Mortality in male and female capacitor workers exposed to polychlorinated biphenyls. J Occup Environ Med 1999;41(3):161-71.


  24. Sinks T, Steele G, Smith AB, et al. Mortality among workers exposed to polychlorinated biphenyls. Am J Epidemiol 1992;136(4):389-98.


  25. Kimbrough RD, Squire RA, Linder RE, et al. Induction of liver tumors in Sherman strain female rats by polychlorinated biphenyl Aroclor 1260. J Natl Cancer Inst 1975;55:1453-9.


  26. Loomis,D.; Browning,S.R.; Schenck,A.P.; Gregory,E.; Savitz,D.A. Cancer mortality among electric utility workers exposed to polychlorinated biphenyls. Occup Environ Med 54(10):720-728. October 1997.


  27. Norback DH and Weltman RH. Polychlorinated biphenyl induction of hepatocellular carcinoma in the Sprague-Dawley rat. Environ Health Perspect 1985;60:97-105.


  28. Schaeffer E, Greim H and Goessner W. Pathology of chronic polychlorinated biphenyl (PCB) feeding rats. Toxicol Appl Pharmacol 1984;75: 278-88.


  29. NCI. Bioassay of Aroclor 1254 for possible carcinogenicity. NCI-GC-TR-38. Bethesda, MD: National Cancer Institute. 1978. NTIS PB279624.


  30. Moore JA, Hardistry JF, Banas DA, et al. A comparison of liver tumor diagnoses from seven PCB studies in rats. Regul Toxicol Pharmacol 1994;20:362-70.


  31. Mayes BA, McConnell EE, Neal BH, et al. Comparative carcinogenicity in Sprague-Dawley rats of the polychlorinated biphenyl mixtures Aroclors 1016, 1242, 1254, and 1260. Toxicol Sci 1998;41(1):62-76.


  32. General Electric Company. An assessment of the chronic toxicity and oncogenicity of Aroclor-1016, Aroclor-1242, Aroclor-1254, and Aroclor-1260 administered in diet to rats. Volume I and II. Final neurotoxicity and neuropathology report. Environmental Research Center, General Electric Company. 1997. Battelle Study No. SC920192.


  33. ATSDR. 1997. Toxicological Profile for Polychlorinated Biphenyls (Update). Agency for Toxic Substances and Disease Registry. U.S. Department of Health and Human Services, Public Health service. September, 1997.


  34. Stehr-Green P.A.,Welty,E., Burse,V.W., Human exposure to polychlorinated biphenyls at toxic waste sites: investigations in the United States. Arch Environ Health, 43,420,1988.


  35. Miller,D.T.; Condon,S.K.; Kutzner,S.; Phillips,D.L.; Krueger,E.; Timperi,R.; Burse,V.W.; Cutler,J.; Gute,D.M., Human exposure to polychlorinated biphenyls in Greater New Bedford, Ma: a prevalence study, Arch Environ Contam Toxicol, 20, 410, 1991.


  36. Behrman, L.E.; Vaughan, V.C., III. 1983. Textbook of Pediatrics. Philadelphia, PA: W.B. Saunders Company.


  37. Carter JW. 1985. Effects of dietary PCBs (Aroclor 1254) on serum levels of lipoprotein cholesterol in Fischer rates. Bull Environ Contam Toxicol 34:427-431.

 

FIGURES

Site Location Map
Figure 1. Site Location Map

Remedial Action Location Map
Figure 2. Remedial Action Location Map

Oral Exposure to PCBs
Figure 3. Oral Exposure to PCBs


APPENDIX A: EVALUATION OF ENVIRONMENTAL CONTAMINATION AND EXPOSURE PATHWAYS

Quality Assurance

In preparing this report, ATSDR relied on the information provided in the referenced documents. ATSDR reviewed the available quality assurance and control data and determined that it was adequate for the purpose of this document.

Human Exposure Pathway Evaluation and the Use of ATSDR Comparison Values

ATSDR assesses a site by evaluating the level of exposure in potential or completed exposure pathways. An exposure pathway is the way chemicals may enter a person's body to cause a health effect. A completed exposure pathway must include all the steps between the release of a chemical and the exposed person: (1) a chemical release source, (2) chemical movement in the environment, (3) a place at which people can come into contact with the chemical, (4) a route of human exposure, and (5) a person that could be exposed. If any of these elements is missing, exposure and the potential for health harm can not occur.

Comparison values are used as screening tools to evaluate environmental data relevant to exposure pathways. Comparison values are concentrations of contaminants that are considered to be not likely to cause health effects. Comparison values used in this document include ATSDR's environmental media evaluation guide (EMEG), and ATSDR's cancer risk evaluation guide (CREG). Comparison values are derived from available health guidelines, such as ATSDR's Minimal Risk Levels (MRLs) and EPA's Reference Doses (RfDs).

The derivation of a comparison value uses conservative exposure assumptions, resulting in values that are much lower than exposure concentrations that have been observed to cause adverse health effects. These comparison values are therefore protective of public health in essentially all exposure situations. That is, if the concentrations in the exposure medium are less than the comparison values, the exposures are not of health concern and no further analysis of the pathway is required. While concentrations below the comparison value are not expected to lead to any observable health effect, it should not be inferred that a concentration greater than the comparison value will necessarily lead to adverse effects. Depending on site-specific environmental exposure factors (for example, duration of exposure) and human activities that result in exposure (time spent in area of contamination), exposure to levels above the comparison value may or may not lead to a health effect. ATSDR's comparison values, therefore, are not used to predict the occurrence of adverse health effects.

The CREG is a concentration at which a theoretical cancer risk is not likely to exceed one extra case of cancer over the background rate in a million persons similarly exposed over a lifetime. The CREG is a very conservative comparison value that is used as a screening value. Consistent with other comparison values, exposure to concentrations exceeding a CREG do not imply that cancer would result, but indicate that further evaluation is needed.

A note about MRLs
MRLs are intended only to serve as a screening tool to help public health professionals decide where to look more closely. They may also be viewed as a mechanism to identify those hazardous waste sites that are not expected to cause adverse health effects. Most MRLs contain a degree of uncertainty because of the lack of precise toxicologic information on the people who might be most sensitive (e.g., infants, elderly, nutritionally or immunologically compromised) to the effects of hazardous substances. 

ATSDR uses a conservative (i.e., protective) approach to address this uncertainty consistent with the public health principle of prevention. Although human data are preferred, MRLs often must be based on animals studies because relevant human studies are lacking. In the absence of evidence to the contrary, ATSDR assumes that humans are more sensitive to the effects of hazardous substances than animals and that certain persons may be particularly sensitive. Thus, the resulting MRL may be as much as a hundredfold below levels that have been shown to be nontoxic in laboratory animals.

It is important to remember that sensitive populations are considered when MRLs and other health-based comparison values are developed. An uncertainty factor (e.g., a factor of 10) is generally applied to help ensure sensitive populations are amply protected. In addition, comparison values are developed to specifically account for children's exposures. Therefore, when comparison values are not exceeded, we can be confident that it is highly unlikely that even the most sensitive populations would be adversely affected.After identifying contaminants in site media above comparison values, ATSDR further evaluates exposures to these contaminants considering information about exposures combined with scientific information from the toxicological and epidemiological literature. If necessary, ATSDR estimates exposure doses, which are estimates of how much contaminant a person is exposed to on a daily basis.

Selecting Contaminants of Concern

Contaminants of concern (COCs) are the site-specific chemical substances that the health assessor selects for further evaluation of potential health effects. Identifying contaminants of concern is a process that requires the assessor to examine contaminant concentrations at the site, the quality of environmental sampling data, and the potential for human exposure. A thorough review of each of these issues is required to accurately select COCs in the site-specific human exposure pathway. The following text describes the selection process.

In the first step of the COC selection process, the maximum contaminant concentrations are compared directly to health comparison values. ATSDR considers site-specific exposure factors to ensure selection of appropriate health comparison values. If the maximum concentration for a chemical was less than the health comparison value, ATSDR would conclude that exposure to that chemical was not of public health concern; therefore, no further data review would be required for that chemical. However, if the maximum concentration was greater than the health comparison value, the chemical would be selected for additional data review, as a contaminant of concern (COC). In addition, any chemicals detected that did not have relevant health comparison values would also be selected as a COC.

ATSDR comparison values have not been developed for some contaminants, and, based on new scientific information, other comparison values may be used that are appropriate for the specific type of exposure (e.g., EPA's Maximum Contaminant Levels (MCLs) for drinking water).

The next step of the process requires a more in-depth review of data for each of the contaminants selected. Factors used in the selection of the COCs include the number of samples with levels above the minimum detection limit, the number of samples with detections above an acute or chronic health comparison value, and the potential for exposure at the sampling location.

Calculating Exposure Doses

The levels of PCBs detected were above at least one of ATSDR's comparison values, and therefore further evaluation of exposure is required. Exposure doses were calculated to estimate the average daily dose for an adult, child, and pica child exposed to the average and maximum concentration of PCBs in residential properties. Exposure pathway-specific exposure estimates were calculated then combined to estimate total dose. ATSDR uses established methodologies for determining how people might be exposed to PCBs and what harmful effects, if any, might result from such exposure (EPA 1989, ATSDR 1992, 2002). The following are the equations and assumptions used in the calculations:

Ingestion of soil

ED (mg/kg/day) = (C(mg/kg) x IR(mg/day) x FI x EF(day/year) x ED(year) x CF(kg/mg)) / BW (kg)

Exposure Factor Value used Explanation/source
Exposure dose (ED) calculated (mg/kg/day)  
Concentration (C) Site-specific Arithmetic mean (average) at each property and maximum detected concentration was used.
Ingestion rate (IR) Adult: 100 mg/day

Child: 200 mg/day

Pica child: 5000 mg/day

EPA 1999
Fraction ingested (FI) 0.65 Fries 1985, Hack and Selenka 1996
Exposure frequency (EF) 350 days/year Assumes resident not home total of two weeks per year
Exposure duration (ED) Child: 6 years

Adult: 30 years

EPA 1999
Conversion factor 1.0E-06 Convert kilogram to milligram
Body weight (BW) Child: 15 kg

Adult: 70 kg

EPA 1999

Dermal contact with soil

ED (mg/kg/day) = (C(mg/kg) x SA(cm2/event) x AF(mg/cm2) x ABS x EF(events/year) x ED(years) x CF(kg/mg)) / BW(kg)

Exposure Factor Value used Explanation/source
Exposure dose (ED) calculated (mg/kg/day)  
Concentration (C) Site-specific Arithmetic mean (average) at each property and maximum detected concentration was used.
Available skin surface area (SA) Child: 2900 cm2/event

Adult: 19400 cm2/event

EPA 1999. Central tendency values for head, forearms, hands and legs.
Soil adherence factor (AF) 0.2 EPA 1992
Absorption factor across skin 0.01 EPA 1992
Exposure frequency (EF) 350 events/year Assumes resident is exposed once a day, and is not home total of two weeks per year.
Exposure duration (ED) Child: 6 years

Adult: 30 years

EPA 1999
Conversion factor 1.0E-06 Convert kilogram to milligram
Body weight (BW) Child: 15 kg

Adult: 70 kg

EPA 1999

Inhalation of fugitive dust

ED (mg/kg/day) = (C(mg)kg) x 1/PEF(m3/kg soil) x IR(m3/day) x EF(days/year) x ET(hours/day) x ED(year) x CF (day/hour)) / BW(kg)

Exposure Factor Value used Explanation/source
Exposure dose (ED) calculated (mg/kg/day)  
Concentration (C) Site-specific Arithmetic mean (average) at each property and maximum detected concentration was used.
Particulate emissions factor (PEF) 4.28 E09 m3/kg soil EPA 1996
Inhalation rate (IR) Child: 8 m3/day

Adult: 15.2 m3/day

EPA 1999
Exposure frequency (EF) 350 days/year Assumes resident not home total of two weeks per year
Exposure duration (ED) Child: 6 years

Adult: 30 years

EPA 1999
Exposure time (ET) 24 hours/day Assumes someone is exposed 24 hours/day
Conversion factor (CF) 0.04 day/hour  
Body weight (BW) Child: 15 kg

Adult: 70 kg

EPA 1999

Evaluating the potential for adverse health effects

The estimated exposure doses can be used to evaluate potential noncancer and cancer effects associated with contaminants detected in site media. When evaluating noncancer effects, ATSDR compares the estimated exposure dose to standard toxicity values, including ATSDR's minimal risk levels (MRLs) and the U.S. Environmental Protection Agency's reference doses (RfDs), to evaluate whether adverse effects may occur. ATSDR also reviews the toxicological literature and epidemiology studies to evaluate the weight of evidence for adverse health effects.

A weight-of-evidence analysis involves the balanced review and integration of relevant exposure, toxicologic, epidemiologic, medical, and health outcome data to help determine whether exposures to contaminant levels under site-specific conditions might result in harmful effects. A weight-of-evidence analysis focuses on studying various site, substance, and population-specific factors that may influence the frequency and magnitude of exposures and may ultimately affect whether exposures to a hazardous substance might lead to illness. The goal of the weight-of-evidence analysis is to decide whether or not harmful effects might be possible in the exposed population by weighing the scientific evidence and by keeping site-specific doses in perspective (ATSDR 2002).

References

Agency for Toxic Substances and Disease Registry (ATSDR). 1992, 2002. Public Health Assessment Guidance Manual. U.S. Department of Health and Human Services. Unites States Public Health Service.

United States Environmental Protection Agency (EPA). 1992. Dermal Exposure Assessment: Principles and Application, EPA/600/8-91/011B, Office of Research and Development, Washington, D.C.

EPA. 1996. Soil Screening Guidance: User's Guide, EPA/540/R-96/018, Office of Emergency and Remedial Response, Washington, D. C.

EPA. 1995. Exposure Factors Handbook, EPA/600/C-99/001, Office of Research and Development, Washington, D.C.

EPA. 1989. Risk Assessment Guidance for Superfund: Volume 1-Human Health Evaluation Manual (Part A), EPA/540/1-89/002, Office of Emergency and Remedial Response, Washington, D.C.

Fries, G. F., Marrow, G. S., & Somich, C. J. (1989). Oral bioavailability of aged polychlorinated biphenyl residues contained in soil. Bull.Environ.Contam Toxicol., 43, 683-690.

Hack, A. & Selenka, F. (1996). Mobilization of PAH and PCB from contaminated soil using a digestive tract model. Toxicol.Lett., 88, 199-210.


APPENDIX B: USE OF QUANTITATIVE CANCER RISK ESTIMATES

Quantitative cancer risk assessments can be used to generate concentration-specific risk estimates that are useful regulatory tools for EPA and useful preliminary screening values for ATSDR. However, the purely hypothetical risks that are "quantified" in such assessments are not to be confused with the actuarial risks that reflect the measurable incidence of adverse health such as deaths due to heart disease or automobile accidents. Quantitative cancer risk estimates are, in fact, not applicable to the prediction of actual cancer incidence in exposed human populations. As stated in EPA's Guidelines for Carcinogen Risk Assessment, "the risk model used by EPA leads to a plausible upper limit to risk that is consistent with some proposed mechanisms of carcinogenesis. Such an estimate, however, does not necessarily give a realistic prediction of the risk. The true value of the risk is unknown and may be as low as zero" (EPA 1986). With this understanding, and for the purposes of perspective only, ATSDR offers the following or "upper limit" risk calculations:

EPA has calculated a range of upper bound slope factors for PCBs of 0.07 to 2 per mg/kg/day, based primarily on the induction of liver tumors in rodents (ATSDR 2000). EPA recommends using the upper reference point of 2 (mg/kg/day)-1 for soil and food chain exposures. Based on the upper slope factor of 2 per mg/kg/day, a 10-6 risk level would correspond to a chronic (i.e., essentially lifetime) dose of 5 x 10-7 mg/kg/day. (SF x Dose = Risk; 10-6/2 = 5 x 10-7 mg/kg/day) A 10-6 risk level implies that, over the course of a 70-year lifetime of exposure at the indicated level, only one "excess" (i.e., above background) cancer might (hypothetically) be expected to occur in a million individuals so exposed. By simple ratio and proportion, a one-in-a-million risk is equivalent to a 0.00003-in-30 risk. (For the purposes of this illustration, it is assumed that there are 30 exposed individuals along Evans Road.)

Detectable Cancer Effect Levels: Thus (based on EPA's most potent slope factor for PCBs), in order to produce even one cancer above background (i.e., a 1.0-in-30 risk), chronic (lifetime) exposures would have to be at least 33,333.33 times 5 x 10-7 mg/kg/day, equivalent to 0.017 mg/kg/day.

In order to obtain the same dose from ingesting soil, assuming a default soil ingestion rate of 100 mg soil/day and a body weight of 70 kg, the soil would have to be contaminated with 11,900 mg/kg PCB (70 kg x 0.017 mg/kg/day = 1.19 mg/day; 1.19 mg/0.0001 kg soil = 11,900 mg/kg). This would be more than 1724 times the maximum soil PCB concentration reported (6.9 ppm) in residential soil along Evans Road.

References

Agency for Toxic Substances and Disease Registry 2000. Toxicological profile for polychlorinated biphenyls (PCBs). Atlanta: U.S. Department of Health and Human Services; Nov. 2000.

EPA. 1986. Guidelines for Carcinogenic Risk Assessment. Fed. Reg., 51: 33997-33998, September 24, 1986.


1 Dose estimates are presented in scientific notation format. Scientific notation is another way to represent numbers, especially useful for very large or small values. 1.5E-06 is equivalent to 0.0000015, were the E-06 indicates places behind the decimal point.

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