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PUBLIC HEALTH ASSESSMENT

TRACY DEFENSE DEPOT
(a/k/a DEFENSE DISTRIBUTION REGION WEST TRACY ARMY)
TRACY, SAN JOAQUIN COUNTY, CALIFORNIA


TABLES

TABLE 1. Operable Units

Operable
Unit No.

Site Description

Waste Disposal History

Contaminated Media

Remedial Alternative

OU 1 VOC groundwater contaminant plume in the Upper Tulare Aquifer emanating from the northern portion of the site and extending off site for approximately one-half mile to the north-northeast. Waste disposal practices and accidental spills in the former open drum and maintenance areas along the northern boundary of the site. Groundwater: TCE, PCE, and DCE A pump-and-treat system to remediate contaminant hot spots, minimize contaminant transport off site, and clean up the plume to EPA or CA MCLs for TCE, PCE, and DCE. It is scheduled for operation in 1997-1998. The system is also expected to control migration of pesticides.
OU 2A Sites with contaminated soil serving as OU 1 sources. OU 2A sites include:
SWMU 1/Area 2 Area contains two sewage lagoons and a drum storage area. Soil: VOCs, SVOCs, pesticides, metals, and total petroleum hydrocarbons No further action required. The sites in OU 2A do not pose a significant threat to groundwater.
Area 1, Building 237 Area reportedly used for cleaning asphalting equipment and solvent storage. Soil: VOCs and SVOCs
Area 3 Historically used for drum storage; site of several accidental spills. Soil: VOCs
OU 2B SWMU 4--Storm Drain Lagoon An unlined lagoon that collected stormwater runoff. Received rinse water from paint stripping and degreasing operations. Sediment: Dieldrin No action. The sediment does not pose a threat to groundwater.
SWMU 8--Burn Pit No. 2 A large burn pit where items used or stored on-site may have been burned. Soil: Total petroleum hydrocarbons Bioventing to prevent threat to groundwater.
SWMU 10A--Possible Medical Waste Burial Pit Area reportedly used to bury medical waste. Soil: VOCs, metals, and pesticides No action. Contaminants in soil were not considered to pose a threat to groundwater.
SWMU 20/23--Aboveground Solvent Tank/Building 26 Recoup Operations SWMU 20 used for a 500-gallon aboveground TCE degreasing unit for cleaning engine parts. SWMU 23 used as a wash rack. Soil: VOCs, SVOCs, and lindane No action. Contaminants in soil do not pose a threat to groundwater.
SWMU 24--Building 247 Petroleum Laboratory Waste Oil Tank Contains a 500-gallon underground petroleum tank and visibly stained soil. Soil: VOCs, SVOCs, total petroleum hydrocarbons, and pesticides Bioventing to prevent threat to groundwater posed by total petroleum hydrocarbons.
SWMU 27--Building 206 Roundhouse Sump Location of the waste oil sump, which received fluids from the cleaning of exterior surfaces of locomotives. Pesticides also were washed down the drain. Soil: SVOCs, PCBs, pesticides, and metals No action. Contaminants in soil do not pose a threat to groundwater.
Day Care Center Located on the west side of the depot near the main entrance, the day care center yard once contained a 1,200-gallon UST. Soil: SVOCs and pesticides Native soil cover to reduce exposure opportunities. Some remedial actions may be warranted.
OU 2C SWMU 2--Present Sewage Lagoon Consists of active unlined sewage lagoons that receive treated effluent from the sewage treatment plant. Soil: Metals, pesticides, and SVOCs Evaluated in DDJC Tracy's Engineering Evaluation and Cost Analysis.
SWMU 3--Industrial Lagoon Consists of two lined industrial lagoons that received industrial wastewater from the recoup, degreasing, paint stripping, and steam cleaning operations. Soil: Metals, SVOCs, and pesticides
SWMU 33--Industrial Waste Pipeline An industrial pipeline used to convey waste streams to the industrial ponds. Soil: SVOCs, pesticides, and metals



TABLE 2. Exposure Pathways

Pathway Name Source of
Contamination
Environmental
Medium
Point of Exposure Route of
Exposure
Exposed
Population
Comment
Completed Exposure Pathway
Private off-site wells TCE: DDJC Tracy
Carbon
Tetrachloride:
unknown
Groundwater Private residences Ingestion, dermal contact, and inhalation Private residents (estimated 8-20 individuals) Past:
  • TCE and carbon tetrachloride were detected in two domestic-use wells in the 1980s and early 1990s at levels greater than comparison values, but below levels associated with adverse health effects.

    Current and Future:

  • No exposure is occurring or expected to occur because VOCs have not been detected above the MCLs in two domestic-use wells and the residents have been provided with bottled water and/or a carbon filtration system.
  • DDJC Tracy will continue to monitor groundwater in the vicinity of the site.
  • Potential Exposure Pathways
    DDJC Tracy
    water supply
    wells
    TCE and PCE:
    DDJC Tracy
    Groundwater DDJC Tracy water supply wells Ingestion, dermal contact, inhalation DDJC Tracy workers and Day Care Center in the past (estimated 1,800 individuals) Past:
  • During the 1980s and early 1990s, WSW 4 was located in the path of the VOC plume.
  • ATSDR concludes that WSW 4 was probably not affected by contaminated groundwater and, therefore, -drinking water from WSW 4 most likely posed no public health hazard.

    Current and Future:

  • Well 4 has not been used for drinking water since it was closed in 1992. Active DDJC Tracy WSWs 8 and 9 are upgradient to areas of contamination and are safe for drinking.
  • On-site surface soil Pesticides: DDJC Tracy Soil Areas of exposed soil Dermal contact DDJC Tracy workers (approximately 1,700 workers) Past, Current, and Future:
  • Only low levels of VOCs, metals, and other site-related contaminants exist in on-site soil. Workers in the contaminated areas should not experience health effects because they will most likely wear protective clothing and/or have only brief, infrequent contact with contaminated soil.
  • On-site surface soil Metals, pesticides: DDJC Tracy On-site surface soil Day care center play yard Dermal contact and ingestion Children attending the day care center (an estimated 80 to 100 children attend each year) Past, Current, and Future:
  • Contaminants at levels above the comparison values were detected in exposed soil in areas of the day care center yard where children play.
  • ATSDR does not expect contaminants to be ingested or appreciably absorbed through children's skin in quantities that might lead to health hazards.
  • On-site lagoon fish Metals, pesticides: DDJC Tracy Fish Stormwater Lagoon Ingestion Anglers and their families (approximately 50­200 individuals) Past:
  • The Stormwater Lagoon once received site runoff and water from WSW 4. People fished at the lagoon and DDJC Tracy held a one-time annual fishing derby there until the lagoon was drained in 1992.
  • No fish monitoring data are available for the lagoon. Based on evaluation of lagoon sediment data, ATSDR determined that the lagoon fish most likely would not accumulate contaminant levels, if any, to levels known to pose health hazards.
  • Area grown crops VOCs: DDJC Tracy Walnuts, fruits, and vegetables Former off-site property Ingestion Consumers of area grown produce (estimated 120 to 5,000 individuals) Past:
  • TCE and PCE were detected in agricultural wells used until 1992 at levels above ATSDR comparison values and EPA and CA MCLs for drinking water.
  • ATSDR determined that the nut and fruit bearing trees and crops are not likely to accumulate VOCs at levels associated with adverse health effects.

    Current, and Future:

  • The wells pose no current or future health hazard. They are sealed and no longer used for irrigation.



  • TABLE 3. Contaminant Concentrations in DDJC Tracy Water Supply Wells1

    Contaminant Concentration (ppb) Number of Detections/
    Number of Samples
    Number of Detections
    Greater than the
    Comparison Value 2
    Comparison Value
    (ppb)
    Minimum Maximum
    TCE ND ND 0/3 0 3 CREG
    5 CA & EPA MCL
    PCE ND ND 0/3 0 0.7 CREG
    5 CA & EPA MCL
    Carbon Tetrachloride ND ND 0/3 0 0.3 CREG
    5 CA & EPA MCL
    Pesticides ND ND 0/20 0 various
    Arsenic 3 10 3/28 3/3 0.02 CREG
    50 CA & EPA MCL
    Lead 3 5 2/29 0/2 15 EPA action level
    Manganese 20 180 16/28 9/16 50 EPA secondary MCL
    50/200 RMEG
    Mercury 1 5 2/29 0/2 2 CA & EPA MCL
    Source: Woodward-Clyde Consultants, 1992b; DDJC Tracy, 1998

    1 WSW 4 metal and pesticide sampling results from 1988, 1990, and 1994 ; WSW 7 VOCs sampling results from 1988 through 1991 and metal and pesticide results from 1988 through 1997; WSWs 8 and 9 metal and pesticide sampling results from 1994 through 1997. For one sample, detection limits for arsenic and lead exceeded the comparison values.
    2 The concentration was compared to the CREG or lowest comparison value.
    3 Pesticides include endrin, lindane, methoxychlor, toxaphene, chlordane, heptachlor, heptachlor epoxide, 2,4-dichlorophenoxy acetic acid, and silex.

    Key: CREG= cancer risk evaluation guide for 1 x 10-6 excess cancer risk.; EMEG=environmental media evaluation guide; RMEG = reference dose media evaluation guide;
    MCL = maximum contaminant level.



    TABLE 4. Contaminant Concentrations in Off-Site Private Wells (Domestic Use)1

    Contaminant Concentration (ppb) Number of Detections/
    Number of Samples
    Number of Detections
    Greater than the
    Comparison Value2
    Comparison
    Value (ppb)
    Minimum Maximum
    TCE 3.4 6.7 3/18 3 3 CREG
    5 CA & EPA MCL
    PCE ND ND 0/18 0 0.7 CREG
    5 CA & EPA MCL
    Carbon tetrachloride 0.6 1.8 6/18 6 0.3 CREG
    5 CA & EPA MCL
    Source: Woodward-Clyde Consultants, 1992b.

    1 Results from 1987 and 1991 private well monitoring.
    2 The concentration was compared to the CREG or lowest comparison value.

    Key: ND = not detected; CREG= cancer risk evaluation guide for 1 x 10-6 excess cancer risk; MCL=maximum contaminant level.


    TABLE 5. Contaminant Concentrations in Off-Site Agricultural Wells1

    Contaminant Concentration (ppb) Number of
    Detections/
    Number of
    Samples
    Number of Detections
    Greater than the
    Comparison Value 2
    Comparison Value
    (ppb)
    Minimum Maximum
    TCE 3.5 12 5/11 5 3 CREG
    5 CA & EPA MCL
    PCE 1.5 4.3 5/11 5 0.7 CREG
    5 CA & EPA MCL
    Carbon tetrachloride ND ND 0/11 0 0.3 CREG
    5 CA & EPA MCL
    Sources: Woodward-Clyde Consultants, 1992b.

    1 Results from 1987 and 1991 agricultural well monitoring.
    2 The concentration was compared to the CREG or lowest comparison value.

    Key: ND = not detected; CREG= cancer risk evaluation guide for 1 x 10-6 excess cancer risk; MCL= maximum contaminant level.


    TABLE 6. Contaminant Concentrations in Day Care Center Surface Soil

    Contaminant Concentration (ppm) Number of
    Detections/ Number
    of Samples
    Number of Detections Greater
    than the Comparison Value

    Comparison Value
    (ppm)

    Minimum Maximum
    Benzo(a)pyrene 0.00207 0.0099 4/5 0 0.1 CREG
    Arsenic 2.45 4.03 5/5 5 0.5 CREG
    Chromium 25.8 28.6 5/5 5 10 RMEG-pica
    Lead 11.1 20.3 3/5 0 no value
    Vanadium 28.6 33 5/5 5 6 RMEG-pica
    DDD 0.128 0.388 5/5 0 3 CREG
    DDE 0.567 3.310 5/5 2/5 2 CREG
    DDT 0.568 2.350 5/5 1/5 2 CREG
    Chlordane 0.00339 0.01386 5/5 0 0.5 CREG
    Dieldrin 0.0741 0.357 5/5 5 0.04 CREG

    Source: Montgomery Watson, 1996b

    Key: CREG = cancer risk evaluation guide for 1 x 10-6 excess risk of cancer; RMEG = reference dose media evaluation guide for nonpica child


    TABLE 7. Contaminant Concentrations in On-Site Surface Soil

    Contaminant Concentration (ppm) Number of
    Detections/
    Number of
    Samples
    Number of Detections
    Greater than the
    Comparison Value
    Comparison Value
    (ppm)
    Minimum Maximum
    Arsenic 1.52 89.3 42/42 42/42 0.5 CREG
    Beryllium 0.245 0.804 30/42 30/42 0.2 CREG
    Chromium 21.3 60.3 42/42 0 4,000 RMEG-adult
    Lead 9.92 95.6 30/42 0 no value
    Vanadium 23.7 55.9 42/42 0 2,000 RMEG-adult
    DDD 0.000674 1.22 35/41 0 3 CREG
    DDE 0.00505 4.2 38/41 3/41 2 CREG
    DDT 0.00284 4.51 38/41 3/41 2 CREG
    Chlordane 0.00335 0.689 36/41 2/41 0.5 CREG
    Dieldrin 0.000726 0.738 38/41 15/41 0.04 CREG

    Source: Montgomery Watson, 1996b.

    Key: CREG = cancer risk evaluation guide for 1 x 10-6 excess cancer risk; RMEG = reference dose media evaluation guide


    FIGURES

    Figure 1. Area Map
    Figure 1. Area Map
    Figure 2. Site Map
    Figure 2. Site Map
    Figure 3. Intro Map
    Figure 3. Intro Map
    Figure 4. ATSDR's Exposure Evaluation Process
    Figure 4. ATSDR's Exposure Evaluation Process
    Figure 5. VOC Plume Associated with OU 1
    Figure 5. VOC Plume Associated with OU 1



    APPENDIX A: Glossary

    Comparison Values
    Estimated contaminant concentrations in specific media that are not likely to cause adverse health effects, given a standard daily ingestion rate and standard body weight. The comparison values are calculated from the scientific literature available on exposure and health effects.

    Concentration
    The amount of one substance dissolved or contained in a given amount of another. For example, sea water contains a higher concentration of salt than fresh water.

    Contaminant
    Any substance or material that enters a system (e.g., the environment, human body, food) where it is not normally found.

    Dermal
    Referring to the skin. Dermal absorption means absorption through skin.

    Environmental contamination
    The presence of hazardous substances in the environment. From a public health perspective, environmental contamination is addressed when it potentially affects the health and quality of life of people living and working near the contamination.

    Exposure
    Contact with a chemical by swallowing, by breathing, or by direct contact (such as through the skin or eyes). Exposure may be short term (acute) or long term (chronic).

    Ingestion
    Swallowing (such as eating or drinking). Chemicals can get in or on food, drink, utensils, cigarettes, or hands where they can be ingested. After ingestion, chemicals can be absorbed into the blood and distributed throughout the body.

    Media
    Soil, water, air, plants, animals, or any other parts of the environment that can contain contaminants.

    National Priorities List (NPL)
    The Environmental Protection Agency's (EPA) listing of sites that have undergone preliminary assessment and site inspection to determine which locations pose immediate threats to persons living or working near the release. These are sites in need of cleanup.

    Parts per billion (ppb)
    A common basis of reporting water quality analysis. As an example, one ppb of trichloroethylene (TCE) equals one drop of TCE mixed in a competition-size swimming pool.

    Parts per million (ppm)
    A common basis of reporting soil analysis. For example, one part per million (ppm) of TCE equals one ounce of TCE in one million ounces of water.

    Public Health Assessment
    The evaluation of data and information on the release of hazardous substances into the environment for a specific site in order to assess any current or future impact on public health, develop health advisories or other recommendations, and identify studies or actions needed to evaluate and mitigate or prevent human health effects; also, the document resulting from the evaluation.

    Plume
    An area of chemicals in a particular medium, such as air or groundwater, moving away from its source in a long band or column. A plume can be a column of smoke from a chimney or chemicals moving with groundwater.

    Potentially Exposed
    The condition that exists if valid information, usually analytical environmental data, indicates the presence of contaminants of public health concern in one or more environmental media which humans contact (e.g., air, drinking water, soil, food chain, surface water), and there is evidence that some persons have an identified route of exposure (e.g., drinking contaminated water, breathing contaminated air, having contact with contaminated soil, or eating contaminated food).

    Risk
    In risk assessment, the probability that something will cause injury, combined with the potential severity of that injury.

    Route of Exposure
    The way in which a person may contact a chemical substance. For example, drinking (ingestion) and bathing (skin contact) are two different routes of exposure to contaminants that may be found in water.

    Volatile Organic Compounds (VOCs)
    Substances containing carbon and different proportions of other elements such as hydrogen, oxygen, fluorine, chlorine, bromine, sulfur, or nitrogen; these substances easily become vapors or gases. A significant number of the VOCs are commonly used as solvents (paint thinners, lacquer thinner, degreasers, and dry cleaning fluids).

    APPENDIX B: List of Comparison Values

    Comparison values represent the media-specific contaminant concentrations that are used to select contaminants for further evaluation to determine the possibility of adverse public health effects. The conclusion that a contaminant exceeds the comparison value does not mean that it will cause adverse health effects.

    Cancer Risk Evaluation Guides (CREGs)

    CREGS are estimated contaminant concentrations that would be expected to cause no more than one excess cancer in a million (10-6) persons exposed over lifetime. ATSDR's CREGs are calculated from EPA's cancer potency factors.

    Environmental Media Evaluation Guides (EMEGs)

    EMEGs are based on ATSDR minimal risk levels (MRLs) and considers body weight and ingestion rates. An EMEG is an estimate of daily human exposure to a chemical (in mg/kg/day) that is likely to be without noncarcinogenic health effects over a specified duration of exposure to include acute, intermediate, and chronic exposures.

    Maximum Contaminant Level (MCL)

    The MCL is the drinking water standard established by EPA for the maximum permissible level of a contaminant in water that is delivered to a free-flowing outlet. MCLs are considered protective of public health over a lifetime (calculated as 70 years) for adults consuming 2 liters of water per day.

    Reference Media evaluation guides (RMEGs)

    ATSDR derives RMEGs from EPA's oral reference doses. The RMEG represents the concentration in water or soil at which daily human exposure is unlikely to result in adverse noncarcinogenic effects.


    APPENDIX C: Estimated Exposures and Health Effects

    Estimates of Human Exposure Doses and Determination of Health Effects

    Deriving Exposures Doses

    ATSDR estimated the human exposure doses for the following pathways: (1) ingestion of private well water; (2) incidental ingestion by children of the surface soil in the day care center's play yard; and (3) ingestion of fish from the stormwater lagoon. Deriving exposure doses requires evaluating the concentrations of the contaminants to which people may have been exposed and the frequency and duration of those exposures. Health effects are also related to individual characteristics-- such as age, gender, and nutritional status--that influence how a chemical might be absorbed, metabolized, and eliminated by the body. Together, these factors help influence the individual's physiological response to chemical-contaminant exposure and potential noncarcinogenic and carcinogenic health outcomes. In the absence of site-specific exposure information, ATSDR applied several conservative exposure assumptions to define site-specific exposure as accurately as possible for residents near the DDJC Tracy site.

    Evaluating Potential Health Hazards

    The estimated exposure doses are used to evaluate potential noncancer and cancer effects associated with chemicals of concern. When evaluating noncancer effects, ATSDR uses standard health guidelines, including ATSDR's minimal risk levels (MRLs) and EPA's reference dose values (RfDs), to determine whether adverse effects will occur. The chronic MRLs and RfDs are estimates of the daily human exposures to a substance that are unlikely to result in adverse noncancer effects over a specified duration. ATSDR compared estimated exposure doses associated with DDJC Tracy exposure scenarios to conservative health guidelines such as chronic MRLs or RfDs, if available, for each contaminant of concern. If the exposure dose is greater than the MRL or RfD, then a possibility exists that noncancer effects could occur.

    In general, MRLs and RfDs are based on levels of exposure reported in animal or human studies and consider the most sensitive outcome observed for oral or inhalation exposures. MRLs and RfDs are derived from the level at which no effects were observed in the study, described as the no-observed-adverse-effects level (NOAEL), or the lowest level at which effects are observed, referred to as the lowest-observed-adverse-effects level (LOAEL). To derive the MRL, uncertainty (safety) factors are applied to the NOAELs or LOAELs to account for variation in the human population and the uncertainty involved in extrapolating from animal studies to reflect human exposures.

    No chronic MRL or RfD exists for TCE. Inadequate data exist for evaluating noncancer effects associated with chronic exposures to TCE. Chronic oral exposure studies (e.g., drinking water studies) in animals have focused on cancer endpoints, not noncancer effects. Furthermore, ATSDR recently withdrew the intermediate MRL TCE. The study on which the intermediate MRL for TCE was based has been questioned because it contains certain flaws and limitations (e.g., the exact amount of TCE-contaminated water consumed by rats in the study is uncertain) (ATSDR, 1997). Therefore, when evaluating possible exposures to TCE, ATSDR considered only cancer.

    To evaluate cancer effects, ATSDR uses cancer potency factors (CPFs) that define the relationship between oral exposure doses and the increased likelihood of developing cancer over a lifetime. The CPFs are developed using data from animal or human studies and often require extrapolation from high exposure doses administered in animal studies to the lower exposure levels typical of human exposure to environmental contaminants. CPFs represent the upper-bound estimate of the probability of developing cancer at a defined level of exposure; therefore, they tend to be very conservative (i.e., overestimate the actual risk) in order to account for a number of uncertainties in the data used in the extrapolation.

    ATSDR estimated the potential for cancer to occur using the following equation. (The estimated exposure doses and CPF values for the contaminants of concern are incorporated into the equation):

      Lifetime Cancer Risk = Estimated exposure dose (mg/kg/day) x CPF (mg/kg/day)-1

    Although no risk of cancer is considered acceptable, it is impossible to achieve a zero cancer risk. Consequently, ATSDR often uses a range of 10-4 to 10-6 estimated lifetime cancer risk (or 1 new case in 10,000 to 1,000,000 exposed persons), based on conservative assumptions about exposure, to determine whether the likelihood of developing cancer is significant.

    In addition to estimating the likelihood of noncancer and cancer effects, ATSDR reviewed the literature to evaluate possible health effects associated with exposure at the doses/concentrations estimated for the pathways described above.


    Estimated Exposure Dose for Consumption of Contaminants in Private Well Water

    ATSDR used the following equation to estimate an exposure dose for ingestion of water:

    Estimated exposure dose = Conc. x CF x IR x EF x ED
    BW x AT

    where:

    Conc. = Maximum concentration in the water (ppb)

    CF

    = Conversion factor: 10-3

    IR

    = Ingestion rate: adult = 2 liters per day; child = 1 liter per day
    EF

    =

    Exposure frequency, or number of exposure events per year of exposure (7 days per week x 50 weeks or 350 days per year)

    ED

    = Exposure duration, or the duration over which exposure occurs: adult = 30 years; child = 6 years

    BW

    = Body weight: adult = 70 kilograms (kg) (154 pounds); child = 16 kg (35.2 pounds)

    AT

    = Averaging time, or the period over which cumulative exposures are averaged: 30 years or 6 years x 365 days

    The estimated exposure doses calculated are conservative estimates and may overestimate actual doses received by private well users. Actual doses associated with exposure to water in the private wells are expected to be less than estimates presented previously, based on the following reasons.

    • The dose is estimated using the maximum contaminant concentration present in private wells. The actual concentration, if any, present in private wells over the possible exposure duration is likely to be much lower.
    • The exposure frequency of 350 days per year is extremely conservative, particularly when assuming that the highest concentrations of contaminants were in the residents' drinking water on a daily basis.
    • Similarly, the exposure duration is extremely conservative. The exposure duration used to estimate the exposure dose was 30 years for adults and 6 years for children. While 30 years has been determined as the upper-bound estimate for the length of time a resident could have occupied a house in this area, it may overestimate the length of exposure.
      Likelihood of Health Effects From Ingestion of Private Well Water

      Noncancer

    TCE was detected, but could not be adequately evaluated for noncancer health effects without a health guideline and conclusive toxicological data. Carbon tetrachloride was detected at 1.8 ppb, above ATSDR's comparison value. Although the source of carbon tetrachloride is not known with certainty, it is believed to be unrelated to the DDJC Tracy site. As a prudent health measure, however, ATSDR evaluated the health significance of drinking water containing carbon tetrachloride. In evaluating exposure, ATSDR assumed that a 70-kg adult drinks 2 liters and a 16-kg child drinks 1 liter of private well water per day. Because it is also not known with certainty for how long or to what levels people might have been exposed, ATSDR made assumptions about exposure duration and concentrations. ATSDR assumed EPA's national upper-bound limit at one residence of 30 years for an exposure duration for an adult and 6 years exposure for a child and assumed that adults drank the maximum concentration of carbon tetrachloride detected over the entire 30-year exposure duration. Actual exposures were probably much less because the residents have been supplied with bottled water and/or a carbon filtration system and no one is thought to have been consistently using water containing the highest levels of contaminants for this extended period of time.

    ATSDR's estimated daily exposure doses of carbon tetrachloride (adult: 0.00005 mg/kg/day; child: 0.0001 mg/kg/day) from drinking private well water are approximately 7 to 14 times less than EPA's chronic RfD of 0.0007 mg/kg/day. Because the estimated exposure doses for both the adult and child are less than the RfD for carbon tetrachloride, ATSDR does not expect that drinking water from private wells, even over a 30-year period, would lead to an increased likelihood of developing noncancer health effects.

    To account for dermal exposure (skin contact) and inhalation exposures (breathing vapors) that might occur during domestic use of the water, ATSDR assumed that each of these exposures equal the exposure from drinking the water. In applying this assumption, ATSDR multiplied the estimated oral dose by three (to consider all three routes: ingestion, inhalation of vapors, and dermal contact). The resulting overall estimated doses are still less than the RfD for carbon tetrachloride.

      Cancer

    The link between TCE and cancer at relatively low levels is controversial, however. Although TCE has been shown to cause cancer in laboratory animals given large doses, available human studies for TCE are inconclusive and the data are inadequate to establish a causal link. Because of these uncertainties, EPA is currently reviewing the scientific literature pertaining to the carcinogenicity of TCE. As a conservative screening measure, ATSDR used a previously derived CPF for TCE of 0.11 mg/kg/day-1. This approach provides a conservative evaluation of the likelihood of past exposure to TCE. Carbon tetrachloride, classified as a probable human carcinogen by EPA, has a CPF available for determining the likelihood of cancer effects.

    Using the CPF for carbon tetrachloride and the previously derived CPF for TCE, ATSDR derived excess cancer risk associated with drinking the private well water. The resulting cancer estimates are 9 x 10-7 for TCE and 3 x 10-6 for carbon tetrachloride, or roughly three new cancer cases over a lifetime in 1,000,000 exposed persons. ATSDR believes that even if people drank water containing the highest detected levels of TCE or carbon tetrachloride for a very long time, it is unlikely that the level of exposure would lead to cancer.

    Estimated Exposure Dose for Incidental Ingestion of Day Care Center Play Yard Surface Soil

    Metals (i.e., arsenic, chromium, and vanadium) and pesticides (i.e., 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene [DDE]; 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane [DDT]; and dieldrin) were present in the day care center play yard surface soil at levels above ATSDR comparison values, but often typical of background concentrations. To determine the health significance of exposure to these contaminants in the surface soil, ATSDR estimated an oral exposure dose from incidental ingestion of soil for a child using very conservative assumptions. ATSDR evaluates soil exposure for a child via ingestion because the pronounced hand-to-mouth activity (pica) displayed by young children presents the greatest chance of increasing their overall exposure.

    ATSDR used the following equation to estimate exposure doses for incidental ingestion of day care center play yard surface soil.

    Estimated exposure dose = Conc. x IR x EF x ED x CF
    BW x AT

    where:

    Conc. = Maximum concentration in the surface soil (ppm)

    IR

    = Ingestion rate: child = 200 mg/day

    EF

    = Exposure frequency, or number of exposure events per year of exposure:
    5 days/week x 50 weeks/year or 250 days per year attendance at the day care center
    ED =

    Exposure duration, or the duration over which exposure occurs = 6 years

    CF

    = Conversion factor, 10-6 kg/mg

    BW

    = Body weight (kg): child (1 to 6 years of age) = 16 kg
    AT

    =

    Averaging time or the time period over which cumulative exposures are averaged (6 years x 365 days/year)
      Likelihood of Health Effects From Ingestion of Day Care Center Play Yard Surface Soil

    Table C-3 summarizes the estimated exposure doses via ingestion of the day care center's play yard surface soil. As the table indicates, estimated doses are less than corresponding health guidelines (i.e., MRLs or RfDs). On the basis of these findings, ATSDR concludes that incidental ingestion of soil is not likely to be harmful for young children playing in the day care center's yard. ATSDR also concludes that dermal contact with play yard soil is unlikely to lead to adverse health effects. If we conservatively assume that contaminant concentrations entering the body through dermal contact are approximately equal to ingestion, the estimated combined dose for both exposure routes is still less than the acceptable MRLs or RfDs. In general, uptake of metals or pesticides through skin is less than uptake through ingestion.

    Estimated Exposure Dose for Ingestion of Fish from the Stormwater Lagoon

    Lead, mercury, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, dieldrin, chlordane, and DDT and its derivatives were detected in lagoon sediment. With the exception of PAHs and dieldrin concentrations, which slightly exceeded ATSDR's conservative CREGs, contaminant concentrations were below ATSDR's comparison values for soil. Because even low sediment concentrations may be associated with elevated levels in fish tissue, ATSDR estimated contaminant concentrations in fish by multiplying the maximum sediment concentrations by a sediment-to-fish bioaccumulation factor (BAF). The BAF considers fish uptake from water, food, and sediment.

    Using the estimated fish tissue concentration, ATSDR then used the following equation to estimate exposure doses for ingestion of lagoon fish.

    Estimated exposure dose = Conc. x IR x EF x ED
    BW x AT

    where:

    Conc. = Estimated concentration in fish (mg/kg) (maximum sediment concentration x compound's bioaccumulation factor [BAF])

    IR

    = Ingestion rate: 0.0065 kg/day (approximately one 8-ounce meal per month), average consumption of fish and shellfish from estuarine and freshwater by the general US population (EPA, 1989)

    EF

    = Exposure frequency, or the number of exposure events (7 days x 50 weeks or 350 days per year)

    ED

    = Exposure duration or the duration over which exposure occurs: 30 years

    BW

    = Body weight (kg): 70 kg (154 pounds)

    AT

    = Average time or the time over which cumulative exposures are averaged (noncancer: 30 years; cancer: 70 years x 365 days)
      Likelihood of Health Effects From Ingestion of Stormwater Lagoon Fish
      Noncancer

    Using the estimated fish tissue concentration, ATSDR estimated exposure doses for a 70-kg adult consuming one 8-ounce fish meal per month (or approximately 0.0065 kg each day). Table C-4 presents the resulting estimated exposure doses. As Table C-4 indicates, the estimated doses are less than the respective MRLs or RfDs. Based on this finding, noncancer health effects are not expected to be associated with past consumption of fish caught from the stormwater lagoon.

      Cancer

    Many of the compounds detected in the lagoon sediment are classified as probable human carcinogens by EPA. Therefore, ATSDR estimated excess lifetime cancer cases associated with consumption of lagoon fish and summarized the estimates in Table C-4. Based on these estimates, it appears that lagoon fish probably did not accumulate contaminants, if any, to levels that would contribute to excess cancer. ATSDR estimated that approximately one additional case of cancer might be expected over lifetime if 10,000 people ate fish from the lagoon for 30 years (based on estimated PCB-fish tissue concentrations). Because the lagoon was infrequently used for fishing, it seems unlikely that the small population of former lagoon anglers would develop cancer from exposure to contaminants in lagoon fish. Therefore, ATSDR concludes that ingestion of fish from the lagoon in the past is not expected to result in an increased likelihood of developing cancer.

    Sources:

    ATSDR. 1997. Agency for Toxic Substances and Disease Registry. US Department of Health and Human Services. Toxicological Profile for Trichloroethylene (Update). September.

    AQUIRE. 1995. US Environmental Protection Agency. Aquatic toxicity information retrieval database.

    Black, J.J. et al. 1981.HPLC Studies of PAH Pollution in a Michigan Trout System. In: Chemical Analysis and Biological Fate: Polynuclear Aromatic Hydrocarbons: Fifth Internal Symposium. Ed. Cooke, M. And Dennis A.J. Batelle Press, Columbus, Ohio. pp.345­355.

    Kraus, M.L. 1989. Bioaccumulation of heavy metals in pre-fledgling tree swallows Tachycineta bicolor. Bulletin of Environmental Contamination Toxicology. Vol. 43.

    EPA. 1989. Exposure Factors Handbook. EPA/600/8-043. 1989


    TABLE C-1. Estimated Exposure Doses--Noncancer Effects
    Drinking Private Well Water


    Contaminant

    Maximum Contaminant
    Concentration (ppb)

    Estimated Exposure Dose
    (mg/kg/day)a
    Chronic
    Health Guideline
    Oral
    (mg/kg/day)
    Basis for Health
    Guideline
    Adult Child
    TCE 6.7 0.0002 0.0004 not available
    Carbon tetrachloride 1.8 0.00005 0.0001 0.0007 RfD

    a Estimated Exposure Dose = Conc. x CF x IR x EF x ED
    BW x AT

    Conc. = Maximum contaminant concentration measured in the private well water (ppb)
    CF = Conversion factor: 10-3
    IR = Ingestion rate: adult = 2 liters per day; child = 1 liter per day
    EF = Exposure frequency or the number of exposure events (7 days x 50 weeks or 350 days per years)
    ED = Exposure duration or the duration over which exposure occurs: adult = 30 years; child = 6 years
    BW = Body weight (kg): adult = 70 kg (154 pounds); child = 16 kg (35.2 pounds)
    AT = Averaging time or the period over which cumulative exposures are averaged (6 years or 30 years x 365 days)

    Key: ppb=parts per billion; ppm = parts per million; mg/kg/day = milligrams contaminant per kilogram body weight per day; RfD= reference dose


    TABLE C-2. Estimated Exposure Doses--Cancer Effects
    Drinking Private Well Water


    Contaminant

    Maximum Contaminant
    Concentration (ppb)

    Estimated Exposure Dose-Cancer
    (mg/kg/day) a
    Cancer Potency Factor Lifetime Cancer Risk b
    TCE 6.7 0.00008 0.011c 9 x 10-7
    Carbon Tetrachloride 1.8 0.00002 0.13 3 x 10-6
    a Estimated Exposure Dose-Cancer = Conc. x CF x IR x EF x ED
    BW x AT
    Conc = Maximum contaminant concentration measured in the private well water (ppb)
    CF = Conversion factor: 10-3
    IR = Ingestion rate: 2 liters per day
    EF = Exposure frequency or the number of exposure events (1 event x 7 days x 50 weeks or 350 days per year)
    ED = Exposure duration or the duration over which exposure occurs = 30 years
    BW = Body weight (kg): 70 kg (154 pounds)
    AT = Average time or the time over which cumulative exposures are averaged (70 years x 365 days)

    b Lifetime Cancer Risk = estimated exposure dose (cancer) x cancer potency factor

    c EPA is currently reviewing the CPF for TCE. ATSDR uses the previously derived CPF for screening purposes

    Key: ppb= parts per billion; ppm = parts per million; mg/kg/day = milligrams contaminant per kilogram body weight per day


    TABLE C-3. Estimated Exposure Doses--Noncancer Effects
    Incidental Ingestion of Day Care Center Play Yard Surface Soil


    Contaminant

    Maximum Contaminant
    Concentration (ppm)

    Estimated Dose
    Child
    (mg/kg/day)
    Health Guideline
    Oral
    (mg/kg/day)
    Basis for Health
    Guideline
    Arsenic 4.03 0.00004 0.0003 MRL
    Chromium 28.6 0.0003 0.005 RfD
    Vanadium 33 0.0003 0.003 MRL
    DDT 3.31 0.00002 0.0005 MRL
    DDE 2.35 0.00003 0.0005 MRL (DDT)
    Dieldrin 0.357 0.000003 0.00005 MRL/RfD
    a Estimated Exposure Dose = Conc. x IR x CF x EF x ED
    BW x AT
    Conc. = Maximum contaminant concentration measured in the day care center play yard soil (ppm)
    IR = Soil ingestion rate for a child: 200 mg/day.
    CF = Conversion factor: 10-6
    EF = Exposure frequency or the number of exposure events (5 days x 50 weeks or 250 days per year)
    ED = Exposure duration or the duration over which exposure occurs: child = 6 years
    BW = Body weight (kg): child = 16 kg (35.2 pounds)
    AT = Averaging time or the period over which cumulative exposures are averaged (6 years x 365 days)

    Key: ppm = parts per million; mg/kg/day = milligrams contaminant per kilogram body weight per day; MRL = minimal risk level; RfD = EPA's reference dose


    TABLE C-4. Estimated Exposure
    Ingestion of Stormwater Lagoon Fish


    Contaminant

    Estimated Fish Tissue Concentration

    Noncancer Effects

    Cancer Effects
    Maximum
    Sediment
    Conc.
    (ppm)
    BAFa Estimated
    Fish
    Tissue
    Conc.
    (ppm)
    Estimated
    Exposure Dosec
    (mg/kg/day)
    Chronic
    Health
    Guideline
    Oral
    (mg/kg/day)
    Estimated
    Exposure
    Dosec
    (mg/kg/day)
    Lifetime
    Cancer
    Riskc
    Lead 0.193 0.3 0.0579 0.000005 not available 0.000002 not applicable
    Mercury 0.22 1 0.22 0.00002 not available 0.000008 not applicable
    Pyrene 1.8 0.008 0.015 0.000001 0.03 (RfD) 0.0000005 4 x 10-6
    PCBs 0.493 4 1.836 0.0002 0.00002 (MRL 0.00007 1 x 10-4
    DDT 0.158 1.4 0.221 0.00002 0.0005 (MRL) 0.000008 3 x 10-6
    DDE 0.815 0.7 0.571 0.00005 0.0005
    (MRL-DDT)
    0.00002 7 x 10-6
    DDD 2.3 0.7 1.6 0.0001 0.0005
    (MRL-DDT)
    0.00006 2 x 10-5
    Chlordane 0.093 1 0.093 0.000008 0.00006 (RfD) 0.000004 5 x 10-6
    Dieldrin 0.205 0.5 0.103 0.000009 0.00005
    (MRL/RfD)
    0.000004 6 x 10-5

    a References: Black et al. 1981; Kraus, 1989; AQUIRE, 1995.

    b Estimated Exposure Dose = Conc. x IR x EF x ED
    BW x AT
    Conc. = Maximum contaminant concentration estimated in lagoon fish (ppm)
    IR = Ingestion rate: 0.0065 kg/day
    EF = Exposure frequency, or the number of exposure events (7 days x 50 weeks or 350 days per year)
    ED = Exposure duration or the duration over which exposure occurs = 30 years
    BW = Body weight (kg): 70 kg (154 pounds)
    AT = Average time or the time over which cumulative exposures are averaged: years (noncancer: 30 years; cancer: 70 years) x 365 days

    c Lifetime Cancer Risk = estimated exposure dose (cancer) x cancer potency factor

    Key: ppm = parts per million; mg/kg/day = milligrams contaminant per kilogram body weight per day ; MRL = minimal risk level; RfD = EPA's reference dose; BAF = bioaccumulation factor.


    APPENDIX D: Responses to Public Comments

    The Agency for Toxic Substances and Disease Registry (ATSDR) received the following comments/questions during the public comment period (June 15 to July 26, 1998) for DDJC Tracy Public Health Assessment (PHA) (June 15, 1998). For comments that questioned the validity of statements made in the PHA, ATSDR verified or corrected the statements. The list of comments does not include editorial comments received concerning such things as word spelling or sentence syntax. ATSDR has not addressed requests for new information to be included in the PHA, unless the party who filed the request provided the supporting documentation.

    1. Comment: WSW 7 was placed on standby status when trichloroethylene (TCE) was detected in a nearby monitoring well. Specify whether any attempts have been made to identify the source of TCE contamination near WSW 7.

      Response: DDJC Tracy has been evaluating possible sources of the TCE contamination. Although DDJC Tracy has not identified a source, the contamination is probably unrelated to site activities because no on-site buildings or other suspect areas exist upgradient of the isolated TCE detections. DDJC Tracy continues to investigate potential sources, including a nearby off-site machine shop.

    2. Comment: Specify whether a one-year monitoring period allows sufficient time to monitor WSW 7 before it is placed back in production. A longer period of monitoring would be prudent.

      Response: Since the time TCE was detected in a monitoring well located near WSW 7, DDJC Tracy has monitored the water supply wells for volatile organic compounds. The continued monitoring has not detected TCE in WSW 7 or in the other two water supply wells. DDJC Tracy will continue to monitor the water supply wells for another three quarters (for a total of five quarters or about 15 months). If the wells continue to test clean, DDJC Tracy will resume production of WSW 7. ATSDR will review the data and information on potential sources to determine whether any additional measures are necessary to protect public health.

    3. Comment: The public health assessment evaluated future exposures based on current conditions. It may be more appropriate to evaluate future exposures based upon potential future conditions.

      Response: DDJC Tracy's mission may change in the future, but the property will continue to be used for commercial or industrial purposes only. Accordingly, ATSDR's assessment should sufficiently characterize the potential for future health hazards.

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