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HEALTH CONSULTATION

BRUNSWICK WOOD PRESERVING
(a/k/a ESCAMBIA TREATING COMPANY)
BRUNSWICK, GLYNN COUNTY, GEORGIA


1.0 INTRODUCTION

1.1 Background on the Agency for Toxic Substances and Disease Registry (ATSDR)

The Agency for Toxic Substances and Disease Registry (ATSDR), in Atlanta, Georgia, is one of the agencies of the U.S. Department of Health and Human Services. ATSDR is required to respond to community concerns and conduct public health assessments (PHAs) for sites proposed for the United States Environmental Protection Agency's (EPA's)National Priorities List (NPL), under authorities provided by the Superfund law (Comprehensive Environmental Response, Compensation, and Liability Act of 1980 [CERCLA]) and its amendments. A PHA is an in-depth evaluation of more than one way that individuals may come in contact with contamination from a given site, which is also referred to as an exposure pathway. ATSDR also produces Health Consultations (HC) in order to provide a response to a specific question or to evaluate one or few exposure pathways at a site. As is the case with this document, HCs are also prepared by ATSDR to update existing PHAs or to evaluate specific community concerns. As part of both the PHA and HC process, relevant environmental data is evaluated to determine whether human health effects are likely to result from exposure.

1.2 Site Description

Brunswick Wood Preserving (BWP) was initially located in the city of Brunswick, Georgia until the late 1950's. At that time, the site was moved from the downtown area and is presently located, north of the city of Brunswick, in north Glynn County, Georgia. The site is located on Perry Lane Road, approximately 1/2 mile east of the intersection of Perry Lane and Highway 341, New Jessup Highway. While most of the activities that took place at the site were restricted to an area of approximately 50 acres, the total property includes 84 acres (EPA, 2000). A site map of BWP is provided in Appendix A, Figure 1.

Wood treatment operations began at the site in 1958. BWP was owned by a number of different wood preserving companies during its operational history and the process utilized for wood preserving also changed over time. Initially, only oil-based preservatives, namely creosote and solutions of pentachlorophenol (PCP) were used at BWP. Unlined surface impoundments, located on the west and east portions of the site, received waste water from on-site processes. In approximately 1969, the company built a separate treatment facility that generated less wastewater and utilized chromated copper arsenate (CCA) preservative. The site ceased operations in 1991, after the owners of the facility filed for bankruptcy (EPA, 2000).

Railroads are located along the east and west ends of BWP. Perry Lane Road borders the north side of the property and the south side is adjacent to residential properties and wooded areas. Drainage from the site flows into nearby Burnett Creek, a tidally influenced stream located to the west of BWP (EPA, 2000).

1.3 ATSDR's Involvement and Objectives at BWP

ATSDR involvement at BWP started with the completion of a HC on May 15, 1992, in response to a petition concerning exposure to soil. The conclusions of this initial evaluation indicated that contaminants, including PCP, dioxins, and polynuclear aromatic hydrocarbons (PAHs), were present in on-site soil at levels above acceptable health guidelines. ATSDR recommended that access to the site be restricted until soil cleanup was completed (ATSDR, 1992a).

BWP was proposed for EPA's NPL in December 1996 and officially listed on the NPL on April 1, 1997. In December 1997, a second petitioned HC was completed by ATSDR to evaluate the available groundwater data and the potential for contaminated groundwater to migrate from the site. However, the potential public health implications via exposure to contaminants in private drinking water wells could not be evaluated. It was concluded that public drinking water supply wells posed no apparent public health hazards as a result of site-related contamination based on 1995 and 1996 sampling of municipal wells. The conclusions of the December 1997 HC indicated that data to adequately characterize the groundwater conditions were not available. Private wells in the vicinity of BWP had not been regularly sampled for site-related contaminants since 1991. Since edible fish tissue data was not available for Burnett Creek at that time, it was also concluded that consumption of fish from the creek by the local community could not be evaluated (ATSDR, 1997).

In response to a community member's concern, an additional HC was completed in December 1998 to further evaluate the potential for exposure to contaminants present in on-site soils (ATSDR, 1998a). Although elevated concentrations of contaminants, including PCP, PAHs, dioxins, furans, arsenic, and chromium were detected in on-site soil and sediment, it was concluded that the potentially exposed individuals (such as workers and trespassers) were not likely to have frequent, long-term exposure to contaminants. Therefore, exposure to these individuals was not expected to result in adverse health effects. Another conclusion of the HC was that soil samples collected along the perimeter of BWP contained low-level contamination and indicated that off-site soil was not likely to pose a public health hazard. While Burnett Creek sediment contained slightly elevated concentrations of dioxins, PAHs, and arsenic, it was also concluded in this report that exposure to sediments in Burnett Creek was infrequent and not likely to occur on a routine or long-term basis. Therefore, exposure to sediment from Burnett Creek was not expected to pose a public health hazard. The December 1998 HC recommended that fish samples be collected from Burnett Creek to evaluate the possible health impacts from human consumption (ATSDR, 1998a).

The results of both the December 1997 and December 1998 HCs were combined to create a PHA for BWP, dated February 9, 1999 (ATSDR, 1999). After release of the February 1999 PHA, ATSDR received an additional request from a citizen to evaluate off-site soil and sediment data (EPA, 2000). A review of these data was conducted and documented in a HC, dated October 30, 2000 (ATSDR, 2000). The report concluded that none of the soil samples collected from five (off-site) residential areas exceeded the established health criteria. Therefore, adverse health effects from exposure to off-site soil were not likely to result. Five PAHs, arsenic, and chromium were present in Burnett Creek sediment at concentrations exceeding the established health guidelines. However, further evaluation of the likely exposure, which included frequency and duration of typical exposures, and a review of the available scientific literature indicated that adverse non-cancerous and cancerous effects were not likely to occur.

Since the October 2000 HC was completed, additional data has been collected at BWP (EPA, 2000; CDM, 2001). The objective of this HC is to evaluate the newly collected samples at BWP. These data include sediment samples collected from Burnett Creek, groundwater samples collected from nearby private drinking water wells, and fish and shellfish samples. This HC evaluates the likely exposure scenarios for each media, the concentrations of contaminants detected in site media, and the available toxicological data. Exposure to on-site soil has also been discussed in this document.


2.0 DISCUSSION

2.1 Available Data

2.1.1 Sediment

Eleven sediment samples were collected along Burnett Creek in November 2000 as part of the Supplemental Sampling Investigation (CDM, 2001). In general, the sample locations from this November 2000 sampling effort are downstream from the sediment samples collected in July 2000 during the Phase III Remedial Investigation (EPA, 2000). As previously stated in this HC, the sediment samples collected in July were evaluated in the October 2000 HC and it was concluded that exposure to concentrations of contaminants present in sediment from Burnett Creek is not expected to result in cancer and non-cancer health effects.

Sediment samples collected from Burnett Creek in November 2000 are evaluated in this HC. These samples were collected at an approximate depth of 6 to 8 inches, about 250 feet apart, and during low-tide conditions. A decontaminated, stainless steel scoop attached to a metal pole was used to collect the sediment samples from the approximate center of the creek. The precise location of these samples has been recorded using a Geographical Positioning System (also referred to as a GPS), and a database containing this information is maintained by EPA. Samples were collected in accordance with EPA Region IV's Standard Operating Procedure (EPA, 1996). Each composite sample consists of 2 or 3 individual samples (also referred to as aliquots), which were collected within two feet of one another. Sediment samples were analyzed for semi-volatile organic compounds (SVOCs), including PAHs and PCP. Samples were also analyzed for dioxins and furans (CDM, 2000).

In general, the types of contaminants detected in Burnett Creek sediment samples collected in November 2000 are similar to those detected during the earlier July 2000 sampling event. These contaminants include 2,3,7,8-tetrachlorodibenzodioxin (2,3,7,8-TCDD), total dioxin Toxicity Equivalency Factors(1) (TEQs), PCP, and various PAHs. However, the samples collected in November 2000 contained lower concentrations of these contaminants, which is likely due to the fact the November 2000 samples were collected further downstream from the source than the July 2000 samples. Although the evaluation of the July 2000 data (which contained higher concentrations of contaminants) indicated that adverse cancer and non-cancer effects were not likely to result based on frequency andduration of typical exposures, an evaluation of the November 2000 sediment data is included in this HC in order to include any new toxicological data that may be available for the detected contaminants.

2.1.2 Fish and Shellfish Tissue

Another objective of the November 2000 sampling event was to collect edible fish species, including speckled trout, redfish, spot, and sheeps head from Burnett Creek, a tributary to Cowpen Creek, which feeds into the Turtle River upriver of Highway 303. However, these larger fish were not available for capture during the field investigation and only ten small mullet were caught at the time of the sampling effort. The fish sample is a composite of these ten small mullet. Filleted fish (with skin-on) and the carcasses of the filleted fish were analyzed separately. Shrimp, crabs, and forage fish (more specifically mummichogs) were also collected from Burnett Creek. Fish and shellfish samples were prepared for analyses in accordance with approved EPA methods (EPA, 1993; EPA, 1996). Samples consisting of the edible portions of the shrimp and crab were also analyzed in order to evaluate potential exposure to the most typical concentrations of contaminants. All samples were analyzed for EPA Target List semi-volatile organic compounds (SVOCs), dioxins, and furans. Fish and shellfish were not available for capture at each location. The following samples were collected from the three locations described below:

  • Location 1 (Immediately upstream of the US 341 Bridge) - fish, shrimp, blue crab and mummichog

  • Location 2 (Immediately downstream and upstream of the Old Jesup Road Bridge) - shrimp and mummichog

  • Location 3 (Along a 100-foot reach located between Perry Lane and Old Jesup Road) - mummichog only

In response to the presence of contamination resulting from nearby industry and unrelated to BWP (mercury and polychlorinated biphenyls [PCBs]) the Georgia Department of Natural Resources (GDNR) has issued a fish consumption advisory for the "Upper Turtle and Buffalo Rivers, Upriver of State Highway 303", which includes Burnett Creek. This advisory recommends that no more than one meal of blue crab, flounder and red drum, caught upriver of Highway 303, be consumed per week. It is also recommended by GDNR that no more than one meal of croaker and spotted seatrout be consumed per month. Additionally, no consumption of black drum was recommended for the area upriver of Highway 303. Due to the density of development in the vicinity of the upper Turtle and Buffalo Rivers upriver of Highway 303, the National Shellfish Sanitation Program has issued a shellfish ban, which recommends no consumption of shellfish (clams, mussels, and oysters) collected from these areas. No restriction has been recommended for the consumption of shrimp (GDNR, 2002). ATSDR recommends that the local community follow these fish advisories and restrictions.

2.1.3 Groundwater

Groundwater refers to water that lies under the surface of the earth. Groundwater can become contaminated when chemicals migrate or leach from contaminated soils (for example, lagoons, surface and buried impoundments).

Individuals that receive their drinking water from the public water supply are not currently exposed to contaminants at concentrations that will result in adverse health effects. The public water supply has been sampled in the past and will continue to be periodically sampled in the future as part of the requirements of EPA's Safe Drinking Water Act (SDWA), which established regulatory limits regarding the concentrations of contaminants that can be present in the public water supply. However, periodic testing and sampling of private wells is not required under EPA's SDWA.

ATSDR's previous evaluation of the available groundwater data indicated that site-related contamination had not been adequately characterized (ATSDR, 1997). Therefore, it was concluded that exposure to groundwater from private wells was an "indeterminate public health hazard". Since that time, extensive sampling of the groundwater has been conducted at BWP. Based on this information, the potential for exposure to contaminated drinking water resulting from site-related activities at BWP has been evaluated further in this document.

There are three well-defined aquifer systems, or groundwater categories, in the vicinity of BWP. In descending order, these aquifer systems are the shallow (or surficial), Miocene, and Floridan aquifers. Various site investigations have focused on characterization of the impact of site-related activities on groundwater underlying BWP. In general, groundwater samples collected from the shallow, intermediate, and deep zones of the surficial aquifer indicate the presence of benzene, toluene, ethylbenzene, and xylenes (also referred to as "BTEX" compounds), PAHs, naphthalene, and PCP. The highest concentrations of these contaminants have been found in shallow groundwater collected from monitoring wells (used for investigation purposes and not for drinking water uses) overlying the western portion of BWP. The general movement of the groundwater is in a westerly and northwesterly direction, in the general direction of Burnett Creek. The contaminated groundwater in the shallow surficial aquifer is not currently used for drinking water purposes and future use of the shallow groundwater beneath BWP will be restricted.

Twenty-one private wells at various residences and businesses in the general vicinity of BWP were sampled in July 2000 (EPA, 2000). These twenty-one private drinking water wells and two additional residential wells were also sampled during the second round of sampling conducted in August 2001 (EPA, 2001a). Each of the samples was analyzed for volatile organic compounds (VOCs), extractable organic compounds (including pesticides, PCBs), and metals. In addition, special analytical services were utilized to evaluate the presence of various other contaminants at concentrations relevant to the drinking water standards for each of these contaminants. Although the depths of each of the private, potable wells are not available, most are generally thought to be in the range of 100 to 120 feet deep, which is within the Miocene aquifer and below the confining bedrock.

2.1.4 Soil

Since the October 2000 HC was conducted, additional soil samples have been collected at BWP. As previously stated, the October 2000 HC concluded that soil collected from residential property (off-site) in the vicinity of BWP does not pose a health hazard to children or adults (ATSDR, 2000). The newly collected data consists of on-site soil samples (CDM, 2001).

Dioxins are the primary contaminants contributing to the potential risk from exposure to on-site soils at BWP. According to EPA's Proposed Plan, soils containing dioxin at concentrations greater than 1 ppb will be excavated and the contaminated soil will be incorporated into the proposed caps (or covers) over the surface impoundments on the west (IM-1/2 ponds) and east (IM-4/5 ponds) portions of BWP (EPA, 2001b). The caps will prevent both leaching (or movement of contaminants from soil to groundwater as a result of rainwater passing through the area of contaminated soil) and direct contact with contamination. The soil remediation goal of 1 part per billion (ppb), established by EPA, is considered health-protective of residential use of the property. However, the site is not currently used for residential purposes, and future residential use of BWP will be prohibited in the form of a deed restriction, as necessary. In addition, portions of BWP are currently restricted and it is recommended that access to areas of the BWP property that require soil remediation be restricted until the clean-up efforts have been completed in order to prevent or mitigate exposure to contaminants present in soil. Frequent or routine exposure to on-site soils at BWP is not expected to occur. It is possible that trespassers or visitors may access BWP, although exposure to these receptors is expected to be infrequent in comparison to future residential receptors present at the site. Since the 1 ppb clean-up level is protective of residential use of the site, it is considered significantly protective of trespassers, as well as other infrequent receptors that may access the site. Therefore, adverse health effects are not expected as a result of exposure to on-site soil. Soil exposure is not discussed further in this document.

2.2 Evaluation Process

A two-stage evaluation process has been utilized in the assessment of the additional sediment, fish and shellfish tissue, and groundwater data. The first step involves the review of the available sampling data (as discussed in the previous section) and the selection of contaminants that warrant further evaluation, based on the potential for exposure to these contaminants to result in adverse health effects.

Contaminant selection for further evaluation considered the following factors:

  • Concentrations of contaminants in wastes and environmental media
  • Relationship of concentrations to ATSDR's Public Health Evaluation Comparison Values
  • Sampling locations and data quality
  • Exposure probability, frequency, and duration
  • Community health concerns

Comparison Values (CVs) are contaminant concentrations below which an exposed person would not likely experience adverse health effects. CVs are used to eliminate contaminants that do not require further evaluation; therefore, focusing the evaluation of potential health impact. Contaminants that were detected, but not selected for additional evaluation, are not addressed further in this HC. The presence of a contaminant at a level above the established CV; however, does not necessarily indicate that human exposure will result in health effects. When a contaminant concentration exceeds its CV, a closer look at the available sampling data, exposure scenario, and the toxicological information is necessary. Maximum detected concentrations of contaminants in each media were compared with their respective CVs to determine the contaminants that require additional evaluation.

The next step in the evaluation process involves an in-depth health-effects evaluation of the contaminants detected in site media (such as soil, groundwater, surface water, sediment, and fish/shellfish) above their respective CVs. The primary focus of this effort is to evaluate the potential for the contaminant(s) to produce cancer and non-cancer health effects as a result of human exposure. This involves the consideration of various site-specific factors, such as the exposure route (for example: ingestion, inhalation, or direct contact), the concentration of a contaminant in a particular media, and the frequency and duration of exposure.

A more detailed description of both steps of the evaluation process is presented in Appendix B (ATSDR, 1992b; EPA, 1989; EPA, 1992; EPA 1995; EPA, 1997). Each of the exposure pathways for which additional data is available and the results of the evaluation process are presented in the following sections of this document.

2.3 Exposure Pathways, Contaminants of Concern, and Public Health Implications

ATSDR identifies human exposure pathways by examining environmental and human components that might lead to contact with contaminants of concern. A pathway analysis considers five principal elements: the source of contamination, transport through environmental media, the point of exposure, the route of human exposure, and the exposed population. Completed exposure pathways are those for which the five elements are evident, and indicate that exposure to a contaminant has occurred in the past, is currently occurring, or will occur in the future. Potential exposure pathways are those for which exposure seems possible, but one or more of the elements is not clearly defined, typically due to the absence of key information. A discussion of each of the completed exposure pathways that have been previously identified at BWP, for which additional data is available and evaluated in this HC, is presented in the following sections of this document.

A detailed discussion of the evaluation process utilized in this HC is presented in Appendix B.

2.3.1 Sediment Pathway

The additional sediment data, collected in November 2000, have been reviewed in order to determine whether exposure to contaminants present in sediment is likely to result in adverse health effects. The maximum detected concentration of total dioxin TEQs of 0.00012 milligrams per kilogram (mg/kg) was found to exceed the CV of 0.000050 mg/kg. Chemical-specific CVs were not available for some contaminants detected in sediment samples, including acenaphthlene, benzo(g,h,i)perylene, and phenanthrene. Therefore, the CV for benzo(a)pyrene was used for comparison, since it is part of the same chemical class. Benzo(a)pyrene is also considered the most toxic chemical among this class of compounds and has been selected in order to conservatively evaluate exposure to the contaminants for which no CVs have been developed. A summary of the November 2000 sediment data is provided in the following table.

Sediment Data from Burnett Creek (mg/kg)

Contaminant

Frequency of Detection

Maximum Detected Concentration

Soil Comparison Value

Source of Comparison Value

Total TEQ

11/11

0.00012

0.000050

Chronic EMEG

Acenaphthylene

10/11

0.016 J

0.10

CREG (a)

Benzo(g,h,i)perylene

11/11

0.028

0.10

CREG (a)

Phenanthrene

11/11

0.021 J

0.10

CREG (a)

NOTES:
Concentrations presented on the table are in mg/kg.
Contaminants that exceed established CVs or detected contaminants for which CVs are unavailable have been included in the above table.
Shaded values indicate that the maximum detected concentration exceeds established comparison values.
(a) Indicates that the comparison value for benzo(a)pyrene (the most toxic chemical in this class) was used as a surrogate since a CV was not available for the specific compound.
J = Estimated value
EMEG = Environmental Media Evaluation Guide (child)
CREG = Cancer Risk Evaluation Guide

The results of the sampling indicate that total dioxin TEQs were the only contaminants detected in sediment above their established CV. Therefore, a more detailed cancer and non-cancer evaluation of this group of dioxin contaminants was conducted. This evaluation considered exposure to sediment via ingestion and dermal (or direct) contact by children and adults during wading or other recreational activities associated with Burnett Creek. The calculated non-cancer dose and excess lifetime cancer risk, which were generated using conservative assumptions and site-specific information, were then compared with the established health guidelines.

The calculated dose for adults exposed to total dioxin TEQs, via ingestion and dermal contact, is 2.2 x 10-10 milligrams per kilograms per day (mg/kg/day), which does not exceed the established health guideline of 1.0 x 10-9 mg/kg/day for adults. The calculated dose for exposure to children was estimated at 3.0 x 10-9 mg/kg/day, which slightly exceeds the established health guideline. Therefore, a more detailed discussion of childhood exposure to contaminants in sediment has been conducted.

Available human and animal data were evaluated to determine the likelihood of health effects resulting from childhood exposure to concentrations of total dioxin compounds detected in sediment in Burnett Creek. Although some human data are available, their application is limited due to uncertainties concerning the exposure doses and other confounding factors. For example, much of the human data is based on occupational exposure to high concentrations of dioxins and, in some cases, various other chemicals present in the work place. Based on the results of the available human investigations, mild liver effects, endocrine dysfunction, chloracne (skin condition), and nervous system effects have been observed among exposed individuals (ATSDR, 1998a).

Animal data indicates that the liver is the primary target organ for dioxin toxicity. Immunological, reproductive, and developmental effects have also been reported among subjects exposed to dioxin compounds. The majority of these studies report adverse health effects at exposure doses between 1.0 x 10-7 mg/kg/day and 1.0 x 10-5 mg/kg/day. The dioxin exposure doses calculated from the available animal data were approximately 100 to 10,000 times greater than the exposure doses calculated for children wading and playing in sediment in Burnett Creek (3.0 x 10-9 mg/kg/day for children) (ATSDR, 1998b). Therefore, non-cancer health effects are not expected based on adult and childhood exposure to contaminants present in sediment from Burnett Creek.

Exposure to high concentrations of dioxin compounds has been associated with an increase in the incidence of various forms of cancer, such as thyroid, liver, kidney, and skin cancer (ATSDR, 1998b). EPA has categorized dioxin compounds as "probable human carcinogens" (or B2 classification), based on the production of liver tumors in rats and mice exposed to concentrations of dioxins thousands of times greater than those calculated for exposure associated with BWP (EPA, 2002). The calculated lifetime cancer risk is equal to 6.1 excess cancer cases per 10,000,000 individuals exposed to total dioxin TEQs in Burnett Creek sediment via ingestion and dermal route. This value indicates an extremely low risk of developing cancer due to exposure. Animal studies indicate that cancer was observed at exposure doses above approximately 1.0 x 10-6 mg/kg/day, which is 4,000 times greater than the calculated dose for exposure to sediment in Burnett Creek (2.2 x 10-10 mg/kg/day).

Therefore, ATSDR concludes that, based on the additional data available for sediment (collected November 2000), cancer and non-cancer health effects are not expected to result among individuals exposed (via ingestion and dermal contact) to total dioxin compounds in Burnett Creek sediment. This conclusion is consistent with the conclusion of the HC, dated October 2000, which evaluated the July 2000 sediment data from Burnett Creek.

2.3.2 Fish and Shellfish Pathway

The fish and shellfish tissue data, collected November 2000, was examined in order to determine whether individuals who consume the fish and shellfish from Burnett Creek are likely to experience adverse health effects. The primary contaminants of concern are total dioxin TEQs, which were detected at maximum concentrations in the fish (mullet) carcass sample at 3.7 x 10-6 mg/kg. No contaminants were detected in the fish (mullet) fillet sample.

Bis(2-ethylhexyl)phthalate was also detected in one of three mummichog samples at a low concentration. Bis(2-ethylhexyl)phthalate was not detected in any other fish or shellfish samples collected from Burnett Creek during the November 2000 sampling event and is not known to be a site-related contaminant. Additionally, this contaminant is a common laboratory-related contaminant and it may not actually exist in the mummichog sample. Mummichog are not typically consumed by individuals, and therefore, exposure is expected to be limited.

A summary of the November 2000 fish and shellfish data is provided in the following table.

Fish and Shellfish Data (mg/kg)

Contaminant

Mullet Fillet

Mullet Carcass

Shrimp (a)

Blue Crab

Mummichog(b)

Comparison Value(c)

Bis (2-e,h) phthalate

ND

ND

ND

ND

2.4

0.23

2,3,7,8-TCDD

ND

8.9 x 10-7

ND

ND

8.6 x 10-7

2.1 x 10-8

Total Dioxin TEQs

ND

3.7 x 10-6

3.0 x 10-7

6.2 x 10-7

3.1 x 10-6

2.1 x 10-8

NOTES:
Concentrations on the table are presented in mg/kg.
Contaminants concentrations that exceed CVs have been included on the above table.
Shaded values indicate that the maximum detected concentration exceeds established CVs.
(a) Shrimp were collected from a total of two locations. The maximum detected concentration of the contaminant from the two samples appears on the above table.
(b) Mummichogs were collected from a total of three locations. The maximum detected concentration of the contaminant from the three samples appears on the above table.
(c) Since fish CVs are not available from ATSDR, the EPA Region III Risk-Based Concentrations have been used in the screening evaluation.
ND = Not Detected

The likelihood of cancer and non-cancer health effects was considered for contaminants that exceed the CVs. For conservatism, exposure via fish and shellfish consumption was estimated by incorporating the maximum detected concentrations detected among the fish, crab, and shellfish samples into the dose calculations (fish carcass sample = 3.7 x 10-6 mg/kg). The calculated doses for ingestion of fish containing total dioxin TEQs by children and adults are 5.0 x 10-9 mg/kg/day and 2.3 x 10-9 mg/kg/day, respectively, which slightly exceed the established health guideline of 1.0 x 10-9 mg/kg/day. Available human and animal data were evaluated to determine the likelihood of health effects at the concentrations of dioxin that have been detected in fish (mullet), shrimp, and crab samples. As previously discussed, human data on dioxin exposure are limited as a result of lack of information on the actual concentrations that individuals were exposed to and other confounding factors, such as exposure to other chemicals in the work place. Also, data from occupational exposures are typically at a much higher concentration than the concentration of dioxin compounds associated with BWP. The results of the available human investigations indicate mild liver effects, endocrine dysfunction, chloracne (skin condition), and nervous system effects (ATSDR, 1998b).

The available animal data for dioxin compounds is more extensive than the human data. Based on animal studies, the liver is the primary target organ for dioxin toxicity. Immunological, reproductive, and developmental effects have also been reported among subjects exposed to dioxin compounds. As previously discussed, the majority of these studies report adverse health effects at exposure doses between 1.0 x 10-7 mg/kg/day and 1.0 x 10-5 mg/kg/day. The dioxin exposure doses calculated from the available animal data were approximately 20 to 4,000 times greater than the exposure doses calculated based on exposure to dioxin compounds associated with fish and shellfish from Burnett Creek (ATSDR, 1998b).

In addition, a number of conservative assumptions have been incorporated into the calculated exposure doses, including the assumption that individuals would consume two meals per week from Burnett Creek and the incorporation of the maximum concentration of dioxin compounds detected among the available fish, shellfish, and crab data. Based on the available data, the highest concentrations of dioxin compounds have been measured in the fish (mullet) carcass sample. This is likely the result of accumulation of dioxin compounds in fatty tissues and organs, which were included in the analysis of the fish carcass sample. In addition, dioxin compounds have not been reported in the fish fillet sample, which is the most likely part of the fish for individuals to consume. Therefore, limited exposure to dioxin compounds in fish from Burnett Creek is expected. Based on this evaluation, ATSDR concludes that adults and children who consume mullet, shrimp, and crab from Burnett Creek are not expected to experience adverse non-cancer health effects.

The excess cancer risk calculated for exposure to dioxin compounds in the fish (mullet) carcass sample is 6.0 x 10-6, which indicates a low cancer risk. Human studies suggest an increase in many different forms of cancer, such as thyroid, liver, kidney, and skin cancer. EPA has categorized dioxin compounds as "probable human carcinogens" (or B2 classification), based on the production of liver tumors in rats and mice exposed to concentrations of dioxins thousands of times greater than those calculated for exposure associated with BWP (EPA, 2002). Animal studies indicate that cancer was observed at exposure doses above approximately 1.0 x 10-6 mg/kg/day, which is over 400 times greater than the calculated exposure dose (2.3 x 10-9 mg/kg/day) for individuals consuming fish and shellfish from Burnett Creek (ATSDR, 1998b). Based on the available data, a significant increase in the incidence of cancer is not expected among individuals who consume fish (mullet), shrimp, and crab from Burnett Creek.

While attempts were made during the sampling effort to collect fish of greater size, these species were not present during the sampling event. In addition, it is difficult to extrapolate contaminant levels detected in one species of fish to a different species for the evaluation of larger fish exposure. However, bioaccumulation of dioxin in larger fish (speckled sea trout, drum, croaker, and flounder) is not thought to be a public health concern for Burnett Creek. In general, dioxin has been found to remain in the environment for long periods of time and has the potential to bioaccumulate in fish. However, bioaccumulation is not likely to occur in Burnett Creek since many areas of the creek are very narrow, even during high tide conditions. The highest concentrations of dioxin have been found in sediments in these narrow areas. Larger fish are not expected to be present or obtain a significant amount of their diets in these areas due to the shallow depth of the creek. Therefore, Burnett Creek does not represent a likely scenario for dioxin bioaccumulation and is not considered a public health concern.

Although bioaccumulation in Burnett Creek is not expected and fish advisories have been recommended for the Burnett Creek to reduce consumption of fish for the protection of human health (due to other non-site-related contaminants, such as mercury and PCBs), the potential for exposure to dioxin compounds in larger fish species could not completely evaluated in the absence of fish tissue data for these larger species. Therefore, GDNR and EPA are planning to collect additional dioxin data in fish from Burnett Creek, as part of the GDNR's fish monitoring program. When available, ATSDR will evaluate the additional fish data and update this document accordingly.

2.3.3 Groundwater Pathway

A summary of the private well data, collected in July 2000 and August 2001, is provided on the following table.

Private Well Data (µg/L)

Contaminant

July 2000 Data

August 2001 Data

Tapwater Comparison Value

Source of Comparison Value

FOD

Maximum Detected Conc.

FOD

Maximum Detected Conc.

Bis (2-e,h)phthalate

1/21

7.0

0/23

ND

3.0

CREG

2-pentanone

1/21

5.0 NJ

0/23

ND

NA

NA

3-penten-2-one

1/21

7.0 NJ

0/23

ND

NA

NA

Butyl Tetradecanoate

2/21

9.0 NJ

0/23

ND

NA

NA

Heptadecane

1/21

2.0 NJ

0/23

ND

NA

NA

Octadecanoic Acid

4/21

14 NJ

0/23

ND

NA

NA

Decanal

1/21

3.0 NJ

0/23

ND

NA

NA

Arsenic

5/21

6.2 (a)

0/23

ND

0.02

CREG

Thallium

2/21

12 (a)

0/23

ND

0.5

LTHA

NOTES:
Concentrations on the table are presented in µg/L.
Contaminants that exceed established CVs or detected contaminants for which CVs are unavailable have been included in the above table.
Shaded values indicate that the maximum detected concentration exceeds established CVs.
(a) These detections have been determined to be false positives (EPA, 2001c).
Conc. = Concentration
FOD = Frequency of Detection (Number of samples with contaminant detection / Total number of samples collected)
NJ = Estimated value; presumptive evidence of the presence of material.
NA = Not Available
ND = Not Detected
CREG = Cancer Risk Evaluation Guide
LTHA = Lifetime Health Advisory

The July 2000 data indicates that a number of organic compounds were detected in private wells at low concentrations and frequencies. Bis(2-ethylhexyl)phthalate was detected in one sample at 7.0 micrograms per liter (µg/L), which slightly exceeds the established CV of 3.0 µg/L. This contaminant has also been classified as a common laboratory contaminant and is not known to be site-related. Additionally, bis(2-ethylhexyl)phthalate was not detected in any of the twenty-three samples collected from private wells in August 2000. Therefore, bis(2-ethylhexyl)phthalate does not appear to be present in potable well water and is not expected to result in adverse non-cancer and cancer effects, based on the available private well data. No further evaluation of bis(2-ethyhexyl)phthalate in groundwater is presented in this document.

Sampling also indicated the presence of various metals in private well water collected in July 2000, including arsenic and thallium at 6.2 µg/L and 12 µg/L, respectively. Based on review of the laboratory techniques used to analyze these samples, it has been determined that the July 2000 detects were false positives (EPA, 2001c). Therefore, it is not expected that arsenic and thallium concentrations were present in the groundwater collected from private wells. In addition, the more recent data, collected in August 2001, indicates that metals were not detected in the same private wells previously sampled and two additional wells. Therefore, no further evaluation of arsenic and thallium in groundwater is presented in this document.

CVs are unavailable for several compounds detected in groundwater samples, which have been included in the data summary table. Estimated concentrations of 2-pentanone, 3-penten-2-one, butyl tetradecanoate, heptadecane, octadecanoic acid, and decanal were also detected in private wells during the first round of sampling. CVs are not available for comparison with the detected contaminant concentrations. However, these contaminants were detected at very low frequencies and concentrations. Re-sampling of the same private wells and two additional wells in August 2001 indicated that none of these contaminants were present in groundwater. Therefore, health effects among individuals exposed to these low-level contaminants in potable water from private wells in the vicinity of BWP is not expected and exposure has not been evaluated further in this document.

The highest concentrations of contaminants in the shallow groundwater at BWP are in the vicinity of the surface impoundments, located on the east and west sides of the site. Private wells in the deeper Miocene aquifer have not been impacted by site activities based on samples collected since 1991. One of the likely reasons that private wells have been protected from migration of site-related contaminants is that a dense weathered limestone (bedrock) layer is present between the surficial and Miocene aquifers, which creates a confining layer that is approximately 20 feet in thickness and provides protection for the private, potable wells in the vicinity of the site (EPA, 2000).

A number of alternatives for soil and groundwater cleanup at BWP have been reviewed. Based on the reviewed information, it has been proposed that caps be constructed over the surface impoundment ponds on the east and west portions of the site (EPA, 2001a). These caps will prevent future leaching of contaminants from soil to groundwater. The caps will be located beyond the boundaries of the ponds, so as to include as much of the groundwater contamination as possible. This clean-up alternative also includes the construction of subsurface barrier walls to halt horizontal movement of the contaminants beneath the surface. These walls would consist of slurry filled trenches that would extend to the weathered limestone at 50-65 feet deep. The proposed clean-up measure will likely prevent any impact to private wells in the vicinity of BWP under future conditions. However, periodic monitoring of private wells used for drinking water purposes in the vicinity of BWP is recommended to ensure that residential wells remain unimpacted over time.


3.0 CONCLUSIONS AND RECOMMENDATIONS

Conclusions

The following conclusions are based upon additional sediment, fish (mullet) and shellfish tissue, and groundwater data for BWP. The categories of public health hazard and a discussion of each of these categories is provided in Appendix C of this document.

  • Ingestion and dermal (or direct) contact with sediment from Burnett Creek has been categorized as "No Apparent Public Health Hazard."

  • Consumption of mullet, shrimp, and crab collected from Burnett Creek has been categorized as "No Apparent Public Health Hazard." However, consumption of larger fish from Burnett Creek, which were not present during the sampling event, has been categorized as an "Indeterminate Public Health Hazard" since data for larger fish species is unavailable and due to the uncertainty in estimating concentrations in larger fish based on data for smaller fish species. When available, ATSDR will evaluate the additional fish data, to be collected by EPA and GDNR, and update this HC, as necessary.

  • Ingestion and dermal contact with groundwater from private drinking water wells has been categorized as "No Apparent Public Health Hazard."

Recommendations

The recommendations are based on the evaluation of the available data and the conclusions of this HC.

  • It is recommended that access to areas of the BWP property that require soil remediation be restricted until the remediation efforts have been completed and confirmed, in order to avoid potential exposure to contaminants present in on-site soil.

  • It is recommended that additional fish tissue sampling be conducted, in an effort to collect larger fish species that are most likely to be consumed by the community, if available. These fish include sea trout, red fish, flounder, and black drum. EPA and the GDNR are currently coordinating this sampling effort.

  • Periodic sampling of the private drinking water wells in the vicinity of BWP should be conducted until clean-up of the site has been completed and long-term remediation measures are in-place, the contamination is contained, and future migration of contaminants has been prevented.

4.0 INDIVIDUALS INVOLVED WITH REPORT PREPARATION

Authors:

Robert Knowles, M.S.
Environmental Health Scientist
Division of Health Assessment and Consultation
Superfund Site Assessment Branch

Annmarie DePasquale, M.P.H.
Environmental Health Scientist
Division of Health Assessment and Consultation
Superfund Site Assessment Branch


Reviewers:

Bob Safay, M.S.
Senior Regional Representative
Office of Regional Operations, Region 4

Lisa Hayes, P.E.
Section Chief
Division of Health Assessment and Consultation
Superfund Site Assessment Branch


5.0 REFERENCES

ATSDR, 2000. Health Consultation, Brunswick Wood Preserving (a/k/a Escambia Brunswick Wood), Brunswick, Glynn County, Georgia. United States Department of Health and Human Services, Agency for Toxic Substances and Disease Registry, October 30, 2000.

ATSDR, 1999. Petitioned Public Health Assessment. Escambia Brunswick Wood (Brunswick Wood Preserving), Brunswick, Glynn County, Georgia. United States Department of Health and Human Services, Agency for Toxic Substances and Disease Registry. February 9, 1999.

ATSDR, 1998a. Public Health Consultation. Soil and Sediment Pathway Evaluation. Brunswick Wood Preserving , Brunswick, Glynn County, Georgia. United States Department of Health and Human Services, Agency for Toxic Substances and Disease Registry. December 31, 1998.

ATSDR, 1998b. Toxicological Profile for Dioxins (Update). United States Department of Health and Human Services, Agency for Toxic Substances and Disease Registry. December 1998.

ATSDR, 1997. Petitioned Health Consultation. Groundwater Pathway Evaluation. Brunswick Wood Preserving, Brunswick, Glynn County, Georgia. United States Department of Health and Human Services, Agency for Toxic Substances and Disease Registry. December 23, 1997.

ATSDR, 1992a. Health Consultation. Brunswick Wood Preserving Site, Brunswick, Georgia. May 15, 1992.

ATSDR 1992b. Public Health Assessment Guidance Manual. United States Department of Health and Human Services, Agency for Toxic Substances and Disease Registry. 1992.

CDM, 2001. Final Supplemental Sampling Investigation Report: Subsurface Site Soils, Groundwater, and Burnett Creek. Brunswick Wood Preserving Site, Brunswick, Georgia. May 7, 2001.

CDM, 2000. Sampling and Analysis Plan Addendum: Soil Boring, DPT, Sediment, and Biota Investigation. Brunswick Wood Preserving Site, Brunswick, Georgia. CDM Federal Programs Corporation. October 30, 2000.

EPA, 2002. Integrated Risk Information System (IRIS), United States Environmental Protection Agency. On-line: http://www.epa.gov.iris .

EPA, 2001a. Report: Second Round of Sampling, Monitoring Wells and Potable Wells. Brunswick Wood Preserving Site, Brunswick, Glynn County, Georgia. United States Environmental Protection Agency, Region 4 Science and Ecosystems Support Division. August 2001.

EPA, 2001b. Proposed Plan for Remedial Action (OU-1). Brunswick Wood Preserving Site, Brunswick, Glynn County, Georgia. United States Environmental Protection Agency, Superfund Program. June 2001.

EPA, 2001c. Update: Brunswick Wood Preserving Site. Brunswick, Glynn County, Georgia. United States Environmental Protection Agency, Superfund Program. February 2001.

EPA, 2000. Final Report, Phase III Remedial Investigation, Brunswick Wood Preserving Superfund Site, Brunswick, Glynn County, Georgia. United States Environmental Protection Agency, Region 4 Science and Ecosystems Support Division. December 2000.

EPA, 1997. Exposure Factors Handbook. United States Environmental Protection Agency, Office of Research and Development, National Center for Environmental Assessment. EPA/600/8-89-043. August 1997.

EPA, 1996. Environmental Investigations Standard Operating Procedures and Quality Assurance Manual (EISOPQAM). United States Environmental Protection Agency, Region 4, Science and Ecosystem Support Division, Athens, Georgia. May 1996.

EPA, 1995. Supplemental Guidance to RAGS: Region 4 Bulletins, Human Health Assessment. United States Environmental Protection Agency, Waste Management Division. November 1995.

EPA, 1993. Fish Field and Laboratory Methods for Evaluating Biological Integrity of Surface Water. United States Environmental Protection Agency, Office of Research and Development, National Exposure Research Laboratory. EPA/600/R-92/111. March 1993.

EPA, 1992. Dermal Exposure Assessment: Principles and Applications. United States Environmental Protection Agency, Office of Research and Development. EPA/600/8-91/011B. January 1992.

EPA, 1989. Risk Assessment Guidance for Superfund, Volume 1, Human Health Evaluation Manual (Part A). United States Environmental Protection Agency, Office of Emergency and Remedial Response. EPA/540/1-89/002. December 1989.

GDNR, 2002. Guidelines for Eating Fish from Georgia Waters, 2002 Update. Georgia Department of Natural Resources. Atlanta, Georgia. 2002. Available On-line at: http://www.state.ga.us/dnr/environ .


APPENDIX A: FIGURES

Site Map
Figure 1. Site Map


APPENDIX B: EXPLANATION OF THE EVALUATION PROCESS

Step 1 - The Screening Process

In order to evaluate the available data, ATSDR used comparison values (CVs) to determine which chemicals to examine more closely. CVs are contaminant concentrations found in a specific media (for example: air, soil, or water) and are used to select contaminants for further evaluation. CVs incorporate assumptions of daily exposure to the chemical and a standard amount of air, water, and soil that someone may inhale or ingest each day. CVs are generated to be conservative and non-site specific. These values are used only to screen out chemicals that do not need further evaluation. CVs are not intended to be used as environmental clean-up levels or to indicate that health effects occur at concentrations that exceed these values.

CVs can be based on either cancer or non-cancer health effects. Cancer-based comparison values are calculated from the U.S. Environmental Protection Agency's (EPA) oral cancer slope factor or inhalation risk unit, which account for lifetime exposure. Non-cancer values are calculated from ATSDR's Minimal Risk Levels (MRLs) and EPA's reference doses (RfDs). When a cancer and non-cancer CV exists for the same chemical, the lower of these values is used in the comparison for conservatism. The chemical and media-specific CVs utilized during the preparation of this Public Health Assessment are listed below:

An Environmental Media Evaluation Guide (EMEG) is an estimated comparison concentration for which exposure is unlikely to cause adverse health effects, as determined by ATSDR based on the toxicological profiles for a specific chemical.

A Cancer Risk Evaluation Guide (CREG) is a comparison concentration that is based on an excess cancer rate of one in a million persons and is calculated using EPA's cancer slope factor.

A Life Time Health Advisory (LTHA) is developed by EPA and is considered a lifetime exposure level for contaminants specifically in drinking water (assuming 20% of an individuals' exposure comes from drinking water) at which adverse, non-carcinogenic health effects would not be expected to occur.

A Risk-Based Concentration (RBC) is developed by EPA Region III and used primarily in the initial screening process of a baseline risk assessment. EPA toxicity factors have been combined with standard default assumptions in order to generate these values.

Step 2 - Evaluation of Public Health Implications

The next step in the evaluation process is to take those contaminants that are above their respective CVs and further identify which contaminants and exposure situations are likely to be a health hazard. Separate child and adult exposure doses are calculated for site-specific exposure scenarios, using assumptions regarding an individual's likelihood of accessing the site and contacting contaminated areas. A brief explanation of the calculation of estimated exposure doses for the site is presented in this appendix. Calculated doses are reported in units of milligrams per kilograms per day (mg/kg/day) (ATSDR, 1992b; EPA, 1989; EPA, 1992; EPA, 1995, EPA, 1997).

Exposure Dose Estimation

When chemical concentrations at the site exceed the established CVs, it is necessary for a more thorough evaluation of the chemical to be conducted. In order to evaluate the potential for human exposure to contaminants present at the site and potential health effects from site-specific activities, ATSDR estimates human exposure to the site contaminant from different environmental media by calculating exposure doses. A brief discussion of the calculations and assumptions is presented below.

Incidental Ingestion of Sediment

It was assumed that a small amount of sediment may have been inadvertently ingested by individuals that are present at Burnett Creek for recreational purposes, such as wading or playing along the banks of the creek. Exposure doses for incidental ingestion of contaminants present in sediment were calculated using the maximum detected concentration of the sample data, in milligrams per kilogram (mg/kg), multiplied by an ingestion rate of 10 milligrams per day (mg/day) for adults and 20 mg/day for children (10% of soil ingestion rate). The product was also multiplied by a conversion factor of 0.0000010 kilograms per milligram (kg/mg) and the total was divided by the average body weights for adults and children of 70 kg (154 pounds) and 10 kg (22 pounds), respectively.

Dermal Contact with Sediment

It was assumed that dermal exposure with sediment occurred during recreational activities in Burnett Creek. Dermal absorption depends on numerous factors, including the area of exposed skin, anatomical location of the exposed skin, length of contact, and the concentration of the chemical in contact with the skin. Because chemicals differ greatly in their potential to be absorbed through the skin, each chemical needs to be evaluated separately.

The maximum detected concentration, in mg/kg, was multiplied by the surface area exposed by the adult and child (infant) receptors. A surface area of 4,200 square centimeters per day (cm2/day) was incorporated for an adult, which accounts for exposure of the feet and lower legs during wading activities. A surface area of 2,300 cm2/day was incorporated for the child, which accounts for exposure to the feet, legs, and hands while wading or playing along the shores of Burnett Creek. This product was then multiplied by a conversion factor of 0.0000010 kg/mg and absorption factor of either 10% for organic compounds and 1% for inorganic compounds. The multiplication product was divided by the average body weights for adults and children of 70 kg (154 pounds) and 10 kg (22 pounds), respectively.

Ingestion of Fish

As part of this evaluation, individuals are assumed to ingest fish that has been collected from Burnett Creek. To calculate an exposure dose for fish consumption, the maximum detected concentration of contaminants measured in the fish (mullet) carcass sample was multiplied by an ingestion rate of 43 grams per day (g/day) for adults and 21.5 g/day for children, which is equal to approximately 2 fish meals per week. The multiplication product was then multiplied by a conversion factor of 0.0010 kilograms per gram (kg/g) and the total multiplication product was divided by average body weights for adults and children of 70 kg (154 pounds) and 16 kg (35 pounds), respectively. The body weight of an older child is used in the fish evaluation in comparison to the sediment evaluation since infants are not likely to consume fish very often. Therefore, toddler exposure was evaluated to be more indicative of the most likely potential exposures to fish from Burnett Creek.

Non-Cancer Health Effects

The doses calculated for exposure to each individual chemical are then compared to an established health guideline, such as a Minimal Risk Level (MRL) or Reference Dose (RfD), in order to assess whether adverse health impacts from exposure are expected. These health guidelines, developed by ATSDR and EPA, are chemical-specific values that are based on the available scientific literature and are considered protective of human health. Non-carcinogenic effects, unlike carcinogenic effects, are believed to have a threshold, that is, a dose below which adverse health effects will not occur. As a result, the current practice for deriving health guidelines is to identify, usually from animal toxicology experiments, a No Observed Adverse Effect Level (NOAEL). This is the experimental exposure level in animals (and sometimes humans) at which no adverse toxic effect is observed. The NOAEL is then modified with an uncertainty (or safety) factor, which reflects the degree of uncertainty that exists when experimental animal data are applied to the general human population. The magnitude of the uncertainty factor considers various factors such as sensitive subpopulations (for example: children, pregnant women, and the elderly), application of animal studies to human populations, and the completeness of available data. Thus, exposure doses at or below the established health guideline are not expected to result in adverse health effects because these values are much lower (and more human health protective) than the doses at which adverse health effects have been observed in laboratory animal studies. For non-cancer health effects, the following health guidelines are described below in more detail. It is important to consider that the methodology used to develop these health guidelines does not provide any information on the presence, absence, or level of cancer risk. Therefore, a separate cancer evaluation is necessary for potentially cancer-causing chemicals detected in samples at this site. A more detailed discussion of the evaluation of cancer risks is presented in the following section.

Minimal Risk Levels (MRLs) - developed by ATSDR
ATSDR has developed MRLs for contaminants commonly found at hazardous waste sites. The MRL is an estimate of daily exposure to a contaminant below which non-cancer, adverse health effects are unlikely to occur. MRLs are developed for different routes of exposure, like inhalation and ingestion, and for lengths of exposure, such as acute (less than 14 days), intermediate (15-364 days), and chronic (365 days or greater). At this time, ATSDR has not developed MRLs for dermal exposure. A list of the available MRLs is provided at http://www.atsdr.cdc.gov/mrls.html.

References Doses (RfDs) - developed by EPA
An estimate of the daily, lifetime exposure of human populations to a possible hazard that is not likely to cause non-cancerous health effects. RfDs consider exposures to sensitive sub-populations, such as the elderly, children, and the developing fetus. EPA RfDs have been developed using information from the available scientific literature and have been calculated for oral and inhalation exposures. Dermal RfDs are currently not available from EPA. A complete list of the available RfDs can be found at http://www.epa.gov/iris .

If the estimated exposure dose for a chemical is less than the health guideline value, the exposure is unlikely to result in non-cancer health effects. It should be noted that health guidelines for ingestion exposure have been modified, per EPA guidance, to account for exposure via the dermal route since specific health guidelines for dermal exposure are unavailable (EPA, 1995). For chemicals that are not likely to result in cancer based on exposure, this modification is made by multiplying the health guideline for ingestion by the chemical's gastrointestinal absorption factor (GAF). Chemical-specific GAFs are available in ATSDR's Toxicological Profiles or default GAFs may be used. According to EPA, default GAFs for volatile organic compounds, semi-volatile organic compounds, and metals are 80%, 50%, and 20%, respectively (EPA, 1995).

If the calculated exposure dose is greater than the health guideline that is used for comparison, the exposure dose is compared to known toxicological values for the particular chemical and is discussed in more detail in the text of the Public Health Assessment. The known toxicological values are doses derived from human and animal studies that are summarized in the ATSDR Toxicological Profiles. A direct comparison of site-specific exposure and doses to study-derived exposures and doses found to cause adverse health effects is the basis for deciding whether health effects are likely to occur.

Summary of Calculated Dose Estimates for BWP

Contaminant

Exposure Pathway

Established Health Guideline (mg/kg/day)

Adult Calculated Exposure Dose Estimates (mg/kg/day) Child Calculated Exposure Dose Estimates (mg/kg/day)
Total Dioxin TEQs Ingestion of fish 1.0 x 10-9 2.3 x 10-9 5.0 x 10-9
Ingestion and Dermal Contact with Sediment 2.2 x 10-10 3.0 x 10-9

Cancer Risks

Exposure to a cancer-causing compound, even at low concentrations, is assumed to be associated with some increased risk for evaluation purposes. The estimated excess risk of developing cancer from exposure to contaminants associated with the site via ingestion was calculated by multiplying the site-specific adult exposure doses (as discussed in the Exposure Dose Estimation section of this appendix) by EPA's chemical-specific, oral cancer slope factors (CSFs or cancer potency estimates), which are available at http://www.epa.gov/iris . An increased excess lifetime cancer risk is not a specific estimate of expected cancers. Rather, it is an estimate of the increase in the probability that a person may develop cancer sometime during his or her lifetime following exposure to a particular contaminant.

Since dermal CSFs are not available, modification of the oral CSFs has also been completed for the evaluation of cancer-causing chemicals. This modification is made by dividing the oral CSF for ingestion by the chemical's GAF. As previously discussed, chemical-specific GAFs are available in ATSDR's Toxicological Profiles or default GAFs may be used. According to EPA, default GAFs for volatile organic compounds, semi-volatile organic compounds, and metals are 80%, 50%, and 20%, respectively (EPA, 1995). The estimated excess risk of developing cancer from exposure to contaminants associated with the site was calculated by multiplying the site-specific adult exposure doses (as discussed in the Exposure Dose Estimation section of this appendix) by oral CSFs or oral CSFs that have been adjusted by the appropriate GAFs.

There are varying suggestions among the scientific community regarding an acceptable excess lifetime cancer risk, due to the uncertainties regarding the mechanism of cancer. The recommendations of many scientists and EPA have been in the risk range of one in one million to one in ten thousand (also referred to as 1 x 10-6 to 1 x 10-4) excess cancer cases. An increased lifetime cancer risk of one in one million or less is generally considered an insignificant increase in cancer risk. An important consideration when determining cancer risk estimates is that the risk calculations incorporate a number of very conservative assumptions that are expected to overestimate actual exposure scenarios. For example, the method used to calculate EPA's CSFs assumes that high-dose animal data can be used to estimate the risk for low dose exposures in humans. As previously stated, the method also assumes that there is no safe level for exposure. Lastly, the method computes the 95% upper bound for the risk, rather than the average risk, suggesting that the cancer risk is actually lower, perhaps by several orders of magnitude.

Because of the uncertainties involved with estimating carcinogenic risk, ATSDR employs a weight-of-evidence approach in evaluating all relevant data. Therefore, the carcinogenic risk is also described in words (qualitatively) rather than giving a numerical risk estimate only. The numerical risk estimate must be considered in the context of the variables and assumptions involved in their derivation and in the broader context of biomedical opinion, host factors, and actual exposure conditions. The actual parameters of environmental exposures must be given careful and thorough consideration in evaluating the assumptions and variables relating to both toxicity and exposure. A complete review of the available toxicological information has been completed for cancer-causing chemicals. A direct comparison of site-specific exposure and doses to study derived exposure and doses found to result in adverse health effects is the basis for determining whether health effects are likely to result based on exposure.

Summary of Excess Cancer Risk Estimates for BWP

Contaminant Exposure Pathway Theoretical Excess Cancer Risk(a)
Total Dioxin TEQs Ingestion of Fish 6.0 per 1,000,000
Ingestion and Dermal Contact with Sediment

6.1 per 10,000,000

NOTES:
(a) Reported as number of excess cancer cases per individuals exposed.


APPENDIX C: LEVELS OF PUBLIC HEALTH HAZARD

ATSDR categorizes exposure pathways at hazardous waste sites according to their level of public health hazard to indicate whether people could be harmed by exposure and site conditions. The categories are:

Urgent Public Health Hazard: This category applies to exposure pathways and sites that have certain physical features or evidence of short-term (less than 1 year), site-related chemical exposure that could result in adverse health effects and require quick intervention to stop people from being exposed.
Public Health Hazard: This category applies to exposure pathways and sites that have certain physical features or evidence of chronic, site-related chemical exposure that could result in adverse health effects.
Indeterminate Public Health Hazard: This category applies to exposure pathways and sites where important information is lacking about chemical exposures and a health determination cannot be made.
No Apparent Public Health Hazard: This category applies to exposure pathways and sites where exposure to site-related chemicals may have occurred in the past or is still occurring; however, the exposure is not at levels expected to cause adverse health effects.
No Public Health Hazard: This category applies to exposure pathways and sites where there is evidence of an absence of exposure to site-related chemicals.


1. The total dioxin concentration in an environmental sample is determined by adjusting the concentration of each detected dioxin compound by its toxicity relative to 2,3,7,8-TCDD (the most toxic dioxin compound). Each of the adjusted values is added together to indicate the total concentration for all detected dioxin compounds (ATSDR, 1998b).



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