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PUBLIC HEALTH ASSESSMENT

SANGAMO/TWELVE-MILE CREEK/HARTWELL PCB
PICKENS, PICKENS COUNTY, SOUTH CAROLINA


ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS

The tables in this section list the contaminants of concern. We evaluate these contaminants in the subsequent sections of this assessment and determine whether exposure to them could have an effect on the public's health. These contaminants are selected and evaluated according to the following factors:

Contaminants that are listed in the data tables for this section should not be interpreted to mean that they will cause harmful health effects. Rather, the list identifies contaminants that need to be evaluated further in later sections of the assessment. When a contaminant of concern is identified in one medium, it will also be mentioned in all media.

Contaminants requiring further evaluation are selected by using medium-specific, comparison values. These values include EMEGs, CREGs, and other relevant guidelines. CREGs are estimated contaminant concentrations based on the probability that 1 additional cancer case may occur in excess of the number that will be expected to occur among 1 million people (assuming they have been exposed to the contaminant for a lifetime). CREGs are calculated from EPA's cancer slope factors. EPA's MCLG is a drinking water health goal. EPA believes that the MCLG represents a level at which no known or anticipated harmful effects to people should be expected to occur. It allows for an adequate margin of safety. MCLs represent contaminant concentrations that EPA deems protective of public health; however, in deriving these levels the EPA takes into consideration the technical feasibility and economics of water treatment. While MCLs are regulatory concentrations, MCLGs are not.

A. On-Site Contamination

In the 1989 Remedial Investigation Study (RI) for OU-1, volatile organic compounds (VOCs) were found in ground water near the wastewater treatment facility and at two other isolated areas on the plant site. These findings will not be discussed further because this public health assessment focuses only on OU-2. A public health assessment on OU-1 will be conducted at a later time.

To date, no groundwater contamination has been associated with OU-2. It is unlikely that local ground water will be contaminated by PCBs from this site because of the demonstrated ability of these compounds to bind tightly to sediments and soils (1). This concern was raised by a local resident who used a private drinking water well within 500 feet from Twelve Mile Creek. There were no PCBs or volatile organic compounds detected in a sample taken from this well (4).

Limited ambient surface water sampling has been conducted. PCBs had been detected in EPA's surface water samples collected from Town Creek in 1976; however, PCBs were below the levels of laboratory detection in the samples collected from Twelve Mile Creek and some of its tributaries. From May 1988 to May 1991, 5 surface water samples were collected from Twelve Mile Creek at SCDHEC sampling stations SV-107 (where Twelve Mile Creek joins the Seneca River Arm of Lake Hartwell) and SV-282 (in the upper part of Twelve Mile Creek near the town of Pickens, SC). All results were below detectable levels; the level of detection for the SCDHEC laboratory was 0.5 parts per billion (ppb).

Data results from the monitoring program have fluctuated greatly between most sampling periods. Since 1983, PCBs have been periodically detected in drinking water samples at most sampling points; however, PCB concentrations at these same locations often returned to levels below laboratory detection (that is, less than 0.1 ppb) by the next sampling period.

Samples were often collected at taps both before allowing water to run through the distribution lines (pre-flush) and after the water was allowed to run for several minutes (post-flush). However, this sampling strategy did not effect the sampling results because PCBs were detected in both kinds of samples. In addition, PCBs that were detected in either pre-flush or post-flush samples at a given sampling location could be found to yield the opposite results during later sampling periods, further confounding these findings.

PCB concentrations listed in Table 2 are reported as total Aroclors. Because all sampling results exceeded the comparison value, these data will be evaluated later in the assessment for their risk to the public's health. Of note, the comparison value used here is well below the limits of laboratory detection.

The EPA has established an MCL for PCBs at 0.5 ppb as decachlorobiphenyl. The data as Aroclors cannot be compared to this MCL without converting the concentration of each mixture into its equivalent decachlorobiphenyl concentration. Currently, there is no accepted methodology to do this.

Samples collected from the fire hydrants had the highest concentrations of PCBs. Sample results from the 2 commercial sink faucets have been below detectable levels for the last 10 sampling periods (See Table 2.I). PCBs were detected in 1 of 3 samples collected from residential taps during the June 1991, sampling period (See Table 2.II). During this same period, PCBs were also detected in all the samples collected from the fire hydrants.

Since 1984, SCDHEC has collected monthly and quarterly samples of the raw and finished water at the 3 Lake Hartwell water treatment plants. PCBs were detected only once at a concentration of 0.13 ppb in a January 1985, raw water sample from the DeFore Mills plant. All other sample results were below the level of detection.

The 1991 data results from the drinking water samples collected at private residences from the 10 water distribution systems are presented in Table 3. Analytical methods differed between SCDHEC and EPA laboratories resulting in different levels of detection (the EPA laboratory used lower standards for quantification). PCBs were detected in 3 of the 21 samples collected by SCDHEC and 17 of the 29 samples collected by EPA. Aroclor 1242 was the principal mixture identified by both laboratories; Aroclor 1016 was identified in one SCDHEC sample and Aroclor 1260 was detected in one EPA sample. PCBs were detected in samples from 6 of the 10 water systems (Easley-Central # I, Southside # I, Highway 88, East Clemson, Town of Central, and Sandy Springs). These water systems directly or indirectly (through Easley-Central # I) use Twelve Mile Creek as the source of their raw water (See Figure 2). The highest concentration (0.29 ppb) was found in a drinking water sample from a private residence in Easley-Central # I. The PCB concentrations detected in these samples exceeded the comparison value for PCBs in drinking water. However, this comparison value is well below the levels of detection for both EPA and SCDHEC laboratories.

SCDHEC has been monitoring Twelve Mile Creek's sediment since 1976 (See Table 4). During these years, samples have been taken at different points along this creek. Samples taken from station SV-107 consistently had the highest PCB concentrations. The data have fluctuated at each sampling point without evidence of increasing or decreasing trends.

There are no data on the amount of sediment that can be consumed during wading or swimming. Thus, the comparison value used in Table 4 is based on the consumption of surface soil; that is, the concentration of PCBs in soil corresponding to a 1 in a million cancer risk from consuming 100 milligrams of soil each day for a lifetime (12). Data for SV-107 have consistently exceeded this value. However, this sampling point is located at SC Highway 133. The public would be unlikely to encounter these sediments through swimming because the water is approximately 10 to 15 meters deep at this location. The public could access contaminated sediments at SV-137, SV-015, and SV-282 (approximately 2 miles below Sangamo Weston, Inc.) because the Creek can be waded at these points. The sampling data generated after 1984 from these sampling points did not exceed the soil CREG, although there appeared to be an increase in PCB concentration in 1989.

EPA also collected fish and sediment samples in 1985 and analyzed them for PCBs, dibenzodioxins (PCDDs), and dibenzofurans (PCDFs). Samples were collected from the top 2 to 3 inches of sediment within a 4 mile stretch of Twelve Mile Creek. No tetrachlorodibenzodioxins (TCDD) were detected (See Table 5). To assess the combined risk from the various congeners of dioxins and furans, a set of toxicity equivalency factors (TEFs) were used to convert the concentration of the various PCDF/PCDD congeners into an equivalent concentration of 2,3,7,8-TCDD. For these calculations the I-TEFs/88 (the TEFs developed in 1988 by an international panel including the EPA) was used (EPA, 1989). The concentrations of PCBs in these sediment samples exceeded the comparison value for consumption of surface soil. ATSDR does not currently have a CREG value to compare to the PCDD/PCDF data from these samples because EPA is in the process of revising its risk estimate for 2,3,7,8-TCDD. The data did not exceed ATSDR's chronic soil EMEG of 700 ppt for 2,3,7,8-TCDD (based on noncarcinogenic effects).

The fish sample results are presented later in this section under Food Chain.

No local surface soil samples have been collected from the shores of these water bodies. Sediment sampling has been limited to midstream locations in an effort to follow the trend of the highest sediment concentrations. The depths of these water bodies have been known to occasionally vary. Shorelines along Town Creek and the upper portion of Twelve Mile Creek could potentially be contaminated because sediments could be deposited on the shores of these shallow waterways during periods when the water level rises. This would not be likely to occur further downstream along Twelve Mile Creek where it meets the headwaters of the Seneca River arm of Lake Hartwell.

No ambient air samples were collected.

Fifteen years of data from SCDHEC's annual fish monitoring program for Twelve Mile Creek/Lake Hartwell are presented in Table 6 (2 pages). Fish were collected primarily at three sampling stations: Twelve Mile Creek (SV-107), Eighteen Mile Creek (SV-532), and at Andersonville Island (SV-535). Fish occasionally were collected at Martin Creek (SV-106), in the Tugaloo portion of Lake Hartwell (SV-641) and at the Hartwell Dam (SV-642) (See Figure 3).

Following the EPA's 1976 study plan, SCDHEC collected fish annually in the 2- to 3-year old size class from 1976 to 1986. Since 1986, SCDHEC has actively sought 2- to 3- pound fish for trend monitoring because creel surveys conducted by the South Carolina Wildlife and Marine Resources Department (SCWMRD) indicated that this weight class was most frequently harvested by the public. The data generated from these samples could best be used to annually update the fishing advisory because they reflected the amount of PCBs the public would typically consume. Sampling has always been targeted for the spring before the spawning season because fish were found to have higher tissue concentrations of PCBs during this season than during the fall (8).

PCBs have been detected in all fish samples and at all sampling stations; however, fish caught in Twelve Mile Creek have consistently had the highest PCB concentrations. A suitable comparison value for PCBs in fish cannot be developed for this site without knowledge of the fish consumption patterns of Lake Hartwell fishermen. The data will be evaluated in later sections of this Assessment.

Any interpretations and/or conclusions drawn from the data in this table should be made with caution. Changes in the protocol used to prepare fish for analysis and difficulties collecting the same species each year have had a direct effect on these sampling results. Sampling stations SV-107, SV-106, SV-532 are within the Seneca River arm of Lake Hartwell, north of SC highway 24; sampling stations SV-535, SV-641, and SV-642 are south of it (see Figure 3). Under the current fishing advisory, both SCDHEC and EPA recommend that all fish caught north of this highway should be released and not eaten. For fish caught south of this highway, the advisory recommends that all fish greater than 3 pounds should not be eaten. The fish monitoring program will be discussed in greater detail in Appendix C.

As stated previously in this section under 3. Sediment and Soil, EPA analyzed fish for the presence of PCDDs, PCDFs, and PCBs. Twenty fish samples of hybrid bass, largemouth bass, and channel catfish were collected in 1985 from 12 stations on Twelve-mile Creek, 3 stations on Eighteen-Mile Creek, and 4 stations on the Tugaloo River. One composite sample of several fish species collected in 1976 from Lake Hartwell was also analyzed. 2,3,7,8-TCDD was not detected in any of the fish tissue samples (level of detection varied from 10 to 20 ppt). 2,3,7,8-TCDF was the principal PCDF congener found in most samples in concentrations ranging from below the detection limit (ranging from 10-20 ppt) to 290 ppt. In 2 of 20 samples, pentachlorodibenzofurans and octachlorodibenzodioxin were detected (See Table 7).

Applying the International Toxicity Equivalent Factors/'88 for assessing risks associated with dioxins and furans to these data, the amount of 2,3,7,8-TCDD equivalents in fish tissue ranged from 0 to 29 ppt. The PCDD/PCDF concentrations in channel catfish collected from Twelve Mile Creek were below EPA's laboratory detection limit of 10 ppt even though PCBs were detected in these samples up to 68 ppm (the size weights of these fish were not available). There is no comparison value for PCDD/PCDFs in fish because there is no site-specific, fish consumption data; in addition, EPA is currently reassessing the toxicity of 2,3,7,8-TCDD. This data, however, will be evaluated in later sections of this Assessment.

These fish samples were also assayed for PCBs. Total PCBs in fish tissue ranged from 1.8 ppm (in a hybrid bass from Eighteen Mile Creek) to 147 ppm (in the 1976 fish composite taken from the lake). The hybrid composites collected from the Tugaloo River (outside of the advisory) ranged from 6-13 ppm. However, the weight of these fish reportedly ranged from 5 to 7 pounds; SCDHEC's fish advisory does not recommend consuming fish of this size.

B. EPA Toxic Chemical Release Inventory (TRI)

TRI for 1989 was searched for facilities reporting PCBs within the 3 South Carolina counties and the 5 Georgia Counties that adjoin Twelve Mile Creek/Lake Hartwell. In 1989, only 1 plant in Greenville, SC reported PCBs to TRI. However, this plant did not report any releases of PCBs directly to the environment; PCB wastes are disposed of in an incinerator in Georgia. Considering the location of this plant in relation to OU-2, any potential on-site PCB releases would not be likely to contaminate Lake Hartwell.

C. Quality Assurance and Quality Control (QA/QC)

SCDHEC personnel collected drinking water, sediment, and fish tissue samples according to set procedures to minimize extraneous contamination of the samples. Established procedures to maintain chain of custody for these samples were strictly followed.

The majority of the PCB analyses of fish tissue, drinking water, and sediments were conducted by SCDHEC's Environmental Quality Control Laboratories. This laboratory conforms to the Quality Assurance requirements of EPA. All laboratory practices follow the procedures outlined in the Quality Control Manual for Chemistry Laboratories, Division of Analytical Services, SCDHEC, January 1987. This manual has been approved by EPA.

The EPA laboratory in Athens, Georgia has periodically done PCB analyses on fish samples. PCDD/PCDF analyses were conducted by both an EPA-contract laboratory in Research Triangle Park, North Carolina and the EPA laboratory in Duluth, Minnesota (they analyzed split samples). We assume that the practices of these laboratories conform to EPA's QA/QC protocols.

SCDHEC had contracted with a private laboratory to conduct PCB analyses on fish samples collected in the years 1987 and 1988. Because of concerns about the quality control used to analyze these samples, the data generated from these samples were discarded.

D. Physical Hazards

No physical hazards other than those normally associated with swimming, boating, and water skiing are evident at this site.


PATHWAYS ANALYSIS

To determine whether nearby residents may be affected by contaminants at the site, we evaluated the environmental and human components that lead to human exposure. This pathways analysis consists of 5 elements: a source of contamination, transport through an environmental medium, a point of exposure, a route of human exposure, and an exposed population.

We identify exposure pathways as completed, potential, or eliminated. Completed pathways require that the 5 elements exist and indicate that exposure to a contaminant has occurred in the past, is currently occurring, or will occur in the future. Potential pathways, however, indicate that at least 1 of the 5 elements is missing, but could exist. Potential pathways indicate that exposure to a contaminant could have occurred in the past could be occurring now, or could occur in the future. Eliminated pathways indicate that at least 1 of the 5 elements is missing and will never be present. Completed and potential pathways, however, may be eliminated when they are unlikely to exist. The discussion that follows identifies the completed, potential, and eliminated pathways at this site.

A. Completed Exposure Pathways (See Table 8).

The primary route of human exposure to PCBs from this site is through the consumption of contaminated fish. Fish become exposed to PCBs when they consume smaller organisms which have been contaminated by PCBs in sediments. To a lesser extent, fish are also exposed to PCBs through the direct ingestion of and dermal contact with contaminated sediments (particularly true for bottom-dwelling fish like catfish). Samples of several species of fish popular with fishermen have consistently been found to contain concentrations of PCBs above FDA's tolerance level of 2.0 ppm. Even though SCDHEC has posted advisory signs at recreational areas around the lake, it is not known whether anglers are complying with this fishing advisory.

Exposures are believed to have occurred in the past (as far back as the early 1960's), are occurring at the present (as indicated by sampling data), and will occur in the future (because of the persistence of PCBs in fish and sediments).

Local residents may be exposed to PCBs through the consumption of contaminated drinking water. PCBs have been detected in water samples collected from taps supplied by those municipal water systems that have directly and indirectly (that is, through interconnections with other water systems) used Twelve Mile Creek as a raw water source. It is believed that PCBs initially entered the Easley-Central # I water system through its raw water intake on Twelve Mile Creek. From this water system, PCBs could have entered the other systems through interconnections. The PCBs are mostly likely bound to the scale within the water distribution lines of these systems, occasionally being released through both desorption from the scale and through resuspension of PCB-laden sediments when the water lines are flushed (see Background section, A.3. Site History).

Exposures are believed to be presently occurring to local residents and may continue in the future. Although it is possible that exposures may have occurred in the past, until 1991, only commercial taps and fire hydrants were sampled. Thus, this sampling data are not indicative of the concentrations that may have existed at the taps of private residences.

PCBs bind tightly to sediments and are very resistant to degradation. The contaminated lake sediments can bioaccumulate through the food chain. Thus, they will continue to serve as a source of contamination into the future.

Past, present, and future exposures to sediment by local residents are possible through the incidental ingestion of contaminated sediments during wading and swimming in Town Creek and Twelve Mile Creek (especially at the ravine described in the Background section, C.2. Land Use). Sediment data for the Twelve Mile Creek recreational area were generated from samples collected midstream and at the bottom of the Creek. Because of the Creek's width and depth at this sampling location, exposure to these sediments would not be likely to occur.

B. Potential Exposure Pathways (See Table 8).

Contaminated sediments could have been deposited along the shoreline because of localized flooding; however, no surface soil samples have been collected to determine if they have been contaminated. Without these data, exposure to contaminated surface soils can only be categorized as a potential pathway of exposure. Additional sampling will be necessary to determine if these areas have actually been impacted.

PCBs will leave the lake water by adsorbing to sediments, reaching higher concentrations than the associated water column. Although adsorption can immobilize PCBs for relatively long periods of time, they have been found to re-enter the water column (ATSDR Tox. Profile for Selected PCBs). PCB-laden sediments may also become resuspended in the water column because of water turbulence created by heavy rainfall.

PCBs were discharged from the plant's wastewater system to nearby Town Creek. From here PCB-laden sediments were carried with the current to Twelve Mile Creek and eventually to Lake Hartwell. Although PCBs have not been used at the plant since 1977, small amounts are still being discharged into Town Creek. This is believed to be due to the release of PCB-laden residues from the wastewater facility's settling basin.

Visitors to Twelve Mile Creek/Lake Hartwell could potentially be exposed to surface water contaminants during wading and swimming. Exposures to contaminants through this pathway will be discussed further in the Public Health Implications section.

C. Eliminated Exposure Pathways

Ground water is not a pathway of concern for this site. In water, PCBs primarily adsorb to sediments or other organic matter; significant leaching into ground water should not occur. This opinion is supported by the data results from the private well sample collected near Twelve Mile Creek (See the Environmental Hazards and Other Contamination section, A.1. Ground water).

Under certain conditions, such as through the action of waves, PCBs could be released in aerosols. This would be unlikely to occur at this site because the lake is a calm water body. PCBs could also volatilize from lake water; however, because they strongly adsorb to sediments and are very insoluble in water, air releases would not be likely to occur. We will not address air exposure to PCBs further in this health assessment.


PUBLIC HEALTH IMPLICATIONS

In this section, we will discuss the impact of the site's contaminants on the public's health, evaluate state and local health data, and address the community's health concerns. Unless otherwise indicated, ATSDR's Toxicological Profile for Selected PCBs was used as the primary source of toxicological and health effects information.

A. Toxicological Evaluation

To determine the health effects that could result from exposures to site contaminants, we will compare estimates of daily exposure at the site to estimates of exposure considered to be acceptable (that is, without health risk). To evaluate the potential exposures to cause non-cancer, adverse health effects, they will be compared to a Minimal Risk Level (MRL). ATSDR has developed MRLs for contaminants commonly found at hazardous waste sites. The MRL is an estimate of daily human exposure to a contaminant below which non-cancer, adverse health effects are unlikely to occur (that is, a threshold dose). MRLs are developed for each route of exposure, such as ingestion, inhalation, and dermal absorption and for the length of exposure, such as acute (less than 14 days), intermediate (15 to 364 days), and chronic (greater that 365 days). For compounds that have been classified as being able to cause cancer, it is believed that there is essentially no level of exposure that does not pose some finite cancer risk. This belief is currently being reexamined by EPA in light of the reassessment of dioxin's cancer risk. For this discussion, however, we will assume that carcinogens have no threshold below which a cancer could not occur. We will compare estimates of daily contaminant exposure to the lifetime average daily exposure dose equivalent to a 1 in a million excess lifetime cancer risk (that is, a risk that is generally recognized as acceptable).

PCBs are clearly the principal contaminants of concern from this site. People have been exposed to these compounds primarily by consuming fish from Lake Hartwell and in particular, Twelve Mile Creek. We are not exactly sure when exposures could have first occurred; fish monitoring only began in 1976. Because the plant began operations in the late 1950's, we can assume that fish could have been contaminated as early as then. We do not know, however, the extent to which they were contaminated. Thus, we will not be able to determine the daily PCB exposure that anglers may have faced.

We know that people presently catch and probably consume the fish from Lake Hartwell, outside the fishing advisory area. We do not know if anglers are complying with this advisory or if they are consuming fish weighing more than 3 pounds. While we have data from a 1982 SCWMRD creel survey on the variety of fish harvested from the lake (See Appendix C), we have no information on the amount and species of fish that local residents typically consume. No surveys to assess statewide or regional consumption patterns have ever been conducted in South Carolina, a state in which fishing is a very popular recreational activity. Consumption rates may have been greater before the fishing advisory was issued in 1976; thus, people who consumed fish prior to the advisory may have faced greater daily exposures than present day fish consumers. Choosing an appropriate fish tissue concentration to use in estimating daily dose is quite difficult, considering all the confounding variables in the fish monitoring data. However, other than for catfish in Twelve Mile Creek, there does not appear to be much change in the tissue concentrations over the last fifteen years.

Considering this uncertainty, the following assumptions were made to estimate a reasonable, daily exposure dose to subsistence fishermen:

o Consumption rates would reflect the subsistence fishermen; that is, those fishermen whose diet relied heavily on Lake Hartwell fish. We assume that this may be 4, 1/2-pound fish meals per week (130 grams fish/day).
o All the fish in their diet came from Lake Hartwell, near Andersonville Island (SV-535).
o The anglers are following the advisory, keeping and consuming only those fish outside of the advisory area that are less than 3 pounds.
o Only the 1977-85 PCB data for fish fillet would be used; data from the samples using the modified whole fish technique (1986 and 1989 data) would not be used.
o 30% of the fish in the diet would be largemouth bass, 30% would be hybrid bass, and 30% would be catfish. We would have preferred to use the percentages reported in the 1982 SCWMRD creel survey, however, we had no Black Crappie fillet data from SV-535 for 1977-85.
o A 70 kilogram (150 pound) adult will be consuming fish under these conditions for a 70-year lifetime.

Under these conditions, the estimated amount of PCBs that a consumer could get from eating this fish greatly exceeds ATSDR's chronic MRL for ingestion. At present, ATSDR does not have an acute or intermediate MRL for ingestion.

Aroclors appear to be toxic to the fetus but have not been found to cause birth defects in various species of laboratory animals (including rats, mice, rabbits, and monkeys); however, these effects may possibly be caused by other contaminants. Slight decreases in birth weight, head circumference, gestational age, and/or neonatal behavioral performance have been reported in infants born to women who had environmental exposures (particularly women who consumed PCB-contaminated fish) or occupational exposures to PCBs; however, these effects cannot be conclusively attributed to PCBs because these women were also exposed to other chemicals. Thus, it is uncertain whether these effects will be exhibited in the children of women who subsisted on Lake Hartwell fish during their pregnancies (1).

Several PCB mixtures have been found to be carcinogenic in feeding studies of laboratory animals but it is not clear from these studies which of the components of the mixture are actually carcinogenic. The liver is the primary target of PCB carcinogenicity. Because of its ability to cause cancer in animals, the EPA has classified PCBs as probable carcinogens (that is, a group of chemicals for which there is sufficient evidence of carcinogenicity in animals but inadequate evidence or no data from human epidemiological studies) (1). Using the results of a feeding study in which female rats were fed Aroclor 1260, they were able to extrapolate the potential cancer risk of PCBs to humans. The EPA cancer potency estimate for Aroclor 1260 applies to all PCB mixtures because there is no information regarding which constituents of any PCB mixture might be carcinogenic. Thus, the effects from Aroclor 1260 is assumed to be representative of all PCB mixtures. Using this cancer potency estimate, subsistence fishermen could have a high increased risk of developing cancer over a lifetime.

This estimate is specific for those individuals who may consume large amounts of fish caught in areas not included in the fishing advisory. Should individuals differ in their consumption rates, in their selection of fish species for consumption, and in their choice of fishing locations, the estimates may vary considerably.

The FDA used different assumptions to set the 2 ppm tolerance limit for PCBs because they were only addressing health risks to consumers of fish sold in interstate commerce. They used average consumption rates for the US population. In addition, they assume only a portion of the fish in the consumer's diet comes from the area of contamination. Thus, their tolerance limit would not be suitable to use in those situations where the diet of local consumers consists primarily of locally-caught fish.

Another important exposure route to local residents is through the consumption of PCB-contaminated, municipal drinking water. Based on the 1985 EPA study (See Background section, 3. Site History), PCBs are most likely being released from the scale that collects within drinking water distribution lines. Although contamination had been detected in the samples collected at main distribution points (primarily fire hydrants), there were essentially no samples taken from residential taps. It was believed that PCBs might be getting through to these taps, but the sampling data to support this belief has only recently been gathered. The residential taps most likely affected are supplied by water systems that directly or indirectly use Twelve Mile Creek as their raw water source. Using this data, the following conservative assumptions were used to estimate a reasonable, worst-case exposure dose for the public consuming contaminated drinking water:

o The average daily concentration of PCBs in the drinking water at all taps is 0.294 ppb (that is, the maximum concentration detected in the sample from a tap within Easley-Central # I).
o We will assume that a 70 kilogram (that is, 150 pound) adult consumes 2 liters of water every day for 70 years from this tap only.
o EPA's cancer potency estimate for Aroclor 1260 is applicable to both Aroclors 1242 and 1248.

In this scenario, exposures to PCBs in drinking water barely exceeded ATSDR's chronic MRLs for ingestion. We estimated that the residents could have a low increased risk of developing cancer from a lifetime of consuming water with this concentration of PCBs. This risk estimate concerns exposures to contaminated drinking water that may be occurring at present and in the future. We cannot address any excess lifetime cancer risk from past exposures because there were no prior sampling data from residential taps; PCB concentrations could have been higher or lower than what was recently detected.

As previously stated, cancer risk estimates are made using a very conservative approach. For example, we have assumed that the PCB concentration in drinking water will remain constant for 70 years. Based on the monitoring data, this is highly unlikely. Because PCBs have probably contaminated the scale within these water systems, they will probably be intermittently detected in future drinking water samples. The fluctuations in the data increases the level of uncertainty in the estimate of the actual risk. Thus, the actual cancer risk is unlikely to be higher than this estimate and may be lower.

Town Creek/Twelve Mile Creek bathers may also be exposed to PCBs through dermal contact with contaminated sediments. The extent to which PCBs can be absorbed through the skin cannot be quantified. ATSDR has not developed MRLs for skin exposure. Exposures could also occur through incidental ingestion of sediments during wading and swimming. Considering the relative infrequency and short duration of these activities, however, exposures via this route are likely to be minimal.

The majority of the PCB-laden sediments should deposit along the midstream bottom of these waterways. Periodic changes in the elevation of Town/Twelve Mile Creek could cause some contaminated sediments to deposit along the shoreline. With rainfall, these sediments would probably wash back into these Creeks. However, there are no sampling data to confirm this assumption. Thus, we cannot assess the health risk to local residents through this medium. We need additional surface soil data from areas of these shorelines that are accessible to the public (particularly from the shoreline within the ravine, near Cateechee).

The EPA is currently reassessing the health risk from exposure to dioxins. Until this study can be completed, however, the following discussion will reflect the EPA's original, conservative scientific opinion.

PCDFs and PCDDs can be formed by the pyrolysis (that is, a chemical change brought about by heat) of PCBs and chlorobenzenes. PCDFs, not PCDDs, can be created as a result of the combustion of PCBs. PCDDs have been formed by the combustion of chlorobenzenes. Chlorobenzenes, together with PCBs, have been used as the dielectric fluid for transformers and capacitors (2). Thus, even though Sangamo did not manufacture or use PCDDs and PCDFs in any of their operations, it was reasonable for EPA to analyze fish and sediments for these compounds.

Only 4 of the 19 fish samples were taken from areas south of SC Highway 24 (specifically, from the Tugaloo River). These 4 fish, however, weighed between 5 to 7 pounds. Under the current advisory, fish weighing more than 3 pounds are not recommended to be eaten. To determine the public health risk to consumers of Tugaloo River hybrids, fish of the 2- to 3- pound weight class should have been collected.

Although fish of this weight class are not recommended for consumption, we evaluated the data to determine the potential public health impact from consuming fish with equivalent concentrations of PCBs and PCDDs/PCDFs. Assuming subsistence fishermen consume this fish for years, their daily exposure dose would exceed ATSDR's chronic MRLs for ingestion for both PCBs and 2,3,7,8-TCDD (the PCDDs/PCDFs data have been converted to their equivalent 2,3,7,8-TCDD concentrations). ATSDR has only developed an MRL for the congener 2,3,7,8-TCDD; it has not developed MRLs for any other PCDD/PCDF congeners. The MRL for 2,3,7,8-TCDD is based on this compound's reproductive toxicity to laboratory rats (2).

These fishermen would also have a very high increased risk of developing cancer from a lifetime of consuming PCBs at this concentration in this fish. However, they would only have a low increased risk from consuming the PCDDs/PCDFs in the same fish.

Thus, the potential cancer risks from these fish essentially comes from the concentration of PCBs in its tissue.

Because of EPA's current reassessment of the toxicity of 2,3,7,8-TCDD, the preceding discussion could have overstated the risk from exposure to this compound. Chloracne, a severe acneiform skin disease, is the only lesion definitively identified in humans resulting from 2,3,7,8-TCDD exposure. This effect has been primarily found in workers who were exposed to certain compounds in which 2,3,7,8-TCDD was a contaminant; however, there are no data available to quantify the dose at which chloracne will occur. Other effects (hepatotoxicity, immunotoxicity, reproductive toxicity, developmental toxicity, carcinogenicity) have only been reported in studies on various laboratory animals. These effects have not been reported in humans. While 2,3,7,8-TCDD has been actively studied, there has been very limited study of the other dioxin congeners and of the dibenzofurans (2).

The principal congener detected in the fish tissue was 2,3,7,8-tetrachlorodibenzofuran; no 2,3,7,8-TCDD was detected in these samples. Because the I-TEFs were derived as a means to convert the concentration of any PCDD/PCDF congener into an equivalent 2,3,7,8-TCDD concentration, use of these factors increases the uncertainty in the estimates of the actual risk from exposures to these congeners (12).

Considering the low levels of PCDFs/PCDDs in the sediment and the infrequent and short duration of contact with sediment during bathing, these compounds do not pose a significant public health risk.

The risk estimates described above were developed to predict a reasonably high risk to the most sensitive members of the exposed population. Conservative assumptions are used such that the actual risk would be unlikely to exceed these estimates. The assumptions chosen for each scenario described above reflect what would be considered a reasonably high exposure scenario. However, by decreasing the exposure dose (for example, by choosing to eat less fish with less contamination for less than a lifetime), these estimates would be substantially lower. The cancer potency factors themselves were developed to be as conservative as possible to ensure that a person will not be at an undue health risk from exposure.

B. Health Outcome Data

Although South Carolina has no population-based, statewide cancer registry, we decided to review the cancer mortality experience for Pickens County from 1985 to 1989. We considered this activity to have some merit since exposures to PCBs may have occurred for 30 years, approximating the latency period of many cancers (that is, the period of time from first exposure to the onset of disease). Certainly, this review is quite limited. We have no way of knowing if any of the individuals who died from a cancer had ever been exposed to PCBs from Lake Hartwell. Even if they were exposed, we have no way of knowing the duration of exposure. We have no way of knowing about those individuals who lived the majority of their lives near Lake Hartwell but died at another residence in another county or state. We have no way of identifying any personal risk factors, such as smoking, which could contribute to the occurrence of cancers. We also had no way of limiting our review to the mortality experience of the population in closest proximity to the lake; thus, any positive findings that may have occurred in this population may be unduly influenced by the lower cancer experience of other unaffected communities.

With these limitations in mind, we compared the county's five-year crude mortality rates to that of Anderson County, Oconee County and the State for the same time period. Pickens County's rate for all cancers was slightly less than the State's rate (162.0 per 100,000 vs. 173.6 per 100,000, respectively). This rate was also below the crude rates for Anderson County (175.5 per 100,000) and for Oconee County (183.7 per 100,000).

We used crude rates because they were readily available. However, the cancer mortality experience of a population depends on its composition by age, race, and sex. For instance, blacks have a higher cancer death rate than whites. Since Pickens County's black population is approximately 1/3 the size of the black population of Anderson County, this difference alone may be responsible for the difference in their crude rates (the age and sex distribution of each county, however, was approximately the same). Thus, these rates should be age-race-sex adjusted to make them more comparable.

The exposure study that was conducted by SCDHEC was quite limited in scope. It assessed PCB body burdens in a small self-selected group of people. Exposure histories were collected using a short, self-administered questionnaire. There was no assessment of the actual amount of fish these individuals consumed; there was only one question asking whether they had ever consumed Lake Hartwell fish (14 individuals reportedly had done so). There were no questions about where these fish were collected or what types of fish were typically consumed. There were no questions about other possible sources of PCB exposures unrelated to the site (4).

These people were primarily long time residents of the Cateechee community; the mean number of years they reportedly lived in the community was 23 years (ranging from 8 to 56 years).

Only 2 of the 27 individuals were found to have PCB levels in excess of 20 ppb (the upper level that would be expected for 95% of the people selected at random from the general US population without evidence of PCB exposure). Both individuals were females; they were 46 and 73 years old. While they both reported to have consumed Lake Hartwell fish for approximately 30 years, there is no information as to the amounts they consumed or the locations where the fish were caught.

At the request of SCDHEC, the results of this survey were reviewed by the Center for Environmental Health, Centers for Disease Control (CDC). In a November 1984 letter from Paul Wiesner, MD, Director, Chronic Diseases Division, they determined that the observation of 2 out of 27 individuals with serum levels greater than 20 ppb would be expected in this situation. They did not recommend any further epidemiologic studies since they considered there to be little direct evidence that significant excess exposures took place. They did recommend that exposure histories of the 2 individuals be ascertained to identify any other sources of exposures.

In the same letter, Dr. Wiesner addressed the self-administered survey conducted by local area residents. They determined that they could not link exposures to any excess prevalence of self-reported health problems in the community because there was no documented evidence of excess exposures to PCBs. They found most of the symptoms to be very nonspecific and likely attributable to other more common etiologies.

C. Community Health Concerns Evaluation

It is quite clear that the community has been and continues to be concerned about this situation since it was first brought public. Despite attempts by SCDHEC, CDC, ATSDR, EPA to address the potential public health effects from this site, the public remains concerned about the health consequences from long term exposures to PCBs. This has been made readily apparent by the public's 2 attempts to conduct their own health studies.

The symptoms and diseases that the community has reported to date are not necessarily related to PCB toxicity. As discussed previously, however, subsistence fishermen may be consuming fish at a level to warrant concern for developmental toxicity to their offspring. While this concern has sporadically been raised by a few residents, the effects that were self-reported (for example, mental retardation, "liver problems," "lung, heart, and liver problems" associated with prematurity) cannot be necessarily attributed to PCB exposure alone.

There have been sporadic anecdotal reports of individuals within this community who had developed different types of the more common cancers. Individuals have been living and possibly consuming contaminated fish for 20 to 30 years, a sufficient period of time for cancers to develop. Site-specific, cancer incidence data is needed to determine if the community has experienced an excess occurrence of cancers.

To adequately address the validity of these complaints, some effort must be made to quantify the amount of PCBs the public, particularly subsistence fishermen, could have been exposed to.

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