PUBLIC HEALTH ASSESSMENT
BURTON, BEAUFORT COUNTY, SOUTH CAROLINA
The tables in this section list the contaminants of concern. We evaluate these contaminants in thesubsequent sections of the Public Health Assessment and determine whether exposure to them haspublic health significance. This Public Health Assessment selects and discusses thesecontaminants based upon the following factors:
- Concentrations of contaminants on and off the site.
- Field data quality, laboratory data quality, and sample design.
- Comparison of on-site and off-site concentrations with background concentrations, if available.
- Comparison of on-site and off-site concentrations with health assessment comparison values for (1) noncarcinogenic endpoints and (2) carcinogenic endpoints.
- Community health concerns.
In the data tables that follow under the On-site Contamination and the Off-site Contaminationsubsections, the listed contaminant does not mean that it will cause adverse health effects fromexposures. Instead, the list indicates which contaminants will be evaluated further in this PublicHealth Assessment.
The data tables include the following acronyms:
|CREG||=||Cancer Risk Evaluation Guide|
|EMEG||=||Environmental Media Evaluation Guide|
|RMEG||=||Reference Dose Media Evaluation Guide|
|MCLG||=||EPA Maximum Contaminant Level Goal|
|MCL||=||EPA Maximum Contaminant Level|
|PMCLG||=||EPA Proposed MCLG|
|PMCL||=||EPA Proposed MCL|
|RfD||=||EPA Reference Dose|
|LTHA||=||EPA Lifetime Health Advisory|
Comparison values for health assessment are contaminant concentrations in specific media that are used to select contaminants form further evaluation. These values include EMEGs, CREGs, and other relevant guidelines. CREGs are estimated contaminant concentrations based on one excess cancer in a million persons exposed over 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 that no known or anticipated adverse effect on the health of persons should occur which allows an adequate margin of safety. PMCLGs are MCLGs that are being proposed. MCLs represent contaminant concentration that EPA deems protective of public health (considering the availability and economics of water treatment technology) over a lifetime (70 years) at an exposure rate of 2 liter water per day. While MCLs are regulatory concentrations, PMCLGs and MCLGs are not. EPA's RfD is an estimate of the daily exposure to a contaminant that is unlikely to cause adverse health effects.
In gathering environmental monitoring information for the Remedial Investigation, PBS&Jcollected environmental samples from soil, surface water, sediment and groundwater (Figures 4, 5and 6). Soil samples were collected only in on-site locations during sampling events in July 1989,March 1990 and September to October 1991. Groundwater samples were obtained in on-site andoff-site areas during four sampling rounds: October 1989, December 1989, February 1990 andOctober 1991. In the same four sampling rounds plus another sampling event in November 1991,surface water and sediment samples were collected from the L-shaped ditch at both on-site andoff-site portions. All samples were analyzed for organic and inorganic compounds (12).
Groundwater samples were obtained from monitoring wells, local residential wells and industrialwells. Monitoring wells were installed within the water table aquifer (designated as MW wells)and the limestone aquifer at a depth of approximate 100 feet (LW wells). Water table wells werecompleted at several depths: approximate 10, 25, 30, 40, 60 and 80 feet. Monitoring wells can beconstructed as a single well or a well cluster. A well cluster contains more than one well. AtKSCI as seen in the Figure 6, a well cluster contains 2 or 3 wells and is designated as, forinstance, MW-46,A,B, with MW-46 be the deepest well and MW-46B the shallowest well. Basedon groundwater flow patterns, historical sampling results and potential contamination sourceareas, PBS&J selected, with consent of the EPA and SCDHEC, 53 monitoring wells, 3 industrialwells (CW, CW-DRINK and CW-PROD) and 3 local wells (GR, MAS and MASL) to obtain groundwater samples during the Remedial Investigation (Figure 6) (12).
Toxic Chemical Release Inventory (TRI)
Project staff searched the Toxic Chemical Release Inventory (TRI) data within a 1-mile radius ofKSCI using geographic coordinates and area zip codes.
TRI is a database managed by the EPA since 1987. The inventory contains information on theannual estimated releases of over 300 toxic chemicals into the environment (air, water and land)by industry.
Mandated by federal regulations, Title III of the Superfund Amendments and Reauthorization Act(SARA) of 1986, facilities with 10 or more full-time employees are required to report to the EPAon releases of any of those 300 toxic chemicals during their business activities. Based on thesereports, a database has been established and is updated annually. The database records the namesand addresses of facilities which manufacture, process, or use these toxic chemicals, and amountsreleased to environment or transferred to waste sites.
The TRI search reported no releases of toxic substances by operating facilities in the KSCI area. However, the TRI database does not completely cover all toxic substances used in this area,especially those used by some companies that terminated their operations before the existence ofthe TRI program, such as KSCI. Table 2 (Appendix B) shows the raw materials and products handled at the site from 1976-1983.
No ambient air samples were taken in the on-site area.
Two common methods can be employed to obtain a soil sample: discrete or composite method. In the discrete method, a sample is obtained from a single depth at one location. While acomposite sample is a mixture of several samples collected either from several different depths ata single location (depth-composition), from the same depth at multi-locations (location-composition), or from multi-depths at different locations (full-composition). These methods wereused to collect soil samples during the RI at KSCI.
85 soil samples were collected in four sampling rounds during the RI. Seventeen of the 85samples were obtained from the depth interval of 0 to 12 inches with depth-composition method. Another 26 location-composition samples were collected from grid A at depths of 1 and 3 feet,and from each grid of grids B through I at depths of 1, 3 and 5 feet (Figures 4 and 5). Theremainder are discrete samples collected from subsurface approximately 1 and 6 feet below theground surface (12). No soil samples were taken from the depth of 0-3 inches. ATSDR definessurface soil as 0-3 inches since persons are most likely to be exposed to soil at that depth.
Shallow subsurface soils in the area immediately west of the operator pad and north of the tilefield (B5A, grids A and B, Figure 4) contained the highest contamination with several organiccompounds including benzene, 1,2-dichloroethane, ethylbenzene and methylene chloride. Elevated levels of lead and mercury were also detected in the vicinity of the operations area(Table 3, Appendix B). Soil samples from various areas across the site detected less compoundsand lower concentrations (12).
In general, concentrations of organic compounds detected at depth interval of 0 to 12 inches werelower, but levels of mercury and lead are generally higher than the respective concentrationsdetected in the samples obtained from depths greater than 1 foot. Contamination also decreaseswith increasing distances from the vicinity of the operations area.
78 on-site groundwater samples were collected from 38 monitoring wells during four samplingrounds. Samples were analyzed for organic and inorganic compounds (Results are in Table 4,Appendix B). Metal sampling analyses were based on non-filtered samples as required by theEPA (12).
Analytical data indicate that more contaminants with higher concentrations are distributed in thewater table aquifer in areas north and northwest of the operations area. Generally, contaminationdecreases with increasing depths and increasing distances from the operations area.
Surface Water and Sediments
In 1987, KSCI sampled surface waters from two locations in the L-shaped ditch, two oxidationponds in the former mobile home park, and a wet weather depression in KSCI property (Figure6). Several volatile organic compounds (VOCs) were detected in samples from the ditch (Table4, Appendix B). No VOCs were detected in the pond samples (12).
In an effort to assess the source of odors that were detected near the L-shaped ditch, SCDHECcollected surface water samples from the ditch in 1988. Benzene and 1,2-dichloroethane weredetected in the samples at levels of 6.6 µg/L and 50.4 µg/L, respectively. These levels wereconsidered insufficient to account for the odors.
During the five sampling events conducted from October 1990 to November 1991, PBS&Jcollected five surface water samples (SW-1 through 5) and two sediment samples (SD-2 andSD-3, Figure 6). Sampling results indicate the presence of several organic compounds andelevated levels of lead and mercury. The highest concentrations occurred in the surface watersample SW-2 and the sediment sample SD-2 (Table 3, Appendix B) (12).
Air and Soil
PBS&J did not collect air or soil samples from off-site areas during the RI.
During the Remedial Investigation, PBS&J collected 40 groundwater samples from fifteen off-sitemonitoring wells and six local wells located to the north (well GR), east (MASL and MAB) andsouthwest (CW, CW-PROD and CW-DRINK - Figure 6). Wells CW and CW-PROD arescreened in the limestone aquifer and are located approximately 700 feet to the southwest fromwell cluster MW-46, from which the highest levels of groundwater contamination were detected. Groundwater flow within the limestone aquifer beneath the site is toward the southwest asindicated by water level measurements during the RI. Therefore, the presence of 1,2-DCA atthese two wells may be the result of contaminant migration from the site (12).
Low levels of acetone (ND-170 µg/L) and methylene chloride (ND-14 µg/L) were detected atseveral off-site monitoring wells and local wells (Table 4, Appendix B). However, these twocompounds were also detected in the associated laboratory blanks. Therefore, the detection ofacetone and methylene chloride in off-site groundwater samples may be attributed to laboratorycontamination (12).
PBS&J conducted field work and sampling activities under Standard Operating Procedures (SOP)approved by EPA. All the samples were analyzed by Ecoter LSI, a member of the EPA ContractLaboratory Program (CLP). These procedures are required to be employed in all environmentalinvestigation activities to ensure that samples are collected and analyzed accurately. SCDHECassumes that adequate quality assurance and quality control measures were followed with regardto chain of custody, laboratory procedures, and data reporting.
Results of the analytical data present fair consistency between different sampling rounds anddifferent media. However, high quantification limits for benzene, carbon tetrachloride, 1,1-dichloroethene, ethylbenzene (500 µg/L), and vinyl chloride (1,000 µg/L), utilized togroundwater sample MW-46A may mask the possible presence of those compounds in thesample. Similar findings were reported for soil and sediment sample analyses.
Additionally, the frequent detections of acetone, methylene chloride andbis(2-ethylhexyl)phthalate in blanks and samples may be indicative of possible laboratorycontamination.
The ditch in the former mobile home park and the abandoned old operation house present aphysical hazard. People who enter the site may fall into the ditch or the hole in the floor of theoperation house.
To determine whether nearby residents are exposed to contaminants migrating from the site,SCDHEC evaluates the environmental and human components that lead to human exposure. Pathway analyses consist of the following five elements: a source of contamination, transportthrough an environmental media, a point of exposure, a route of human exposure, and ultimatelythe exposed population.
SCDHEC identifies exposure pathways as completed, potential, or eliminated. Completedpathways are those that include all five elements listed above. Potential pathways indicate thatexposure to a contaminant may have occurred, may be occurring, or may occur in the future. Apotential pathway exists when one of the above listed five elements is missing, but could exist. An eliminated pathway occurs when at least one of the five elements is missing and will never bepresent.
Because we could not define a receptor population, we do not believe that exposures haveoccurred, are occurring, or will occur. Therefore, no completed exposure pathways exist for theKSCI site at this time.
Table 5 summarizes the potential exposure pathways that exist at KSCI.
Past, present, and future exposures to contaminated soil are possible at the KSCI site. In the past,exposure to contaminants at the KSCI site could have occurred to anyone who may havewandered onto the site or to on-site workers. No data are available concerning the possibleexposures and/or length of exposures; therefore, adverse health effects from past exposures to on-site soils cannot be evaluated. The routes of exposure could have been dermal contact with,ingestion of, or inhalation of soil particles.
Currently, exposure to contaminants in soil may occur to anyone who enters site. However, wefeel that the likelihood of exposure to on-site soil contaminants is minimal because the site isvegetated. Frequent trespass onto the site is unlikely because the access to the site is restricted bythe wooded area partially surrounding the site. Site vegetation and the surrounding forest areexpected to prevent the migration of soil contaminants due to the effects of the wind. Therefore,exposures to the on-site soil contaminants through inhalation is not a concern at the present time.Soil contamination detected off-site may lead to exposure through ingestion or dermal contactwith contaminants. However, there is currently to off-site surface soil data with which to evaluatethis pathway.
In the future, potential exposure pathways could become completed if the site is developed. Inparticular, if future commercial or residential development of the property occurs, exposures tocontaminated soil could occur if the soil is disturbed through construction or other activities.
Current and future exposure pathways for groundwater could exist. Available data do notindicate that past exposure to contaminants in groundwater is likely.
Currently, 1,2-DCA has been detected in wells CW and CW-PROD. Because these wells are onlyused for production purposes by the concrete company and not as a drinking water supplies,exposures through ingestion should not occur. However, the possibility of exposure throughinhalation of 1,2-DCA vapors and through skin contact may exist. We have no data to confirmthat exposures are occurring. Current and future human exposures may occur through inhalationor dermal contact with other contaminants in groundwater. Inhalation exposure is only likely tooccur if the following conditions are met:
- The use of contaminated groundwater occurs in an open system that allows the contaminant to evaporate to air.
- The operation occurs in an enclosed environment. (operations that occur in outdoor environments are unlikely to lead to significant exposure.)
- Operations that involve spraying of groundwater will lead to larger amounts of thecontaminants evaporating from the groundwater than operations that involve a stream ofwater.
Past, current, and future exposures to contaminated sediment are possible. Contaminatedsediments detected in the ditch in the former mobile home park area present a potential forexposure through ingestion and skin contact to the people who enter the site and/or the ditch. However, we do not consider this to be a probable exposure scenario.
Surface Water Pathway
Past, present, and future exposures to contaminants in surface water are possible. In the past,exposure to contaminants may have occurred to anyone who ingested or had skin contact withcontaminated surface water in the L-shaped ditch.
Currently, there are no known completed routes of human exposure associated with surfacewater. Several contaminants have been detected in the surface water samples collected from theL-shaped ditch. The ditch ultimately connects with a state highway drainage ditch and is notdirectly connected with a classified water body of the State. Because the ditch is not utilized fordrinking water supplies, agricultural, industrial, or recreational purposes, the only potential forpublic exposure to the contaminated surface water would be through accidental ingestion and skin contact.
This potential exposure pathway could become completed in the future. Anyone who ingests orhas skin contact with contaminated surface water may be exposed to the identified contaminants. However, this would not appear to be a significant pathway.
In this section we will discuss the health effects which may impact on people exposed to site-related contaminants. To evaluate health effects which may result from an exposure, ATSDR hasdeveloped Minimal Risk Levels (MRLs). MRLs estimate an exposure which is not likely to causedeleterious health effects; exposure to even lower amounts would be even less likely to causeadverse health effects. MRLs are specific to the route of exposure and the length of exposure. Routes of exposure may include ingestion (eating and drinking), inhalation (breathing), anddermal absorption (absorption through the skin). The duration of exposure is commonly classifiedas acute (less than 14 days), intermediate (15 to 364 days), and chronic (greater than 365 days)exposures.
ATSDR developed MRLs to assess the possible toxicity of compounds to body organs. MRLs donot include information on the potential of compounds to cause cancer. In general, we assumethat a person exposed to small amounts of a carcinogenic compound will incur a small increase inthe statistical probability of developing cancer. A person exposed to larger doses of thecompound will incur a larger increase in the statistical probability of developing cancer.
This Public Health Assessment expresses the additional probability of developing cancer as aresult of an exposure to a chemical in terms of no increased risk, no apparent increased risk, a lowincreased risk, a moderate increased risk, and a high increased risk. EPA has developed amathematical methodology for estimating the extreme maximum probability that a person willdevelop cancer as a result of exposure to a chemical. The EPA Risk expresses estimates in thecorresponding terms of less than one-in-a-million risk, one-in-one-hundred-thousand risk, one-in-ten-thousand risk, one-in-one-thousand risk, and one-in-one-hundred risk.
ATSDR also develops Toxicological Profiles for chemical contaminants commonly found athazardous waste sites. These documents provide information on health effects, environmentaltransport, human exposure, and regulations affecting these substances.
The human exposure pathways section of this Public Health Assessment lists the routes by whichsite-related contaminants may enter the human body. As stated above, an evaluation of thesehazards relies on an accurate estimation of the amount of these chemicals to which a person maybe exposed. This estimate will use several standardized assumptions.
We will assume that an adult weighs 70 kilograms (154 pounds) and a child weighs 10 kilograms(27 pounds). An adult ingests 2 liters of water per day (2 L/day, the same as a 2-liter sodabottle). A child drinks half that amount (1 l/day). During the course of the day, adults typicallyingest 50 to 100 milligrams of soil per day (mg/day); this occurs by both inhaling small soilparticles carried in the air and by placing soiled hands and other objects in the mouth. Becausesmall children typically place objects in their mouths, it is assumed that they ingest a greateramount of soil, typically 200 mg/day.
The following discussions of chemicals rely on the preceding assumptions combined with theinformation in the Pathways Analyses section.
Benzene is a naturally occurring substance produced by volcanoes and forest fires and is presentin many plants and animals. It is also a major industrial chemical made from coal and oil and isfound in gasoline, adhesives, household cleaning products, and art supplies (3).
No completed human exposure pathway exists for benzene; therefore, no adverse health effectsare occurring at the present time. However, potential pathways could become completed in thefuture.
If the contaminated groundwater migrates off site and reaches private wells, ingestion ofgroundwater from those wells could lead to doses of benzene approximately five times EPA's1-day and 10-day Health Advisories. ATSDR has not developed acute, intermediate, and chronicMRLs for benzene due to insufficient human and animal data studies. According to the ATSDRDraft Toxicological Profile for Benzene, levels of benzene approximately twenty-times greaterthan those at the KSCI have led to detrimental changes in the blood of exposed rats (3).
Exposure to benzene is associated with the development of cancer in humans and laboratoryanimals (3). The lifetime (70 years) ingestion of maximally contaminated groundwater would leadto an "moderate increased risk" of developing cancer. Doses received from other media wouldcontribute much lower doses and could increase this risk by lower amounts.
1,2-Dichloroethane is a clear liquid that is not found naturally in the environment. It is used tomake other chemicals, as a component in several solvents, and is a former ingredient in somepesticides (5).
Currently, no completed exposure pathway exists for this chemical. However, potential exposurepathways identified for 1,2-dichloroethane may become completed in the future.
Children who ingest maximally contaminated groundwater may experience adverse health effects. In mice, acute oral doses similar to those in groundwater have caused a decreased immuneresponse. However, levels of 1,2-dichloroethane in groundwater are significantly less than levelsthat have caused a decrease in the number of white blood cells, serious effects on the immunesystem, liver damage, and death (3).
The ingestion of 1,2-dichloroethane from private wells if the highest levels found in on-sitegroundwater migrated to those wells, would not cause adverse, non-cancerous health effects in anadult. However, the theoretical, lifetime ingestion of maximally contaminated groundwater couldlead to a highly significant risk of developing cancer.
1,1-Dichloroethylene (DCE) is a chemical used to make other chemicals, such as some plasticwrap (6).
No completed exposure pathway exists for this chemical. However, potential pathways maybecome completed in the future if contaminated groundwater is ingested or if it comes intocontact with skin.
A child who ingests contaminated groundwater would receive a dose four times greater thanATSDR's MRL. However, adverse health effects from exposure to the levels of DCE ingroundwater are not anticipated to result in adverse health effects due to the wide variance incontaminant concentrations detected at the KSCI site and because of the safety factors used inderiving the MRL.
Some evidence suggests that DCE may cause cancer in laboratory animals (6). EPA lists DCE asa possible human carcinogen. Because of the lack of human data, the paucity of animal data, andthe lack of a plausible chronic exposure pathway, we cannot address the risk of cancer at this sitefrom future exposures.
No completed exposure pathway was identified for ethylbenzene. Therefore, no adverse healtheffects are anticipated at the present time. However, potential pathways identified for thischemical may become completed in the future.
An infant exhibiting soil pica behavior (ingesting large amounts of soil) and ingesting maximallycontaminated groundwater would receive a dose of ethylbenzene approximately ten times EPA'sreference dose. ATSDR has not established an MRL for ethylbenzene. The December 1990Toxicological Profile indicates that little human and animal toxicity is available. However, animaldata suggest that the liver, kidney, and blood system may be adversely affected from exposure toethylbenzene (7). However, these effects have not be documented in humans.
Methylene chloride is a commonly used solvent and paint stripper. Because many laboratoriescommonly use methylene chloride, it often appears as a contaminant in laboratory samples (10). Because the laboratory also detected methylene chloride in the associated laboratory blanks, thisHealth Assessment cannot assess the possible future health effects which may result from thiscompound at KSCI.
Vinyl chloride is also known as monochloroethylene is mainly used to make polyvinyl chloride(PVC). PVC is used to manufacture a variety of plastic and vinyl products including pipes, wiresand cable coatings, packaging materials, wall coverings and automotive parts (11).
No completed exposure pathways for vinyl chloride were identified. However, potential exposurepathways may be completed in the future if contaminated sediment is ingested or if it comes intocontact with skin.
A child who ingests maximally contaminated sediment would receive a dose of vinyl chlorideequal to ATSDR's chronic MRL. Therefore no adverse health effects are anticipated.
Because vinyl chloride appeared in a limited number of samples from only one specific medium,chronic exposure to this chemical appears highly unlikely. Therefore, carcinogenic effects will notbe discussed.
Lead is a naturally occurring element found in most environmental media. It has a wide range ofuses including storage batteries (automobile batteries), solders, pipes, various chemicals, and,formerly, gasoline additives (8).
Although lead may cause both acute and chronic effects, major concern has been focused on twochronic effects of lead toxicity. Chronic lead toxicity is associated with irreversible centralnervous system and peripheral nervous system damage in children; it is also associated withhypertension in some adult males (8).
ATSDR has not established an MRL for lead and the EPA has not established a reference dose forlead. Although exposure to certain lead salts have been associated with an increased rate ofcancer in laboratory animals, EPA has not estimated the carcinogenic potency of lead.
At KSCI, current exposure to lead is not currently of concern. Similarly, the lead levels are not ofconcern as long as the site remains vacant or industrial. However, if the site should becomeresidential, the ingestion of lead from soil and possibly the limited ingestion of stream sedimentswould be of concern.
Mercury is a chemical element that occurs naturally in several forms. The most familiar is thesilvery liquid metal used in some thermometers and other common products. Mercury also occursin combination with other elements. One form of mercury, methylmercury, can accumulate incertain fish (9). Analyses at KSCI did not differentiate between organic and inorganic mercury.
The levels of mercury found at the site are not of concern unless the site should becomeresidential in the future. Even then, the levels of mercury would be of concern for a young childexhibiting soil pica behavior who ingests maximally contaminated soil. In this case, the childwould receive a dose ten times the ATSDR's chronic MRL. Because testing did not show awidespread presence of mercury and because surface soil (0-3") samples were not analyzed aspart of the remedial investigation, the actual dose may be much less than "the worst case" models. Therefore, mercury will not be considered of concern at the present time.
Sodium is commonly found in nature combined with other chemicals. Sodium and chloride formtable salt. Sea water contains large amounts of sodium.
Because of medical conditions, some people need to limit their sodium intake. For example, somepeople with high blood pressure often benefit from a low salt diet and should consult with theirphysician before ingesting groundwater containing the levels of sodium found at this site.
As there are no completed pathways, and no health outcome data exists for the KSCI site, healthoutcome data were not evaluated at this time.
SCDHEC records document citizen complaints' of "noxious odors" emanating from the site. These complaints began in 1973 and continued until KSCI closed in 1983. SCDHEC and PBS&Jinvestigations could not determine the origin of the odors. We cannot address this issue at thistime because of a lack of data. No other community health concerns were documented.