PUBLIC HEALTH ASSESSMENT
MALVERN TCE SITE
MALVERN, CHESTER COUNTY, PENNSYLVANIA
ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS
The tables in this section list the contaminants of concern. We evaluate these contaminants in the following sections of the public health assessment and determine whether exposure to them has public health significance. PADOH selects and discusses these contaminants based upon several factors, including (a) concentration of chemicals on site and off site, (b) comparison of on-site and off-site concentrations with health assessment comparison values for carcinogenic and noncarcinogenic endpoints and, (c) community health concerns.
In the data tables presented in the On-Site Contamination and Off-Site Contamination sections, the fact that a contaminant is listed does not mean that it will cause adverse health effects from exposure. Instead, the list indicates which contaminants will be evaluated further in the public health assessment. When selected as a contaminant of concern in one medium, the contaminant will be reported in all media sampled.
Comparison values for public health assessments are contaminant concentrations in specific media that are used to select contaminants for further evaluation. These values include Environmental Media Evaluation Guides (EMEGs), Cancer Risk Evaluation Guides (CREGs), and other relevant guidelines. CREGs are estimated contaminant concentrations based on one excess cancer in a million persons exposed over a lifetime (70 years). Maximum Contaminant Levels (MCLs) represent contaminant concentrations that EPA deems protective of public health over a lifetime at an exposure rate of 2 liters of water per day for adult users of contaminated water. In establishing MCLs, EPA considers other factors, such as available technology, in addition to public health factors when establishing MCLs. Proposed Maximum Contaminant Levels (PMCLs) are being proposed by EPA.
PADOH conducted a search of the EPA Toxic Chemical Release Inventory (TRI) for the site and local area, but TRI did not list any other facilities having chemical releases. It is known, however, that the Transcontinental Gas Pipeline Company (Station 200) one mile southwest of the site is under investigation by PADER for improper waste disposal. Benzene (to 320 ppb), ethylbenzene (to 350 ppb) and total xylenes (to 1,300 ppb) have already been detected in groundwater beneath that facility (conversation with PADER and site investigation by the author). The Foote Mineral Superfund site is 1.5 miles southwest of Malvern TCE. That facility generated large amounts of lithium and boron wastes which contaminated groundwater east of Planebrook (Figure 1).
As of December 1991, the last date for which data were available for this report, the PSWC well (Figures 2, 5, and 6) contained low levels of TCE (1.4 ppb) and TCA (0.4 ppb). Of 48 samples collected in 1991, TCE and TCA levels ranged from non-detect to 1.4 ppb and 1.1 ppb, respectively. Over half of the samples showed neither contaminant present. That PSWC well pumps about 80 gallons per minute, 24 hours a day and serves an unknown number of local users. Though contaminant levels are presently within EPA drinking water standards, the potential for future increase of contaminant levels in that water supply should not be ignored.
Soil
Four surface soil samples were collected from the fenced area at the FDA (Figure 4) at a depth
interval from 0 to 6 inches. Table 1 reports the contaminants of concern and maximum
concentrations for each. Chemclene's contractor also took composite soil samples several feet
below ground level at 12 boring locations during tank and pit excavations (Figures 8 and 9).
These results are reported in Table 2. A soil sample taken at the time of tank excavation and
analyzed by the PADER laboratory contained xylene (a component of gasoline) at 4,000 ppb (5).
Though some leakage of gasoline may have occurred, the level of xylene contamination is not
above comparison values, and there is no evidence of xylene in on-site groundwater (see Table 3).
Table 1. Contaminant Concentrations in On-Site Surface Soil (5)
|
|
(PPB) |
||
| Trichloroethene (TCE) | |||
| 1,1,1-Trichloroethane (TCA) | |||
| Tetrachloroethene (PCE) | |||
Table 2. Contaminant Concentrations in On-Site Soil Borings (5)
|
|
(PPB) |
||
| Trichloroethene (TCE) | |||
| 1,1,1-Trichloroethane (TCA) | |||
| Tetrachloroethene (PCE) | |||
Groundwater - Monitoring Wells
Fourteen monitoring wells were installed on the Malvern TCE site beginning in 1980 and ending in 1992. Figures 3 and 4 show the well locations, and Table 3 contains the maximum concentrations reported in on-site groundwater for the 13-year period from 1980 to 1992, inclusive. All maximum values occurred in 1990 from wells drilled near the sites of previously buried tanks. Wells were drilled into the first water producing zone (approximately 100-400 feet deep) that would sustain well purging and sampling. Wells were not nested in sufficient numbers (three or more per nest) or with sufficient density (on-site and off-site) to adequately monitor the vertical distribution of groundwater contamination.
Table 3. Contaminant Concentrations in On-Site Groundwater Monitoring Wells (4)
|
|
CONC. (PPB) |
||
| Trichloroethene | |||
| 1,1,1-Trichloroethane | |||
| Tetrachloroethene | |||
Groundwater - Residential Wells
About 60 residential wells and springs on Hillbrook Circle and northwest of Phoenixville Pike have been sampled sporadically since 1980. PADER and consultants for Chemclene performed most of the sampling for which records are available. Apparently, the decision to install carbon filtration units was based on one or two area-wide groundwater sampling rounds in the early 1980s. After that, some residents claim that little or no resampling was done, and they are concerned that the contaminant plume may have migrated to previously unaffected wells. Indeed, 1992 sampling of some wells by Chemclene's consultant did reveal an increase in contamination in at least one residential well. However, no comprehensive, volatile organic sampling for all residential wells in the area has been conducted in the last ten years. It is particularly important that new (deep) private wells (60-150 feet deep) be sampled for volatile organic compounds. Such wells are drawing groundwater from different fractures deeper in the flow system and may be supplying water chemically different from previously used shallow wells.
Chemclene maintains 15 carbon filtration units on private wells. The carbon units are replaced approximately yearly. An unknown number of residents purchased their own treatment systems. Since 1980, at least 14 private wells have shown TCE concentrations above the EPA drinking water standard of 5 ppb. Table 4 reports the contaminants of concern in off-site groundwater and the maximum concentrations of each. The reported concentrations for TCE and TCA occurred in a single well (1983 and 1982, respectively) about 750 feet south of the FDA. The maximum concentration for PCE was detected in a well in 1982 nearly 2,500 feet southwest of the FDA.
One private well, sampled and analyzed by the well owner's consultant in October 1991, contained benzene at 18.87 ppb. This chemical has not been confirmed (detected) in water samples taken by Chemclene's consultant using a different laboratory. The presence of benzene may have been a "false positive" because of sample contamination or laboratory error. The well is, therefore, not included in the 14 affected wells even though Chemclene has furnished a carbon filtration unit for the home. More sampling of the well will be necessary to resolve the issue of possible benzene contamination. Based upon all available information, benzene does not appear to be associated with the Malvern TCE site, nor has it been detected in other residential wells.
Table 4. Contaminant Concentrations in Off-Site Residential Wells (5)
|
|
CONC. (PPB) |
||
| Trichloroethene (TCE) | |||
| 1,1,1-Trichloroethane (TCA) | |||
| Tetrachloroethene (PCE) | |||
C. Quality Assurance and Quality Control
In preparing this public health assessment, PADOH relies on information provided in the referenced documents and believes that adequate quality assurance and quality control (QA/QC) measures were followed regarding chain-of-custody, laboratory procedures and data reporting. However, much of the data available for the Malvern TCE site are ten years old or older. QA/QC measures for these data are unknown. Groundwater samples collected since about 1990 were apparently analyzed at a laboratory following EPA Contract Laboratory Protocol (CLP). Nevertheless, the sampling points were selected based upon past contamination and may not represent current groundwater quality in all wells.
The Malvern TCE site contains no known physical or other hazards.
To determine whether nearby residents are exposed to contaminants migrating from the site, PADOH evaluated the environmental and human components that lead to human exposure. An exposure pathway consists of five elements: a source of contamination, transport through an environmental medium, a point of exposure, a route of human exposure, and an exposed population.
PADOH categorizes an exposure pathway as a completed or potential exposure pathway if the exposure pathway cannot be eliminated. In completed pathways, the five elements exist and exposure has occurred, is occurring, or will occur in the future. In potential exposure pathways, at least one of the five 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. An exposure pathway can be eliminated if at least one of the five elements is missing and will never be present. Tables 5 and 6 summarize exposure pathways and estimated populations affected by the Malvern site.
Table 5. Completed Exposure Pathways
|
|
|
|
TRANSPORT |
EXPOSURE |
EXPOSURE |
POPULATION |
| Private Wells (at Hillbrook Circle & Phoenixville Pike) | Current Future |
Site |
Ingestion Dermal |
60 people |
Table 6. Potential Exposure Pathways
|
|
|
|
TRANSPORT |
EXPOSURE |
EXPOSURE |
POPULATION |
| Public & Private Wells | Current Future |
Site |
Ingestion Dermal |
A. Completed Exposure Pathways
Private Well Pathways
Contaminants move from the source areas at the plant and FDA as precipitation carries the contaminants to groundwater. Contaminants in the groundwater then migrate through a complex geologic fracture network to wells where groundwater users downgradient of the site are exposed. The natural gas pipeline right-of-way is a man-made feature which probably acts as a diversion trench to further complicate contaminant migration toward Hillbrook Circle and beyond.
Since 1980, at least 14 private wells have shown one or more contaminants of concern (Tables) above comparison values. The people who used the well water were exposed to the contaminants in the water through ingestion, inhalation of the volatilized contaminants, and skin contact. Carbon filters, which were added to wells with levels above EPA's MCL, have reduced the levels of contaminants in the well water.
One private well, sampled and analyzed by the owner's consultant in October 1991, contained benzene at 18.87 ppb. This chemical has not been confirmed (detected) in water samples taken by Chemclene's consultant using a different laboratory. The presence of benzene may have been a "false positive" because of sample contamination or laboratory error. The well is, therefore, not included in the 14 affected wells even though Chemclene has furnished a carbon filtration unit for the home. More sampling of the well will be necessary to resolve the issue of possible benzene contamination. Based upon all available information, benzene does not appear to be associated with the Malvern TCE site, nor has it been detected in other residential wells.
Due to drought and aquifer dewatering by a public well, two quarries (Figure 5), and area residential wells, the hydrogeology near and beneath the Malvern TCE site and Hillbrook Circle keeps changing dramatically. Contaminant migration is expected to become more confusing in the near future as more wells are drilled, groundwater use increases, and more contaminant sources are discovered (see Background section). The quality of groundwater in this area and the number of people exposed before 1980 (when carbon filters were first installed) are unknown. Several residents interviewed stated that they had lived in the Hillbrook Circle subdivision for over 20 years. Others purchased their homes since the site investigation began without knowing the seriousness of either the groundwater contamination or the decline of the water table.
B. Potential Exposure Pathways
There is a potential for area residents to be exposed to TCE, TCA, and PCE through the use of contaminated groundwater from both private and public wells. Unless an alternate water supply is provided for Hillbrook Circle, the falling water table will force more home owners to drill more and, perhaps, deeper wells. Those new wells could intercept more heavily contaminated groundwater from deep flow zones. Depending upon the volume pumped, the plume of contamination could be drawn toward existing wells which are now uncontaminated. This scenario may already have occurred at residence #65 (Figure 7). After more than a decade of monitoring, only this year (1992) did TCE and PCE reach concentrations (12 ppb and 19 ppb, respectively) in this drinking water well and required water treatment. There is insufficient information to determine whether the source of this contamination is the Chemclene plant area or the FDA.
A north-south trending petroleum pipeline passes just west of Hillbrook Circle (Figure 7) and
should be considered a potential pollution source for volatiles such as benzene, toluene, and
xylene. The line was repaired topographically upgradient from the subdivision in 1992, but no
leaks were reported at that time by the company.
In this section of the public health assessment, we will discuss the health effects in persons exposed to specific contaminants, evaluate state and local health data bases, and address specific community health concerns.
Introduction
To assist in evaluating noncarcinogenic health effects, either a Minimal Risk Level (MRL) for contaminants developed by ATSDR, or a Reference Does (RfD) developed by EPA has been used. The MRL is an estimate of daily exposure to a contaminant below which non-cancer adverse health effects are unlikely to occur. The RfD is an estimate of a daily exposure (mg/kg/day) to the general public (including sensitive groups), which is likely to be without an appreciable risk of harmful effects during a lifetime exposure (chronic RfD) or exposure during a limited time interval (subchronic RfD). Carcinogenic endpoints are evaluated using EPA's Cancer Slope Factors, when available. Also, exposures to mixtures of contaminants and multiplicity of exposure routes is not considered in the following evaluations.
Trichloroethylene (TCE)
TCE exposure has occurred and is occurring to off-site residents through use of contaminated well water. The levels to which people are exposed have decreased because of the use of carbon filters on the wells where contamination exceeded the MCL. Exposure is through the routes of ingestion, inhalation, and skin contact. Currently, there are no chronic MRL or RfD values available for this chemical. The level of exposure does not exceed the ATSDR intermediate oral MRL. Therefore, no non-carcinogenic adverse health effects are expected to occur because of ingestion of TCE at levels found in private wells if exposures are at a maximum of 1 year. However, because no health criteria are available to help evaluate exposures to the levels in private wells that last for more than 1 year, no evaluation of possible chronic effects can be made. The nervous system is the most sensitive system to adverse health effects from chronic exposure to TCE. (6)
Occupational studies of workers exposed to TCE at much higher levels than those detected in private wells near the site have not detected TCE-induced cancer, but several animal studies have shown that TCE can produce lung and liver cancer (6). Animal studies also have shown that TCE can cause leukemia, a cancer of the tissues that form white blood cells. In reviewing the animal studies, the Department of Health and Human Services (DHHS) National Toxicology Program could not find clear evidence that TCE causes cancer in animals. The International Agency for Research on Cancer (IARC), an agency that classifies chemicals according to their carcinogenicity, has decided that TCE is not classifiable as carcinogenic in humans. However, EPA classifies TCE as a probable human carcinogen based upon some animal studies (6). For that reason, exposure to TCE should be kept to a minimum.
Tetrachloroethene (PCE)
PCE exposure has occurred and is occurring to off-site residents through use of contaminated well water. The levels to which people are exposed have decreased because of the use of carbon filters on the wells where contamination exceeded the MCL. Exposure to the PCE is through the routes of ingestion, inhalation, and skin contact. Exposure to the levels of PCE found in private wells does not result in a dose that exceeds the RfD. The RfD is based on animal studies (7). People exposed to PCE at the levels detected in their residential wells are not expected to develop non-cancerous adverse health effects.
Studies of occupational workers have not linked PCE to cancer in humans. Animal studies, however, have shown that PCE will cause cancer in the animals studied (7). The animals in the studies were exposed to much higher levels of the contaminant than the people with private well contamination. EPA classifies PCE as a probable human carcinogen. If people drank the maximum amount of PCE found in private well water over a lifetime, those people may have an increased risk of developing cancer because of those exposures (7). Although the carbon filters reduce the amount of PCE available to the people with contaminated wells, any exposures should be avoided if possible.
1,1,1-Trichloroethane (TCA)
TCA exposure has occurred and is occurring to off-site residents through use of contaminated well water. The levels to which people are exposed have decreased because of the use of carbon filters on the wells where contamination exceeded the MCL (14). Exposure to the TCA is through the routes of ingestion, inhalation, and skin contact. ATSDR does not have MRLs for TCA, nor does EPA have RfDs; however, levels of TCA detected in pre-treated well water exceed EPA's Lifetime Health Advisory (LTHA) of 200 ppb. The duration of exposures to those levels is unknown, but no one has been exposed over a 70-year period (the duration of exposure on which the LTHA is based). Therefore, no adverse non-cancerous health effects are expected to occur as a result of exposures. EPA and IARC have decided that TCA is not classifiable as to its carcinogenicity to humans (14).
B. Health Outcome Data Evaluation
The Malvern TCE site is located in East Whiteland Township, Chester County. Twenty-one years of all cause mortality and cancer mortality (total cancer and eight cancer sites) were collected for East Whiteland, an area that includes, but is much larger, than the exposed population. The 1980-1990 East Whiteland Township data were analyzed using Pennsylvania's 1984-1986 mortality experience as a standard and the 1990 Census population for age and sex.
Total deaths (all causes) totaled 752 for the period 1980-1990 in East Whiteland Township. The expected number of deaths for the period was 742 and the calculated Standard Mortality Ration (SMR) was 1.01. An "expected" death is a statistical term used for measuring mortality among a specified population. In this case, the age-sex specific death rates by 5 year age groups for a selected cause of death for Pennsylvania is applied to the same age-sex population in East Whiteland Township to obtain an "expected" number of deaths. This tells the investigator how many deaths one would expect to see in East Whiteland Township if the mortality rate was the same as in the standard population - Pennsylvania. The SMR is a ratio of the deaths observed divided by the expected deaths. An SMR of one indicates the observed deaths equal the expected number of deaths.
Total cancer deaths observed in the 1980-1990 period were higher than expected with 191 cancer deaths observed and 169.8 cancer deaths expected for an SMR of 1.12. This is not a statistically significant difference. Statistical significance in this application indicates that there was at least a 95 percent surety that the difference in the observed number of deaths versus expected deaths was not a chance occurrence. The cancer sites evaluated were: (a) buccal cavity and pharynx; (b) digestive system; (c) respiratory system; (d) bone, connective tissue, skin and breast; (e) genitourinary system; (f) other and unspecified sites; (g) leukemia; and (h) other lymphatic and hematopoietic tissues. These eight cancer sites are those routinely reported on and made available through the State Health Data Center.
The only one of the eight cancer groupings that was statistically significantly different from expectation was cancer of other and unspecified sites which had 31 cancer deaths in the 11-year period when 19 deaths would have been expected (SMR 1.632).
The proportion of cancer deaths to total deaths was 25.4 percent of mortality which is slightly higher than the Pennsylvania proportion 22.6 percent. There has been a rather steady increase in both the number of cancer deaths and the cancer death rates for the period 1970 to 1990.
It is not unusual for mortality data to vary considerably from year to year in small populations. The range of total deaths and cancer deaths for the years 1980-1990 were 50 to 84 and 13 to 28, respectively. The number of cancer deaths did not deviate significantly from the expected number of deaths; however, the observed cancer deaths are higher than the calculated expected value (SMR 1.12). It cannot be determined from these aggregate data if there is an increase in cancer in the immediate vicinity of the site. Cancer mortality data will be reviewed annually for East Whiteland Township.
C. Community Health Concerns Evaluation
We have addressed the community concerns about health as described below.
The current status of the water quality for residential well #50 is not known. However, May 1986 sampling data indicate the well was free from contaminants at that time. A current hydrogeologic evaluation of the site leads to the conclusion that well #50 is not within the contamination plume associated with the site. PADOH will recommend additional sampling of this well in order to determine if recent changes in water quality have occurred. If further sampling data indicate no contamination, it is likely that this residential well has never been impacted by the site. Therefore, exposure to water at this location would not be responsible for causing tumors or any other chemically-induced disease. A newly drilled deep well on the same lot as well #50 did not indicate the presence of hazardous chemicals at levels of concern.
Carbon filtration units furnished by Chemclene and changed approximately yearly are probably effective in removing contaminants at levels detected in Hillbrook Circle water supplies. The units must be changes on a regular basis to assure their effectiveness. The frequency of their replacement should depend on the concentrations of chemicals present in the water, the amount of water used by the family, and the size of the filter. Periodic sampling of the water before and after the filters is advisable to determine their effectiveness. Please see the Recommendations section of this report.
The adverse health effects associated with exposure to TCE in well water are discussed in the Toxicological Evaluation subsection. It is unlikely that any non-cancer health effects would occur to those who were or are exposed to TCE at levels found in Hillbrook Circle water wells. There is uncertainty in the scientific community regarding the carcinogenicity of this chemical to humans.
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