PRELIMINARY PUBLIC HEALTH ASSESSMENT
DUBLIN WATER SUPPLY ENVIRONMENTAL
DUBLIN, BUCKS COUNTY, PENNSYLVANIA
The tables in this section list contaminants of concern. However, their listing does not imply that a health threat exists. When selected as a contaminant of concern in one medium, that contaminant will be reported in all media. PADOH evaluates these contaminants in subsequent sections and determines whether exposure to them has public health significance. PADOH selected these contaminants based upon the following factors: on and off-site concentrations; field and laboratory data quality; sample design; and comparison of on- and off-site concentrations with health assessment comparison values for noncarcinogenic and carcinogenic endpoints.
Comparison values for public health assessments are contaminant concentrations in specific media that are used to select contaminants for further evaluation. Values used in this public health assessment include ATSDR's Environmental Media Evaluation Guides (EMEGs) and other relevant guidelines such as a Reference Dose Media Evaluation Guides (RMEGs). RMEGs are calculated from EPA's Reference Dose (RfD), which is an estimate of the daily exposure to a contaminant that is unlikely to cause noncarcinogenic health effects. EPA's Maximum Contaminant Level Goal (MCLG) is a drinking water health goal. The MCLG represents a level where no known or anticipated adverse health effect on human health should occur. The MCLG allows an adequate margin of safety. Proposed Maximum Contaminant Level Goals (PMCLGs) are MCLGs that are being proposed. Maximum Contaminant Levels (MCLs) represent contaminant concentrations that EPA deems protective of public health over a lifetime of 70 years at an exposure rate of 2 liters of water per day. The MCL takes into consideration the availability and economics of water treatment technology. While MCLs are regulatory concentrations, PMCLGs and MCLGs are not.
In addition, the EPA Toxic Chemical Release Inventory data base was accessed by PADOH
through the National Library of Medicine's Toxicology Data Network. This data base was
searched for estimated annual releases of toxic chemicals to the environment from industries near
the site to identify possible facilities that could contribute to the contamination of groundwater
and other media near the site. The nearest facilities to report releases of toxic chemicals for the
years 1987-1991 are about four miles west of the site and are not expected to influence site
conditions.
A. ON-SITE
Groundwater
Samples from two wells (#1 and #2) at the site were obtained during the summer of 1986 by BCHD. Analysis of the samples by DER (1,2) provided data only for TCE, 1,1,1-TCA, and PCE. Analyses of samples taken on June 23, 1986, revealed elevated levels of TCE from both well #1 (5,000 ppb) and well #2 (100 ppb). Analysis of a follow-up sample taken on July 15, 1986, from well #1 revealed the highest level found in any of the well water testing conducted by BCHD (10,000 ppb TCE).
Table I represents a summary of the EPA groundwater data base (8) for the chemicals of concern on site based on well water sampling and analysis conducted in Dublin from 1986 to 1989. Only TCE and PCE were present at levels above comparison values. Other contaminants, such as 1,1,1-TCA, were detected at levels below comparison values.
Table I
On-Site Groundwater Contamination (8)
Concentration Range* (ppb)
Chemical |
1986 |
1987 |
1988 |
1989 |
Comparison Value (ppb) |
| Trichloroethylene Tetrachloroethylene |
2-10,000 8.6 |
<1-4,800 <1 |
10-5,900 10-12 |
77-243 -- |
3.0 0.7 |
CREG CREG |
Soil
Soil boring studies were conducted by BCM Eastern, Inc., in order to determine the potential
source of volatile organic compounds (VOCs), particularly TCE, that were detected in high
concentrations in the groundwater near the site. The results of these studies indicated, that
although some VOCs were present in subsurface soils, none were present at levels of concern (9).
Surface soil data were not available. VOCs are not expected to accumulate in surface soils;
rather they are expected to volatilize near the source and disperse in the surrounding air. No soil
gas data or air data were available for evaluation.
B. OFF-SITE
Sixty-one tap water samples (58 off-site and 3 on-site) were taken and analyzed by DER and private laboratories (37 samples analyzed by DER, 24 by private laboratories) for TCE, 1,1,1-TCA, and PCE in 1986. The analyses revealed the presence of TCE in all samples and the presence of 1,1,1-TCA (at levels below comparison values) and PCE in some samples. TCE concentrations at the tap included: 25 samples with non-detectable levels of TCE; 12 samples with levels between 0 and 5 ppb (EPA's Maximum Contaminant Level (MCL) for TCE is 5 ppb); 12 samples with levels between 5 and 200 ppb; 11 samples with levels greater than 200 ppb; and one sample which had TCE present, but no level was reported. Only one sample demonstrated a PCE level above 5 ppb (EPA's MCL for PCE), and no samples contained 1,1,1-TCA levels above 200 ppb comparison value.
Table II represents a summary of the EPA groundwater data base (8) for all contaminants of
concern, based on well water sampling conducted in Dublin from 1986 to 1989, reported off-site.
Other contaminants, such as 1,1,1-TCA, were present but at levels below comparison values.
Table II
Off-site Groundwater Contamination (8)
Concentration Range* (ppb)
Chemical |
1986 |
1987 |
1988 |
1989 |
Comparison Values (ppb) |
| Trichloroethylene Tetrachloroethylene Vinyl Chloride Bromodichloromethane Cis-1,3-Dichloropropene Methylene Chloride 1,2-Dichloropropane Trans-1,3-Dichloropropene |
<1-1,000 1-2 -- -- -- -- -- -- |
<1-1,590 -- 1.8 <1-49 <1-3 <1-76 <1-21 <1-9 |
<1-3,970 <1-5 <1-17 -- -- -- -- -- |
<1-4,450 <1-4 <1-25 -- -- -- -- -- |
3.0 0.7 0.2 0.6 3 5 5 3 |
CREG CREG RMEG(C) CREG RMEG(C) CREG MCL RMEG(C) |
Quarterly or biannual monitoring results for September 1993 were reviewed. Private wells were
sampled before the water was treated and after treatment when access to indoor taps was
available. High levels of TCE are still present in some wells prior to treatment. The highest
TCE levels were detected in a well at a business at 3,000 ppb. PCE was detected in that well at
2.3 ppb. The treated water was not tested because the building was unoccupied and the indoor
tap could not be accessed. Some water contained TCE above the MCL as late as 1992 at the
midpoint of the double carbon filter system. The finished tap water was not tested, but filters are
changed when breakthrough of the first filter is detected.
C. QUALITY
In preparing this public health assessment, PADOH relies on the information provided in the
referenced documents and assumes that adequate quality assurance and quality control measures
were followed regarding chain-of-custody, laboratory procedures, and data reporting. The
validity of the analyses and the conclusions drawn are based on the availability and reliability of
the referenced information.
D. PHYSICAL
There are no physical hazards associated with the site.
To determine whether nearby residents are exposed to contaminants migrating from the site, PADOH and ATSDR evaluate the environmental and human components that lead to human exposure. This pathways analysis 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 and ATSDR identifies exposure pathways as completed or potential exposure pathways if the exposure pathway cannot be eliminated. In completed exposure pathways, the five elements exist and indicate that exposure to a contaminant has occurred in the past, is occurring, or will occur in the future. In potential pathways, however, 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, or could occur in the future. In eliminated exposure pathways, at least one of the five elements is missing and will never be present. The discussion which follows identifies the completed and potential pathways at this site.
Contaminants have migrated in groundwater from the site toward the northwest, the direction of groundwater flow, and have entered drinking water supply wells. In 1986, when the contamination was first detected, the groundwater contaminant plume was defined as 2,600 feet long and 1,600 feet wide. At that time, an estimated 500 people were exposed to contaminants, primarily TCE, through ingesting the contaminated water, through inhaling the contaminants as they volatilized from the water, and through direct skin contact with the contaminants in the water.
Water supplies, both public and private, that are known to be contaminated have been supplied with treatment systems to remove or diminish the amount of contaminants in the groundwater that is used. The treatment systems, where designated in the EPA work plan, were installed beginning in mid-1987. No data are available to indicate how long drinking water supplies were contaminated prior to the discovery in 1986; however, solvents were reportedly used at the site as early as mid-1959.
The groundwater contaminant plume likely continues to migrate farther from the site. Private
and public water supply wells that tap the contaminant plume as it migrates are likely to have
become or will become contaminated. People who use the contaminated groundwater will be
exposed to contaminants through ingestion, inhalation, and direct skin contact with the
contaminated water. No other potential exposure pathways have been identified.
PUBLIC
In this section, PADOH discusses the health effects that may occur in persons exposed to site
contaminants in groundwater, evaluates the relevance of state health data bases to provide
information for the Dublin TCE site, and evaluates community health concerns.
A. Toxicological
As reported in the Environmental Contamination and Other Hazards section, groundwater that is used for drinking water and other purposes is contaminated with VOCs.
To evaluate health effects, ATSDR developed Minimal Risk Levels (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. MRLs are developed for routes of exposure (ingestion, inhalation, and skin contact) for different lengths of time, such as acute (less than 14 days), intermediate (15 to 364 days), and chronic (365 days or greater). EPA's Reference Dose (RfD) is an estimate of the daily exposure to a contaminant that is unlikely to cause adverse, non-cancer health effects. PADOH will give consideration to health guidelines (MRLs, RfDs, etc.) and environmental guidelines such as drinking water standards and criteria developed by other organizations to determine whether the groundwater in the vicinity of the site is acceptable to use as a potable water supply. The contaminants selected for further evaluation that were found in water supplies include TCE, PCE, vinyl chloride, bromodichloromethane, cis-1,3-dichloropropene, methylene chloride, 1,2-dichloropropane, and trans-1,3-dichloropropene. These discussions focus on exposure to the individual contaminants; the health effects that may occur as a result of exposure to a mixture of contaminants have not been well studied, and conclusions cannot be drawn about exposures to mixtures.
Trichloroethylene (TCE)
TCE was detected in on-site well water at a maximum of 10,000 ppb and in off-site tap water at a maximum of 4,450 ppb. In 1986, when the contamination was detected, ATSDR issued a health consultation stating that exposure to levels of TCE found in drinking water supplies represented an imminent health threat. No data exist to establish the length of time people were exposed to high levels of TCE, but that compound was used at the site as early as mid-1959; therefore, people were possibly exposed for up to 28 years before water treatment systems were placed on wells beginning in 1987. A second health consultation conducted by ATSDR in 1990 (see Background section) pointed out concerns about the long-term effectiveness of carbon filtration systems.
An intermediate oral MRL has been established for exposure to TCE. The estimated ingestion dose for adults ingesting drinking water containing 10,000 ppb does not exceed the MRL; therefore, no adverse, non-cancer health effects are expected for adults. If children were exposed to that level for 15 or more days, they may develop non-cancer, adverse health effects such as effects to the liver, kidneys, blood, and central nervous system (12). Long-term exposure to TCE at levels found in water supplies may pose a significant increase in the risk of developing cancer.
Animal studies show that ingesting or breathing levels of TCE that are much higher than typical environmental levels can lead to liver and kidney damage, nervous system damage, effects in the blood, and tumors of various organs such as the kidney, liver, and male sex organs (12).
For humans, research reported in the literature indicated that principal targets following TCE exposure were the central nervous system, liver, kidney, and the hematologic system (20). Because of the small amount of relevant study information and the uncertainties in interpreting the study findings reported in the literature, neither the lowest observable adverse effect levels (LOAELs) nor the no observable adverse effect levels (NOAELs) for most effects in humans could be specified (20).
Carcinogenic effects of TCE in humans have not been conclusively demonstrated. Several studies have indicated an association between leukemia and drinking water contaminated with organic chemicals including TCE. However, a direct relationship between TCE and the increased rates of leukemia could not be determined because of the multiple chemical exposures and other study limitations (12). Other epidemiological studies have failed to establish a relationship between the incidence of liver tumors in workers and exposure to TCE via inhalation (12). Because of the inconclusive studies, EPA is conducting more investigations to determine TCE's cancer classification.
Certain populations that may be especially sensitive to TCE exposure include chronic consumers of alcohol and persons with heart disease. Persons taking disulfiram, a medication used for the treatment of alcoholism, may also be at an increased health risk through TCE exposure (12).
Tetrachloroethylene (PCE)
Past exposures to PCE have occurred through ingestion, inhalation, and skin contact with PCE-contaminated water as a result of contamination at the Dublin TCE site . Chronic exposures to PCE may be associated with development of cancer and adverse effects of the central nervous system, liver, and kidneys (13).
A maximum concentration of PCE was detected in on-site well water at 12 ppb and in off-site tap water at 5 ppb. Exposure to those levels are not expected to result in non-cancer, adverse health effects. Chronic exposures to these levels of PCE may result in a low increased risk of developing cancer. Epidemiological studies of dry-cleaning and laundry workers who use large amounts of PCE and other solvents have suggested a possible association between chronic exposure to PCE and an increased risk of developing cancer (13). However, the results of these studies are somewhat inconclusive because of exposure to multiple solvents and factors that were not controlled such as smoking and socioeconomic status (13). Because of these studies and animal studies showing a relationship between PCE exposures and cancer, EPA has classified PCE as a probable human carcinogen (13).
Some people are more sensitive to PCE exposure than others. PCE can cross the placenta and has been found in breast milk; therefore, fetuses and nursing babies may be at an increased risk of adverse health effects when the mother has been exposed. In addition, workers in dry-cleaning and laundry facilities who use contaminated water may also be exposed to PCE at their workplace (13).
Vinyl Chloride
Past exposures to vinyl chloride have occurred through use of contaminated groundwater. The routes of this exposure would be through inhalation, ingestion, and dermal absorption. Vinyl chloride has been classified by the EPA as a human carcinogen (10).
The maximum concentration of vinyl chloride detected at drinking water taps or wells was 25 µµg/L. Long-term exposure to that level of vinyl chloride may result in non-cancer, adverse health effects. As a known human carcinogen, exposure to vinyl chloride over a long period of time may also increase the risk of developing cancer (10).
Health effects associated with chronic, low-level ingestion and inhalation exposure in humans in a non-occupational setting have not been studied. The primary target organs of vinyl chloride toxicity are the liver and the central nervous system (10). In the occupational setting, ingestion and inhalation of vinyl chloride may cause nausea, vomiting, diarrhea, and abdominal pain. Other health effects include fatigue, damage to the liver and lungs. Vinyl chloride exposure in occupational settings has been associated with angiosarcoma of the liver and, perhaps, brain cancer (10).
Some people may be exposed to more vinyl chloride or be more sensitive to exposures than others. Populations typically associated with vinyl chloride exposures include people living over landfills where vinyl chloride is disposed or where vinyl chloride is a degradation product of TCE, PCE, or 1,1,1-TCA. Workers involved in the production or polymerization of vinyl chloride may constitute a group at risk because of the potential for occupational exposure. Smokers may be at increased risk of exposure to higher levels of vinyl chloride as the compound has been detected in tobacco smoke (10).
Bromodichloromethane
Exposures to bromodichloromethane have occurred through use of contaminated groundwater. People have been exposed to the contaminant through ingestion, inhalation, and skin contact. Bromodichloromethane is classified by EPA as a probable human carcinogen (14).
The maximum level of bromodichloromethane detected in tap water or well water is 49 µg/L. Exposure to that level of bromodichloromethane is not expected to cause non-cancer, adverse health effects. Long-term exposure to that level may result in a slight increased risk of developing cancer. Animals that have been exposed to bromodichloromethane for long periods of time develop cancer of the liver, kidney, and intestines (14).
People who work in chemical plants or laboratories where bromodichloromethane is made or used may be exposed to the chemical in addition to that found in the drinking water. People with liver diseases may be particularly susceptible to the hepatotoxic effects of the chemical, and people with kidney disease may also be more sensitive to toxic effects. Additionally, people who consume large amounts of alcohol or take certain drugs that affect the liver may also be more susceptible to the adverse effects of bromodichloromethane exposure (14).
Cis- and Trans-1,3-Dichloropropene
Past exposure to both cis- and trans-1,3-dichloropropene has occurred. People were exposed through ingestion, inhalation, and skin contact with the chemicals. The two forms of the chemical behave very much alike and are usually combined in different amounts to form mixtures (15). Therefore, the compounds will be discussed as 1,3-dichloropropene. EPA classifies 1,3-dichloropropene as a probable carcinogen (15).
The maximum level of 1,3-dichloropropene detected in tap or well water is 9 µg/L of the trans form. An adult who ingests that level over a long period of time is not expected to have non-cancer, adverse health effects as a result of exposure. However, a child who ingests that amount for very long periods of time may develop some non-cancer, adverse health effects (15). No cancer slope factor has been developed to provide information on what risk may exist for exposed people to develop cancer. However, because of the cancer classification, some increased risk of developing cancer may be expected if people ingest the maximum amount over a long period of time (15).
Inhalation of 1,3-dichloropropene at high levels may cause nausea, vomiting, irritation of the skin, eyes, nose and throat, coughing, headache, and fatigue. Animal studies indicate that adverse effects have occurred after ingestion, inhalation, or contact with the chemical on the skin. Those effects have included skin irritation, bleeding from the lungs, stomach, under the skin, difficulty in walking, and hair loss. The levels given to those animals are much higher than those detected in water near the site (15).
No subpopulations have been identified as being more sensitive to health effects from exposure to 1,3-dichloropropene. However, people with kidney disease may be more susceptible as well as those with depletion of glutathione pools because of the metabolic process of the chemical (15).
Methylene Chloride
Past exposure to methylene chloride has occurred through use of contaminated groundwater. People were exposed to the chemical through ingestion, inhalation, and direct skin contact. Methylene chloride is classified by EPA as a probable carcinogen (16).
Methylene chloride, also known as dichloromethane, was detected in tap or well water at a maximum of 76 µg/L. Exposures to those levels are not expected to result in non-cancer, adverse health effects. Long-term exposure to those levels may result in a slight increased risk of developing cancer (16).
As with most VOCs, people that may be more susceptible to the toxic effects of methylene chloride include the elderly and the very young because of their declining or undeveloped organ functions. Smokers and people with cardiovascular disease are also at increased risk (16).
1,2-Dichloropropane
Past exposure to 1,2-dichloropropane has occurred through use of contaminated groundwater. People were exposed to the chemical through ingestion, inhalation, and direct skin contact. The chemical has not been classified as to carcinogenicity potential by EPA (17).
The maximum amount of 1,2-dichloropropane detected in tap or well water was 21 µg/L. Exposure to that level is not expected to cause non-cancer, adverse health effects (17). No cancer has been reported in people who have breathed or ingested 1,2-dichloropropane for short periods of time; however, long-term oral exposure to some animals has produced evidence of liver and breast cancer (17).
No populations have been identified that may be particularly susceptible to 1,2-dichloropropane
toxicity (17).
B. Health
The Dublin TCE site is located in Dublin Borough, Bucks County. Twenty-one years of all cause mortality and cancer mortality (total cancer and eight cancer sites) were collected for Dublin Borough (18). The 1979-1989 data were analyzed using Pennsylvania's 1979-1981 mortality experience as a standard and the 1980 Census population for age and sex.
Total deaths (all causes) were below the expected number of deaths for the 1979-1989 period for Dublin Borough. An "expected" death is a statistical term used for measuring mortality among a specified population. In this case, the age-sex specific deaths in Pennsylvania is applied to the same age-sex population in Dublin Borough to obtain an "expected" number of deaths. This tells the investigator how many deaths one would expect to see in the Borough if the mortality experience was the same as in the standard population - Pennsylvania. (This is known as the indirect method of mortality adjustment). The observed number of deaths divided by the expected number of deaths produces a ratio known as the Standard Mortality Ratio (SMR). In Dublin Borough, 103 deaths were observed, which was less than the 130 deaths expected (SMR 0.792) (19).
In Dublin Borough, the observed cancer deaths were less than expected with 20 observed cancer
deaths and 27.7 cancer deaths expected, which is not a statistically significant result for that
period of time. Analyses of eight cancer sites also indicated no significant results. The cancer
sites investigated were: (1) buccal cavity and pharynx; (2) digestive system; (3) respiratory
system; (4) bone, connective tissue, skin, and breast; (5) genitourinary system; and (6) other and
unspecified sites: (7) leukemia and (8) other lymphatic and hematopoietic tissues.
C. Community
Concerns expressed about the site are centered on the potential for other water supplies to become contaminated and any health impacts resulting from exposure. The groundwater contaminant plume has migrated from the site and has contaminated drinking water supplies that tap the contaminated groundwater. The levels of contamination found in some water supplies were considered imminent health threats. Those water supplies are currently being treated to remove or lessen the amount of the contaminants in the water. The contaminant plume is expected to continue to migrate, thereby contaminating other drinking water wells that tap the contaminated groundwater. For that reason, all wells that are downgradient of the site should be identified and monitored on a regular schedule. EPA and the Potential Responsible Party (PRP) have agreed to monitor contaminated wells quarterly. Additionally, they have extended the area monitored to include other homes and businesses that are downgradient. EPA believes all wells that have been contaminated to date have been identified; however, investigation of the plume continues to ensure that any additional wells that are threatened are identified. To do this adequately, the contaminant plume must be monitored carefully to determine where it is going and how far it has reached. With time, the contaminant levels are expected to decrease. The contamination is expected to decrease over time because the facility is no longer putting chemicals into the ground where they can enter the groundwater and the in-plume well specified in the ROD will extract and treat the contaminated water.
As discussed in the Toxicological Evaluation subsection of this document, some of the contaminants do pose a health concern if exposure occurs at the maximum levels detected. The possible health effects for the chemicals that are at levels of health concern are discussed in that subsection. By identifying and monitoring threatened water supplies, exposure, thus possible adverse health effects that may result from exposure, can be avoided.
Another concern that ATSDR voiced in its 1990 health consultation involved the long-term effectiveness of using carbon filtration systems for treatment of contaminated water supplies. Not only is breakthrough and charcoal channeling a possibility, but some carbon filtration systems can support the growth of potentially harmful bacteria. The health consultation also questioned the effectiveness of the Tier II decision (see Appendix B) in preventing exposure to contaminants through inhalation. The December 1991 ROD addresses those concerns and provides for a long-term, safe water supply for affected people.
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