HEALTH CONSULTATION NO. 2
Review of June 2001 Private Well Sampling Results
WATSON JOHNSON LANDFILL
RICHLAND TOWNSHIP, BUCKS COUNTY, PENNSYLVANIA
At the request of the U.S. Environmental Protection Agency in Region III (EPA), the Pennsylvania Department of Health (PADOH), working under a Cooperative Agreement with the Agency for Toxic Substances and Disease Registry (ATSDR), prepared this Health Consultation (HC) to determine if residents near the Watson Johnson Landfill (the Site) are exposed to trichloroethene (TCE) in their private well water at levels that would harm their health.
Exposure to TCE represents no apparent health hazard for all of the residents living in locations discussed in this HC. With the exception of one home south of the Site, well water from all private wells discussed in this HC contained levels of TCE that were less than the federal drinking water standard. The levels of TCE present in a few residential wells along Richlandtown Pike do not pose a threat to the health of the residents using their wells. TCE was also present in a few residential wells south of the site. All residents living south of the site in homes where well water was sampled and the results discussed in this HC are using bottled water or carbon filtration units to mitigate or prevent exposure to TCE.
There are private residential wells south of the Site in the area of concern that were not sampled and could not be evaluated in this HC. We do not know if residents using water from these wells are exposed to TCE because data are not available. Therefore, exposure to TCE in water from the unsampled residential wells south of the Site is an indeterminate public health hazard due to lack of data. We recommend sampling of all residential wells in the area immediately south of the Site.
The interpretation, conclusions, and recommendations regarding the Watson Johnson Landfill are site specific and do not necessarily apply to any other site.
BACKGROUND AND STATEMENT OF ISSUES
The Watson Johnson Landfill is in Richland Township, Bucks County, Pennsylvania. The Site lies about 2000 feet south of East Pumping Station Road and 2000 feet west of Route 212. The approximately 32-acre landfill is northeast of the Tohickon Creek and 750 feet south of a farmhouse on East Pumping Station Road (Figures 1 & 2). Based on a review of aerial photography, it appears that the landfill began operations sometime after 1955. However, there is anecdotal information that the landfill began accepting wastes as early as 1936. In the mid 1960s the landfill accepted 3,200 tons of waste from W.R. Grace & Company's Quakertown chemical facility. The landfill has been inactive since 1973 [1].
Geology in the Quakertown area is dominated by the Brunswick Formation. This formation consists mostly of reddish brown shale and sandstone that have developed a well-defined system of vertical joints and faults. Secondary porosity (groundwater moving through joints and faults) is the primary pathway for the ground water flow. The ground water flow through the Brunswick Formation is difficult to determine due to the different size and frequency of the fractures. The water table is approximately 15-35 feet from the land surface, and the saturated thickness is approximately 150 feet. The shallow ground water is expected to flow toward the Tohickon Creek, southwest of the Site [1].
Approximately 90 people are served by private residential wells (RWs) near the Site. During September 1998, EPA sampled several RWs near the Site. During July 1999, EPA also sampled several RWs, a water supply well serving the Walnut Bank Farm Development and two Quakertown Borough Water Supply (QBWS) wells. PADOH and ATSDR evaluated the results of EPA's sampling and prepared a health consultation (HC) to address their findings [1]. The HC recommended that additional sampling of wells not previously sampled in an area south of the Site be conducted to determine if contaminants were migrating offsite to the south.
During June 2001, EPA sampled residential wells south of the Site in the recommended area (Figure 3). TCE was detected in four of the residential wells (Table 1). The maximum concentration of TCE in well water (RW-31) in this area was 15.0 micrograms per liter (µg/L). EPA also sampled RWs near the Site along Richlandtown Pike. TCE was present in a few of the private wells (RWs 3-6 & RW-30) along Richlandtown Pike at concentrations ranging from an estimated 0.1 µg/L to a known concentration of 4.0 µg/L in RW-30 [2]. In this HC, we evaluate the results of EPA's sampling and determine the public health significance of exposure to TCE detected in several residential wells.
On August 20, 2001, J.E. Godfrey, Hydrogeologist and Robert M. Stroman, Health Assessor from PADOH surveyed the topography around the study area to determine the location of the homes sampled in June 2001. During this Site Visit, homes near the Watson Johnson Landfill were observed that are reported to have TCE present in their private well water.
On August 28 and 31, 2001, Dr. Geroncio Fajardo and Robert Stroman met with residents along North Ambler (RW-31), Woodland Avenue (RW-14 and RW-20), North Penrose (RW-16), and Richlandtown Pike (RW-30), where TCE was detected in their private wells. Fajardo and Stroman discussed with the residents possible public health implications if exposure were to occur for a lifetime. During the visit, residents living in the homes served by RWs 14, 16, 20, 30, and 31 shared the information that they use bottled water for cooking and drinking. Residents living in the home served by RW-20 also have an in-line carbon filtration unit that is designed to prevent exposure from all pathways (ingestion, inhalation, and dermal) to volatile organic compounds, including TCE.
Very low concentrations (less than 0.3 µg/L) of TCE are present in a few of the residential wells along Richlandtown Pike. The levels are below levels of health concern and do not threaten the health of the residents using their well water. A low concentration of TCE (4 µg/L) present in one residential well in this area is also below a level of health concern and does not threaten the health of the residents using that well water.
TCE is also present in a few residential wells south of the Site along North Ambler Street, Woodland Avenue and North Penrose Street at concentrations ranging from 0.8 µg/L to 15.0 µg/L (Table 1). With the exception of one home along North Ambler Street that has a concentration of 15.0 µg/L of TCE in its well, all the other homes that were sampled during this investigation contained TCE in their well water at concentrations of less than EPA's maximum contaminant level of 5.0 µg/L.
Exposure to TCE at a concentration of 15.0 µg/L which is above the federal drinking water standard, in the home along North Ambler Street, will not threaten the health of the residents of this home who use this water during bathing and showering. This family uses bottled water for drinking and cooking. Exposure to TCE during bathing and showering in all of the other homes (south of the Site) evaluated in this HC will also not threaten the health of the residents using their well water. All residents south of the Site whose private well water was sampled during this investigation use bottled water or have inline carbon filtration units to mitigate or eliminate their exposure to TCE.
To determine the public health significance of past exposure to TCE in well water, we assume a maximum residential exposure to TCE in off-site ground water of 15.0 µg/L and a worst case exposure period of 45 years since the landfill appears to be in operation after 1955. This is a very conservative approach because exposure should be currently limited to showering and bathing (inhalation of volatile TCE) for the residents using bottled water and would only occur for residents using an inline carbon filtration unit in the event that the filter became full (saturated with TCE) and was not cleaned or replaced.
To determine the possible health effects of site-specific chemicals, ATSDR has developed health-based comparison values (CVs) that are chemical-specific concentrations to help identify environmental contaminants of health concern. We use CVs to determine which contaminants require further evaluation. These values include Environmental Media Evaluation Guides (EMEGs,) and Reference Dose Media Evaluation Guides (RMEGs) for noncancerous health effects and Cancer Risk Evaluation Guides (CREGs) for cancerous health effects. If environmental media guides cannot be established because of a lack of available health data, other comparison values may be used to select a contaminant for further evaluation. While media concentrations less than a CV are unlikely to pose a health threat, media concentrations above a CV do not necessarily represent a health threat. Therefore, CVs should not be used as predictors of adverse health effects or for setting clean-up levels.
PADOH also researches scientific literature and uses the ATSDR's minimal risk levels (MRLs), the EPA's reference doses (RfDs), and the EPA's Cancer Slope Factors (CSFs). MRLs are estimates of daily exposure to contaminants below which noncancerous adverse health effects are unlikely to occur. RfDs are estimates (with uncertainty spanning perhaps an order of magnitude) of daily oral exposure, in milligrams per kilogram per day (mg/kg/day), to the general public (including sensitive groups) that are likely to be without an appreciable risk of noncancerous harmful effects during a lifetime (70 years). When RfDs and MRLs are not available, a no observed adverse effect level (NOAEL) or lowest observed adverse effect level (LOAEL) may be used to estimate levels below which no adverse health effects (noncancerous) are expected.
Health guidelines such as MRLs and RfDs, however, do not consider the risk of developing cancer. To evaluate exposure to carcinogens, EPA has established CSFs for inhalation and ingestion that define the relationship between exposure doses and the likelihood of an increased risk of cancer, compared with controls that have not been exposed to the chemical. Usually derived from animal or occupational studies, cancer slope factors are used to calculate the exposure dose likely to result in one excess cancer case per one million persons exposed over a lifetime (70 years).
Because children generally receive higher doses of contaminants than adults under similar circumstances, the PADOH uses the higher doses in forming its conclusions about the health effects of exposures to site-related contaminants when children are known or thought to be involved (see Child Health Initiative section). Also readers should note that researchers conduct animal studies using doses at levels much higher than those experienced by most people exposed to contaminated groundwater originating from hazardous waste sites.
In evaluating the residential exposures from private wells, PADOH estimated exposures for children and adults from the three routes of exposure (inhalation, ingestion, and dermal). Assuming that the inhalation dose and dermal dose are approximately equal to the estimated ingestion dose, the respective doses for children and adults would be three times the ingestion dose. This is a conservative assumption because the dermal dose should be less than the ingestion and inhalation doses.
Trichloroethene (TCE)
TCE is a nonflammable, colorless liquid with a somewhat sweet odor and a sweet, burning taste. It is used mainly as a solvent to remove grease from metal parts, but it is also an ingredient in adhesives, paint removers, typewriter correction fluids, and spot removers. TCE is not thought to occur naturally in the environment. However, it is present in some underground water sources and many surface waters as a result of the manufacture, use, and disposal of the chemical. TCE does not build up significantly in plants and animals, which includes humans [3].
Noncarcinogenic-Health Effects
To evaluate for acute exposure (14 days or less), we assumed that children living near the Site consumed one liter of water per day contaminated with TCE at the highest detected level of 15.0 µg/L. In this scenario, PADOH believes that children would not have experienced noncancerous adverse health effects because the estimated dose experienced at that level is less than the ATSDR's acute oral Minimal Risk Level ((MRL) by a factor of about 133. Similarly, assuming that adults living near the Site consumed two liters of water per day contaminated with TCE at a level of 15.0 µg/L, the estimated dose experienced at this level from all exposure routes (i.e., ingestion, inhalation and dermal) is also below the acute MRL by a factor of about 500. Therefore, we do not expect any adverse noncancer health effects to occur from short-term exposure to TCE at this site.
For chronic exposure, ATSDR has not expanded a chronic oral MRL for TCE [4]. The EPA has placed the RfD for TCE under review [5]. Therefore, PADOH evaluated the potential for noncancerous health effects after long-term exposure at the levels found during this investigation using the available toxicological literature. PADOH does not expect any noncancerous health effects when multiple exposure routes (inhalation, ingestion and dermal contacts) are evaluated. The estimated total dose for children and adults would be 0.0045 and 0.0012 milligrams per kilogram per day (mg/kg/day), respectively. The estimated total doses are several thousand times below doses at which adverse health effects would be expected based on animal studies [4]. Therefore, we also do not expect any noncancer adverse health effects to occur from chronic exposure to TCE at this site.
Carcinogenic Health Effects
In studies using high doses of TCE in animals, tumors in the lungs, liver and testes were found, providing some evidence that a high dose of TCE can cause cancer in experimental animals [3]. Based on the limited data in humans regarding TCE exposure and cancer, and evidence that high doses of TCE can cause cancer in animals, the International Agency for Research on Cancer (IARC) has determined that TCE is probably carcinogenic to humans. Recently, the Department of Health and Human Services (National Toxicology Program) determined that TCE may reasonably be anticipated to be a carcinogen. This was based on limited evidence from studies in humans, sufficient evidence of malignant tumor formation in experimental animals, and convincing relevant information that TCE acts through mechanisms indicating it would likely cause cancer in humans. Currently, the National Toxicology Program is considering possible upgrading of TCE to a known human carcinogen. The EPA is also reviewing its classification for TCE's carcinogenicity in humans [4].
Epidemiological data are limited for evaluating the carcinogenicity of TCE in humans. Studies have suggested that occupational exposure to TCE causes cancer of the liver, biliary tract and non-Hodgkin's lymphoma. Another study has indicated that occupational exposure to TCE has been associated with cancer of the kidneys [6]. However, the actual exposure levels were not provided in these studies. There is one study that used the concentration of a TCE urinary metabolite (known as trichloroacetic acid or TCA) and inferred the level of exposure experienced by study subjects. The investigators reported that a urinary TCA level below 50 mg/L corresponds to a TCE exposure concentration of 20 parts per million (ppm). They found no correlation between exposure concentration or exposure time and cancer incidence [4]. However, because TCE is a probable human carcinogen, PADOH recommends that exposure to TCE should be eliminated or reduced to the lowest level possible.
In order to evaluate the possible cancer risk associated with the exposures to TCE at the maximum concentration (15.0 µg/L) that occurred to people who used contaminated well water during this investigation, we calculated the theoretical cancer risk using the cancer slope factor (CSF) of (0.011 mg/kg/day)-1 that EPA has placed under review. These calculations are based on the assumptions that 1) there is no safe level of exposure to a chemical that may cause cancer, 2) a person is exposed for a lifetime to the chemical, and 3) that inhalation and dermal doses are approximately equal to the estimated ingestion dose. However, these calculated risks are not exact and tend to overestimate the risk associated with exposures that occurred. Based on the theoretical cancer risk estimation for those people who were exposed to TCE at the maximum concentration (15.0 µg/L) for the past 45 years, the predicted cancer occurrence would be about nine additional cancers per 1,000,000 people [4]. Therefore, it is our opinion that (possible) past exposure to TCE (for 45 years) posed no significant cancer risk for the people who used water from the private wells.
PADOH and ATSDR recognize that the unique vulnerabilities of infants and children demand special emphasis in communities faced with contamination of environmental media. As part of ATSDR's Child Health Initiative, ATSDR public health consultations indicate whether site-related exposures are of particular concern for children.
In general, children appear to be more sensitive to the effects of TCE, presumably because of a higher body burden. However, there is no evidence that the pharmacokinetics (absorption, distribution, metabolism, and excretion) of TCE differ in children [4].
PADOH and ATSDR conclude the following:
PUBLIC HEALTH ACTIONS COMPLETED OR PLANNED
. Atlanta: ATSDR, February 9, 2001.. 9/12/2001.Robert M Stroman, B.S., Pharm.
Health Assessor
Pennsylvania Department of Health
Geroncio C. Fajardo, M.D., M.B.A., M.S.
Epidemiology Program Specialist
Pennsylvania Department of Health
This Watson Johnson Landfill Site Health Consultation has been prepared by the Pennsylvania Department of Health under Cooperative Agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the health consultation was initiated.
Roberta Erlwein
Technical Project Officer, SPS, SSAB, DHAC
The Division of Health Assessment and Consultation, ATSDR, has reviewed this Health Consultation and concurs with its findings.
Sven E. Rodenbeck
for Richard E. Gillig
Chief, SPS, SSAB, DHAC, ATSDR
Table 1. Levels of trichloroethene detected in residential wells sampled
| Residential Wells (RW) | Trichloroethene (TCE)* |
| RW-3 | 0.1 J** |
| RW-4 | 0.1 J |
| RW-5 | 0.2 J |
| RW-6 | 0.1 J |
| RW-14 | 1.0 |
| RW-16 | 0.8 |
| RW-20 | 4.0 |
| RW-30 | 4.0 |
| RW-31 | 15.0 |
* All results in ug/L or ppb
** J = analyte present; reported value is estimated; concentration is outside the range for accurate quantitation
