PUBLIC HEALTH ASSESSMENT
LOWER SALFORD TOWNSHIP, MONTGOMERY COUNTY PENNSYLVANIA
The data in this section list the site contaminants of concern. ATSDR and PADOH evaluate these contaminants in the subsequent sections of the public health assessment to determine whether exposure to them has public health significance. ATSDR and PADOH select and discuss these contaminants based upon the following factors:
- Concentrations of contaminants on and off the site.
- Field data quality, laboratory data quality, and sample design.
- Comparison of concentrations with public health assessment comparison values for (1) non-carcinogenic endpoints and (2) carcinogenic endpoints.
- Community health concerns.
In the data that follow under the On-Site Contamination subsection and the Off-Site Contamination subsection, the listed contaminant does not mean that it will cause adverse health effects from exposures. 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, that contaminant will be reported in all media for which sample results are available.
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 a one excess cancer in a million persons exposed over a lifetime. CREGs are calculated from EPA's cancer slope factors.
EPA's Maximum Contaminant Level Goal (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. Proposed Maximum Contaminant Level Goals (PMCLGs) are MCLGs that are being proposed. Maximum contaminant levels (MCLs) represent contaminant concentrations that a regulatory agency, e.g. EPA, deems protective of public health (considering the availability and economics of water treatment technology) over a lifetime (70 years) at an ingestion rate of 2 liters of water per day. MCLs are regulatory concentrations.
EPA's Reference Dose (RfD) and Reference Concentration (RfC) are estimates of the daily exposure to a contaminant that is unlikely to cause adverse health effects. The environmental contamination section includes sampling data from a variety of media sources including: soil; air; and building. Contaminants of concern are selected by comparing contaminant levels detected at the site to public health assessment comparison values. These values may include ATSDR EMEGs and CREGs. Selected contaminants are further evaluated in subsequent sections of the public health assessment to determine whether exposure to these contaminants are likely to result in harmful health effects in humans.
Since no RI has been conducted for the site, very little data is available. Monitoring well sampling results are the only on-site data available to PADOH. A maximum boron concentration of 374 ppm was detected in monitoring well No. 2 (Figures 4 and 5) in a 1991 sampling event (2). Trichloroethene (TCE) was detected at that time in on-site groundwater at 0.02 ppm (20 ppb). No other contaminants were detected at levels of health concern in on-site groundwater and no other media were sampled on the site.
Boron was detected in a private well at a concentration of 24.7 ppm in 1991 (4). Five other homes indicated boron at concentrations above 10 ppm in the same sampling round. Neither monitoring wells nor private wells indicated TCE at levels of health concern. Best estimates of (boron) plume extent through private well monitoring ( 0.3 ppm or 300 ppb isocon) suggest a length of about 8000 feet with extreme narrowing toward the southwest end (Figure 3). Estimating an exposed population is nearly impossible because residential density has not been constant over time. During the 1991 sampling, approximately 200 residents in 60 homes were affected by the plume.
EPA contractors sampled a spring near the site (Figure 5) and reported a boron concentration of 139 ppm (139,000 ppb) in 1983 (2). We do not believe that spring is used for drinking. In 1989, a contractor for National Gypsum (ENVIRON) resampled the spring and reported a boron concentration of 31.5 ppm (31,500 ppb), a dramatic decrease from the 1983 level (5). We do not know if the boron concentration has continued to decrease over time.
In preparing this public health assessment, ATSDR and PADOH relied on the information provided in the referenced documents and assumes that adequate quality assurance and quality control measures were followed with regard to chain-of-custody, laboratory procedures, and data reporting. The validity of analyses and conclusions drawn for this health assessment is determined by the completeness and reliability of the referenced information.
There are no physical or other hazards associated with the site.
The TRI search for the years from 1990 to 1994 did not list any reported emissions of chemicals that are pertinent to this public health assessment.
To determine whether nearby residents at the site are exposed to site related contaminants, ATSDR/PADOH evaluate the environmental and human components that lead to human exposure. This pathways analysis consists of five elements: (a) a source of contamination; (b) transport through an environmental medium; (c) a point of human exposure; (d) route of human exposure; and (e) an exposed population.
The ATSDR/PADOH classify exposure pathways into three groups: (1) "completed pathways", that is, those in which exposure has occurred, is occurring, or will occur; (2) "potential pathways", that is, those in which exposure might have occurred, may be occurring, or may yet occur; and (3) "eliminated pathways", that is those that can be eliminated from further analysis because one of the five elements is missing and will never be present, or in which no contaminants of concern can be identified. A summary of the pathways for the GSMS are discussed below.
Past Domestic Well Pathway
PADOH has identified one past completed exposure pathway for the Salford Quarry site (the site). The ingestion of boron in groundwater pumped from domestic wells constituted this exposure pathway. Currently, this pathway has been interrupted as the U.S. Environmental Protection Agency extended an existing public water supply line to all homes affected by the boron in groundwater.
A potential exposure pathway will occur if a new well is drilled in the plume and someone drinks the water. That event is unlikely based upon the availability of an approved public water supply.
Although our data on surface water is limited, we believe there is a possibility of exposure
through spring water near the site based upon two historically high boron concentrations over the last 15 years (2).
In this section, we will discuss potential health effects that may result from exposure to environmental contaminants, available health outcome data, and community health concerns. The Toxicological Evaluation section will assess the noncarcinogenic and carcinogenic effects of exposure to contaminants that are above comparison values. The Health Outcome Data Evaluation section will assess available community health information to determine whether adverse health effects have occurred. The Community Health Concerns Evaluation section discusses public health concerns voiced by the community about possible exposure to contaminants relative to documented exposures and potential health effects.
In this section, PADOH discusses health effects that could result from past exposure to site-related boron. To evaluate health effects, ATSDR used its minimal risk level (MRL). The MRL is an estimate of daily exposure to a contaminant below which noncancerous adverse health effects are unlikely to occur.
Boron in Groundwater
The maximum concentration of boron that was detected in the residential well water was 25 parts per million (ppm) in September 1991. Assuming that the water intake for adults and infants is 2 liters and 1 liter per day, respectively, and that body weights are 70 kilograms (kg) and 10 kg, respectively, ingestion of maximum levels of boron in contaminated well water resulted in exposures of about 0.71 mg/kg/d for adults and about 2.5 mg/kg/d for infants. These exposure levels were above ATSDR's 0.09 mg/kg/d MRL for boron for intermediate exposure (15-364 days) via oral ingestion. ATSDR concluded in 1991 that these levels of exposure posed a threat to human health. As stated in Appendix B, the effects from oral exposure to boron at a level of 25 ppm may include neurological deficits and kidney effects (R. Williams' 12/13/91 addendum to health assessment, Appendix B). However, by 1997 all human exposures to elevated levels of boron had been stopped by the extension of a public water supply to all affected homes. PADOH currently believes that there are no human exposures to elevated levels of boron in groundwater near the site. Thus, the site no longer poses a public health hazard.
Boron was not classified as a human carcinogen by the Department of Health and Human Services, the International Agency for Research on Cancer, or EPA (6 ). Thus, the cancer mortality and incidence data are not relevant to the health outcome data evaluation.
There are no morbidity data available for the Lower Salford Township to evaluate possible health effects from ingesting boron (i.e., irritation of skin or stomach, or fertile effects among males). Because many confounding factors can inadvertently contribute to these possible health effects and no adverse health effects have been reported to the PADOH from the community, further data collection and analysis was not warranted.
PADOH evaluated the concern of the citizen who phoned about the illness of his child. That illness could not have been caused by the site because the well serving the home was beyond the plume boundary by at least one-quarter mile.