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PUBLIC HEALTH ASSESSMENT

NORTH PENN-AREA 1
SOUDERTON, MONTGOMERY COUNTY, PENNSYLVANIA

ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS

The tables in this section list the contaminants of concern. However, their listing does not imply that a health threat exists. This public health assessment 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 and sample design; comparison of site-related concentrations with background concentrations; and comparison of site-related concentrations with public health assessment comparison values for carcinogenic and noncarcinogenic endpoints. Comparison values for public health assessments are contaminant concentrations in specific media that are used to select contaminants for further evaluation. These values include Environment Media Evaluation Guides (EMEGs), Cancer Risk Evaluation Guides (CREGs), and other relevant guidelines.

In the data tables which follow under on-site contamination and off-site contamination subsections, the listed contaminant 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, that contaminant will be reported in all media. The groundwater investigation of this site analyzed for only six VOCs (2). They were: 1,1,1-trichloroethane; 1,1-dichloroethane (1,1-DCA); 1,1-dichloroethene (1,1-DCE); and 1,2-DCE (cis, trans and total); PCE; and TCE.

The EPA Toxic Chemical Release Inventory data base was accessed by PADOH through the National Library of Medicine's Toxicology Data Network and searched for estimated annual release of toxic chemicals to the environment, from industries within a 2-mile radius of the North Penn Area 1 site, to identify possible facilities that could contribute to air or groundwater contamination near the site. No significant releases which would affect the air or groundwater quality near the site were reported in the 1987, 1988, and 1989 data bases.

North Penn Area 2 is an NPL site less than 2 miles east of North Penn Area 1. The site is now fenced and guarded 24 hours a day. Ametek, Inc. (PRP) took measures to clean up several areas of soil contamination in 1987. EPA conducted sampling of 16 residential wells located near the site in 1989; none of the wells sampled was found to be contaminated above drinking water standards. EPA has scheduled resampling of residential wells to determine whether there has been any change in water quality since the testing in 1989 (11).

A. On-Site Contamination

Groundwater - Granite Knitting Mills Well

On August 28, 1986, NUS Field Investigation Team (FIT) III obtained water samples and NPWA analyzed them. Figure 4 indicates the location where samples were collected, and Table 1 indicates the concentrations of contaminants of concern.

Table 1. Maximum Contaminant Concentrations in On-Site Well (Granite Knitting Mills)(1)

CONTAMINANT MAXIMUM CONCENTRATION
ug/L
COMPARISON VALUE
ug/L Source
1,1-Dichloroethene 9.9 0.06 CREG
Tetrachloroethene 33.5 0.7 CREG
Trichloroethene 12.2 3.0 CREG

CREG - Cancer Risk Evaluation Guide
ug/L - Microgram Per Liter

Groundwater - North Penn Water Authority (NPWA)

On August 28, 1986, NUS FIT III obtained water samples and NPWA analyzed them. NPWA performed regular sampling from January 1985 through August 1987. All analysis was done by NPWA except for a sample taken in 1980 for which the laboratory was unknown. Figure 4 indicates the location where samples were collected, and Table 2 indicates the maximum concentration of contaminants.

Table 2. Maximum Contaminant Concentrations in On-Site Wells (North Penn Water Authority)(1, 2)

CONTAMINANT MAXIMUM
CONCENTRATION
µg/L
COMPARISON VALUE
µg/L Source
1,1-Dichloroethene 1.0 0.06 CREG
Tetrachloroethene 24.7 0.7 CREG
Trichloroethene 1.0b 3.0 CREG

CREG - Cancer Risk Evaluation Guide
b - Estimated Result
µg/L - Microgram Per Liter

Groundwater - Residential Wells and Old Souderton Borough Well

As indicated in the Natural Resources Use section, the residential wells are shallow, hand-dug wells, served as monitoring points, and were not being used for potable water. The Old Souderton Borough Well, a deeper well, also served as a monitoring well for the site investigation.

On August 28, 1986, NUS FIT III collected a sample from nine residential wells. The residential wells were not purged. At the Old Souderton Borough Well (Well 679 in Figure 4), NUS took a sample before and after a two-hour purge. NPWA performed all analysis. Figure 4 indicates the location where samples were collected, and Table 3 indicates the maximum concentrations of contaminants.

Table 3. Maximum Contaminant Concentration in On-Site Residential Wells
and Old Souderton Borough Well (1, 2)

CONTAMINANT MAXIMUM
CONCENTRATION
µg/L
COMPARISON VALUE
µg/L Source
1,1-Dichloroethene 0.5b 0.06 CREG
Tetrachloroethene 14.1 0.7 CREG
Trichloroethene 5.0a 3.0 CREG

CREG - Cancer Risk Evaluation Guide
b    - Estimated Result
a    - Results from Souderton Borough Well after purge.
µg/L - Microgram Per Liter

B. Off-Site Contamination

Groundwater - North Penn Water Authority (NPWA)

March 1988 sampling did not reveal any contamination in sampling the NPWA well S-2. NPWA well S-4 showed PCE levels from 2.3 to 3.4 µg/L during the sampling period March to September 1988. NPWA wells are sampled monthly and analyzed by the NPWA. Figure 4 indicates the location where samples were collected, and Table 4 indicates the maximum concentrations of contaminants.

Table 4. Maximum Contaminant Concentrations in Off-Site Wells (North Penn Water Authority) (1, 2)

CONTAMINANT MAXIMUM
CONCENTRATION
µg/L
COMPARISON VALUE
µg/L Source
1,1-Dichloroethene ND 0.06 CREG
Tetrachloroethene 3.4 0.7 CREG
Trichloroethene ND 3.0 CREG

CREG - Cancer Risk Evaluation Guide
ND - Not Detected
µg/L - Microgram Per Liter

Groundwater - Residential Wells

On August 28, 1986, NUS sampled two residential wells and NPWA analyzed the samples. These wells were shallow, hand-dug wells and were not used for potable water. Figure 4 indicates the location where samples were collected, and Table 5 indicates the maximum concentrations of contaminants.

Table 5. Maximum Contaminant Concentrations in Off-Site Residential Wells (1, 2)

CONTAMINANT MAXIMUM
CONCENTRATION
µg/L
COMPARISON VALUE
µg/L Source
1,1-Dichloroethene 0.5b 0.06 CREG
Tetrachloroethene 0.5b 0.7 CREG
Trichloroethene 0.5b 3.0 CREG

CREG - Cancer Risk Evaluation Guide
µg/L - Microgram Per Liter
b - Estimated Result

C. Quality Assurance and Quality Control

CH2M Hill has been contracted by EPA to perform an RI/FS on North Penn Area 1. CH2M Hill has not ascertained the quality of the data used in this public health assessment. Samples taken on August 28, 1986, were collected by FIT III (NUS) and were analyzed by NPWA. All other samples were both collected and analyzed by NPWA.

QA/QC procedures reported to have been used by FIT III to maintain and monitor sample quality included the following:

(1) At the Souderton Borough Well (#679), samples were taken before and after a two-hour purge, and pH and conductivity were monitored during purging.
(2) At NPWA, wells S-9 and S-10 were purged for an unspecified length of time before collection.
(3) A field blank and a field duplicate were collected.

The private wells were not purged. A sample log was completed, but chain-of-custody forms are not in the record. Additional QA/QC procedures may have been implemented without being reported.

The NPWA sample collection and analysis procedures are documented in the QA manual. NPWA wells are generally sampled on a monthly basis. Sample collection QA procedures include specification for, but not documentation of, the following: sample containers, sample labels, preservatives, sample collection, and sample storage.

The QA manual requires that no headspace be allowed in the volatile organic analysis (VOA) vials and that the samples be stored on ice. Sample analysis QA procedures include specification for, but not documentation of, the following: (1) preparation of calibration standards and equipment calibration; (2) EPA quality control and performance evaluation samples; (3) sample documentation; (4) laboratory blanks; (5) laboratory duplications; (6) spiked samples; (7) holding times; and (8) corrective action.

The following assumptions regarding data quality were made on the basis of this QA/QC information:

(1) All data reported by the laboratories and organizations were used for RI/FS planning. This conclusion was based on the reputations of the laboratories and organizations and on the consistency and reproductivity of the data.
(2) No data have been successfully validated; therefore, none of the data can be used for [quantitative] risk assessment.

D. Physical and Other Hazards

No hazards were apparent at any of the five PRP locations.

PATHWAYS ANALYSES

To determine whether 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 media, a point of exposure, a route of human exposure, and an exposed population.

PADOH and ATSDR identify exposure pathways as completed, potential or 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 exposure pathways, however, at least one of the five elements is missing, but could exist. Potential exposure 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. The only known human exposure pathway at this site is through the use of groundwater. No data are available for surface water, soil, sediment, or air. Table 6 identifies the completed exposure pathways.

A. Completed Exposure Pathway

Public Water Supply Pathway

People have been exposed in the past, are currently exposed, and may be exposed in the future to contaminants present in NPWA water supply wells. Contamination of PCE was discovered in well S-9 in 1979. Pumping of well S-9 was discontinued at that time, and the blending of water from other wells reduces contamination levels to within drinking water standards.

Based on the information available, there appears to be a single plume of groundwater contamination affecting the Granite Knitting Mills well, NPWA wells, and possibly some residential wells at the site. However, existing water quality data from which the extent of the plume was estimated by NUS were obtained from wells of undocumented construction; therefore, it is not possible at present to assess to what degree the data represent the actual plume distribution. There are no additional data on the vertical and horizontal extent and nature of contamination at the site, nor on rates of movement of either groundwater or contaminants (1).

Table 6. Completed Exposure Pathway

PATHWAY
NAME
TIME SOURCE MEDIA &
TRANSPORT
POINT OF EXPOSURE ROUTE OF EXPOSURE EXPOSED POP.
Public Supply (North Penn Water Authority (NPWA) Past
Present
Future
5 PRPs Groundwater (Municipal Water) Residences
(Taps)
Ingestion
Inhalation
Dermal
5,000 Est.
Private Well Past 5 PRPs Groundwater
(Private Well)
Residences
(Outdoor Pump)
Ingestion
Inhalation
Dermal
A Small
Number Est.
Under 50

In 1979, elevated levels of PCE were found in NPWA well S-9. This well was used by NPWA to supply an undetermined but substantial number of people. Those people are exposed to contaminants through ingestion of the contaminated water, inhalation of the volatile organic compounds released when taps are turned on, and by direct skin contact with the contaminated water. PADOH does not know precisely when well S-9 became contaminated or the level of contamination at the tap since wells are blended. However, a spill of 75 gallons of PCE was documented at Gentle Cleaners in the early 1970s. This documentation states that PCE flowed out the rear door onto the grassed area behind the building (1).

Private Well Pathway

A recently completed well survey indicates that there are no residential wells in the area used for potable water. This area is served totally by the North Penn Water Authority. Only a few wells remain with hand pumps that can provide water for outdoor use. People who used the contaminated well water for watering plants or animals, were exposed to the contaminants through direct skin contact and through inhalation of the volatile organic compounds. Ingestion was not likely a route of exposure. Most of the hand-dug wells are totally inactive and only served as monitoring points in field investigations. Little is known about prior use of the wells; however, NPWA has been in existence over 25 years, indicating that exposure to contamination through ingestion was most likely minimal from residential wells. Preliminary evidence is that this pathway can be eliminated in future considerations.

B. Potential Exposure Pathway

There is currently limited groundwater sampling in the area. There has been no surface water, soil, sediment, or air testing performed. Potential exposure pathways may be identified when additional groundwater data become available and other media are addressed. Conjecture and site observation indicate groundwater is the dominant pathway of contamination, but other pathways cannot be overlooked. A detailed Sampling Analysis Plan (SAP) will answer these questions in the Plan II RI/FS. Currently, other possible exposure pathways cannot be discussed because of the data gaps.

PUBLIC HEALTH IMPLICATIONS

A. Toxicologic Evaluation

Introduction

In this section, 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. EPA developed Maximum Contaminant Levels (MCLs) for drinking water. Primary MCLs are federal drinking water standards declared under the Safe Drinking Water Act. Generally, an MCL for a toxic chemical represents the allowable lifetime exposure to the contaminant for a 70-kg adult who is assumed to ingest 2 liters of water per day. In addition to health factors, an MCL is required by law to reflect the technological and economic feasibility of removing the contaminant from the water supply. The limit set must be feasible given the best available technology and treatment techniques. EPA's Reference Dose (RfD) is an estimate of the daily exposure to a contaminant over a 70-year period that is unlikely to cause non-cancer adverse health effects. ATSDR has developed Minimal Risk Levels (MRLs) for many contaminants found at hazardous waste sites. MRLs provide an estimate of daily exposure, below which, non-cancer adverse health effects are unlikely to occur.

EPA has developed Cancer Slope Factors for some contaminants that are determined to be or possibly are human carcinogens. The Cancer Slope Factor is used to determine if an exposed person's risk of developing cancer in his lifetime may be increased as a result of that exposure.

As indicated in the Environmental Contamination and Other Hazards section, only six VOCs were analyzed and evaluated. In the following discussion, we are addressing three of these VOCs, which were determined to be contaminants of concern. They are TCE, PCE, and 1,1-DCE.

Trichloroethylene (TCE)

TCE exposure through inhalation, skin contact, and ingestion has occurred to residents through use of contaminated drinking water. No remedial actions have been undertaken at North Penn Area 1 after taking S-9 out of service. Water from NPWA well S-10 is not treated but is blended with water from other wells to meet drinking water standards. There are presently no residential wells used for potable water.

Exposure to residents to TCE has occurred to Souderton Borough residents through use of NPWA water, specifically through contamination of well S-9. Although the duration of the contamination and the maximum concentration of contamination is not known (only an estimated 1 µg/L in well S-9, but 12.2 µg/L at the Granite Knitting Mills well as found during the site investigation), the exposure at the taps should have been less due to blending with other wells that were not found to be contaminated. Future exposure may occur at very low concentrations, and treatment of the water (air strippers or carbon filtration) could be undertaken if levels exceed safe drinking water standards. If people were to drink the maximum amount of TCE detected to date (12.2 µg/L), the MRL would not be exceeded (13). Therefore, no non-cancer adverse health effects are expected to result from the exposure.

Occupational studies of workers exposed to TCE (levels which are much higher than the levels found in the groundwater at the site) have not detected TCE-induced cancer, while some animal studies have shown that TCE can produce lung and liver cancer (13). 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 which classifies chemicals for their carcinogenicity, has decided that TCE is not classifiable as to human carcinogenicity. However, EPA classified TCE as a probable human carcinogen based upon some animal studies (13). Currently, EPA is reevaluating the carcinogenicity of TCE. EPA has developed a Cancer Slope Factor for TCE (13). If the maximum level of TCE detected to date were ingested for 70 years, the people exposed would not be at an increased risk of developing cancer.

Tetrachloroethene (PCE)

Exposure to PCE has occurred in the past through use of contaminated water in NPWA well S-9, which was taken out of service. We do not know the highest exposure from the taps of residences or the time when the first contamination began. However, the concentration at well S-9 during the site investigation was 24.7 µg/L and at the on-site Granite Knitting Mills well was 33.5 µg/L, representing the maximum concentrations. Ingestion of that amount of PCE does not exceed the MRL or the RfD. If people were exposed to those maximum levels, no non-cancer adverse health effects are expected as a result of those exposures.

Animal studies conducted with concentrations much higher than most people are exposed to show that PCE can cause liver and kidney damage and kidney cancer (14). Based on these studies, PCE has been identified as a carcinogen by the Department of Health and Human Services/National Toxicological Program, EPA and the International Agency on Research of Cancer. EPA has developed a Cancer Slope Factor for PCE (14). If people drink water containing the maximum amount of PCE found in the water supplies, those people would be a moderate increased risk of developing cancer as a result of that exposure. However, actual levels to which people are exposed are expected to be much lower. Therefore, there is likely little risk.

1,1-Dichloroethene (DCE)

Exposure to DCE has occurred through use of contaminated well water. The maximum amount of DCE found in well water to date is 9.9 µg/L in the Granite Knitting Mills well. Much lower levels were found in NPWA wells. Exposure to the maximum level detected would not result in a dose that would exceed the MRL (15). Therefore, no non-cancer adverse health effects would be expected to result because of ingesting that level.

Exposure to high levels of DCE in animal studies have caused lung, liver, kidney, heart damage and also have caused nervous system disorders (15). The amount of damage depends on the level and duration of exposure. Exposure by inhalation of DCE appears to be more harmful in animals than expected to occur in humans after exposures to high levels of DCE. An increased risk for cancer has been shown in one study where animals were exposed to high levels of DCE (10-25 ppm). DHHS has not classified DCE with respect to carcinogenicity. IRAC has determined that DCE is not classifiable as to its carcinogenicity to humans. EPA has determined that DCE is a probable human carcinogen. However, no relationship between the occurrence of cancer in humans and occupational exposure to DCE has been demonstrated (15). EPA has developed a Cancer Slope Factor for DCE (15). If the maximum level of DCE (12.2 µg/L in the Granite Knitting Mills well) is ingested for 70 years, the people drinking that amount would be at an increased risk of developing cancer as a result of exposure. However, the maximum levels found to date in the public water supply would result in very little, if any, increased risk for the exposed people.

B. Health Outcome Data Evaluation

The North Penn Area 1 site is located in Souderton Borough, Montgomery County. Twenty-one years of all cause mortality and cancer mortality (total cancer and eight cancer sites) were collected for Souderton Borough (16). 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) and total cancer deaths were statistically fewer for the period than for the state as a whole. This is found by comparing observed deaths with expected deaths and calculating a Standard Mortality Ratio (SMR) and using a Poisson table (17). There were 521 observed deaths and 872.9 deaths expected (SMR 0.744) (17). An expected death is a statistical term used for measuring mortality among a specified population. Montgomery County also had significantly less all cause mortality for the 1979-1989 period with an SMR of 0.920. However, in contrast, deaths to cancer in Montgomery County were statistically high, with an SMR of 1.129. The individual cancer sites analyzed for Souderton Borough were: (1) buccal cavity and pharynx; (2) digestive system; (3) respiratory system; (4) bone, connective tissue, skin and breast; (5) genitourinary system; (6) other and unspecific sites; (7) leukemia; and (8) other lymphatic and hematopoietic tissues. Digestive cancer was significantly low for the period with 31 observed deaths and 51.2 deaths expected (SMR 0.605). All other cancer sites analyzed were below expectation except cancer of the other lymphatic and hematopoietic tissues which had 9 deaths in the study period with 8.8 deaths expected.

C. Community Health Concerns Evaluation

We have addressed the community concern about health as follows:

Is my health at risk as a result of exposure to contamination in the NPWA water supply?

As noted in the toxicological evaluation, there was exposure to PCE and TCE through the use of water from well S-9, which is now out of service. Although the exact time of initial exposure and duration of exposure are unknown, the duration of exposure at levels of health concern was most likely short. No adverse health effects or discernible increased risk of cancer would be expected at the levels of exposure. The NPWA is sampled regularly and consumers would be alerted if the water was at unsafe levels.


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