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PUBLIC HEALTH ASSESSMENT

MODERN SANITATION LANDFILL
YORK, YORK 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; sample design; comparison of site-related concentrations with background concentrations; and comparison of site-related concentrations with ATSDR health screening values for carcinogenic and noncarcinogenic endpoints. In addition, the U.S. EPA Toxic Release Inventory data base was accessed by the PADOH through the National Library of Medicine's Toxicology Data Network and searched for estimated annual releases of toxic chemicals to the environment, from industries within a 2-mile radius of the Modern Landfill 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, 1989, and 1990 data bases.

A. ON-SITE CONTAMINATION

During the course of the Remedial Investigation, two on-site media were identified and sampled to determine whether they were sources of environmental contamination and/or presented a public health risk. These environmental media included ambient air and groundwater.

Ambient air monitoring was conducted at Modern Landfill on October 27, 1988, in the air around the 66-acre unlined area, to evaluate potential harmful health effects to on-site workers breathing this air. The air quality evaluation involved monitoring of levels of VOCs and radiation.

One of the most biologically important aspects of radiation is how much energy they deposit in living matters. The deposited energy is referred to as the "dose". The roentgen is a term used for dose. Radiation levels were monitored with a Ludlum detector and probe. Levels of organic constituents were monitored with both a flame-ionization detector (FID) organic vapor analyzer and a photoionization detector (PID). A few compounds, most notably methane, are not detected by the PID; therefore, the difference between readings of the FID and PID can generally be attributed to methane. Because of the limited effectiveness of cartridge respirators to remove vinyl chloride, Draeger detector tubes and a Draeger bellows pump were used to sample and detect selectively for the presence of vinyl chloride.

Radiation was not detected above a background level of 0.02 to 0.05 milliroentgen/hr in any area of Modern Landfill investigated. No organic vapor readings in the ambient air were detected at concentrations over 4 parts per million (ppm). Because only trace levels of organic vapors were detected in ambient air and no radiation above background was detected during this site air monitoring survey, no further evaluation of the air exposure pathway was conducted.

Since the 66-acre unlined landfill has received a PADER-approved cover which is being upgraded with a low permeability cap, it is not a source of direct contact exposure. Based on this consideration, combined with the lack of information on the exact locations of potential contaminant source areas and the fact that capping the 66-acre unlined landfill has reduced accessibility to such source areas, it was determined that surface soil sampling within the 66-acre unlined landfill itself would not be feasible or necessary. Therefore, soil sampling was not conducted during the Remedial Investigation.

An EPA contractor collected one round of filtered groundwater samples from 18 on-site wells during Phase 1A (July 1988) and Phase 1B (March and April 1989). All samples were analyzed for Target Compound List (TCL) and Target Analyte List (TAL) inorganics. The results appear in Table 1.

TABLE 1. On-Site Contaminants of Concern (1)

Contaminant Groundwater
Monitoring Wells
Max. Conc. (µg/L)
Comparison Value
µg/L Source
1,1-Dichloroethene 8.0 0.06 CREG
1,2-Dichloroethene (Total) 1149.0 700.00 RfD*
Benzene 37.0 1.21 CREG
Carbon Tetrachloride 85.0 0.27 CREG
Methylene Chloride 610.0 4.70 CREG
Tetrachloroethene 100.0 5.00 MCL
Trichloroethene 427.0 5.00 MCL
Vinyl Chloride 270.0 2.00 MCL

*EPA RfD - Reference Dose for Trans-1,2-Dichloroethene
CREG - Cancer Risk Evaluation Guide
EPA MCL - Maximum Contaminant Level

B. OFF-SITE CONTAMINATION

During the course of the Remedial Investigation three off-site media were identified and sampled to determine whether they were sources of environmental contamination and/or presented or public health risk. These environmental media included groundwater, surface water, and sediments.

An EPA contractor collected one round of filtered groundwater samples from 75 off-site monitoring wells during Phase 1A (July 1988) and Phase 1B (March and April 1989). This sampling included 37 off-site monitoring wells within the Modern Landfill property, 27 extraction wells and 11 site-specific background monitoring wells upgradient of the site. All samples were analyzed for TCL and TAL inorganics. The results appear in Table 2.

TABLE 2. Off-Site Contaminants of Concern (1)

Contaminant Groundwater
Extraction Wells
Max. Conc. µg/L
Comparison Value
µg/L Source
1,1-Dichloroethene 17.5 0.06 CREG
1,2-Dichloroethene (Total) 220.0 700.00 RfD*
Benzene 5.4 1.21 CREG
Carbon Tetrachloride 13.0 0.27 CREG
Methylene Chloride 68.8 4.70 CREG
Tetrachloroethene 94.0 5.00 MCL
Trichloroethene 168.0 5.00 MCL
Vinyl Chloride 47.0 2.00 MCL

*EPA RfD - Reference Dose for Trans-1,2-Dichloroethene

An EPA contractor collected surface water and sediments from the Eastern and Western Tributary on December 14, 1989. None of the contaminants identified in Table 2 were detected.

C. QUALITY ASSURANCE AND QUALITY CONTROL

In preparing this 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 conclusions drawn for this Health Assessment are determined by the availability and reliability of the referenced information.

D. PHYSICAL AND OTHER HAZARDS

Sedimentation basins may pose a physical hazard to trespassing children.

PATHWAYS ANALYSES

To determine whether nearby residents are exposed to contaminants migrating from the site, PADOH and ATSDR evaluates 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 identifies exposure pathways as completed, potential, or eliminated. Completed pathways require that the five elements exist and indicate that exposure to a contaminant has occurred in the past, is currently occurring, or will occur in the future. Potential pathways, however, require that 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. A potential pathway can be eliminated if there exists at least one missing element and this element(s) is unlikely to ever exist. The discussion which follows identifies the completed, potential, and eliminated pathways at this site.

A. COMPLETED EXPOSURE PATHWAY

Ambient Air

Volatilization of organic compounds from subsurface wastes and subsurface soil and their subsequent transport through the surface soil cap into the ambient air is the main release mechanism into air at the Modern Landfill site. On-site workers are most likely to be affected by this process through inhalation of volatile contaminants within the breathing zone of the ambient air. As indicated in the Environmental Contamination and Other Hazards section, organic vapors were detected in air at concentrations less than or equal to 4 ppm.

B. POTENTIAL EXPOSURE PATHWAY

Residential Private Well

The groundwater extraction systems at Modern Landfill have lowered the groundwater surface elevation along both the eastern and western extraction systems. These drawdown troughs cause groundwater to flow toward the extraction wells, effectively capturing the majority of contaminated groundwater. Groundwater flows towards the eastern and western extraction systems with the possible exception of the groundwater flowing from beneath the north-central area of the 66-acre unlined landfill, which may be bypassing the western extraction system. As a preventive measure, residences north of the site were provided with municipal water, thereby eliminating the potential for future exposure to site contaminants in the event groundwater bypassed the extraction system. We therefore believe this potential future exposure pathway has been eliminated.

Currently, there are no residents using private well water for potable purposes immediately adjacent to the landfill to the south, east and west. A potential exposure pathway does exist, however, in the unlikely event of future off-site migration of contaminated groundwater and the future installation of private wells with the intention of using groundwater for potable purposes.

PUBLIC HEALTH IMPLICATIONS

Introduction

In this section, we discuss the health effects that may occur in persons who may become exposed to site contaminants in on-site air and groundwater from private wells, evaluate the relevancy of state health data bases to provide information for Modern Landfill, and evaluate community health concerns.

A. TOXICOLOGICAL EVALUATION

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 contamination below which non-cancer, adverse health effects are unlikely to occur. MRLs are developed for routes of exposure, such as ingestion and inhalation and for the length of exposure, such as acute (less than 14 days), intermediate (15 to 364 days), and chronic (greater than 365 days). ATSDR also developed Cancer Risk Evaluation Guides (CREGs). 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. The U.S. EPA developed Maximum Contaminant Levels (MCL). Primary MCLs are federal drinking water standards promulgated 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. MCLs are applicable at the tap where the water will be provided directly to 25 or more people or will be supplied to 15 or more service connections, but in addition are relevant and appropriate requirements against which to evaluate all groundwater quality. The PADOH will give consideration to 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.

Volatile Organic Compounds in Air

VOCs, as a general class of compounds, have been detected in on-site ambient air at concentrations less than or equal to 4 ppm. However, as indicated earlier, chemical-specific data is unavailable. In the absence of chemical-specific data, potential human exposure and the corresponding public health implications cannot be addressed.

Volatile Organic Compounds in Groundwater

Groundwater, beneath the site, exceeded state and federal drinking water standards for most of the on-site contaminants of concern, identified in Table 1. These contaminants are presently not a public health concern because the residential private well water pathway has been eliminated due to the existence of monitoring wells to the north of the site which would detect any migration, the availability of a public water supply line, and the fact that on-site groundwater is extracted and treated in the existing wastewater treatment plant. However, in the unlikely event of future migration of site contaminants off the Modern Landfill property and their subsequent use as a potable private well water supply, exposure to VOC contamination in water could pose a public health threat. Following exposure to the following chemicals, several factors determine whether harmful effects will occur. These factors include the amount, route and the length of time of exposure.

1,1-Dichloroethene

Exposure to high levels of 1,1-dichloroethene in animal studies have caused lung, liver, kidney, heart damage and nervous system disorders (3). The amount of damage depends on the level and duration of exposure. Exposure by inhalation of 1,1-dichloroethene appears to be more harmful in animals than exposure through food or water (3). The same kind of effects can be expected to occur in humans after exposures to high levels of 1,1-dichloro-ethene. An increased risk for cancer has been shown in one study where animals were exposed to high levels (10-25 ppm) of 1,1-dichloroethene. EPA has identified 1,1-dichloroethene as a possible carcinogen based on limited evidence from animal studies. However, no relationship between the occurrence of cancer in humans and occupational exposure to 1,1-dichloroethene has been demonstrated.

EPA's RfD for 1,1-dichloroethene is 9 µg/kg/day. This level is equivalent to 315 µg/L for a 70-kg adult consuming 2 liters of contaminated water per day and 90 µg/L for a 10-kg child consuming 1 liter of contaminated water per day. Therefore, persons who may be exposed in the future by drinking contaminated well water at 8 µg/L, which is the highest detected level in on-site groundwater, should not experience any non-cancer health problems.

1,2-Dichloroethene

There are two forms of 1,2-dichloroethene, one form is called cis-1,2-dichloroethene and the other is called trans-1,2-dichloroethene. The concentrations of 1,2-dichloroethene detected in on-site groundwater (1,149 µg/L) exceeded EPA's Long Term Health Advisory (LTHA) and EPA's MCL of 70 µg/L for cis-1,2-dichloroethene and 100 µg/L for trans-1,2-dichloroethene. Also, the concentration of trans-1,2-dichloroethene exceeded EPA's RfD of 0.02 mg/kg/day (equivalent to 700 µg/L). Therefore, long-term future exposure to 1,2-dichloroethene at concentrations greater than 700 µg/L (which is the on-site groundwater contamination level) may cause non-cancer health effects such as decreased numbers of red blood cells (4).

Benzene

The Department of Health and Human Service (DHHS)/National Toxicology Program (NTP), the International Agency for Research on Cancer (IARC) and the EPA have determined that benzene is a known human carcinogen. Long-term exposure to high levels of benzene can cause leukemia, a cancer of the tissues that form white blood cells. Exposure through inhalation to low levels of benzene (700-3,000 ppm) can cause drowsiness, dizziness and headaches. In most cases, these effects will cease once exposure ends and fresh air is obtained (5). The health effects that may result from eating or drinking foods containing low levels of benzene are not known. However, animal studies indicate that oral exposure to benzene can damage the blood and the immune system and may also cause lymphoma, a type of leukemia. ATSDR could not develop a MRL from the known animal and human toxicity studies because the data were insufficient. Also, EPA has not developed a RfD. Since there are no MRLs or RfD available to provided guidance to the safe level of exposure to benzene, we cannot determine, with certainty, whether exposure to benzene at 37 µg/L, which is the on-site groundwater contamination level, would cause non-cancer health effects. However, we know that the amount of benzene exposure from drinking 2 liters of water each day would be several hundred times lower than the level that is known to cause non-cancer effects in animals. As for cancer effects, a lifetime exposure to 37 µg/L in drinking water is suspected of an increased risk of getting leukemia.

Carbon Tetrachloride

Based on animal studies, DHHS/NTP, IARC and EPA have determined that carbon tetrachloride is a carcinogen.

EPA's RfD for carbon tetrachloride is 0.7 µg/kg/day. This level is equivalent to 24.5 µg/L for 70-kg adults consuming 2 liters of contaminated water per day and 7 µg/L for a 10-kg child consuming 1 liter of contaminated water per day. Therefore, persons who may be exposed in the future for a long-term period to this chemical by drinking contaminated water at a concentration of 85.0 µg/L, which is the highest detected level in on-site groundwater, may experience some non-cancer health problems. These health problems may include central nervous system depression, gastrointestinal symptoms and liver and kidney damage following long-term exposure (6). A lifetime exposure to 85 µg/L in drinking water is suspected of causing an increased risk of liver cancer.

Methylene Chloride

EPA and IARC have determined that methylene chloride is a possible human carcinogen. This determination was based mainly on inhalation exposure studies performed in animals. Studies in animals suggest breathing methylene chloride does not cause birth defects or affect reproduction. Animal studies indicate exposure to vapors of methylene chloride may irritate eyes and affect the cornea (7).

EPA's RfD for methylene chloride is 60 µg/kg/day. This level is equivalent to 2,100 µg/L for a 70-kg adult consuming 2 liters of contaminated water per day and 600 µg/L for a 10-kg child consuming 1 liter of contaminated water per day. Therefore, adults who may be exposed in the future to this chemical by drinking contaminated water at a concentration of 610.0 µg/L, which is the highest detected level in on-site groundwater, may not experience any non-cancer health problems. Children may, however, experience non-cancer health effects following long-term exposure to on-site groundwater containing 610.0 µg/L of methylene chloride.

Vinyl Chloride

Vinyl chloride is a known human carcinogen as identified by DHHS/NTP, EPA and IARC. Long-term exposure to high levels of vinyl chloride can cause liver cancer. Studies in animals show that exposure to extremely high levels of vinyl chloride can damage the liver, lungs and kidneys (8). Some people who have breathed vinyl chloride over several years have developed changes in the structure of their livers. People are more likely to develop these changes if they breathe high levels of vinyl chloride. Some people who have worked with vinyl chloride have developed nerve damage and others have developed an immune reaction. The lowest levels that cause liver changes, nerve damage and change in the functioning of the immune system in humans are not known.

ATSDR's chronic MRL for this chemical is 0.02 µg/kg/day. The EPA has not developed a RfD. The concentration of vinyl chloride detected in the on-site groundwater (270 µg/L) exceeds ATSDR's MRL. Therefore, long-term exposure to vinyl chloride in the future at 270 µg/L, which is the on-site groundwater contamination level, may cause non-cancer health effects. A lifetime exposure to 270 µg/L in drinking water is suspected of causing an increased risk of liver cancer.

Tetrachloroethene (PCE)

Animal studies conducted with concentrations much higher than most people are exposed to show that PCE can cause liver and kidney damage and liver and kidney cancer (9). Based on these studies, PCE has been identified as a carcinogen by DHHS/NTP, EPA and IARC.

EPA's RfD for PCE is 10.0 µg/kg/day. This level is equivalent to 350 µg/L for 70-kg adults consuming 2 liters of contaminated water per day and 100 µg/L for a 10-kg child consuming 1 liter of contaminated water per day. Therefore, persons who may be exposed in the future to this chemical by drinking contaminated water at a concentration of 100 µg/L, which is the highest detected level in on-site groundwater, should not experience non-cancer health problems.

Trichloroethene (TCE)

Occupational studies of workers exposed to TCE at levels which are much higher than the levels found in the environment have not detected TCE-induced cancer; however, some animal studies have shown that TCE can produce lung and liver cancers (10). 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, DHHS/NTP could not find clear evidence that TCE caused cancer in animals. The 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. Recently, EPA has withdrawn this classification while conducting a review of the carcinogenicity of TCE.

ATSDR could not develop a MRL from the known animal and human toxicity studies because the data were insufficient. Also, EPA has not developed a RfD. Since there are no MRLs or RfD available to provide guidance on the safe level of exposure to TCE, we cannot determine, with certainty, whether long-term exposure to TCE at 427.0 µg/L, which is the on-site groundwater contamination level in residential well water, would cause non-cancer health effects. However, we know that the amount of TCE exposure from drinking 2 liters of water each day would be several times lower than the level that is known to cause non-cancer effects in animals.

B. HEALTH OUTCOME DATA EVALUATION

As discussed in the Community Health Concerns Evaluation, a receptor population for site related contamination does not exist. There were no community concerns regarding adverse health effects. For these reasons, health outcome data was not included in this Public health assessment.

C. COMMUNITY HEALTH CONCERNS EVALUATION

We have addressed the community health concern about health as follows:

    What is the likelihood of my private well becoming contaminated from off-site migration of contaminants from the Modern Landfill site and when will municipal water be available?

    Because of the influence of the currently operating groundwater extraction system, which draws groundwater from beneath the site and directs it toward the extraction wells, all groundwater flow beneath the site is contained within the landfill boundaries. At the extraction wells, the groundwater is removed and then treated in an on-site treatment plant. As part of EPA's proposed remedy, additional monitoring and extraction wells will be installed at the site if deemed necessary by EPA and PADER. The proposed remedy calls for installing a cap and a final cover over the unlined landfill to prevent surface water, such as rain and melting snow, from penetrating the waste materials and then carrying contaminants into the groundwater. By reducing the infiltration of precipitation, the cap system will ultimately reduce the quantity of contaminants in the groundwater. By altering and redirecting the flow of groundwater beneath the landfill, the groundwater extraction system will continue to act as a hydraulic barrier to groundwater flow from the site and will also continue to remove groundwater containing hazardous substances.

    Municipal water is available to downgradient residents north of the site. Residents east and southeast of the site reside in the Cabin Creek Drainage Basin and are not likely to have their well water contaminated by the site. Residents southwest and west of the site reside in the Kreutz Creek drainage basin and are also not likely to have their well water affected by the site.


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