PUBLIC HEALTH ASSESSMENT
WEST KINGSTON TOWN DUMP
AND
UNIVERSITY OF RHODE ISLAND (PLAINS RD) DISPOSAL AREA (URI)
SOUTH KINGSTON, WASHINGTON COUNTY, RHODE ISLAND
ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS
Limited on-site sampling and analyses suggest that contaminants associated with the wastes have been released to surface water and sediment contained in ponds on the properties, to surface and subsurface soils, and to the underlying groundwater system. No analytical data are available to confirm the extent of contamination in air media. Essentially, all of the on-site sampling and analytical data ATSDR obtained are for environmental media at the URIDA portion of the property. At WKTD, data were obtained for only pond water and sediment.
Tables identified in this section list contaminants of concern that have been selected for further evaluation in subsequent sections of the public health assessment to determine whether exposure to them is a concern for public health. Listing contaminants in those tables does not imply that exposure would actually result in adverse health effects.
ATSDR considers the following factors when selecting contaminants of concern:
ATSDR conducted a search of the EPA Toxic Chemical Release Inventory (TRI) for the site and county. That search did not disclose information about either of the disposal areas and identified chemical releases for only one industrial plant in the site vicinity--located about one and a half miles southwest of the site. TRI shows the plant reported releasing xylene to the atmosphere at a rate of 20,000 pounds per year. The database does not provide sufficient information to estimate airborne concentrations either at the plant or downwind. For this reason, and because xylenes have not been reported at elevated levels for any media at the site, the xylene releases reported by that plant will not be further considered in this assessment.
Contaminants of concern that will be further evaluated in this
assessment are listed in Table 1.
| Table 1. Contaminants of Concern in One or More Media |
|
| Chloroform | Gasoline |
| Trichloroethylene (TCE) | Aldicarb |
| Tetrachloroethylene (PCE) | Aluminum |
| Benzo(a)pyrene (BAP) | Lead |
| Bis(2-ethylhexyl)phthalate (BEHP) | Manganese Thallium |
Data that summarize the occurrence and concentrations of contaminants of concern are provided in Tables 2 through 12, in Appendix B. Those tables contain abbreviations, which are explained below:
Comparison Values Abbreviations
* EMEGEnvironmental Media Evaluation Guide
* CREG Cancer Risk Evaluation Guide
* RfDG Reference Dose-based Guide
* LTHA Lifetime Health Advisory
* MCL Maximum Contaminant Level
* ALG Action Level Guide
* OSV Other Selection Value
Data Clarifier Abbreviations
* ppb parts per billion
* ND not detected
* NI no information
* NA no analyses
* J estimated value
Comparison Values--EMEGs are estimated comparison concentrations that are based on information presented in ATSDR's Toxicological Profiles of specific chemicals. CREGs are estimated comparison concentrations for specific chemicals based on an excess cancer rate of one in a million persons and are calculated using EPA's cancer slope factors. RfDG comparison concentrations are based on EPA's estimates of daily exposures that are not likely to cause adverse health effects. EPA's MCLs represent contaminant concentrations that EPA deems protective of public health (considering the availability and economics of water treatment technology) over a lifetime (70 years) at an exposure rate of two liters of water per day. EPA's LTHA identifies the contaminant level in drinking water at which adverse health effects would not be anticipated over a lifetime, with a margin of safety. MCLs are regulatory concentrations, but LTHAs are not. ALG is an EPA regulatory concentration that, if exceeded, requires public water systems to initiate specified response actions.
Other Selection Values--OSVs are estimated selection values that are based on other types of quantitative and qualitative federal or state health-related data and toxicological or epidemiological data.
Waste Material
A sample of waste material taken from one of the several drums on URI property was analyzed. Low concentrations of several pesticide and semi-volatile organic compounds and metals were found in the wastes, but none of the contaminants of concern were detected. ATSDR does not consider the results of this limited sampling to be representative of all the wastes that are present at the site. Information about contaminants of concern is summarized in Table 2, of Appendix B.
Groundwater - Monitoring Wells
Analysis of samples from several on-site groundwater monitoring wells showed several contaminants of concern--PCE, BEHP, aluminum, lead, manganese, and thallium. It is unclear whether all of the contaminants detected originated from site waste materials. Aluminum, manganese, and sometimes lead are natural constituents of groundwater. However, the available on-site and off-site groundwater data for those elements are insufficient for determining their natural concentrations. The lowest contaminant levels detected were in samples taken from the monitoring well that is located upgradient of the disposal area--except for BEHP. Information about contaminants of concern is summarized in Table 3, of Appendix B.
Surface Water
Samples of water from one of the on-site ponds showed three contaminants of concern--TCE, PCE, and lead. Information about contaminants of concern is summarized in Table 4, of Appendix B.
Sediment
BAP, BEHP, and lead were the only contaminants of concern detected in samples of sediment taken from the two on-site ponds. Information about contaminants of concern is summarized in Table 5, of Appendix B.
Surface Soil
Two surface-soil samples were taken near two drums on URI property. BAP, BEHP, and lead were the only contaminants of concern detected. Information about contaminants of concern is summarized in Table 6, of Appendix B.
Subsurface Soil
Laboratory analyses of subsurface soil samples taken from depths of 15 to 135 feet at explorations close to the disposal area tentatively identified, but did not confirm or quantify, two of the contaminants of concern (TCE, PCE). That information is summarized in Table 7, of Appendix B.
Ambient Air
No sampling or analytical data is available for ambient air.
Groundwater - Monitoring Wells
Analyses of groundwater samples from monitoring wells west and southwest of the site showed evidence of three contaminants of concern--BAP, BEHP, and manganese. Some or all of the manganese could occur naturally in the groundwater system, and therefore, may not be site-related. Information about contaminants of concern is summarized in Table 8, of Appendix B.
Groundwater - Private Wells
Groundwater has been analyzed at about 55 private wells on both sides of the river system.
Three Nearby Residences (Now Connected to Public Water)
Groundwater samples taken at three nearby residences contained as many as three of the contaminants of concern--TCE, PCE, and gasoline. URI personnel report that those residences were connected to the university's water system in 1988. Information about contaminants of concern is summarized in Table 9, of Appendix B.
Other Off-Site Private Wells
Sampling at the remainder of the private wells detected five contaminants of concern--chloroform, TCE, PCE, aldicarb, and manganese--in seven of them. Six of those wells are on the west side of the river system; one of the wells is a distance south of the site, near State Route 138. Those locations appear to be beyond the area in which groundwater is likely to be influenced by site releases. Thus, the detection of contaminants in the wells suggests that multiple sources of contamination may be present in the community. Also, manganese is a common naturally occurring element in groundwater. Aldicarb is an herbicide commonly used in potato farming. Information about contaminants of concern is summarized in Table 10, of Appendix B.
Groundwater - Public Wells
Samples from the URI and Kingston Water District well systems were analyzed. The analysis showed low levels of two of the contaminants of concern--lead and manganese. Aldicarb was also reported in 1984 in water samples from the Kingston Water District wells. Aldicarb was not analyzed for in the URI wells. Lead was detected in only one of the raw well water samples taken from each of the well systems. Manganese was detected most often. Manganese and lead (less frequently) can be natural constituents of groundwater. The considerable distance from the site to the wells and the apparent groundwater flow patterns in the site vicinity suggest that there are multiple sources of lead and manganese if they are not naturally occurring in the groundwater system. Aldicarb likely results from agricultural applications of chemicals. Information about contaminants of concern information is summarized in Table 11, of Appendix B.
Surface Water -- Hundred Acre Pond
Analyses of surface water samples from Hundred Acre Pond, which is hydrogeologically downgradient from the site, did not detect any of the contaminants of concern. Information about contaminants of concern is summarized in Table 12, of Appendix B. No water quality data are known to be available for Thirty Acre Pond or the Chipuxet River.
Sediment
No sediment sampling or analytical data are known to be available for Hundred Acre Pond, Thirty Acre Pond or the Chipuxet River.
Fish
No sampling or analytical data are known to be available for fish from the Hundred Acre Pond, Thirty Acre Pond, or the Chipuxet River.
Ambient Air
No sampling or analytical data are known to be available for ambient air.
Soil Gas
No sampling or analytical data are known to be available for soil gas.
C. QUALITY ASSURANCE AND QUALITY CONTROL
ATSDR has received little quality assurance information for laboratory data and for field sampling activities. ATSDR has presumed that appropriate protocols were followed and that analytical results are valid. The completeness and reliability of information could affect the validity of ATSDR's conclusions.
ATSDR observed nothing in the site vicinity that should pose any
usual kind of physical hazard to the public. Another, less
conventional, hazard might be attributed to soil gases released
below ground from contaminated groundwater if the gases rise to
the ground surface or enter buildings and accumulate at levels
that support combustion (explosion). ATSDR estimated the soil
gas concentrations that might reasonably correspond to VOC levels
detected in groundwater. ATSDR determined that the gases were
not combustible or the estimated levels were considerably below
the explosive range (7). Thus, soil gas does not appear to be a plausible explosion hazard.
ATSDR identifies human exposure pathways by examining environmental and human pathway components that lead to contact with contaminants. ATSDR considers five elements when analyzing a pathway: a source of contamination, transport through an environmental medium, a point of exposure, a route of human exposure, and an exposed population. Completed exposure pathways are those for which the five elements are evident and indicate that exposure to a contaminant either has occurred in the past, is currently occurring, or will occur in the future. Potential exposure pathways are those for which one or more elements is not clearly defined but could be present. Potential pathways indicate that exposure to a contaminant could have occurred in the past, could be occurring now, or could occur in the future.
Pathway analyses conducted for the site area indicate that there are several completed pathways associated with wastes, groundwater, and air. The completed pathway elements are summarized in Table 13 of this section.
Analyses also show that human contact with contaminants can occur through wastes, soils, surface water, air, and groundwater media. The potential pathway elements are summarized in Table 14 of this section.
Estimates of the number of exposed persons for completed exposure pathways and the number of potentially exposed persons for potential exposure pathways are shown in Table 15 of this section.
TABLE 13 COMPLETED EXPOSURE PATHWAYS
| PATHWAY NAME | EXPOSURE PATHWAY ELEMENTS | TIME | ||||
| SOURCE | MEDIUM | POINT OF EXPOSURE |
ROUTE OF EXPOSURE |
EXPOSED POPULATION |
||
| Worker-Waste Material | On-site wastes | Waste material | Handling, storage, and disposal areas | Skin contact Inhalation Ingestion |
Workers | Past |
| Nearby private wells | On-site wastes |
Groundwater | Nearby residences | Ingestion Inhalation Skin contact |
Residents | Past |
| Other private wells | Uncertain Other wastes? Natural? |
Groundwater | Several area
residences & businesses |
Ingestion Inhalation Skin contact |
Residents | Past Present Future |
| Off-site public water supplies | Source uncertain, Natural? |
Groundwater | University Residences Businesses |
Ingestion Inhalation Skin contact |
URI staff &
students Residents Workers |
Past Present Future |
| On-site ambient air | On-site
wastes & fires |
Air | On site | Inhalation | Workers | Past |
| Off-site ambient air | On-site fires | Air | Residences | Inhalation | Residents Field workers |
Past |
TABLE 14 POTENTIAL EXPOSURE PATHWAYS
| PATHWAY NAME | EXPOSURE PATHWAY ELEMENTS | TIME | ||||
| SOURCE | MEDIUM | POINT OF EXPOSURE |
ROUTE OF EXPOSURE |
EXPOSED POPULATION |
||
| On-site wastes | On-site
workers/ wastes |
Waste materials | On-site waste disposal areas | Skin contact Inhalation Ingestion |
Remedial workers | Future |
| On-site soils |
On-site wastes |
Soils | On site | Skin contact Ingestion |
Workers Remedial workers |
Past Future |
| On-site surface water | On-site wastes | Surface water | On-site ponds | Skin contact Inhalation Ingestion |
Workers Remedial workers |
Past Future |
| On-site sediment | On-site wastes | Sediment | On-site ponds | Skin contact Ingestion |
Workers Remedial workers |
Past Future |
| On-site ambient air | On-site wastes | Air | On-site access road | Inhalation | URI athletes | Past Present Future |
| Off-site other private wells | Uncertain Other wastes? Natural? |
Groundwater | Residences Businesses |
Ingestion Inhalation Skin contact |
Residents Workers |
Future |
| Off-site air/soil gas | On-site wastes | Groundwater, soil gas & air | Residences | Inhalation | Residents | Past Present Future |
| Off-site air/cooling tower | Treated wastewater | Air | Area surrounding cooling tower | Inhalation Skin contact |
Residents URI staff & students |
Future |
Table 15 ESTIMATED POPULATION FOR COMPLETED AND POTENTIAL EXPOSURE PATHWAYS
Sheet 1 of 3
| ESTIMATED EXPOSED POPULATIONS |
Affected by a Completed Exposure Pathway* : | |||||||||||
| Completed Exposure to Contaminants** | ||||||||||||
| Location | Number | CHL | TCE | PCE | BAP | BHP | AL | PB | MN | TL | GA | AD |
| Past workers on-site | 10 presumed |
ws? ai? |
ws? ai? |
ws? ai? |
ws? ai? |
ws? ai? |
ws? ai? |
ws? ai? |
ws? ai? |
wa? ai? |
||
| Residents previously supplied by three affected private wells | 10 | gw | gw | gw | ||||||||
| Residents supplied by seven affected private wells | 20 | gw | gw | gw | gw | gw | ||||||
| Public water users | 17,000 | gw | gw | gw | ||||||||
| Nearby residents, field workers during fires | 20 | ai? | ai? | ai? | ai? | ai? | ai? | ai? | ai? | ai? | ||
| ? Indicates laboratory data not available to confirm this specific contaminant was present. * Refer to Tables 13 and 14 for summary of completed and potential exposure pathways. ** Refer to Sheet 3 of 3 for explanation of alpha information. | ||||||||||||
Table 15 (Continued) ESTIMATED POPULATION FOR COMPLETED AND POTENTIAL EXPOSURE PATHWAYS
Sheet 2 of 3
| ESTIMATED POTENTIALLY EXPOSED POPULATIONS |
Affected by a Potential Exposure Pathway * : | |||||||||||
| Potential Exposure to Contaminants** | ||||||||||||
| Location | Number | CHL | TCE | PCE | BAP | BHP | AL | PB | MN | TL | GA | AD |
| Future workers on-site | 25 presumed |
ws? ai? so? |
ws? ai? so? sw |
ws? ai? so? sw |
ws? ai? so? |
ws? ai? so? |
ws? ai? so? |
ws? ai? so? sw |
ws? ai? so? |
ws? ai? so? |
||
| Past workers onsite | 10 presumed |
so? | so? sw |
so? sw |
so? se |
so? se |
so? | so? sw se |
so? | so? | ||
| URI cross country, other athletes on access road | 50 presumed |
ai? | ai? | ai? | ||||||||
| Other residents on currently unaffected private wells | Unknown | gw | gw | gw | gw | gw | gw | |||||
| Interior of nearest residences | 10 | ai? | ai? | ai? | ||||||||
| Near co-generation plant cooling tower | 100 presumed |
ai ?? |
ai ?? |
ai ?? |
ai ?? |
ai ?? |
ai ?? |
ai ?? |
ai ?? |
ai ?? |
ai ?? |
ai ?? |
| ? Indicates laboratory data not available to confirm this specific contaminant was present. ?? Cooling tower not yet in operation: pathway and contaminant uncertain. * Refer to Tables 13 and 14 for summary of completed and potential exposure pathways. ** Refer to Page 3 of 3 for explanation of alpha information. | ||||||||||||
Table 15 (Continued) ESTIMATED POPULATION FOR COMPLETED AND POTENTIAL EXPOSURE PATHWAYS
Sheet 3 of 3
| Alpha Code |
Contaminant | Alpha Code |
Pathway |
| CHL | Chloroform | ws | Wastes |
| TCE | Trichloroethylene | gw | Groundwater |
| PCE | Tetrachloroethylene | ai | Air |
| BAP | Benzo(a)pyrene | so | Soils |
| BHP | Bis(2-ethylhexyl)phthalate | sw | Surface water |
| AL | Aluminum | se | Sediment |
| PB | Lead | ||
| MN | Manganese | ||
| TL | Thallium | ||
| GA | Gasoline | ||
| AD | Aldicarb |
A. COMPLETED EXPOSURE PATHWAYS
On-Site Worker/Waste Material Pathway
While waste disposal and waste transfer operations were in progress and during site closure, on-site workers would have been exposed to contaminants associated with waste materials through skin contact, inhalation, and incidental ingestion. Since only one sample of waste was analyzed and none of the contaminants of concern were detected, the sample is not considered representative of all the wastes that have been deposited at the site. Therefore, ATSDR believes worker exposure might have included any or all the contaminants of concern shown in Table 1. The extent of exposure and uptake of specific contaminants cannot be evaluated with the information available.
Off-Site Nearby Private Wells Pathway
The site is on the eastern slope of the Chipuxet River basin, which is a major groundwater reservoir. Ground surface across the eastern half of the valley rises to an irregular ridgeline. The ridgeline, east of the site, approximately coincides with Old North Road. The water surface at the river, west of the site, is approximately Elevation 100, and ground surface along the ridgeline is approximately Elevation 250. Ground surface on site appears to vary from about Elevation 135 on the perimeter down to Elevation 120 in the disposal areas.
The river basin contains extensive glacial outwash deposits, which are underlain by granite gneiss (2). The average thickness of the saturated soil zone within the basin has been estimated to be 70 feet. Overburden soils in the site vicinity consist principally of sand and gravel materials. Bedrock is relatively deep to the west of the property and rises in elevation toward the east. Bedrock is exposed at the eastern edge of the site and on the nearby university campus.
The river system flows in a general southward direction. Regional groundwater flow in overburden is also reported to trend southerly. However, investigations at the site vicinity have shown that local flow direction is westerly, following the ground surface gradient, toward Hundred Acre Pond (1)(2). Thus, any contaminants released from the site are likely to be transported westward. On the other side of the river, beneath the west slope of the valley, the predominant local flow direction in overburden is expected to be easterly, toward the river system. Groundwater flow in underlying bedrock is most likely confined to secondary features such as fractures because of the low permeability of the rock mass (2). The flow direction of groundwater within shallow bedrock is likely to be similar to that which occurs within the immediately overlying soils. However, flow direction in rock at greater depth may follow some other regional pattern.
Analyses have shown that three of the contaminants of concern--TCE, PCE, and gasoline--were detected in some of the groundwater samples taken from each of three nearby residential wells during three or four sample events that were conducted in 1987. In the final sample, gasoline was detected in two of the wells. Some of the samples showed no contaminants--indicating some inconsistency, either in groundwater quality or in the analytical procedures. The three residences are on the west side of Plains road--between the site and the river system--in the direction of local groundwater flow. Thus, it is expected that the contaminants detected in the wells originated at the site. Those three residences and the nearest house to the north where no contamination was detected were all connected to the URI public water system in 1988. Residents, who used groundwater from the three affected private wells, appear to have been exposed to low levels of TCE and PCE through ingestion, inhalation (showering), and skin contact. Similar exposures to gasoline are indicated for users of two of the wells.
Off-Site Other Private Wells Pathway
Analyses of groundwater samples taken from more than 50 other private wells in the site area between 1988 and 1991 showed that six wells west of the river system and one well on the east side contained low levels of chloroform, TCE, PCE, aldicarb, or manganese. ATSDR's review of hydrogeologic information in relation to those contaminated well locations suggests that the site is not a likely source of the contaminants. The aldicarb likely results from agricultural applications of chemicals. ATSDR's reconnaissance of the areas immediately surrounding the seven wells did not disclose any other obvious sources for the chemicals. This could mean that unidentified sources exist in the area. Chemicals used to clean septic tanks and household chemical releases to septic systems are plausible sources. The woolen mill that operated well upstream along the river conceivably could be a source. Residents that use the affected private wells appear to be exposed to the contaminants through ingestion, inhalation (showering), or skin contact.
Off-Site Public Water Supplies Pathway
URI operates three public water supply wells about a half mile southwest of the site, and the Kingston Water District has two public water supply wells about one and a fourth miles to the southwest. Those wells are on the east side of the Chipuxet River system. Available sampling data shows evidence of low levels of two of the contaminants of concern (lead and manganese) in water produced by the wells. Aldicarb was analyzed for and detected in the Kingston Water District wells in 1984. Thus, public water system users--past, present, and future--are exposed to low concentrations of contaminants through ingestion, inhalation, and skin contact.
Laboratory data and hydrogeologic information provide no substantive indication that water quality at the public supply wells is being affected by contaminant releases to groundwater on site. Results of groundwater studies, coupled with general hydrogeologic information, suggest that the predominant local groundwater flow direction at the site is westward to the Chipuxet River system--not southward toward the public water supply wells. Whatever quantities of site-related contamination are transported by groundwater to the river would be further diluted as they are carried southward in stream water. VOCs will soon volatilize from the stream and portions of other contaminants would tend to attach to particles in the water column or sediment. If the groundwater system that supplies the public wells is recharged in part by stream water, it is conceivable that diluted quantities of site-related contaminants being carried by the stream could be entrained in groundwater and withdrawn by the well systems. However, information is insufficient to evaluate the viability of a stream water-to-public well pathway.
On-Site Ambient Air Pathway
Waste handling activities and fires that reportedly occurred periodically while the disposal sites were operational are likely to have released contaminants to the air, either bound to particulates or in gaseous form. Sampling and analytical data are not available to confirm the contaminant species or concentrations. Workmen at the site are likely to have been exposed in the past to airborne contaminants, principally through the inhalation route. However, the extent of inhalation exposure and uptake of specific contaminants cannot be evaluated with the available information.
Off-Site Ambient Air Pathway
Residents' periodic complaints about fires and poor air quality while the facilities were in operation indicate that wind transported smoke and unknown species of gaseous or particulate contaminants onto off-site properties. Complaints indicate that past releases resulted in inhalation exposure for nearby residents and possibly for anyone working in nearby fields. However, the extent of inhalation exposure and the uptake of specific contaminants cannot be evaluated without more information.
B. POTENTIAL EXPOSURE PATHWAYS
On-Site Worker/Waste Pathway
If remedial activities are required, workers could be exposed through skin contact, inhalation, and incidental ingestion of contaminants in waste materials unless adequate protective measures are taken. Analytical data for the one waste sample tested are not considered representative of all the wastes that have been disposed. Therefore, ATSDR believes that any future on-site workers might be exposed to any or all of the contaminants of concern. The extent of potential exposure and any contaminant uptake can be mitigated by safe work procedures and protective equipment and cannot be estimated.
On-Site Soil Pathway
Contaminants associated with the waste materials could readily have migrated from the disposal area to adjacent surface soils. However, surface soil sampling data are not available to confirm that the suspected migration has occurred. ATSDR believes that the two surface soil samples that were taken near the exposed drums are not likely to be representative of all surface soils in the area, especially those adjacent to the disposal site. If surface soils are contaminated, there is a potential that past workers were exposed and any future remedial workers may be exposed to contaminants of concern principally through skin contact and incidental ingestion. However, the extent of potential exposure and contaminant uptake cannot be estimated.
On-Site Surface Water Pathway
Sampling data show that water in at least one of the on-site ponds contains TCE, PCE and lead. Past workers might have been exposed and any future remedial workers might be exposed to those contaminants, and possibly other contaminants of concern, through skin contact, inhalation, and incidental ingestion. However, the extent of potential exposure and contaminant uptake cannot be estimated.
On-Site Sediment Pathway
Sampling at two of the on-site ponds shows that sediment contains BAP, BEHP and lead. Past workers might have been exposed and any future remedial workers might be exposed to those contaminants, or other contaminants of concern, principally through skin contact and incidental ingestion. However, the extent of potential exposure and contaminant uptake cannot be estimated.
On-Site Ambient Air Pathway
The results of air quality sampling conducted at the face of the disposal areas has shown that low levels of nonspecific volatile contaminants are being released by the waste materials. Therefore, students who cross the site on the access road during athletic training might be exposed to low levels of one or more of the volatile contaminants of concern through inhalation. The extent of potential exposure and contaminant uptake cannot be estimated.
Off-Site Additional Private Wells Pathway
Groundwater is used extensively for private water supplies in the site vicinity. Therefore, as the area is further developed, any new wells installed nearby--especially any placed westward, between the site and the river--have a potential of withdrawing contaminated groundwater. If that occurs, persons using contaminated well water for potable purposes are likely to be exposed to some of the contaminants of concern through ingestion, inhalation, and skin contact. However, the extent of potential exposure and contaminant uptake cannot be estimated.
Contaminants have also been detected in groundwater at isolated well locations for which no specific source is evident. Contaminated groundwater at those locations may flow toward other water supply wells and result in exposure of additional users.
Off-Site Air/Soil Gas Pathway
At residences positioned above groundwater that contains VOCs, soil gas released from the groundwater might rise to ground level and accumulate in living areas. Should that occur, occupants would be exposed to airborne contaminants through inhalation. However, ambient air monitoring data are not available for residences, and groundwater analytical data are too limited to fully evaluate that pathway.
ATSDR's analyses of available groundwater contamination data and plausible groundwater/soil gas partitioning factors suggests that there would not be an explosion or fire threat from the accumulation of combustible gases in residences.
Off-Site Air/Cooling Tower Pathway
The concentrations of some chemicals, especially nonvolatile organic compounds and inorganic contaminants, contained in (or added to) wastewater that will supply co-generation cooling needs could increase several fold as a result of normal cooling cycle operations. Therefore, some of the chemicals contained in cooling tower drift (droplets) are likely to be at greater concentrations than they were in the source water. Tower drift might also contain microorganisms and viruses. Populations downwind from the tower potentially could be exposed through inhalation and skin contact to at least low levels of contaminants contained in the drift. Incidental ingestion is also plausible. Specific contaminants and the extent of their uptake cannot be estimated from the information now available.
Unlikely Potential Pathways
On-Site Subsurface Soil Pathway
Analyses of soil samples taken below ground surface on site tentatively identified, and did not quantify, TCE and PCE at depths of 15 to 135 feet. Human exposure to contaminated soil at those depths is unlikely; thus, the subsurface soils are considered an unlikely potential pathway and are not further considered in this assessment.
Off-Site Fish and River/Pond Surface Water Pathways
Groundwater that flows beneath the site appears to discharge into
the nearby Chipuxet River system, which includes Hundred Acre and
Thirty Acre Ponds. Limited laboratory data showed that none of
the contaminants of concern were detected in Hundred Acre Pond
surface water. That information, coupled with fate and transport
characteristics of the contaminants, suggests--but does not
confirm--that the river system and fish are not likely pathways
for substantive contaminant exposure. Thus, those pathways are
not further considered in this assessment.
Introduction
ATSDR staff have determined that it is not possible to evaluate the extent of human exposure to and uptake of specific contaminants with the information available for the following completed exposure pathways, designated in the previous section as: on-site worker/waste material (past exposures), off-site public water supplies, on-site ambient air (past exposures), off-site ambient air, off-site air/cooling tower, and off-site private wells (present exposures). ATSDR staff have also determined that it is not possible to evaluate the extent of human exposure to and uptake of specific contaminants with the information available for the following potential exposure pathways, designated in the previous section as: on-site worker/waste (future exposures), on-site soil, on-site surface water, on-site sediment, on-site ambient air (present exposures), off-site private wells (future exposures), and off-site air/soil gas. The toxicologic implications of these pathways are not discussed below.
The extent of human exposure to and uptake of contaminants in nearby and other private wells has been evaluated by ATSDR staff. Human health effects associated with exposure to PCE, TCE and gasoline in nearby wells and to chloroform and aldicarb in other wells are discussed below. Estimated human doses of other contaminants found in those wells are below levels of public health concern and will not be further discussed in this section. The extent of human exposure to and uptake of aldicarb in off-site public water supplies is discussed below. Estimated human doses of other contaminants are below levels of public health concern and will not be further discussed in this section.
Cancerous and Non-cancerous Health Effects
ATSDR staff have examined available scientific literature about various adverse health effects associated with exposure to site-related contaminants. The adverse health effects may broadly be grouped as cancer and non-cancer. Below is a brief discussion of adverse health effects in general, followed by contaminant-specific discussions.
Cancer is a large group of diseases characterized by uncontained growth and spread of abnormal cells. Cancer cells multiply uncontrollably, destroying normal cells, and can spread to other parts of the body (8). A chemical that is capable of causing damage leading to cancer is called a carcinogen. The latency period, or amount of time between exposure and disease, may range from years to decades (9). One contaminant of concern at this site, PCE, has been classified as a probable human carcinogen--a chemical that has been shown experimentally to cause cancer in animals. There is inadequate evidence, however, about PCE's human carcinogenicity, but based on a lifetime exposure, PCE is suspected of causing cancer in people. There is inconclusive evidence whether TCE, another contaminant of concern, causes cancer in animals or people. Cancer risks are estimated by using EPA's Cancer Potency Factor. That method assumes that high dose animal data can be used to estimate the risk for low dose exposures in humans (10). The method also assumes that there is no safe level of exposure (11). There is little experimental evidence to confirm or refute those two assumptions. Lastly, the method computes the 95% upper bound risk, rather than the average risk, meaning there is a 95% chance the risk is actually lower, perhaps by several orders of magnitude (12).
Chemical exposure might result in adverse health effects other than cancer. Those effects may be acute (resulting from a short-term exposure of less than 14 days), intermediate (resulting from an exposure of more than 14 days but less than one year) or chronic (resulting from an exposure of more than a year). ATSDR has developed Minimal Risk Levels (MRLs) as health comparison guidelines of contaminant exposure. An MRL is an estimate of daily human exposure to a chemical that is not likely to cause an appreciable risk of deleterious noncancerous effects over a specified duration (acute, intermediate or chronic) of exposure. The mere presence of a contaminant does not imply that harm will result from exposure. A contaminant at a concentration lower than that chemical's MRL should pose no appreciable public health hazard with respect to noncancerous adverse health effects.
Health Effects By Contaminant
Tetrachloroethene (PCE)
Users of contaminated well water may have been exposed to PCE via ingestion, inhalation and skin contact with well water. The maximum level detected at this site is 52 ppb in a private well.
PCE has been classified by EPA as a Probable Human Carcinogen (13). Animal studies indicate that inhalation of PCE leads to leukemia and liver cancer in rats. EPA bases its determination that PCE is a Probable Human Carcinogen in part on those animal studies.
Available information is not sufficient to determine whether PCE causes cancer in humans (14). ATSDR staff have estimated the risk of a person getting cancer from several decades of exposure to PCE at this site. No apparent increase in the risk of cancer is expected from exposure to PCE at levels such as those found in the contaminated wells.
The maximum PCE concentration detected in the well water is below the ATSDR MRL for intermediate exposure via ingestion. Therefore, noncarcinogenic adverse health effects would not be expected to occur. ATSDR has not developed Minimum Risk Levels for chronic ingestion or dermal absorption of PCE.
Trichloroethene (TCE)
Users of contaminated well water may have been exposed to TCE via ingestion, inhalation and skin contact with well water. The maximum level detected at this site is 90 ppb in a private well.
TCE is considered a possible to probable human carcinogen; EPA has not conclusively determined TCE's cancer classification. Increased incidences of tumors have been observed in some animals experimentally exposed to TCE by ingestion or inhalation. Some laboratory studies indicate that some mice exposed to TCE by ingestion developed liver cancer. Additional studies in mice suggest that inhalation may result in liver and lung cancer. Some of the TCE studies use questionable methods and have inconclusive results, making it difficult to determine TCE's "true" carcinogenicity (15). ATSDR used available data to estimate the increased cancer risk associated with exposure to TCE at this site; the levels of TCE found represent no apparent increased risk of cancer for persons ingesting the water over many decades.
The maximum TCE concentration detected in the well water is below the ATSDR MRL for intermediate exposure via ingestion. Therefore, noncarcinogenic adverse health effects are not expected to occur. ATSDR has not developed Minimum Risk Levels for chronic ingestion or dermal absorption of TCE.
Gasoline
Users of contaminated well water may have been exposed to gasoline via ingestion, inhalation and skin contact with well water. The maximum level detected at this site is 11 ppb in a private well.
Gasoline is a common name for many different mixtures of chemicals. Typically, gasoline consists of from 20% to 49% benzenes and alkylbenzenes (16). Benzene is a known human carcinogen. ATSDR staff cannot accurately estimate the risk of getting cancer from exposure to gasoline at this site because the exact chemical composition is unknown. However, ATSDR staff members have estimated the risk of a person getting cancer from ingestion of gasoline consisting of 49% benzene (the most extreme case). Considering the low level of contamination and the briefness of the maximum possible time people could have been exposed to gasoline, there is no increased risk of getting cancer from this exposure. Similarly, no non-cancerous adverse health effects could be found in the literature at doses anywhere near what people might have been exposed to at this site given the low level of the contaminant and the short exposure duration (15).
Chloroform
Users of contaminated well water may be or may have been exposed to chloroform via ingestion, inhalation and skin contact with well water. The maximum level detected at this site is 9 ppb in a private well.
Chloroform has been classified by EPA as a Probable Human Carcinogen. Animal studies indicate that ingestion of chloroform leads to kidney and liver cancer in mice, rats and beagles. EPA bases its determination that chloroform is a Probable Human Carcinogen in part on those animal studies. Available information is not sufficient to determine whether chloroform causes cancer in humans (13,17). ATSDR staff have estimated that there is no apprent increase in the risk of a person getting cancer from exposure to chloroform at this site. However, as with all carcinogens, exposure to this chemical should be minimized.
The maximum chloroform concentration detected in the well water is below the ATSDR MRL for chronic exposure via ingestion. Therefore, noncarcinogenic adverse health effects are not expected to occur. ATSDR has not developed Minimum Risk Levels for intermediate ingestion or dermal absorption of chloroform.
Aldicarb
Users of contaminated well water and the contaminated public water supply may be or may have been exposed to aldicarb via ingestion, inhalation and skin contact with contaminated water. The maximum levels detected at this site are 12 ppb in a private well and 2 ppb in the public water supply. Aldicarb contamination does not appear to be related to the West Kingston/URI site.
Aldicarb has been classified by EPA as Not Classifiable as to Carcinogenicity (13). There is inadequate or no data about aldicarb's human and animal carcinogenicity. Therefore, cancer associated with exposure to aldicarb will not be discussed in this public health assessment.
ATSDR has not developed Minimum Risk Levels for aldicarb. However, ATSDR staff members have estimated safe levels of exposure to aldicarb based on the Reference Dose (RfD) developed by the EPA for chronic exposure (18). Those estimates indicate ingesting water contaminated with aldicarb at levels found in two private drinking wells may be a health concern if ingestion occurs over many years. Levels of aldicarb contamination are not of concern for acute exposures. Because sampling for aldicarb in the private wells occurred only once, it is not known if aldicarb is still in the private drinking water wells. City water is not provided to those residents. Therefore, exposures may still be occurring.
Because levels of aldicarb in public water supplies are low and the duration of exposure is short, aldicarb contamination in the public water supply does not represent a public health concern.
EPA based the aldicarb RfD primarily on the following three studies (18). These three studies all used exposure levels higher than those associated with 12 ppb in drinking water. Therefore, adverse effects associated with the studies are not likely to occur in people who drink aldicarb-contaminated water at this site.
Studies of dogs indicate that exposure to aldicarb is associated with decreased levels of cholinesterase. Two acute human studies examined effects from one-time exposures. Those studies also indicate cholinesterase inhibition (18).
Cholinesterase is an enzyme that plays an important role in nervous system functioning; insufficient cholinesterase may lead to diarrhea and other adverse intestinal effects, loss of muscle function, and respiratory problems such as bronchoconstriction and increased secretions into the lungs. The cholinesterase inhibiting capability of pesticides such as aldicarb, however, has been shown to be reversible over time (19).
Several human studies indicate that aldicarb may be associated with compromised immune system function. One study that indicated compromised immune system function included women who drank water contaminated with aldicarb at levels only somewhat higher than those reported in this public health assessment (<61 ppb) (20).
Because the exposure levels and durations of exposure to aldicarb are not known, ATSDR cannot evaluate with certainty whether exposure to aldicarb at this site represents a public health concern.
B. HEALTH OUTCOME DATA EVALUATION
Because a small number of people were exposed to significantly low levels of contaminants, and because that exposure has ended, ATSDR staff believe it is unlikely that anyone will develop cancer because of that exposure. In addition, ATSDR staff are unaware of any recent community health concerns of the residents. ATSDR staff did not examine health outcome data because no known effects are expected. If new information becomes available, or if nearby residents have health concerns about contaminants associated with the site, ATSDR will reconsider evaluating health outcome data.
C. COMMUNITY HEALTH CONCERNS EVALUATION
ATSDR staff are not aware of any recent community health concerns.