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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 contaminantsassociated with the wastes have been released to surface waterand sediment contained in ponds on the properties, to surface andsubsurface soils, and to the underlying groundwater system. Noanalytical data are available to confirm the extent ofcontamination in air media. Essentially, all of the on-sitesampling and analytical data ATSDR obtained are for environmentalmedia at the URIDA portion of the property. At WKTD, data wereobtained for only pond water and sediment.

Tables identified in this section list contaminants of concernthat have been selected for further evaluation in subsequentsections of the public health assessment to determine whetherexposure to them is a concern for public health. Listingcontaminants in those tables does not imply that exposure wouldactually result in adverse health effects.

ATSDR considers the following factors when selecting contaminantsof concern:

  1. concentrations of contaminants on site and off site,
  2. sampling plan design, field data quality, and laboratory data quality,
  3. relationship of on-site and off-site concentrations to Health Assessment Comparison Values for noncarcinogenic health endpoints and for carcinogenic endpoints,
  4. unavailability of Health Assessment Comparison Values,
  5. evidence of carcinogenicity, and
  6. community health concerns.

ATSDR conducted a search of the EPA Toxic Chemical ReleaseInventory (TRI) for the site and county. That search did notdisclose information about either of the disposal areas andidentified chemical releases for only one industrial plant in thesite vicinity--located about one and a half miles southwest ofthe site. TRI shows the plant reported releasing xylene to theatmosphere at a rate of 20,000 pounds per year. The databasedoes not provide sufficient information to estimate airborneconcentrations either at the plant or downwind. For this reason,and because xylenes have not been reported at elevated levels forany media at the site, the xylene releases reported by that plantwill not be further considered in this assessment.

Contaminants of concern that will be further evaluated in thisassessment are listed in Table 1.

Table 1.

Contaminants of Concern in One or More Media


ChloroformGasoline
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 ofcontaminants of concern are provided in Tables 2 through 12, inAppendix B. Those tables contain abbreviations, which areexplained 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 concentrationsthat are based on information presented in ATSDR's ToxicologicalProfiles of specific chemicals. CREGs are estimated comparisonconcentrations for specific chemicals based on an excess cancerrate of one in a million persons and are calculated using EPA'scancer slope factors. RfDG comparison concentrations are basedon EPA's estimates of daily exposures that are not likely tocause adverse health effects. EPA's MCLs represent contaminantconcentrations that EPA deems protective of public health(considering the availability and economics of water treatmenttechnology) over a lifetime (70 years) at an exposure rate of twoliters of water per day. EPA's LTHA identifies the contaminantlevel in drinking water at which adverse health effects would notbe anticipated over a lifetime, with a margin of safety. MCLsare regulatory concentrations, but LTHAs are not. ALG is an EPAregulatory concentration that, if exceeded, requires public watersystems to initiate specified response actions.

Other Selection Values--OSVs are estimated selection values thatare based on other types of quantitative and qualitative federalor state health-related data and toxicological or epidemiologicaldata.

A. ON-SITE CONTAMINATION

Waste Material

A sample of waste material taken from one of the several drums onURI property was analyzed. Low concentrations of severalpesticide and semi-volatile organic compounds and metals werefound in the wastes, but none of the contaminants of concern weredetected. ATSDR does not consider the results of this limitedsampling to be representative of all the wastes that are presentat the site. Information about contaminants of concern issummarized in Table 2, of Appendix B.

Groundwater - Monitoring Wells

Analysis of samples from several on-site groundwater monitoringwells showed several contaminants of concern--PCE, BEHP,aluminum, lead, manganese, and thallium. It is unclear whetherall of the contaminants detected originated from site wastematerials. Aluminum, manganese, and sometimes lead are naturalconstituents of groundwater. However, the available on-site andoff-site groundwater data for those elements are insufficient fordetermining their natural concentrations. The lowest contaminantlevels detected were in samples taken from the monitoring wellthat is located upgradient of the disposal area--except for BEHP. Information about contaminants of concern is summarized inTable 3, of Appendix B.

Surface Water

Samples of water from one of the on-site ponds showed threecontaminants of concern--TCE, PCE, and lead. Information aboutcontaminants of concern is summarized in Table 4, of Appendix B.

Sediment

BAP, BEHP, and lead were the only contaminants of concerndetected in samples of sediment taken from the two on-site ponds. Information about contaminants of concern is summarized inTable 5, of Appendix B.

Surface Soil

Two surface-soil samples were taken near two drums on URIproperty. BAP, BEHP, and lead were the only contaminants ofconcern detected. Information about contaminants of concern issummarized in Table 6, of Appendix B.

Subsurface Soil

Laboratory analyses of subsurface soil samples taken from depthsof 15 to 135 feet at explorations close to the disposal areatentatively identified, but did not confirm or quantify, two ofthe contaminants of concern (TCE, PCE). That information issummarized in Table 7, of Appendix B.

Ambient Air

No sampling or analytical data is available for ambient air.

B. OFF-SITE CONTAMINATION

Groundwater - Monitoring Wells

Analyses of groundwater samples from monitoring wells west andsouthwest of the site showed evidence of three contaminants ofconcern--BAP, BEHP, and manganese. Some or all of the manganesecould occur naturally in the groundwater system, and therefore,may not be site-related. Information about contaminants ofconcern is summarized in Table 8, of Appendix B.

Groundwater - Private Wells

Groundwater has been analyzed at about 55 private wells on bothsides of the river system.

Three Nearby Residences (Now Connected to Public Water)

Groundwater samples taken at three nearby residences contained asmany as three of the contaminants of concern--TCE, PCE, andgasoline. URI personnel report that those residences wereconnected to the university's water system in 1988. Informationabout 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 fivecontaminants of concern--chloroform, TCE, PCE, aldicarb, andmanganese--in seven of them. Six of those wells are on the westside of the river system; one of the wells is a distance south ofthe site, near State Route 138. Those locations appear to bebeyond the area in which groundwater is likely to be influencedby site releases. Thus, the detection of contaminants in thewells suggests that multiple sources of contamination may bepresent in the community. Also, manganese is a common naturallyoccurring element in groundwater. Aldicarb is an herbicidecommonly used in potato farming. Information about contaminantsof concern is summarized in Table 10, of Appendix B.

Groundwater - Public Wells

Samples from the URI and Kingston Water District well systemswere analyzed. The analysis showed low levels of two of thecontaminants of concern--lead and manganese. Aldicarb was alsoreported in 1984 in water samples from the Kingston WaterDistrict wells. Aldicarb was not analyzed for in the URI wells. Lead was detected in only one of the raw well water samples takenfrom each of the well systems. Manganese was detected mostoften. Manganese and lead (less frequently) can be naturalconstituents of groundwater. The considerable distance from thesite to the wells and the apparent groundwater flow patterns inthe site vicinity suggest that there are multiple sources of leadand manganese if they are not naturally occurring in thegroundwater system. Aldicarb likely results from agriculturalapplications of chemicals. Information about contaminants ofconcern information is summarized in Table 11, of Appendix B.

Surface Water -- Hundred Acre Pond

Analyses of surface water samples from Hundred Acre Pond, whichis hydrogeologically downgradient from the site, did not detectany of the contaminants of concern. Information aboutcontaminants of concern is summarized in Table 12, of Appendix B. No water quality data are known to be available for Thirty AcrePond or the Chipuxet River.

Sediment

No sediment sampling or analytical data are known to be availablefor Hundred Acre Pond, Thirty Acre Pond or the Chipuxet River.

Fish

No sampling or analytical data are known to be available for fishfrom the Hundred Acre Pond, Thirty Acre Pond, or the Chipuxet River.

Ambient Air

No sampling or analytical data are known to be available forambient air.

Soil Gas

No sampling or analytical data are known to be available for soilgas.

C. QUALITY ASSURANCE AND QUALITY CONTROL

ATSDR has received little quality assurance information forlaboratory data and for field sampling activities. ATSDR haspresumed that appropriate protocols were followed and thatanalytical results are valid. The completeness and reliabilityof information could affect the validity of ATSDR's conclusions.

D. PHYSICAL AND OTHER HAZARDS

ATSDR observed nothing in the site vicinity that should pose anyusual kind of physical hazard to the public. Another, lessconventional, hazard might be attributed to soil gases releasedbelow ground from contaminated groundwater if the gases rise tothe ground surface or enter buildings and accumulate at levelsthat support combustion (explosion). ATSDR estimated the soilgas concentrations that might reasonably correspond to VOC levelsdetected in groundwater. ATSDR determined that the gases werenot combustible or the estimated levels were considerably belowthe explosive range (7). Thus, soil gas does not appear to be a plausible explosion hazard.


PATHWAYS ANALYSES

ATSDR identifies human exposure pathways by examiningenvironmental and human pathway components that lead to contactwith contaminants. ATSDR considers five elements when analyzinga pathway: a source of contamination, transport through anenvironmental medium, a point of exposure, a route of humanexposure, and an exposed population. Completed exposure pathwaysare those for which the five elements are evident and indicatethat exposure to a contaminant either has occurred in the past,is currently occurring, or will occur in the future. Potentialexposure pathways are those for which one or more elements is notclearly defined but could be present. Potential pathwaysindicate that exposure to a contaminant could have occurred inthe past, could be occurring now, or could occur in the future.

Pathway analyses conducted for the site area indicate that thereare several completed pathways associated with wastes,groundwater, and air. The completed pathway elements aresummarized in Table 13 of this section.

Analyses also show that human contact with contaminants can occurthrough wastes, soils, surface water, air, and groundwater media. The potential pathway elements are summarized in Table 14 of thissection.

Estimates of the number of exposed persons for completed exposurepathways and the number of potentially exposed persons forpotential exposure pathways are shown in Table 15 of thissection.



Table 13.

COMPLETED EXPOSURE PATHWAYS
PATHWAY NAMEEXPOSURE PATHWAY ELEMENTS TIME
SOURCEMEDIUMPOINT OF
EXPOSURE
ROUTE OF
EXPOSURE
EXPOSED
POPULATION
Worker-WasteMaterialOn-sitewastes WastematerialHandling,storage, anddisposalareasSkin contact
Inhalation
Ingestion
WorkersPast
NearbyprivatewellsOn-site
wastes
GroundwaterNearbyresidencesIngestion
Inhalation
Skin contact
ResidentsPast
OtherprivatewellsUncertain
Other
wastes?
Natural?
GroundwaterSeveral arearesidences &
businesses
Ingestion
Inhalation
Skin contact
ResidentsPast
Present
Future
Off-sitepublic watersuppliesSource
uncertain,
Natural?
GroundwaterUniversity
Residences
Businesses
Ingestion
Inhalation
Skin contact
URI staff &students
Residents
Workers
Past
Present
Future
On-siteambient airOn-sitewastes &
fires
AirOn siteInhalationWorkers Past
Off-siteambient airOn-sitefiresAirResidencesInhalationResidents
Field
workers
Past




Table 14.

POTENTIAL EXPOSURE PATHWAYS
PATHWAY NAMEEXPOSURE PATHWAY ELEMENTS TIME
SOURCEMEDIUMPOINT OF
EXPOSURE
ROUTE OF
EXPOSURE
EXPOSED
POPULATION
On-sitewastesOn-siteworkers/
wastes
WastematerialsOn-site wastedisposalareasSkin contact
Inhalation
Ingestion
RemedialworkersFuture
On-site
soils
On-site
wastes
SoilsOn siteSkin contact
Ingestion
Workers
Remedial workers
Past
Future
On-sitesurfacewaterOn-sitewastesSurface waterOn-site pondsSkin contact
Inhalation
Ingestion
Workers
Remedial workers
Past
Future
On-sitesedimentOn-sitewastesSedimentOn-site pondsSkin contact
Ingestion
Workers
Remedial workers
Past
Future
On-siteambient airOn-sitewastesAirOn-siteaccess roadInhalationURI athletesPast
Present
Future
Off-siteotherprivatewellsUncertain
Other wastes?
Natural?
GroundwaterResidences
Businesses
Ingestion
Inhalation
Skin contact
Residents
Workers
Future
Off-siteair/soil gasOn-sitewastesGroundwater,soil gas &airResidencesInhalationResidentsPast
Present
Future
Off-siteair/coolingtowerTreatedwastewater AirAreasurroundingcooling towerInhalation
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**
LocationNumberCHLTCEPCEBAPBHPALPBMNTLGAAD
Past workers on-site10
presumed
ws?
ai?
ws?
ai?
ws?
ai?
ws?
ai?
ws?
ai?
ws?
ai?
ws?
ai?
ws?
ai?
wa?
ai?


Residentspreviouslysupplied by threeaffected privatewells10
gwgw





gw
Residentssupplied by sevenaffected privatewells20gwgwgw



gw

gw
Public waterusers17,000





gwgw

gw
Nearby residents,field workersduring fires20ai?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**
LocationNumberCHLTCEPCEBAPBHPALPBMNTLGAAD
Future workers on-site25
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 onsite10
presumed
so?so?
sw
so?
sw
so?
se
so?
se
so?so?
sw
se
so?so?

URI cross country,other athletes onaccess road50
presumed
ai?ai?ai?







Other residents oncurrentlyunaffected privatewellsUnknowngwgwgw



gw
gwgw
Interior of nearestresidences10ai?ai?ai?







Near co-generationplant cooling tower100
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.




Sheet 3 of 3">

Table 15 (Continued).

ESTIMATED POPULATION FOR COMPLETED AND POTENTIAL EXPOSURE PATHWAYSSheet 3 of 3
Alpha
Code
ContaminantAlpha
Code
Pathway
CHLChloroformwsWastes
TCETrichloroethylenegwGroundwater
PCETetrachloroethyleneaiAir
BAPBenzo(a)pyrenesoSoils
BHPBis(2-ethylhexyl)phthalateswSurface water
ALAluminumseSediment
PBLead
MNManganese
TLThallium
GAGasoline
ADAldicarb

A. COMPLETED EXPOSURE PATHWAYS

On-Site Worker/Waste Material Pathway

While waste disposal and waste transfer operations were inprogress and during site closure, on-site workers would have beenexposed to contaminants associated with waste materials throughskin contact, inhalation, and incidental ingestion. Since onlyone sample of waste was analyzed and none of the contaminants ofconcern were detected, the sample is not consideredrepresentative of all the wastes that have been deposited at thesite. Therefore, ATSDR believes worker exposure might haveincluded any or all the contaminants of concern shown in Table 1. The extent of exposure and uptake of specific contaminants cannotbe 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 acrossthe eastern half of the valley rises to an irregular ridgeline. The ridgeline, east of the site, approximately coincides with OldNorth Road. The water surface at the river, west of the site, isapproximately Elevation 100, and ground surface along theridgeline is approximately Elevation 250. Ground surface on siteappears to vary from about Elevation 135 on the perimeter down toElevation 120 in the disposal areas.

The river basin contains extensive glacial outwash deposits,which are underlain by granite gneiss (2). The average thicknessof the saturated soil zone within the basin has been estimated tobe 70 feet. Overburden soils in the site vicinity consistprincipally of sand and gravel materials. Bedrock is relativelydeep to the west of the property and rises in elevation towardthe east. Bedrock is exposed at the eastern edge of the site andon the nearby university campus.

The river system flows in a general southward direction. Regional groundwater flow in overburden is also reported to trendsoutherly. However, investigations at the site vicinity haveshown that local flow direction is westerly, following the groundsurface gradient, toward Hundred Acre Pond (1)(2). Thus, anycontaminants released from the site are likely to be transportedwestward. On the other side of the river, beneath the west slopeof the valley, the predominant local flow direction in overburdenis expected to be easterly, toward the river system. Groundwater flow in underlying bedrock is most likely confined tosecondary features such as fractures because of the lowpermeability of the rock mass (2). The flow direction ofgroundwater within shallow bedrock is likely to be similar tothat which occurs within the immediately overlying soils. However, flow direction in rock at greater depth may follow someother regional pattern.

Analyses have shown that three of the contaminants of concern--TCE, PCE, and gasoline--were detected in some of the groundwatersamples taken from each of three nearby residential wells duringthree or four sample events that were conducted in 1987. In thefinal sample, gasoline was detected in two of the wells. Some ofthe samples showed no contaminants--indicating someinconsistency, either in groundwater quality or in the analyticalprocedures. The three residences are on the west side of Plainsroad--between the site and the river system--in the direction oflocal groundwater flow. Thus, it is expected that thecontaminants detected in the wells originated at the site. Thosethree residences and the nearest house to the north where nocontamination was detected were all connected to the URI publicwater system in 1988. Residents, who used groundwater from thethree affected private wells, appear to have been exposed to lowlevels of TCE and PCE through ingestion, inhalation (showering),and skin contact. Similar exposures to gasoline are indicatedfor users of two of the wells.

Off-Site Other Private Wells Pathway

Analyses of groundwater samples taken from more than 50 otherprivate wells in the site area between 1988 and 1991 showed that six wells west of the river system and one well on the east sidecontained low levels of chloroform, TCE, PCE, aldicarb, ormanganese. ATSDR's review of hydrogeologic information inrelation to those contaminated well locations suggests that thesite is not a likely source of the contaminants. The aldicarblikely results from agricultural applications of chemicals. ATSDR's reconnaissance of the areas immediately surrounding theseven wells did not disclose any other obvious sources for thechemicals. This could mean that unidentified sources exist inthe area. Chemicals used to clean septic tanks and householdchemical releases to septic systems are plausible sources. Thewoolen mill that operated well upstream along the riverconceivably could be a source. Residents that use the affectedprivate wells appear to be exposed to the contaminants throughingestion, inhalation (showering), or skin contact.

Off-Site Public Water Supplies Pathway

URI operates three public water supply wells about a half milesouthwest of the site, and the Kingston Water District has twopublic water supply wells about one and a fourth miles to thesouthwest. Those wells are on the east side of the ChipuxetRiver system. Available sampling data shows evidence of lowlevels of two of the contaminants of concern (lead and manganese)in water produced by the wells. Aldicarb was analyzed for anddetected in the Kingston Water District wells in 1984. Thus,public water system users--past, present, and future--are exposedto low concentrations of contaminants through ingestion,inhalation, and skin contact.

Laboratory data and hydrogeologic information provide nosubstantive indication that water quality at the public supplywells is being affected by contaminant releases to groundwater onsite. Results of groundwater studies, coupled with generalhydrogeologic information, suggest that the predominant localgroundwater flow direction at the site is westward to theChipuxet River system--not southward toward the public watersupply wells. Whatever quantities of site-related contaminationare transported by groundwater to the river would be furtherdiluted as they are carried southward in stream water. VOCs willsoon volatilize from the stream and portions of othercontaminants would tend to attach to particles in the watercolumn or sediment. If the groundwater system that supplies thepublic wells is recharged in part by stream water, it isconceivable that diluted quantities of site-related contaminantsbeing carried by the stream could be entrained in groundwater andwithdrawn by the well systems. However, information isinsufficient to evaluate the viability of a stream water-to-public well pathway.

On-Site Ambient Air Pathway

Waste handling activities and fires that reportedly occurredperiodically while the disposal sites were operational are likelyto have released contaminants to the air, either bound toparticulates or in gaseous form. Sampling and analytical dataare not available to confirm the contaminant species orconcentrations. Workmen at the site are likely to have beenexposed in the past to airborne contaminants, principally throughthe inhalation route. However, the extent of inhalation exposureand uptake of specific contaminants cannot be evaluated with theavailable information.

Off-Site Ambient Air Pathway

Residents' periodic complaints about fires and poor air qualitywhile the facilities were in operation indicate that windtransported smoke and unknown species of gaseous or particulatecontaminants onto off-site properties. Complaints indicate thatpast releases resulted in inhalation exposure for nearbyresidents and possibly for anyone working in nearby fields. However, the extent of inhalation exposure and the uptake ofspecific contaminants cannot be evaluated without moreinformation.

B. POTENTIAL EXPOSURE PATHWAYS

On-Site Worker/Waste Pathway

If remedial activities are required, workers could be exposedthrough skin contact, inhalation, and incidental ingestion ofcontaminants in waste materials unless adequate protectivemeasures are taken. Analytical data for the one waste sampletested are not considered representative of all the wastes thathave been disposed. Therefore, ATSDR believes that any futureon-site workers might be exposed to any or all of thecontaminants of concern. The extent of potential exposure andany contaminant uptake can be mitigated by safe work proceduresand protective equipment and cannot be estimated.

On-Site Soil Pathway

Contaminants associated with the waste materials could readilyhave migrated from the disposal area to adjacent surface soils. However, surface soil sampling data are not available to confirmthat the suspected migration has occurred. ATSDR believes thatthe two surface soil samples that were taken near the exposeddrums are not likely to be representative of all surface soils inthe area, especially those adjacent to the disposal site. Ifsurface soils are contaminated, there is a potential that pastworkers were exposed and any future remedial workers may beexposed to contaminants of concern principally through skincontact and incidental ingestion. However, the extent ofpotential exposure and contaminant uptake cannot be estimated.

On-Site Surface Water Pathway

Sampling data show that water in at least one of the on-siteponds contains TCE, PCE and lead. Past workers might have beenexposed and any future remedial workers might be exposed to thosecontaminants, and possibly other contaminants of concern, throughskin contact, inhalation, and incidental ingestion. However, theextent of potential exposure and contaminant uptake cannot beestimated.

On-Site Sediment Pathway

Sampling at two of the on-site ponds shows that sediment containsBAP, BEHP and lead. Past workers might have been exposed and anyfuture remedial workers might be exposed to those contaminants,or other contaminants of concern, principally through skincontact and incidental ingestion. However, the extent ofpotential exposure and contaminant uptake cannot be estimated.

On-Site Ambient Air Pathway

The results of air quality sampling conducted at the face of thedisposal areas has shown that low levels of nonspecific volatilecontaminants are being released by the waste materials. Therefore, students who cross the site on the access road duringathletic training might be exposed to low levels of one or moreof the volatile contaminants of concern through inhalation. Theextent of potential exposure and contaminant uptake cannot beestimated.

Off-Site Additional Private Wells Pathway

Groundwater is used extensively for private water supplies in thesite vicinity. Therefore, as the area is further developed, anynew wells installed nearby--especially any placed westward,between the site and the river--have a potential of withdrawingcontaminated groundwater. If that occurs, persons usingcontaminated well water for potable purposes are likely to beexposed to some of the contaminants of concern through ingestion,inhalation, and skin contact. However, the extent of potentialexposure and contaminant uptake cannot be estimated.

Contaminants have also been detected in groundwater at isolatedwell locations for which no specific source is evident. Contaminated groundwater at those locations may flow toward otherwater 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 leveland accumulate in living areas. Should that occur, occupantswould be exposed to airborne contaminants through inhalation. However, ambient air monitoring data are not available forresidences, and groundwater analytical data are too limited tofully evaluate that pathway.

ATSDR's analyses of available groundwater contamination data andplausible groundwater/soil gas partitioning factors suggests thatthere would not be an explosion or fire threat from theaccumulation of combustible gases in residences.

Off-Site Air/Cooling Tower Pathway

The concentrations of some chemicals, especially nonvolatileorganic compounds and inorganic contaminants, contained in (oradded to) wastewater that will supply co-generation cooling needscould increase several fold as a result of normal cooling cycleoperations. Therefore, some of the chemicals contained incooling tower drift (droplets) are likely to be at greaterconcentrations than they were in the source water. Tower driftmight also contain microorganisms and viruses. Populationsdownwind from the tower potentially could be exposed throughinhalation and skin contact to at least low levels ofcontaminants contained in the drift. Incidental ingestion isalso plausible. Specific contaminants and the extent of theiruptake 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 sitetentatively identified, and did not quantify, TCE and PCE atdepths of 15 to 135 feet. Human exposure to contaminated soil atthose depths is unlikely; thus, the subsurface soils areconsidered an unlikely potential pathway and are not furtherconsidered in this assessment.

    Off-Site Fish and River/Pond Surface Water Pathways

Groundwater that flows beneath the site appears to discharge intothe nearby Chipuxet River system, which includes Hundred Acre andThirty Acre Ponds. Limited laboratory data showed that none ofthe contaminants of concern were detected in Hundred Acre Pondsurface water. That information, coupled with fate and transportcharacteristics of the contaminants, suggests--but does notconfirm--that the river system and fish are not likely pathwaysfor substantive contaminant exposure. Thus, those pathways arenot further considered in this assessment.


PUBLIC HEALTH IMPLICATIONS

A. TOXICOLOGIC EVALUATION

Introduction

ATSDR staff have determined that it is not possible to evaluatethe extent of human exposure to and uptake of specificcontaminants with the information available for the followingcompleted exposure pathways, designated in the previous sectionas: on-site worker/waste material (past exposures), off-sitepublic water supplies, on-site ambient air (past exposures), off-site ambient air, off-site air/cooling tower, and off-siteprivate wells (present exposures). ATSDR staff have alsodetermined that it is not possible to evaluate the extent ofhuman exposure to and uptake of specific contaminants with theinformation available for the following potential exposurepathways, designated in the previous section as: on-siteworker/waste (future exposures), on-site soil, on-site surfacewater, on-site sediment, on-site ambient air (present exposures),off-site private wells (future exposures), and off-site air/soilgas. The toxicologic implications of these pathways are notdiscussed below.

The extent of human exposure to and uptake of contaminants innearby and other private wells has been evaluated by ATSDR staff. Human health effects associated with exposure to PCE, TCE andgasoline in nearby wells and to chloroform and aldicarb in otherwells are discussed below. Estimated human doses of othercontaminants found in those wells are below levels of publichealth 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 humandoses of other contaminants are below levels of public healthconcern and will not be further discussed in this section.

Cancerous and Non-cancerous Health Effects

ATSDR staff have examined available scientific literature aboutvarious adverse health effects associated with exposure to site-related contaminants. The adverse health effects may broadly begrouped as cancer and non-cancer. Below is a brief discussion ofadverse health effects in general, followed by contaminant-specific discussions.

Cancer is a large group of diseases characterized by uncontainedgrowth and spread of abnormal cells. Cancer cells multiplyuncontrollably, destroying normal cells, and can spread to otherparts of the body (8). A chemical that is capable of causingdamage leading to cancer is called a carcinogen. The latencyperiod, or amount of time between exposure and disease, may rangefrom years to decades (9). One contaminant of concern at thissite, PCE, has been classified as a probable human carcinogen--achemical that has been shown experimentally to cause cancer inanimals. There is inadequate evidence, however, about PCE'shuman carcinogenicity, but based on a lifetime exposure, PCE issuspected of causing cancer in people. There is inconclusiveevidence whether TCE, another contaminant of concern, causescancer in animals or people. Cancer risks are estimated by usingEPA's Cancer Potency Factor. That method assumes that high doseanimal data can be used to estimate the risk for low doseexposures in humans (10). The method also assumes that there isno safe level of exposure (11). There is little experimentalevidence to confirm or refute those two assumptions. Lastly, themethod computes the 95% upper bound risk, rather than the averagerisk, 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 otherthan cancer. Those effects may be acute (resulting from ashort-term exposure of less than 14 days), intermediate(resulting from an exposure of more than 14 days but less thanone year) or chronic (resulting from an exposure of more than ayear). ATSDR has developed Minimal Risk Levels (MRLs) as healthcomparison guidelines of contaminant exposure. An MRL is anestimate of daily human exposure to a chemical that is not likelyto cause an appreciable risk of deleterious noncancerous effectsover a specified duration (acute, intermediate or chronic) ofexposure. The mere presence of a contaminant does not imply thatharm will result from exposure. A contaminant at a concentrationlower than that chemical's MRL should pose no appreciable publichealth hazard with respect to noncancerous adverse healtheffects.

Health Effects By Contaminant

Tetrachloroethene (PCE)

Users of contaminated well water may have been exposed to PCE viaingestion, inhalation and skin contact with well water. Themaximum 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 toleukemia and liver cancer in rats. EPA bases its determinationthat PCE is a Probable Human Carcinogen in part on those animalstudies.

Available information is not sufficient to determine whether PCEcauses cancer in humans (14). ATSDR staff have estimated therisk of a person getting cancer from several decades of exposureto PCE at this site. No apparent increase in the risk of canceris expected from exposure to PCE at levels such as those found inthe contaminated wells.

The maximum PCE concentration detected in the well water is belowthe ATSDR MRL for intermediate exposure via ingestion. Therefore, noncarcinogenic adverse health effects would not beexpected to occur. ATSDR has not developed Minimum Risk Levelsfor chronic ingestion or dermal absorption of PCE.

Trichloroethene (TCE)

Users of contaminated well water may have been exposed to TCE viaingestion, inhalation and skin contact with well water. Themaximum level detected at this site is 90 ppb in a private well.

TCE is considered a possible to probable human carcinogen; EPAhas not conclusively determined TCE's cancer classification.Increased incidences of tumors have been observed in some animalsexperimentally exposed to TCE by ingestion or inhalation. Somelaboratory studies indicate that some mice exposed to TCE byingestion developed liver cancer. Additional studies in micesuggest that inhalation may result in liver and lung cancer. Some of the TCE studies use questionable methods and haveinconclusive results, making it difficult to determine TCE's"true" carcinogenicity (15). ATSDR used available data to estimate the increased cancer risk associated with exposure toTCE at this site; the levels of TCE found represent no apparentincreased risk of cancer for persons ingesting the water overmany decades.

The maximum TCE concentration detected in the well water is belowthe ATSDR MRL for intermediate exposure via ingestion. Therefore, noncarcinogenic adverse health effects are notexpected to occur. ATSDR has not developed Minimum Risk Levelsfor chronic ingestion or dermal absorption of TCE.

Gasoline

Users of contaminated well water may have been exposed togasoline via ingestion, inhalation and skin contact with wellwater. The maximum level detected at this site is 11 ppb in aprivate well.

Gasoline is a common name for many different mixtures ofchemicals. Typically, gasoline consists of from 20% to 49%benzenes and alkylbenzenes (16). Benzene is a known humancarcinogen. ATSDR staff cannot accurately estimate the risk ofgetting cancer from exposure to gasoline at this site because theexact chemical composition is unknown. However, ATSDR staffmembers have estimated the risk of a person getting cancer fromingestion of gasoline consisting of 49% benzene (the most extremecase). Considering the low level of contamination and thebriefness of the maximum possible time people could have beenexposed to gasoline, there is no increased risk of getting cancerfrom this exposure. Similarly, no non-cancerous adverse healtheffects could be found in the literature at doses anywhere nearwhat people might have been exposed to at this site given the lowlevel of the contaminant and the short exposure duration (15).

Chloroform

Users of contaminated well water may be or may have been exposedto chloroform via ingestion, inhalation and skin contact withwell water. The maximum level detected at this site is 9 ppb ina private well.

Chloroform has been classified by EPA as a Probable HumanCarcinogen. Animal studies indicate that ingestion of chloroformleads to kidney and liver cancer in mice, rats and beagles. EPAbases its determination that chloroform is a Probable HumanCarcinogen in part on those animal studies. Availableinformation is not sufficient to determine whether chloroformcauses cancer in humans (13,17). ATSDR staff have estimated thatthere is no apprent increase in the risk of a person gettingcancer from exposure to chloroform at this site. However, aswith all carcinogens, exposure to this chemical should beminimized.

The maximum chloroform concentration detected in the well wateris below the ATSDR MRL for chronic exposure via ingestion. Therefore, noncarcinogenic adverse health effects are notexpected to occur. ATSDR has not developed Minimum Risk Levelsfor intermediate ingestion or dermal absorption of chloroform.

Aldicarb

Users of contaminated well water and the contaminated publicwater supply may be or may have been exposed to aldicarb viaingestion, inhalation and skin contact with contaminated water. The maximum levels detected at this site are 12 ppb in a privatewell and 2 ppb in the public water supply. Aldicarbcontamination does not appear to be related to the WestKingston/URI site.

Aldicarb has been classified by EPA as Not Classifiable as toCarcinogenicity (13). There is inadequate or no data aboutaldicarb's human and animal carcinogenicity. Therefore, cancerassociated with exposure to aldicarb will not be discussed inthis public health assessment.

ATSDR has not developed Minimum Risk Levels for aldicarb. However, ATSDR staff members have estimated safe levels ofexposure to aldicarb based on the Reference Dose (RfD) developedby the EPA for chronic exposure (18). Those estimates indicateingesting water contaminated with aldicarb at levels found in twoprivate drinking wells may be a health concern if ingestionoccurs over many years. Levels of aldicarb contamination are notof concern for acute exposures. Because sampling for aldicarb inthe private wells occurred only once, it is not known if aldicarbis still in the private drinking water wells. City water is notprovided to those residents. Therefore, exposures may still beoccurring.

Because levels of aldicarb in public water supplies are low andthe duration of exposure is short, aldicarb contamination in thepublic water supply does not represent a public health concern.

EPA based the aldicarb RfD primarily on the following threestudies (18). These three studies all used exposure levelshigher than those associated with 12 ppb in drinking water. Therefore, adverse effects associated with the studies are notlikely to occur in people who drink aldicarb-contaminated waterat this site.

Studies of dogs indicate that exposure to aldicarb is associatedwith decreased levels of cholinesterase. Two acute human studiesexamined effects from one-time exposures. Those studies alsoindicate cholinesterase inhibition (18).

Cholinesterase is an enzyme that plays an important role innervous system functioning; insufficient cholinesterase may leadto diarrhea and other adverse intestinal effects, loss of musclefunction, and respiratory problems such as bronchoconstrictionand increased secretions into the lungs. The cholinesteraseinhibiting capability of pesticides such as aldicarb, however,has been shown to be reversible over time (19).

Several human studies indicate that aldicarb may be associatedwith compromised immune system function. One study thatindicated compromised immune system function included women whodrank water contaminated with aldicarb at levels only somewhathigher than those reported in this public health assessment (<61ppb) (20).

Because the exposure levels and durations of exposure to aldicarbare not known, ATSDR cannot evaluate with certainty whetherexposure to aldicarb at this site represents a public healthconcern.

B. HEALTH OUTCOME DATA EVALUATION

Because a small number of people were exposed to significantlylow levels of contaminants, and because that exposure has ended,ATSDR staff believe it is unlikely that anyone will developcancer because of that exposure. In addition, ATSDR staff areunaware of any recent community health concerns of the residents. ATSDR staff did not examine health outcome data because no knowneffects are expected. If new information becomes available, or ifnearby residents have health concerns about contaminantsassociated with the site, ATSDR will reconsider evaluating healthoutcome data.

C. COMMUNITY HEALTH CONCERNS EVALUATION

ATSDR staff are not aware of any recent community health concerns.



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