EAST MULTNOMAH COUNTY GROUND WATER CONTAMINATION
GRESHAM, MULTNOMAH COUNTY, OREGON
A. On-Site Contamination
Because the proposed National Priorities List (NPL) site incorporates the total known area ofgroundwater contamination and possible future migration of groundwater contamination, there isno off-site contamination. Therefore, this public health assessment will not have a separatesection for discussion of off-site contamination. This Environmental Contamination and OtherHazards section is divided into three subsections. The first subsection discusses theenvironmental contamination found at the sources of the groundwater contamination. Theenvironmental contamination found off the source properties is discussed in subsection two. Thelast subsection will discuss the contamination found in residential wells near the sources ofcontamination.
In order to determine what environmental contaminants might constitute a concern, the Agencyfor Toxic Substances and Disease Registry (ATSDR) staff has evaluated all availableenvironmental monitoring data from 1985 to present. Comparison values were used as a basis forevaluation of the data and to determine which contaminants should be looked at more closely. Comparison values are estimated health-based environmental concentrations below which noknown or anticipated adverse effect on the health of persons should occur. The values allowadequate margins of safety. Appendix 3 contains descriptions of the comparison values used inthis public health assessment.
A contaminant is selected for further evaluation if the contaminant concentration in a validenvironmental sample exceeds comparison values. The presence of a contaminant on the lists inthe tables of this section does not mean that either exposure to the contaminant or adverse healtheffects have occurred or will occur. Inclusion in the list indicates only that the potential forhuman exposures to the selected contaminants and the potential for adverse human health effectsas a result of any exposures to the selected contaminants are discussed in more detail in latersections of this public health assessment.
1. Environmental Contamination at the Sources of the Groundwater Contamination
To date, the U.S. Environmental Protection Agency (EPA) and the Oregon Department ofEnvironmental Quality (ODEQ) have identified three sources of the groundwater contamination:Boeing Company, Cascade Corporation, and Swift Adhesives (1,4). Environmental investigationsat each facility have identified several causes for the groundwater contamination. At the Boeingfacility, waste material from Boeing and other former owners/operators at the property had beendisposed of at various locations. The Boeing Company is remediating both the Troutdale GravelAquifer (TGA) groundwater contamination and the sources of contamination (i.e., pumping andtreating the contaminated groundwater and soil remediation) at its facility (5-7).
Leaking underground storage tanks and the former degreasing operations were the main sourcesof environmental contamination at the Cascade Corporation facility (8-14). The contaminationfrom underground storage tanks and the degreasing operations are being remediated (i.e., removalof the contaminated soils and tanks and pumping and treating the contaminated TGA groundwater are underway).
The cause of the environmental contamination at the Swift Adhesives plant was land disposal ofwaste adhesives (15-17). These wastes were removed in 1990. Swift Adhesives is presentlyevaluating methods of remediating the groundwater contamination found at and near its facility.
The environmental investigations have identified the extent of contamination at the three facilities. Appendix 4, Tables 1, 2, and 3 present the results of the investigations for the Boeing Company,Cascade Corporation, and Swift Adhesives, respectively. Environmental samples taken at thesefacilities were checked for all of the compounds on the EPA Target Compound List. Onlychlorinated organic solvents (i.e., 1,2-dichloroethane; 1,1-dichloroethylene; cis-1,2-dichloroethylene; tetrachloroethylene; 1,1,1-trichloroethane; trichloroethylene [TCE]; and vinylchloride) were detected above health comparison values (5-17).
Chlorinated organic solvents have been detected in the soils and groundwater at each facility. Most of the soil contamination is located several feet below the ground surface and is generallynot accessible to people unless the soil is excavated (5-17).
Because most of the waste materials and the leaking storage tanks were buried, surface soilcontamination is unlikely.
Analytical results of groundwater samples taken at the Boeing Company and CascadeCorporation facilities indicate that the contamination has migrated into the two uppergroundwater regional aquifers in Multnomah County (i.e., the TGA and the Troutdale SandstoneAquifer [TSA]) (5-14). The results of the groundwater investigations at the Swift Adhesivesfacility indicate chlorinated organic solvents have not entered the regional aquifers but havemigrated into a local perched aquifer (localized lens of groundwater which is separated from aregional aquifer) (15-17).
Cascade Corporation formerly had a well at its facility. The groundwater obtained from this wellwas used for process water; it was never used as a source of drinking water (8). Analytical resultsof samples taken from this well indicated that TCE was in the well (upwards of 410 microgramsof TCE per liter of water [µg/L]). This well was abandoned.
There are no bodies of surface water at any of the source areas. Therefore, surface water andsediment samples were not taken. Because no foodstuff is grown or produced at these facilities,biota samples were not taken.
No ambient air samples were taken at the three source facilities. Air monitoring (e.g., monitoringusing Hnu or other portable air monitoring equipment) was conducted during the siteinvestigations. The monitoring activities did not detect any significant air contamination at thesefacilities (5-17).
A preliminary environmental investigation at the Firestone facility (see Appendix 1, Figure 1 forlocation) indicates that there might be some groundwater contamination at that location (4). Based on the Swift Adhesives investigation and the spatial distribution of contaminants atFirestone, it is unlikely that the source of the detected contaminants at Firestone are from anupgradient source. Monitoring of downgradient wells of this facility have not shown anycontamination.
2. Environmental Contamination Beyond the Property Lines of the Sources
Appendix 4, Tables 4, 5, and 6 present the results of the environmental investigations conductedaway from the three known sources of groundwater contamination within the proposed NPL site(Boeing Company of Portland, Cascade Corporation, and Swift Adhesive, respectively) (5-17). These results indicate that the groundwater contamination found at the three facilities has movedbeyond the property lines (see Appendix 1, Figure 3).
The groundwater contamination that originated from the Cascade Corporation facility has movedtowards the north, northeast and northwest. The northwest portion of the Cascade groundwatercontamination has moved onto and beyond the property of the Boeing Company. Thegroundwater contamination that originated from the Boeing Company has mixed with theCascade groundwater contamination (5-14). Appendix 1, Figures 2 and 3 depict the approximateextent of groundwater contamination within the regional groundwater aquifers at the proposedNPL site. The groundwater contamination from Swift Adhesive facility is not depicted inAppendix 1, Figures 2 and 3 because the groundwater contamination from the Swift Adhesive hasnot moved into the regional aquifer system.
Surface water samples have been taken from the two springs near the Cascade facility, from thedrainage ditch near the Cascade facility, and from the Columbia Slough near the Boeing facility. Sediment samples were also taken from the drainage ditch and the Columbia Slough (5-14). Noenvironmental contaminants were detected above health comparison levels in the sediment andsurface water samples taken from the drainage ditch near the Cascade facility (8-14). Chlorinatedorganic solvents above health comparison values were detected in the surface water samples takenfrom the springs and the Columbia Slough (see Appendix 4, Tables 4 and 5) (5-14). No soilcontamination was found beyond the property lines of the sources (5-17).
The Boeing Company and Cascade Corporation are evaluating methods of remediating thegroundwater contamination that has migrated from their facilities.
3. Residential Well Contamination
Residential wells located near the three sources of groundwater contamination have been sampled(4-7,11-13). A detailed well inventory has been conducted by ODEQ, Boeing Company, andCascade Corporation. Analytical results of these samples indicate that TCE andtetrachloroethylene have migrated into some wells at levels above comparison values (seeAppendix 4, Table 7).
The highest residential well contamination was found near (northeast) and downgradient of theCascade Corporation facility (i.e., TCE as high as 105 µg/L). Contaminated residential wellsdowngradient of the Boeing Company are reported to have TCE as high as 40 µg/L (7). Thereare no contaminated residential wells near the Swift Adhesive facility.
B. Quality Assurance and Quality Control
ATSDR was able to obtain quality assurance and quality control (QA/QC) information for mostof the data presented in this public health assessment. This information indicates appropriateQA/QC was performed for the samples. The conclusions presented in this public healthassessment are based in part on the data presented. The validity of the conclusions, therefore,depends on the accuracy and reliability of the data provided.
C. Physical and Other Hazards
D. Review of Toxic Chemical Release Inventory (TRI) Data
To identify facilities that might contribute to the environmental contamination within the proposedEast Multnomah County Groundwater Contamination NPL Site and to determine whether peoplemaybe exposed to hazardous substances in addition to their possible exposures from theproposed NPL site, ATSDR searched the 1987-1991 files of the Toxic Chemical ReleaseInventory (TRI) databases for site-related contaminants being discharged within the proposedNPL site (18). TRI was developed by the EPA from chemical release (air, water, and soil)information provided by certain industries.
Several limitations of TRI data should be noted (19). The air release data in TRI could beestimates or actual measurements. Many of the reported data are estimates based on conservative(overestimated) scenarios. Consequently, the levels of emissions recorded in TRI are often biasedon the high side. In addition, reporting is restricted to specific chemicals that are used or releasedabove specified amounts. Finally, investigators believe there have been and still are industries thatdo not report releases. Representatives of smaller industries might not be aware that reportingrequirements exist or that they are responsible for such reports.
The search of TRI indicates that only one facility within the proposed NPL site has released site-related chemicals to the environment (18). For the five years for which TRI data were evaluatedand available, the Boeing Company reported that it released an average of 157,653 pounds of1,1,1-trichloroethane per year to the ambient air. The significance of this emission is discussed inthe Potential Pathways section of this public health assessment.
In this section of the Public Health Assessment, the possible environmental exposure pathways areevaluated to help determine whether individuals have been, are, or will be exposed to site-relatedcontaminants. The pathway analysis consists of five elements:
- identifying contaminants of concern possibly related to the site;
- determining that contaminants have been, are being, or will be transported through anenvironmental medium;
- identifying a point of exposure (i.e., a place or situation where people might be exposed to thecontaminated media);
- determining that there is a plausible route of human exposure (i.e., can the contaminant enterthe body?); and
- identifying an exposed population (i.e., how many people, if any are at the point of exposure).
An environmental exposure pathway is considered complete when there is good evidence that allfive elements exist (20). The presence of a completed pathway indicates that human exposure tocontaminants has occurred in the past, is occurring, or has the potential to occur in the future. When one or more of the five elements of an exposure pathway are missing, that pathway isconsidered potential. The presence of a potential exposure pathway indicates that humanexposure to contaminants could have occurred in the past, could be occurring, or could occur inthe future. An exposure pathway can be eliminated from consideration if at least one of the fiveelements is missing and will never be present. If there is uncertainty about the site-relatedness ofthe contaminants of concern in an exposure pathway, the pathway will be evaluated as if thecontaminants were site-related.
The completed, potential, and no known environmental exposure pathways are discussed below. In addition, Tables 1 and 2 in Appendix 5 present the estimates of the number of exposedindividuals at the proposed East Multnomah County Groundwater Contamination NationalPriorities List (NPL) site. The population estimate for the completed environmental exposurepathway was developed by using a computer geographic information system (GIS). Theapproximate extent of groundwater contamination (Appendix 1, Figure 3) was digitized andcorrelated to the 1990 U.S. Census information. The results of the GIS analysis is presented inAppendix 1, Figure 5.
A. Completed Environmental Exposure Pathways
There is good evidence that people have been, are being, and can be exposed (ingestion,inhalation, and skin contact) to site-related contaminants via residential drinking water wells. Analytical results of environmental samples taken from the regional groundwater aquifers(Troutdale Gravel Aquifer [TGA] and Troutdale Sandstone Aquifer [TSA]) indicate that variouschlorinated organic solvents have moved beyond the property boundaries of the Boeing Companyand Cascade Corporation facilities. Many residences near these facilities obtained their drinkingwater from the regional groundwater aquifers via private wells. Analytical results of samplestaken from the private wells show that trichloroethylene (TCE) and tetrachloroethylene havemigrated into some of the wells at levels above health comparison values.
Because of the complex hydrogeology within the proposed NPL site, it is not possible todetermine precisely when each well became contaminated. Because of the total extent ofgroundwater contamination (see Appendix 1, Figure 2), the average linear velocity ofgroundwater within the TGA and TSA aquifers (0.1 to 2.3 feet per day and 0.07 to 0.3 feet perday, respectively), and the fact that the industrial operations have been conducted at the BoeingCompany and Cascade Corporation facilities since the 1963 and 1953 respectively, it is possiblethat the drinking water wells near the Boeing Company and Cascade Corporation facilities mighthave been contaminated for more than 10 years. No matter when TCE and tetrachloroethyleneentered the residential drinking water wells, it is likely that the initial concentrations would havebeen well below health comparison values (i.e., 3 micrograms of TCE per liter of water [µg/L]and 0.7 µg/L for tetrachloroethylene) (5). The TCE and tetrachloroethylene residential drinkingwater well concentrations would have slowly increased over time until the concentrations in someof the well water reached the levels detected recently (a maximum of 105 µg/L for TCE and 3µg/L for tetrachloroethylene) (see Appendix 4, Table 7).
Most of the people with contaminated wells have been given alternative drinking water sources. However, two homeowners have refused to accept alternative drinking water and might still beobtaining drinking water from the contaminated well they jointly use. Until the regionalgroundwater contamination is remediated, the level of contamination in the well is likely toincrease over time, because higher concentrations of site-related contaminants have beenmonitored upgradient from this well. The complex hydrogeology within the proposed NPL sitemakes it difficult to predict how high the level of contamination in the well might become. Groundwater samples from monitoring wells upgradient from this contaminated well indicate thatTCE contamination of around 100 µg/L is near this well. Therefore, it is possible that thecontamination in this residential well may eventually become contaminated with TCE at that level.
Nineteen wells have been shown to be contaminated. In addition, Boeing Company and itspredecessors operated two production wells that were used for drinking water supply prior to1986.
It is estimated that 1,076 people live within the area that encompasses the approximate extent ofgroundwater contamination (see Appendix 1, Figure 5). These people might have been exposed to site-related contaminants if they obtained drinking water from private or trailer park wells. This estimate is probably an overestimation of the exposed population because not everyone wholived within the groundwater contamination area relied upon wells for their drinking water.
Only two families have chosen to continue using water from a well known to be contaminated atlevels of public health concern. These are the only persons known to have ongoing exposure tocontaminated water at levels of public health concern.
There are several private wells in use that have detectable levels of TCE (below healthcomparison values). In addition, the mobile home park wells are possibly being used for irrigationwater and for swimming pool water. Human exposures to contaminated water from these wellsare not likely to be at levels of health concern.
B. Potential Environmental Exposure Pathways
There are five environmental exposure pathways through which people could have possibly beenexposed to site-related contaminants. People could possibly be exposed to site-relatedcontaminants because of future migration of contaminated groundwater into drinking water wells,worker exposures, contaminated subsurface soil being disturbed, discharges to the ambient air,and surface water contamination.
1. Future Groundwater Migration
Three wells for the City of Portland's backup water system are downgradient of the contaminatedgroundwater areas (i.e., wells that withdraw water from the TSA or SGA). Analytical samplingresults of these wells indicate the wells are not presently contaminated with site-relatedcontaminants. Pumping tests of these wells indicate that site-related contaminants could possiblymigrate into the city wells if these wells are used for an extensive period of time (years) and theareas of groundwater contamination are not controlled or remediated. The City of Portland wellsin the TSA and SGA are not now being used as a drinking water supply.
In addition to the City of Portland wells, there are several residential and small community wells(West Interlachen Corporation, Interlachen Corporation, and the Blue Lake Co-op) downgradientof the contaminated groundwater areas. These wells could also become contaminated with site-related contaminants if the areas of groundwater contamination are not controlled or remediated. Analytical results of samples taken from these wells indicate the wells are not contaminated withsite-related compounds and are not contaminated with any other chemical at levels of healthconcern.
If these wells are used and become contaminated, people could be exposed in the future to site-related contaminants at levels of public health concern via ingestion, inhalation, and skin contact.
EPA, the Oregon Department of Environmental Quality (ODEQ), Boeing Company, and CascadeCorporation are evaluating ways to control and remediate the areas of groundwatercontamination, and have taken interim measures to control migration while the city of Portlandpumps from supply wells that only withdraw water from the Blue Lake Aquifer. (Note: Pumptests indicate that it is unlikely that the contaminants will enter the Blue Lake Aquifer.)
According to EPA, 750,000 people use the affected groundwater aquifers for standby or as theirprimary drinking water sources. If the groundwater contamination is not remediated or controlledand if the TSA and SGA City of Portland supply wells are used, there is the potential that thesewells could be contaminated and all of the people could possibly be exposed to some site-relatedcontaminants.
2. Worker Exposures
When waste materials were disposed of at the Boeing Company, Cascade Corporation, and SwiftAdhesive facilities, workers could have been exposed via ingestion, inhalation, and skin contact inthe past to chlorinated organic solvents. The extent of exposure would depend upon whatpersonal protection equipment (e.g., gloves, protective clothing, and respirator) the workerswore; the length of contact; and the amount of waste material ingested, inhaled, and accumulatedon the skin. The Agency for Toxic Substances and Disease Registry (ATSDR) does not haveadequate information to estimate how extensive the occupational exposures might have been.
In addition to material handling, waste disposal, and other occupational exposures, workers at theBoeing Company and Cascade Corporation facility might have inhaled site-related contaminantsfound in the Boeing Company and Cascade Corporation industrial wells. Depending on how thewell water was handled inside the plants, the chlorinated organic solvents in the well water couldhave volatilized into the work areas of the plants. ATSDR does not have adequate information toestimate how extensive the exposures might have been.
Boeing Company of Portland and Cascade Corporation are pumping contaminated groundwaterout of the ground at their facilities. The contaminated groundwater is being treated by an airstripping process at each facility. This air stripping process results in the emission of chlorinatedorganic solvents into the air. Workers at these facilities could inhale these air contaminants. Evaluations conducted by Boeing Company and Cascade Corporation indicate that the airstrippers are discharging at levels below regulatory limits. Although the levels are belowregulatory limits, the workers are presently being exposed to low levels of chlorinated organicsolvents in addition to the exposures from the past. ATSDR is not able to evaluate the publichealth implications of the continued low level inhalation exposure to workers exposed in the pastto higher concentrations of chlorinated organic solvents from drinking water because the scientificinformation concerning this type of exposure situation is not clear.
3. Subsurface Soil
Analytical results of soil samples taken at the Boeing Company, Cascade Corporation, and SwiftAdhesive facilities indicate that subsurface soils were contaminated with chlorinated organicsolvents above health comparison values. Individuals could have been exposed via inadvertentconsumption, inhalation (i.e., dust), and skin contact with the contaminated soil whenever thesesoils were excavated or disturbed. Because of the inadvertent nature of these possible exposurepathways and because the subsurface soils are not disturbed frequently, it is unlikely that peoplehave been exposed to any significant amounts of site-related contaminants above levels of healthconcern from soil.
4. Ambient Air
A search of the EPA Toxic Chemical Release Inventory (TRI) database indicates that the BoeingCompany released approximately 157,653 pounds (average) of 1,1,1-trichloroethane per year intothe ambient air during the years 1987 through 1991. People living near the Boeing facility mighthave inhaled and might still be inhaling some of the 1,1,1-trichloroethane being released to theambient air. This possible exposure route is in addition to the drinking water exposures tochlorinated organic solvents. Because no ambient air monitoring data is available, ATSDR is notable to determine the extent of human exposure associated with this air discharge.
5. Surface Water
Environmental samples taken from the Shepard Spring, the Taggart Spring, and the ColumbiaSlough indicate that chlorinated organic solvents (see Appendix 4, Tables 4 and 5) have migratedfrom the groundwater into these bodies of water. Neither the springs nor the slough are currentlybeing used as a drinking water source. The Shepard Spring was used in the past to waterlivestock. The Columbia Slough has been and is being used for recreation. People couldpotentially have been exposed, could be exposed now, and could be exposed in the future to thesurface water contaminants via inadvertent consumption and inhalation of the surface water andskin contact with the water or volatilized solvents. However, these exposures are not likely tooccur very frequently and are not likely to result in exposures to any significant amounts of site-related contaminants above levels of health concern.
C. No Known Environmental Exposure Pathways
None of the chlorinated organic solvents detected at the proposed East Multnomah CountyGroundwater Contamination NPL site accumulate in animals or plants (21-27). Therefore, it isunlikely people will be exposed to foodstuffs contaminated with site related contaminants.
PUBLIC HEALTH IMPLICATIONS
As discussed in the Pathways Analyses section, the residential drinking water wells exposurepathway is considered completed (i.e., human exposure occurred or is occurring) for persons whoused or use contaminated wells. The contaminants of concern - those detected above comparisonvalues - in this pathway are trichloroethylene (TCE) and tetrachloroethylene. No othernonoccupational exposure pathways are apparent for persons living in the affected area.
The Toxicological Evaluation portion of this section discusses the possible health hazard frompast and future exposures to the two contaminants of concern in the residential drinking waterwells. The community health concerns are addressed in the Community Health ConcernsEvaluation section. The reasons that health outcome data were not evaluated are discussed in theHealth Outcome Data Evaluation section.
A. Toxicologic Evaluation
Typically, the toxicological evaluation in a public health assessment is a comparison of theexposure dose - the amount of a substance individuals in an exposure pathway are exposed todaily - to an appropriate health guideline. For noncarcinogens, this is usually the Agency forToxic Substances and Disease Registry's (ATSDR's) Minimal Risk Levels (MRLs) or the U.S.Environmental Protection Agency's (EPA's) Reference Doses (Rfds). The MRLs and Rfds areestimates of daily human exposure to a contaminant below which noncarcinogenic adverse healtheffects are unlikely to occur (20). That means that any exposure dose below the appropriateMRL or Rfd does not represent a hazard to human health excluding cancer risks. However, forexposure doses above an MRL or Rfd, there is a wide zone of uncertainty whether adverse healtheffects will occur. Therefore, a review of the toxicological literature is done to determine whetherthe specific exposure situation represents a hazard to public health. The results of the comparisonof exposure doses to health guidelines and the methodology for calculating the exposure doses aredescribed in Appendix 6.
Adults and children exposed to the maximum levels of TCE (105 micrograms of TCE per liter ofwater [µg/L]) in the residential drinking water did not exceed the intermediate health guidelines(exposure durations of 15 through 364 days). However, there is some indication from recentstudies that health effects from exposures of more than a year might occur at the TCE levelsfound in the residential drinking water supply. Because of this, the possible health consequencesof exposure to TCE will be discussed in the next subsection. In addition, the limitations of therecent studies will be discussed.
Adults and children exposed to the maximum levels of tetrachloroethylene (3 µg/L) in residentialdrinking water did not result in human exposres that exceed the chronic health guidelines. Therefore, it is unlikely that adverse health effects would occur to people exposed totetrachloroethylene contaminated residential drinking water.
TCE and tetrachloroethylene are considered probable human carcinogens (28). The risk ofcarcinogenic health effects from TCE and tetrachloroethylene exposure was evaluated using themethods described in Appendix 6. Based on this evaluation, the past exposures to TCE andtetrachloroethylene in the residential drinking water wells represents no apparent increased risk ofcancer. However, two homeowners are presently using a contaminated drinking water well andhave refused alternative drinking water supplies. It is possible that the amount of TCE andtetrachloroethylene will increase in the well. Thus, people ingesting the contaminated water fromthe well might have a low increased risk of developing cancer.
2. Discussion of Possible Health Consequences
The possible health consequences of exposure to TCE are described in the following paragraphs.
Health assessors determine the possibility of health consequences by comparing the exposure tothe results of epidemiologic evaluations of human exposures to a chemical. If valid human dataare not available, information from properly conducted animal studies is used. The type of dataused for an evaluation is indicated for each chemical.
Several recent studies of individuals exposed to TCE in drinking water identified several healtheffects which had rates greater than rates in comparison groups (29-34). The health effectsreported in those studies were stroke and impaired hearing (29); slowed eye blink response(30,31); several abnormal neurophysiological and neuropsychological parameters (31);impairment of the immune system (32); increased occurrence of the symptoms related to lupus(33); and congenital cardiac malformations (34). Those studies are discussed in this section.
When results were compared with results for respondents to the National Health InterviewSurvey, elevated rates for several health outcomes were found in participants in the ATSDR TCEexposure registry (29). These outcomes included (for various age and sex groups) speechimpairments, hearing impairments, hypertension, stroke, liver problems, anemia and other blooddisorders, diabetes, kidney disease, urinary tract disorders, heart conditions, and skin rashes. Onlythe rates for strokes and impaired hearing were related to the concentration of TCE. Theapproximately 4,300 participants in this registry were exposed to 2 to 19,380 µg/L of TCE indrinking water for up to 18 years. These results are limited by the lack of confirmation of thehealth conditions and less than complete identification of exposure levels. The results do notestablish a cause-and-effect relationship between exposure and adverse health outcomes.
Significantly slower eye blink responses were identified in TCE-exposed individuals fromWoburn, Massachusetts and Tucson, Arizona (30,31). Those slower responses were considered asubclinical effect (i.e., not harmful). The validity of these results is limited by the nonrandomselection of the participants and the lack of an identification of a dose-response relationship. Inaddition, a recent study of workers exposed for an average of 16 years to TCE concentrationsmany times stronger than those found in Arizona and Massachusetts found no change in the eyeblink response (35).
Impairment of the immune system was observed in TCE-exposed individuals from Woburn,Massachusetts (32). This immunologic impairment was evidenced by altered T-cell ratios (T-cells are a type of white blood cell), increased incidence of autoantibodies, increased infections, andrecurrent rashes. The validity of these results is limited by the nonrandom selection of theparticipants (they were all relatives of children who had leukemia) and the lack of identification ofa dose-response relationship.
Increased occurrence of the 10 symptoms used to diagnose lupus was identified in TCE-exposedindividuals from Tucson, Arizona (33). The validity of these results is limited by the non-randomselection of the participants and the lack of identification of a dose-response relationship.
Another study of the TCE contamination in Tucson found that the rate of total congenital cardiacmalformations was higher in the area where TCE-contaminated water was probably ingested thanin areas without TCE contamination. These results are limited by uncertainty about the extent ofthe contamination and the lack of information needed for evaluation of a dose-responserelationship.
The results of the studies reviewed indicate that further investigation of low dose TCE exposuresis needed. However, they do not offer any evidence about a cause-effect relationship betweenTCE exposure and specific health effects. Thus they do not offer any assistance in interpretingthe possibility of health consequences from the exposure to TCE in the East Multnomahresidential drinking water wells.
Based on studies of workers and laboratory animals, the past exposure to TCE in the proposedEast Multnomah County Groundwater Contamination National Priorities List (NPL) site arearesidential drinking water wells does not appear to be a high enough concentration to result innoncarcinogenic health effects (26).
B. Health Outcome Data Evaluation
In this section, the reasons why cancer data for Multnomah County were not evaluated arediscussed. In addition, the guidelines that ATSDR follows for evaluating information from healthoutcome databases are reviewed.
In a public health assessment, available health outcome databases are identified for the area nearthe site. From those data, ATSDR selects health outcomes for further evaluation based onbiological plausibility or community health concerns (20).
For biological plausibility, the decision to evaluate health outcome data depends on whether acompleted exposure pathway exists for a chemical suspected of causing the health outcome ofconcern (20). The selection of a noncarcinogenic health outcome is based on a review of thetoxicologic literature for that contaminant of concern.
When a contaminant of concern has been identified as a carcinogen, health outcomes for themajor anatomical sites are usually selected for evaluation (20). Designation of a chemical as acarcinogen (for purposes of health outcome data evaluation) is based on the following:
- classification by the National Toxicology Program (NTP)(1) in its Annual Report on Carcinogens as a "known human carcinogen" or "reasonably anticipated to be a carcinogen"; or
- classification by the International Agency for Research on Cancer (IARC)(2) as a 1, 2A, or 2B carcinogen; or
- classification by the United States Environmental Protection Agency (EPA)(3) as an A, B1, or B2 carcinogen; or
- classification by the United States Occupational Safety and Health Agency (OSHA).(4)
A latency period of at least 10 years between exposure and diagnosis has been observed in moststudies of human cancer (20). If exposure began less than 10 years before collection of the latest data available, analysis of health outcome data for cancer incidence or mortality is not likely to beuseful, particularly if the exposure level is low.
Even when health outcomes do not meet ATSDR's guidelines for biological plausibility, healthoutcome data can be evaluated as a basis for addressing community health concerns.
For the proposed East Multnomah County Groundwater Contamination NPL site, cancer isconsidered a biologically plausible health outcome for the following reasons:
- 1) TCE and tetrachloroethylene are considered probable human carcinogens (24,26) and
2) people were exposed to this contaminant in the residential drinking water-wells (i.e., they werein a completed exposure pathway) for more than 10 years.
Based on current scientific studies, developmental or birth defects are not considered biologicallyplausible health outcomes. Neither TCE nor tetrachloroethylene is strongly associated with thoseeffects (24,26).
The county was the smallest population unit for which health outcome data were readilyavailable. It would be impossible to detect any elevation of health outcomes that could possiblybe associated with site-related exposures because of the tremendous difference in populations(i.e., Multnomah County [570,000] vs. the exposed population [less than 1,076]). Therefore,cancer data for Multnomah County were not evaluated in this public health assessment.
C. Community Health Concerns Evaluation
The community health concerns identified during the public availability sessions are addressed asfollows:
Is the incidence of cancer elevated within the proposed NPL site?
- As discussed in the Health Outcome Data Evaluation section, it was not possible to identify thecancer occurrence rates for the area within the proposed East Multnomah County GroundwaterContamination NPL site using the databases available to ATSDR. An evaluation of theoccurrence of cancer should be conducted if data for the site area can be obtained.
Are the symptoms indicated by a mother related to the proposed NPL site?
- Of the reported symptoms--muscle aches and pains, fatigue, and headaches--only headaches andfatigue have been associated with exposure to TCE and the other contaminants known to be inresidential wells near the site (21-26). However, maximum exposure levels possible from the most contaminated wells in the area would not be sufficient to cause headaches or any other acutesymptom of illness. Therefore, it is unlikely that the reported symptoms resulted from contaminants known to be in the residential wells.
Can stillbirths and birth defects in horses be caused by the contaminants found in thespring water?
- There are no conclusive data linking TCE and tetrachloroethylene with birth defects andreproductive effects (stillbirths) in humans or animals (24,26). Therefore it is unlikely that the stillbirths and birth defects in horses resulted from exposure to TCE. For more information, see the discussion of TCE in the Toxicological Evaluation section.