PUBLIC HEALTH ASSESSMENT
DOWNERS GROVE GROUNDWATER INVESTIGATION
(a/k/a ELLSWORTH INDUSTRIAL PARK)
DOWNERS GROVE, DUPAGE COUNTY, ILLINOIS
Illinois Environmental Protection Agency (Illinois EPA) requested that the Illinois Department ofPublic Health (IDPH) evaluate data from an investigation of residential wells in Downers Grove,DuPage County, Illinois. This public health assessment contains IDPH's determination ofwhether current conditions pose a public health hazard.
The village of Downers Grove is in suburban DuPage County, 25 miles west of Chicago(Attachment 1). Most of the homes in this 50,000-member community are connected to a publicwater supply. Residents in several unincorporated areas within the village use private wells astheir water sources.
A recent public health assessment for residential wells in the nearby community of Lisle includedsampling eastward toward Downers Grove (1). In the spring of 2001 Illinois EPA began agroundwater investigation east of Interstate 355 near Downers Grove. In April and May 2001, inresponse to community concerns about the private well sampling in Lisle, IDPH also collectedgroundwater samples from residential wells. Results of the samples showed contamination insome of the private wells. The contamination west of I-355 was mainly trichloroethylene (TCE),but both TCE and tetrachloroethylene (PCE) were found east of I-355, in Downers Grove.Because these results suggested differing sources of contamination, Illinois EPA initiated aseparate investigation to identify contaminated wells and potential sources of contamination inDowners Grove (2).
In July 2001, Illinois EPA began sampling residential wells in southwestern Downers Grove andhas since tested about 525 residential wells. Because several wells were found to contain one ormore volatile organic compounds (VOCs), IDPH sent letters to residents, providing them with ahealth interpretation of the analytical results for their well water samples. These letters alsooffered guidance on how residents could reduce their exposure to the chemicals in their wellwater. The contaminated wells found so far are in an area extending from near I-355 east to LeeAvenue and from Inverness Avenue south to 63rd Street (Attachment 1).
About 200 wells (38%) contained TCE, PCE, or both chemicals at concentrations greater than the USEPA drinking water standard of 5 micrograms per liter of water (µg/L) for each chemical. The remaining wells had levels of TCE, PCE, or a combination of the two chemicals less than the drinking water standards or had no detectable levels of either chemical. The highest levels of TCE and PCE detected were 16.6 µg/L and 12.1 µg/L, respectively. The highest combined level of TCE and PCE was 18.6 µg/L. Low levels of 1,1,1-trichloroethane (TCA) were also found in 153 samples.
In September 2001, IDPH began assisting Illinois EPA with well sampling efforts. Illinois EPAdistributed information on how residents would be notified of their well water results. Thisincluded an IDPH letter and fact sheets explaining the possible health effects of exposure to TCEand PCE. On October 11, 2001, public availability sessions were held at the Downers GrovePublic Works office to discuss the groundwater investigation with residents. Personnel fromIDPH were present along with representatives from other agencies and organizations.
The U.S. Environmental Protection Agency (USEPA) joined the groundwater investigation inDecember 2001 to help Illinois EPA determine the contamination source in Downers Grove.Sampling efforts targeted the Ellsworth Industrial Park as a source of the contamination. USEPAand Illinois EPA installed more than 40 monitoring wells in the area and have used a Geoprobe®to collect soil borings and groundwater samples from various depths. Investigation results led ,USEPA and Illinois EPA to conclude that Ellsworth Industrial Park is the source of thegroundwater contamination (2).
In August 2002, USEPA and Illinois EPA notified 14 businesses and a public utility in theEllsworth Industrial Park area that they might potentially be liable for the groundwatercontamination. On October 15, 2002, USEPA notified 20 businesses, public entities andindividuals in Ellsworth Industrial Park that they had 60 days to provide a good faith offer toaddress the groundwater contamination problem. Also in October 2002, a group of homeownersfrom unincorporated Downers Grove with contaminated wells notified 10 businesses in theEllsworth Industrial Park that the homeowners intended to sue them for contaminating theirdrinking water (2).
In January 2003, to help cover a large portion of the costs associated with connecting affectedhomes to a public water supply, a state grant was awarded to the village of Downers Grove.Construction of the water mains is expected to begin in Spring 2003.
IDPH compared the results of each groundwater sample collected with the appropriatecomparison values (CVs) to select chemicals for further evaluation for exposure and possiblecarcinogenic and noncarcinogenic health effects. Chemicals found at levels greater than CVs orthose for which no CVs exist were selected for further evaluation. The types of CVs used in thishealth assessment are discussed in Attachment 2. IDPH assumed that the samples were collectedand handled properly and that appropriate analytical techniques were used. The chemicals ofinterest are TCE and PCE.
Residents who use private well water with TCE or PCE present, either individually or incombination, are exposed to these chemicals by drinking the water, inhaling the chemicals duringshowering or bathing, and by skin contact with the water. The potential for exposed persons toexperience adverse health effects depends on
- the specific chemicals to which a person is exposed,
- the concentration of the chemicals present,
- the length of time a person is exposed, and
- the health condition of the person exposed.
IDPH used exposure scenarios based on adults drinking 2 liters (about 2 quarts) of water per dayand children drinking 1 liter (about 1 quart) of water per day. We also assumed residents would beexposed to the chemicals while bathing and showering.
TCE and PCE each have a maximum contaminant level (MCL) of 5 µg/L. To reduce the chances of adverse health effects from drinking contaminated water, USEPA has established MCLs for public water supplies. The standards are well below levels for which health effects have been observed. MCLs are enforceable limits that public water supplies must meet.
TCE and PCE are closely related chemicals with similar health endpoints and the same MCL. In our review of residential well data, IDPH considered any individual or combined level of these chemicals greater than 5 µg/L to exceed the MCL. The highest combined TCE-PCE level found was 18.6 µg/L.
The highest level of TCE detected in a private well was 16.6 µg/L. IDPH estimated the dose of TCE for children and adults exposed to groundwater containing 16.6 µg/L and found that exposure to that level of TCE might pose a very low increased cancer risk.
The estimated exposure to children and adults is less than the USEPA reference dose. A referencedose is an estimate of a daily exposure to the human population that is not likely to cause adversehealth effects during their lifetime.
The updated toxicological profile for TCE (3) included studies of humans exposed to low levelsof TCE in drinking water. These studies suggested that adverse health effects might include skinrashes, liver problems, urinary disorders, anemia and other blood disorders, and diabetes. Theestimated exposure for Downers Grove residents is less than the USEPA reference dose, so theseeffects are considered unlikely to occur.
Recent studies in Massachusetts and New Jersey suggested elevations in childhood leukemia,neural tube defects, oral cleft defects, respiratory defects, eye defects, and small-for-gestational-age effects can be associated with TCE in drinking water. The Massachusetts studies have severallimitations, however, including the presence of other contaminants and the small sample size (3).Studies in Tucson, Arizona, suggested an elevation in heart defects and low birth weightsassociated with TCE in drinking water. A study at Camp LeJeune, North Carolina, suggested anelevation in males-small-for-gestational-age associated with TCE in drinking water. But thelevels of TCE in drinking water in these studies were several times greater than the levels detectedin Downers Grove (4,5,6).
In the mid-1990s, USEPA withdrew the reference dose and cancer potency factor for TCE forreview. To evaluate the potential health hazards of exposure to TCE in Downers Grove, IDPHused information from human and animal studies, the former cancer potency factor, and thecurrent MCL for TCE. In August 2001, USEPA released a draft toxicological reassessment ofTCE for comment. Although the data in the reassessment have not been yet adopted as USEPApolicy, the proposed cancer potency factor would be greater than before. Using the proposedcancer potency factor, IDPH estimated that persons exposed to TCE at levels greater than thecurrent MCL could experience a low increased risk for liver and kidney cancer. If USEPA adoptsthe proposed cancer potency factor, the agency also might re-evaluate the current MCL for TCE.
The highest level of PCE detected in a private well was 12.1 µg/L. IDPH estimated the dose of PCE for children and adults exposed to groundwater containing 12.1 µg/L and found that exposure to that level of PCE might pose a very low increased cancer risk.
The estimated exposure to children and adults is less than the USEPA reference dose. A reference dose is an estimate of a daily exposure to the human population that is not likely to cause adverse health effects during their lifetime. The health effects of breathing PCE in air or drinking water with low levels of PCE are not well established. Results of animal studies, conducted with amounts much higher than those found in the Downers Grove well water samples, suggest that PCE can cause liver and kidney damage as well as liver and kidney cancers (7).
On October 11, 2001 and September 4, 2002, public availability sessions were held in DownersGrove to give residents an opportunity to comment on the site evaluation, ask questions, andexpress their health concerns. IDPH participated in these sessions along with representatives fromthe Agency for Toxic Substances and Disease Registry, the Village of Downers Grove, theDuPage County Health Department, the Water Quality Association of Lisle, and Illinois EPA.
Many area residents who attended the public availability sessions expressed anger about the highcost of connecting to the Downers Grove public water system. Depending on the home, the costcould be greater than $10,000.
Previously, the village of Downers Grove put water main pipes in most of the affected area withthe agreement that homeowners would eventually be annexed to the village. The village watermanager has stated that the annexation deadline is in 6 to 8 years. Many homeowners have soughtannexation because of the well contamination. Part of the affected area does not have water mainpipes in place. Approximately half the homeowners in that area have signed a petition to beannexed to the village.
Many area residents have ignored or refused offers by Illinois EPA to test their wells for thepresence of contaminants. It is possible that some residents fear their property values will decreaseif they are asked to disclose the presence of contaminants in their well water.
At public availability sessions, some residents alleged that the Illinois EPA Bureau of Water andthe DuPage County government knew that the Belmont Highwood Water District wells werecontaminated with VOCs in the late 1980s and early 1990s. They also alleged that private wellowners in the area were not informed. Illinois EPA stated that public water systems were notrequired to test for VOCs until 1990. After VOCs were detected in 1992, the Belmont HighwoodWater District would have been required to notify only their end users of the presence of VOCs inthe water. Also, Illinois EPA prepared a Well Site Survey Report summarizing this informationand provided the report to DuPage County. Illinois EPA was unaware of private wells in the area.Due to the ineffectiveness of the previous notification process, new legislation was drafted byIllinois EPA in consultation with IDPH. New statewide procedures are now in place to make surethat private well owners are notified of known groundwater contamination in their area. SenateBill 2072 was enacted in July 2002 by which Illinois EPA notifies IDPH about public water wellcontamination. IDPH then works with the local health department to notify private will owners ofpotential groundwater contamination in the area of their wells.
Residents also had general questions about the health effects associated with TCE and PCE, andexpressed concern about cancer rates.
A copy of the draft public health assessment for the Downers Grove Groundwater Investigationsite was available for public review and comment at the Downers Grove Public Library at 1050Curtiss Street in Downers Grove, Illinois from November 17, 2002 to January 3, 2003. Comments received can be found in Attachment 4.
The IDPH Division of Epidemiologic Studies reviewed the incidence of cancer for DownersGrove ZIP codes 60515 and 60516 from 1989 to 1998 (Attachment 3) The rate of kidney and livercancers combined was less than the expected number of cases (78 cases observed and 90 casesexpected). No other biologically plausible type of cancer related to TCE or PCE exposure was statistically significant (8).
IDPH recognizes that children are especially sensitive to some contaminants. Children get a larger dose from drinking contaminated water than adults because they drink more water per kilogram of body weight than do adults. IDPH includes children when evaluating exposures to contaminants and considers children the most sensitive population evaluated in this public health assessment. The doses children experienced by drinking contaminated well water were not at levels known to cause noncarcinogic health effects. Long-term exposure to TCE and PCE could pose a very low increased cancer risk. The findings of studies done in Massachusetts and New Jersey suggested that childhood leukemia and adverse birth outcomes were associated with exposure to TCE during gestation (4,5,6). The TCE concentrations found in drinking water in these studies were several times greater than levels found in Downers Grove.
About 200 wells (38%) contained TCE and PCE at levels greater than the USEPA drinking water standard (MCL) of 5 µg/L for each chemical. Because the MCLs for TCE and PCE in drinking water are considered to be protective of public health, prudent public health practice supports considering exposure to contaminated groundwater in Downers Grove a public health hazard.
Based on the information currently available, IDPH also concludes that while long-term exposureto contaminated well water could pose a very low increased cancer risk, no health studies areavailable definitively associating an adverse health effect in animals or humans exposed to thelevels of TCE and PCE observed in Downers Grove.
A review of cancer incidence data indicated that kidney cancer and liver cancer have not occurredmore often than would be expected among residents within the ZIP code area. The cancer casesare distributed throughout the ZIP code area and are not clustered near the contaminated wells.Depending on future findings regarding the nature and extent of TCE and PCE contamination, anadditional evaluation could be considered.
Data are not yet available to help evaluate whether levels of TCE and PCE in private wells areincreasing over time. Should TCE or PCE levels increase, then long-term use of contaminatedgroundwater could result in a slightly increased cancer risk. Because other health effects fromlong-term use of drinking water with low levels of TCE and PCE contamination are not wellstudied, IDPH offers the following recommendations and public health action plan.
IDPH recommends the following:
- Residents with levels of VOCs greater than the MCL should seek a remedy to reduce orprevent future exposure to contaminated groundwater. Municipal water or a watertreatment unit meeting the National Sanitation Foundation standard number 53 forremoval of VOCs are two alternatives. IDPH has provided information through lettersand fact sheets distributed to residents before and after well sampling.
- Illinois EPA and USEPA should conduct sampling to determine the source of thegroundwater contamination. An investigation of Ellsworth Industrial Park is currentlyunderway.
- Public availability sessions should be held to provide health information to arearesidents. IDPH has met this recommendation by participating in public availabilitysessions in October 2001 and September 2002. Staff from IDPH, Illinois EPA, theDuPage County Health Department, and the Illinois Attorney General Office werepresent to answer questions from area residents, and to provide updates for the ongoinggroundwater investigation. IDPH will participate in future availability sessions asneeded.
Illinois Department of Public Health
Ken Runkle, Jennifer Davis
Illinois Department of Public Health
ATSDR Regional Representative
Office of Regional Operations
ATSDR Technical Project Officers
W. Allen Robison
Division of Health Assessment and Consultation
Division of Health Studies
Division of Health Education and Promotion
- Agency for Toxic Substances and Disease Registry. Public health assessment for LisleResidential Wells, Lisle, DuPage County, Illinois. Atlanta: US Department of Health andHuman Services; 2002 Aug.
- Illinois Environmental Protection Agency. Files concerning the groundwater contaminationinvestigation in Downers Grove, Illinois. Springfield, Illinois: Illinois EnvironmentalProtection Agency; 1985-2002 Oct.
- Agency for Toxic Substances and Disease Registry. Toxicological profile fortrichloroethylene (update). Atlanta: US Department of Health and Human Services; 1997Sep.
- Costas KS. A case-control study of childhood leukemia in Woburn, MA: the relationshipbetween leukemia incidence and exposure to public drinking water. Sci Total Environ. Inpress 2002.
- Cohn P, Klotz J, Bove F, et al. Drinking water contamination and the incidence of leukemia and non-Hodgkin's lymphoma. Environ Health Perspect 1994;102:556-561.
- Bove F, Shim Y, Zeitz P. Drinking water contamination and adverse pregnancy outcomes:A review. Environ Health Perspect 2002;110(supplement 1):61-74.
- Agency for Toxic Substances and Disease Registry. Toxicological profile fortetrachloroethylene (update). Atlanta: US Department of Health and Human Services; 1997Sep.
- Illinois Department of Public Health Division of Epidemiologic Studies. Incidence ofcancer in ZIP codes 60515 and 60616 of Downers Grove, Illinois, 1989-1998. Springfield,Illinois; 2001 Sep.
This Downer's Grove public health assessment was prepared by the Illinois Department of PublicHealth under a cooperative agreement with the Agency for Toxic Substances and Disease Registry(ATSDR). It is in accordance with approved methodology and procedures existing at the time the health consultation was begun.
W. Allen Robison
Technical Project Officer
Superfund Site Assessment Branch (SAAB)
Division of Health Assessment and Consultation (DAC)
The Division of Health Assessment and Consultation, ATSDR, has reviewed this healthconsultation and concurs with its findings.
Sven E. Rodenbeck
for Roberta Erlwein
Chief, State Programs Section
SSAB, DHAC, ATSDR
To reduce the chances of adverse health effects occurring from exposure to contaminated drinking water, maximum contaminant levels (MCLs) have been established by USEPA for public water supplies . These standards are well below levels for which health effects have been observed; they also take into account the financial feasibility of achieving specific contaminant levels. MCLs are enforceable limits that public water supplies must meet.
Lifetime health advisories for drinking water (LTHAs) have been established by USEPA fordrinking water. They are the concentration of a chemical in drinking water that is not expected tocause any adverse noncarcinogenic effects over a lifetime of exposure. LTHAs are conservative values which incorporate a margin of safety.
Prepared by the:
Division of Epidemiologic Studies
Illinois Department of Public Health
The Illinois Department of Public Health, Division of Environmental Health, contacted theDivision of Epidemiologic Studies, with a request to evaluate the cancer incidence in DownersGrove, DuPage County. They had received a report from the Illinois Environmental ProtectionAgency that some private wells in Downers Grove were contaminated with trichloroethylene andtetrachloroethylene which are both categorized by the International Agency for Research on Canceras reasonably anticipated to be human carcinogens. Dr. Tiefu Shen, Chief of the Division ofEpidemiologic Studies, initiated a study of the cancer incidence.
The study area was defined by the Division of Environmental Health as ZIP code areas60515 and 60516 of Downers Grove. All cases of cancer diagnosed among residents of the studyarea for the most recent ten years of complete data, 1989 through 1998, were identified. The sourcefor these data was the Illinois State Cancer Registry (ISCR). Identification of cancer cases in ISCRis dependent upon reporting by diagnostic and therapeutic facilities as mandated by state law.
In addition, ISCR has agreements with other central cancer registries to send back Illinoiscancer data which are identified outside the state. These registries include Arkansas, California,Florida, Indiana, Iowa, Kentucky, Michigan, Mississippi, Missouri, North Carolina, Washington,Wisconsin, Wyoming, Barnes-Jewish Hospital in St. Louis, and the Mayo clinic in Minnesota. Completeness of out-of-state reporting depends upon the years of operation of these other centralregistries, the extent of their identification of out-of-state residents, and their standards of quality.Out-of-state diagnoses among residents of the study area accounted for less than one percent of thetotal number of cases reported and were included in the study. Completeness of reporting from allreporting sources, assessed using the NAACCR Standard,1 is considered to be 95 percent completefor this time frame (1989-1998).
All cancer cases from the study area were grouped by tumor site, sex, and age. These arereferred to as the observed cases. Age- and sex-specific rates from a comparable population inIllinois were applied to each age group of the study population and to each tumor site to obtain anexpected number of cases for the study area.2 The comparable population was defined as an areawith a similar population density and race distribution as the study area. Population data wereobtained from the 1990 U.S. Census, the most reliable source for population counts by age and sexfor small areas.
The observed number of cases was compared with the expected number of cases. Based onthe Poisson model, a probability of 0.01 or less for an observed number of cancer cases that washigher or lower than the expected number was considered to be a statistically significantdifference.3
When a significant excess was identified, and when appropriate for the site in question,other data elements and risk factor data, as reported to ISCR, were reviewed. These may includestage of disease at diagnosis, tobacco and alcohol use, occupational information, morphologic typeof tumor, and location of residence within the study area.
When the observed number is less than six cases for a specific tumor site, the number isnot mentioned in this report to protect the privacy of individuals. If possible, the cases are groupedwith other sites within body organ systems, or when not possible, they are included in the All OtherSites category.
Results and Discussion
For all cancer sites combined, the incidence of cancer among males in the study area was1,283 cases with 1,318 cases expected. In females, 1,523 cases were observed while 1,585 caseswere expected. These differences were not statistically significant for either sex. In addition, noneof the differences between observed and expected numbers of cases for each site group wasstatistically significant. The numbers have been aggregated in the table to protect the privacy ofindividuals.
In drawing conclusions from these data, two aspects of the statistical method need to beaddressed. First, random fluctuations in disease occurrence cannot be completely ruled out inexplaining differences between the observed and expected numbers, even when the difference isstatistically significant.
The second aspect is the power of the statistical test, that is, the probability that a truedeparture from the expected number can be detected by significance testing. A non-significant difference sometimes reflects the low statistical power rather than the absence of differences. Thepower of a test varies with the number of cases expected.4 In the study area, the power of detectinga doubling was low in both sexes for cancers of the esophagus, liver and bone and for Hodgkin'slymphomas and myelomas.
In addition, the latency between the time of exposure and the onset of clinically-recognizable disease for most adult cancers is between 10 and 20 years. Specific cancers may varysomewhat in the length of the latent period, but generally speaking, recent exposure, that isexposures in the last 10 years, cannot be expected to be associated with current cancer incidence.The history of residency for cases included in the present study could not be assessed because thisinformation is not collected by the cancer registry, nor is such information available for the generalpopulation in the area.
Cancer is a common disease, sometimes more common than many people believe. In theU.S., one in two men have a lifetime risk of developing cancer. For women, the lifetime risk is onein three.5 The number of people with cancer is increasing in most communities because morepeople are living to the ages of greatest cancer occurrence.
Many people could reduce their chances of developing or dying from cancer by adopting ahealthier lifestyle and by visiting their physician regularly for a cancer-related checkup. Screeningexaminations, conducted regularly by a health care professional, can result in the detection ofcancers of the breast, tongue, mouth, colon, rectum, cervix, prostate, testis, and melanomas atearlier stages, when treatment is more likely to be successful. More than half of all new cancercases occur in the nine screening-accessible cancer sites listed above.5
Current knowledge suggests that the leading preventable cause of cancer is cigarettesmoking.6 Exposures to carcinogenic chemicals, ionizing radiation, and other agents produced byhumans is responsible for less than five percent of human cancers.6 Generally speaking, anypossible risk associated with the environment would most likely only have a small effect on cancerincidence relative to that of tobacco.5 The following table shows the best current estimates for thecauses of cancer.
|Causes of Cancer in the United States||Percent|
|adult diet and obesity |
|reproductive factors |
prenatal factors and growth
|environmental pollution |
ionizing and UV radiation
|viruses and other biologic agents |
prescription drugs and medical procedures
food additives and contaminates
family history of cancer
|Source: Harvard School of Public Health. Harvard Report on Cancer Prevention Volume 1: Causes of Human Cancer. Cancer Causes and Control. London: Rapid Science Publishers; 1996:Vol 7.|
- Data Evaluation and Publication Committee. NAACCR Standard to Assess theCompleteness of Case Ascertainment. Winter 1997 Newsletter. Sacramento, CA: NorthAmerican Association of Central Cancer Registries, November 1996.
- Mattson DE. Statistics: Difficult Concepts, Understandable Explanations. Oak Park, IL: Bolchazy-Carducci Publishers Inc; 1986:386-389.
- Gustafson TL. True Epistat Manual. Richardson, TX: Epistat Services; 1987:6-19.
- Selvin S. Statistical Analysis of Epidemiological Data (Second Edition). New York, NY: Oxford University Press; 1996:83-102.
- American Cancer Society. Cancer Facts and Figures - 2001. New York, NY: AmericanCancer Society; 2001.
- Lave L. Environmental regulation and policy making. In Schottenfeld D, FraumeniJF (eds). Cancer Epidemiology and Prevention. Philadelphia: WB Saunders Co;1996:1453-1470.
Illinois State Cancer Registry
Division of Epidemiologic Studies
Illinois Department of Public Health
|Cancer Site Group||Obs.||Exp.a||Obs.||Exp.a|
|Breast invasive |
Breast in situ
| 495 |
| 506 |
|All Other Sites||121||123||115||138|
SOURCE: Illinois State Cancer Registry, October 2000.
a Expected numbers are based on the age-and sex-specific incidence rates in an area of Illinois with a similar population density and race distribution as the study area.
Comment 1. On page 1 in the third paragraph of Background and Statement of Issues, it states that the northern boundary is Maple Avenue. This is incorrect. The affected area actually extends north to Inverness Avenue.
The text has been changed to indicate the correct northern boundary of the affected area.
Comment 2. Your report compares the incidence of cancer rates across the entirety of the ZIP code populations of 60515 and 60516 to those in a much larger control group. This comparison, and therefore the conclusion, is flawed because the contamination plume does not extend to the entirety of ZIP codes 60515 and 60516.
Cancer data is reported in data sets by either county or ZIP code to protect confidentiality of theindividuals. The best data available from the Illinois State Cancer Registry for the affected areawas the 60515 and 60516 ZIP codes. Data about cancers in the exact area affected by thecontamination is not available.
Comment 3. Can a health study look at other disorders such as auto-immune diseases and other non-cancer effects?
At this time, IDPH does not have plans for this type of health study in Downers Grove. Theestimated exposure for Downers Grove residents is less than the USEPA reference dose, so non-cancer effects are unlikely. The main public health focus is reducing or eliminating futureexposures for persons with elevated levels of contaminants in their private well water. Dependingon future findings regarding the nature and extent of TCE and PCE contamination, an additional evaluation could be considered.