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IDPH compared the maximum concentration of each chemical detected with appropriate comparison values to select chemicals for further evaluation for exposure and for both cancer and non-cancer health end points. The chemicals that exceeded comparison values and that were selected for further evaluations are TCE, PCE, and DCE.

The comparison values are used only to screen for chemicals that should be evaluated further. Levels of exposure greater than these values do not necessarily mean that adverse health effects can be expected. The amount of the chemical, the duration of exposure, routes of exposure, and the health status of exposed individuals are important factors in determining the potential for adverse health effects. A detailed discussion of each of the comparison values used is found in Attachment 3.

Identifying the potential for adverse health effects to occur from exposure to chemicals is done by evaluating human exposure pathways. These pathways are generally separated into completed and potential exposure pathways and are then classified by the environmental media contaminated. An exposure pathway consists of five elements: 1) a source of contamination; 2) transport through an environmental medium; 3) a point of exposure; 4) a route of human exposure; and 5) an exposed population.

Completed pathways require that the five exposure elements exist and that exposure occurred in the past, is occurring, or will occur in the future. Potential pathways have at least one element missing, but evidence suggests that exposure could have occurred in the past, could be occurring, or could occur in the future. An exposure pathway is eliminated if one or more of the elements are missing and will never be present [7]. Tables 4 and 5 list the completed and potential exposure pathways.

The past and present use of domestic groundwater is the most significant completed and potential exposure pathway for this site. The primary exposure routes include ingestion and inhalation of VOCs during such activities as showering and cooking. Although inhalation might be an important exposure route, it is not discussed in this public health assessment because no indoor air sampling exists. Dermal absorption is an additional exposure route, but the VOCs found are not absorbed through the skin to any great extent.

IDPH has sampled a small number of wells on a routine basis since 1990. To date, approximately 524 samples have been collected from 320 drinking water wells in the area. Approximately 243 residential wells have had VOCs above detection limits. While the total level of VOCs (except PCE) have been decreasing with time, several water supplies still contain levels of VOCs greater than USEPA maximum contaminant levels (MCLs) [3]. MCLs are levels of contaminants in drinking water that USEPA deems protective of public health (considering the availability and economics of water treatment technology) over a lifetime exposure.

As an exposure scenario, IDPH assumed a 17-year exposure period and that adults weigh 70 kilograms and drink 2 liters of water per day and that children weigh 15 kilograms and drink 1 liter of water per day. The evaluation does not include possible health outcomes as a result of exposure to multiple chemicals that attack the same organ systems.


TCE is the primary chemical of concern at this site. The maximum level detected was 91 parts per billion (ppb) in 1991. The MCL of 5 ppb was used as the comparison value. TCE has been detected in the water supply of 128 households at or above the MCL. Based on 1990 U.S. Census data, approximately 384 persons are potentially exposed to levels of TCE in excess of 5 ppb.

IDPH estimated the oral exposure dose to children and adults for this chemical (Table 3); however, no health guidelines were available with which to compare this exposure dose. The oral reference dose (RfD) is currently under review by USEPA, and ATSDR's minimum risk level (MRL) of 0.2 milligrams/kilogram/day (mg/kg/day) is for acute exposure. No MRL is available for chronic exposure, which is exposure of more than one year. Although USEPA is currently reviewing the carcinogenic potential for this chemical, existing data suggest that exposure to the maximum TCE level found to date should not result in an appreciable cancer risk increase.

ATSDR has established a TCE exposure subregistry to monitor individuals exposed to TCE. Health outcome data from the TCE exposure subregistry suggest excess numbers (over the national sample) of heart disease, stroke, respiratory cancer deaths, anemia, other blood disorders, liver disease, kidney disease, urinary tract disorders, hearing and speech impairments, and skin rashes [9]. These data are self-reported by participants in the subregistry and do not reflect physician diagnoses or potential causes of the illnesses.

Two recent studies have reported an association between exposure to TCE and birth defects such as neural tube defects and oral clefts; however, there are limitations with these studies [8]. Current research is still far from conclusive regarding TCE and birth defects.


The maximum level of PCE detected was 5.8 ppb in 1991. The MCL of 5 ppb was used as the comparison value. ATSDR's comparison value of 100 ppb is based on USEPA's RfD and is for noncarcinogenic health effects [10].

IDPH estimated the oral exposure dose to children and adults for this chemical and compared it with health guidelines (Table 3). The estimated exposure to children and adults did not exceed guidelines, so no adverse health effects would be expected. USEPA is currently reviewing the carcinogenic potential for this chemical.


The maximum level of DCE detected was 7.2 ppb. The MCL is 7 ppb, and ATSDR's comparison value of 0.06 ppb is based on DCE's carcinogenic potential [11].

IDPH estimated the oral exposure dose to children and adults for this chemical and compared it with health guidelines (Table 3). The estimated exposure to children and adults did not exceed guidelines, so no adverse health effects would be expected. USEPA has determined that DCE is a possible human carcinogen, but based on our exposure scenario, IDPH believes DCE poses no increased cancer risk at this site.

Present and future exposure pathways should be eliminated with the construction of a public water system. In addition, future exposure pathways are not likely to occur in the undeveloped area of the contamination plume north-northeast of the site. The boundaries of the plume are well defined and any future development will likely include public water.

The contaminant plume has been found to extend from the area north-northeast of the site to residential wells along the Rock River, suggesting possible release of contaminants into surface waters via groundwater discharge. No surface water samples have been collected from the Rock River or Dry Creek [4]. The Rock River is not used as a source of drinking water, but it is used for recreational and fishing activities. Dry Creek is not used for either drinking water or, to any great extent, recreational and fishing activities. Because the VOCs in the groundwater would be diluted when discharged into the river, IDPH does not consider this potential exposure scenario a public health hazard.


On November 17, 1998, USEPA held a public meeting in Roscoe to give area residents the opportunity to comment on the site evaluation and express their health concerns. Another public meeting was held July 28, 1999, to discuss the public water extension into Evergreen Manor. The following questions summarize health concerns, and IDPH provides answers to those questions.

1. Can carbon filters cause more damage if they are not changed in time?

Yes. Carbon filters are effective only for a limited amount of time. If they are not changed or maintained according to the manufacturer's recommendations, the filters could become saturated and not remove the chemicals from the water. In addition, once saturated, they could reintroduce chemicals back into the water supply.

2. Has there been any study of an increased rate of illness?

No study has been done specifically at this site; however, as part of the National Exposure Registry mandated by CERCLA and Superfund, ATSDR established the TCE Subregistry to explore the possible association of adverse health effects with long-term exposure to TCE. Participants in the TCE subregistry have reported a higher incidence of some illnesses than the general population, but no study has been conducted to date that links TCE exposure to those illnesses.


IDPH and ATSDR recognize that children are especially sensitive to some contaminants. For that reason, IDPH includes children when evaluating exposures to contaminants. Children are the most sensitive population considered in this public health assessment, and results of their estimated exposures are presented in the Discussion section of this document.

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