PUBLIC HEALTH ASSESSMENT
MUSKEGO SANITARY LANDFILL
MUSKEGO, WAUKESHA COUNTY, WISCONSIN
UPPER LEVEL ESTIMATES OF LIFETIME CANCER
RISKS ASSOCIATED WITH POTENTIAL FUTURE
CONSUMPTION OF CONTAMINANTS IN GROUND WATER
Chemical contaminants in on-site ground water currently do not pose a cancer risk becausepeople are not exposed to this water. The upper level estimates of lifetime cancer risks listed inthe table below offer a perspective on the relative cancer risks the contaminants in on-siteground water would pose if that water were used for drinking water. In general, the chemicalswith the highest estimated risk pose the greatest threat to downgradient wells. Obviously, themaximum concentrations found on site are not the concentrations likely to reach off-site wells. The estimates below are only a relative index of the potential cancer risks that the chemicalspose. A more detailed discussion of the potential toxic effects of each chemical begins on page 25
|Upper Level |
|Benzene||21||A||8.3 x 10-7||17|
|Vinyl chloride+||7||A||5.4 x 10-5||380|
|1,2-Dichloropropane+||5||B2||1.9 x 10-6||10|
|Methylene chloride||2||B2||2.1 x 10-7||< 0|
|Tetrachloroethylene+||1||B2||1.5 x 10-6||2|
|1,2-Dichloroethylene||12||C||1.7 x 10-5||26|
|Trichloroethylene+||7||B2||3.2 x 10-7||16|
|1,2-Dichloroethane||9||B2||2.6 x 10-6||23|
* Source: 
+ chemicals marked "+" are under review by the U.S. EPA.
EPA Carcinogen Group
The EPA uses one of five groups to classify the carcinogenic potential of a chemical, accordingto the weight of evidence from epidemiological studies and animal studies. The following listexplains categories listed on the above table:
Group A - Human Carcinogen (sufficient evidence of carcinogenicity in humans);
Group B2 - Probable Human Carcinogen (sufficient evidence of carcinogenicity in animalsand inadequate or no evidence of carcinogenicity in humans);
Group C - Probable Human Carcinogen (limited evidence of carcinogenicity in animals andinadequate or no evidence of carcinogenicity in humans).
NA - This is not an EPA category. This notation indicates that information is "notavailable" because the EPA has not evaluated this chemical.
The EPA estimates the level of cancer risk posed by exposure to relatively low doses ofcarcinogens. The EPA uses the available data and a theoretical "model" of how chemicals causecancer to estimate the carcinogenic potency of a chemical. This potency is an "upper-boundestimate." In other words, the true risk is not likely to be higher and may be lower. Theestimated lifetime cancer risk is the upper bound estimate of the increase in one's probability ofcontracting cancer as a result of ingesting the chemical in drinking water for a lifetime. The"unit cancer risk" is the EPA's estimate of one's increased risk from drinking 1 µg of thechemical per liter of drinking water for a lifetime. The higher the unit risk, the greater is theestimated carcinogenic potency of the chemical .
The "upper level estimated lifetime cancer risk" is the product of the maximum concentration ofthe chemical in ground water at the Muskego Sanitary Landfill site and the unit cancer risk. Theestimated risk is rounded to one significant digit because of the great uncertainty involved inestimating the risk. At best the order of magnitude of the risk reflects the relative carcinogenichazard that a chemical poses. The table does not include risks associated with breathing VOC'sreleased from residential water or from dermally absorbing carcinogens in the water. As ageneral rule of thumb, exposure to VOC's would be roughly twice that from drinking thecontaminated water .
- The Agency for Toxic Substance Disease Registry.
- Cancer Risk Evaluation Guide (CREG):
- An estimate of the excess upper-bound lifetime probability (at or less than 1 in 1,000,000) of an individual developing cancer from an exposure to a concentration of a specific chemical or substance.
- Cancer Slope Factor (CSF):
- The upper limit on the lifetime probability (at or less than 1 in 1,000,000) thata cancer causing chemical will can cancer at a dose of 1.0 mg/kg/day.
- A substance which has been proven to cause cancer in humans or animals.
- The Comprehensive Environmental Response, Compensation, andEnvironmental Liability Act. Also known as "Superfund", this program isadministered by the U.S. Environmental Protection Agency.
- Division of Health, Wisconsin Department of Health & Social Services.
- Drinking Water Lifetime Health Advisory:
- That portion of an individual's total exposure to a chemical that is attributed todrinking water, and is considered protective of noncarcinogenic health effectsduring a lifetime exposure.
- Environmental Media Evaluation Guideline
- Maximum Contaminant Level (MCL):
- Drinking water health goals set by the U.S. EPA at which "no known oranticipated adverse effect on the health of persons occur and which allows anadequate margin of safety".
- Milligrams per Kilograms per Day
- Minimum Risk Level
- National Priorities List (NPL):
- U.S. EPA's list of top priority hazardous waste sites that are eligible forinvestigation and cleanup under Superfund.
- Parts Per Billion or Micrograms per Liter (µg/L)
- Parts Per Million or Milligrams per Liter (mg/L)
- Reference Dose (RfD):
- An estimate of a daily exposure level to a substance for the human populationthat is likely to be without an apparent risk of causing damaging health effectsduring a lifetime of exposure.
- Remedial Investigation and Feasibility Study (RI/FS):
- Two parts of the Superfund process. The Remedial Investigation includes thecollection and evaluation of data to define site conditions, including the natureof hazardous substances found at a site and the extent that those hazardoussubstances were released from the site. These releases are evaluated to assessthe effect on public health and the environment. The Feasibility Study definesa range of likely alternatives for cleaning up a site.
- Semi-Volatile Organic Compounds
- Target Compound List / Target Analyte List
- U.S. EPA:
- United States Environmental Protection Agency
- Micrograms per Liter or Parts Per Billion
- Micrograms per Cubic Meter
- Volatile Organic Compounds
- Waste Management of Wisconsin, Inc.
- Wisconsin Department of Natural Resource