2ND MOMENT METHOD FOR EVALUATING HUMAN HEALTH RISKS FROM GROUNDWATER CONTAMINATED BY TRICHLOROETHYLENE

Pollutants in groundwater aquifers may constitute a significant human health risk A large variation in response may result among human popul ations experiencing the same level and duration of exposure to polluta nts. Variability in response, as a result of exposure to a carcinogeni c contaminant such as trichloroethylene (TCE), can be represented by a distribution function of safe doses. Spatial variability in aquifer c haracteristics and contaminant transport parameters requires the use o f stochastic transport models to quantify variability in exposure conc entrations. A second moment method is used to evaluate the probability of exceeding safe dose levels for a contaminated aquifer. The name of this method stems from the fact that the formulation is based on the first and second moments of the random variables. With this method, th e probability is a function of the variability of contaminant concentr ation (which incorporates variability in hydrogeologic parameters such as hydraulic conductivity) and the variability in response in the hum an population. In this manner, the severity of the heath risk posed by a contaminated aquifer and the evaluation of appropriate strategies a nd technologies for aquifer remediation are a function of contaminant concentrations and human heath risks. The applicability and limitation s of this method are demonstrated with data on groundwater contaminate d by TCE at Hill Air force Base, Utah.