A Comparison of Risk Estimates Among Various Exposure Scenarios of Volatile Organic Compounds in Tap Water. Y. Chung, D. C. Shin, J. M. Kim and S. E. Park, Institute for Environmental Research, Yonsei University, Seoul, Korea
Risk assessment process, which include processes for the estimation of human cancer potency using animal bioassay data and calculation of human exposure, entail uncertainties. In the exposure assessment process, exposure scenarios with various assumption could affect the estimated exposure and hence, excess cancer risk. We compared risk estimates among various exposure scenarios of vinyl chloride, trichlorethylene and tetrachloroethylene in tap water sample in Seoul from 1993 to 1994. The oral and inhalation cancer potencies of the contaminants were estimated using multistage, Weibull, Log-normal, and mantel-Bryan models in TOX-RISK computer software. In the first case, human excess cancer risk was estimated by US EPA method used to set MCI (Maximum Contaminant Level). In the second and third case, the risk was estimated for multi-route exposure with and without adopting Monte-Carlo simulation, respectively. In the second case, exposure input parameters and cancer potencies used probability distributions, and in the third case, those values used point estimates (mean, and maximum or 95% upper-bound value). As a result, while the excess cancer risk estimated by the US EPA method considering only direct ingestion tended to be under estimated, the risk which was estimated by considering multi-route exposure without Monte-Carlo simulation and then using the maximum or 95% upper-bound value as input parameters tended to be overestimated.
In risk assessment for volatile organic compounds, considering multi-route exposure with adopting Monte-Carlo analysis seems to provide the most reasonable estimations.