Air Toxics Risk Assessment: A Case Study for 1,1,1-Trichloroethane in a Multimedia Environment. J. Swider and W. E. Kastenberg, University of California, Los Angeles, 48-121 Engineering IV, Los Angeles, CA 90024-1597
According to the EPA's Toxics Release Inventory 1,1,1-Trichloroethane (TCA) is a chemical with the largest release in California and 99.72% of this release has been emitted into the atmosphere. This toxic air contaminant is stable in the atmosphere, with very low daily loss rate, and is known as hazardous to human health. The presence of such amount of this halogenated hydrocarbon in the atmosphere of California endangers the population. Therefore, it is of public interest to evaluate its potential adverse effect on public health. TCA is a colorless liquid used as a solvent and is irritating to eyes and tissue. In the Toxic Hazard Rating, TCA obtained a designation of slight to moderate, what means that it may cause both irreversible and reversible changes, but they are not severe enough to cause immediate death or permanent injury. However, there is no information about long-term consequences. In order to determine potential adverse health effects, an understanding of TCA's behavior in the environment is necessary. Therefore, a multimedia transport model must be employed to predict the long-term fate of the chemical in the environment. The model will also serve as a means to determine the dominant exposure pathways. Probabilistic risk assessment methodology will be applied to conduct this analysis. Evaluation of the airborne 1,1,1-Trichloroethane emissions and comparison of the results with EPA's standards will be presented. The analysis will include: characterization of the emission sources, assessment of human exposure pathways and risks as well as quantification of uncertainties in each step above.