A POPULATION-BASED EXPOSURE MODEL FOR BENZENE

A model of daily-average inhalation exposures and total-absorbed doses of benzene to members of large populations was developed as part of a series of multimedia exposure and absorbed dose models. The benzene e xposure and dose model is based upon probabilistic rather than sequent ial simulation of time-activity patterns, a simpler approach to modeli ng personal benzene exposures than other existing models. An important innovation of the benzene model is the incorporation of an anthropome tric module for generating correlated exposure factors used to estimat e absorbed doses occurring from inhalation, ingestion, and dermal abso rption of benzene. A preliminary validation exercise indicates that th e benzene model produces reasonable estimates of the distribution of b enzene personal air concentrations expected for a large population. Un certainty about specific percentiles of the predicted distributions of personal air concentrations was found to be dominated by uncertainty about microenvironmental benzene concentrations rather than time-activ ity patterns, and uncertainty about total absorbed doses was dominated by a lack of knowledge about the true absorption coefficient for benz ene in the lung rather than knowledge gaps about microenvironmental co ncentrations or intake rates. The results of this modeling effort have implications for environmental control decisions, including evaluatio n of source control options, characterization of population and indivi dual risk, and allocation of resources for future studies.