Multimedia Transport of Organic Contaminants and Exposure Modeling,

Human exposures to organic contaminants in the environment area complex function of human factors, physicochemical properties of the contaminants, and characteristics of the environmental media in which the contaminants reside. One subject of interest in the screening of organic chemicals for the purpose of identifying exposure pathways of potential concern is the relationship between exposures and contaminant properties. To study such relationships, a multimedia environmental model termed GEOTOX is used to predict the equilibrium partitioning and transport of reference organic chemicals between compartments representing different media i.e., soil layers, groundwater, air, biota, etc. of a contaminated landscape. Reference chemicals, which are added to the surface soil of a landscape, are defined by properties consisting of the Henrys law constant, soil water-soil organic carbon partition coefficient, and bioconcentration factors. The steady-state concentrations of the chemicals in the GEOTOX compartments then are used to estimate lifetime average exposures in milligrams per kilogram per day to the contaminants for individuals living in the contaminated landscape. Exposure pathways addressed include ingestion, inhalation, and dermal absorption. Local sensitivity analyses are performed to determine which chemical and landscape properties have the greatest effect on the exposure estimates.