Screening the potential risks of toxic substances using a multimedia compartment model: estimation of human exposure

Managing environmental health risks requires the assessment of environmental fate, exposure, and health risk of an ever-increasing list of contaminants. The magnitude of this list precludes an experimental evaluation of each contaminant. For this reason, computer models are being used more frequently to simulate the transport and transformation of chemicals based on physical and chemical properties. This paper describes a multimedia compartment model that we have developed for screening toxic substances. This model, referred to as GEOTOX, uses a combination of physical, chemical, and landscape properties to establish the partitioning, reaction, and interphase-transport characteristics of a chemical. These properties are used to estimate concentrations in the air, soil, water, and food of a representative or generic environment. We use these concentrations in exposure-pathway models to calculate the quantities absorbed by humans; then dose-response data are used to estimate health risks. The capability of GEOTOX as a screening tool is illustrated in a sample ranking of three chemicals (i.e., 2,4,6-trinitrotoluene, hexahydro-1,3,5-trinitro-1,3,5-triazine, and benzene) being continuously added to the upper-soil compartment. We find that ranking based on both toxic potency and environmental fate can enhance the risk-management process when compared to ranking based on toxic potency alone.