Incorporating Lifecycle Emission Information in Promoting Chemical Exposure Screening

Abstract

While high-throughput human chemical exposure screening often relies on hazard indicators such as persistence and bioaccumulation potential, realistic human chemical exposure and potential health risks are also dependent on factors such as chemical use information and chemical-specific exposure pathways. Multimedia, multi-pathway exposure models are being used for chemical prioritization and screening, the parameterization of which requires chemical specific use and emission information (e.g., how is it emitted? how much?). This information, however, is often insufficient or missing for most chemicals in commerce. To address this issue, we propose integrating substance flow analysis, which is a powerful tool to derive chemical emissions throughout the chemical/product lifecycle, into high-throughput screening for human exposure potential. As an illustrative example, we combine a substance flow model (a simplified version of CiP-CAFE) with chemical fate and exposure models (RAIDAR and RAIDAR-ICE), to create a modeling continuum from the quantity produced or imported to human aggregate exposure. Our model requires inputs of basic properties of chemicals (e.g., partitioning coefficients, and degradation/biotransformation rates) and associated products (e.g., use categories, lifespans and material characteristics). These properties can either be retrieved from existing data resources or calculated by models, which enables the model's wide applicability to high-throughput screening of both existing and new substances. The model allows "forward" evaluation of human aggregate exposure to chemicals arising from their actual use, or "back" calculation of the critical production/import quantities of a chemical that would not cause an unacceptable level of risk (the latter depends on the availability of toxicological data). Overall, the approach demonstrates promise in high-throughput exposure screening of the myriad of chemicals.