Human Exposure Model (HEM): A Modular, Web-based Application to Characterize Near-field Chemical Exposures and Releases

摘要

The U.S. EPA's Chemical Safety and Sustainability research program is developing the Human Exposure Model (HEM) to assess near-field exposures to chemicals that occur in various populations over the entire life cycle of a consumer product. The model will be implemented as a web-based, modular system that will produce estimates of population distributions of chemical exposure by route and releases to the environment, with one intended use to support human health impact assessments in Life Cycle Impact Assessments (LClAs). The model determines aggregate doses of thousands of chemicals from the use of over 300 categories of consumer products over one year. Fundamental components of the model included in the beta-HEM release (September 2017) are the Residential-Population Generator (RPGen), Human Behavior, product formulation, and Source-to-Dose modules. The RPGen module generates synthetic populations, together with characteristics that may drive product use such as detailed demographic and residential information for each household. The Human Behavior module uses agent-based modeling to determine longitudinal patterns of macro activities (eating, sleeping, commuting, working, and 'idle' time) and a product usage scheduler to define the use of consumer products on each day. CPDat, a database of product composition and chemical functional use data, is used to generate empirical product formulations. The Source-to-Dose module uses these outputs and data on chemical properties to calculate doses (by chemical, route and product category) for each individual, and corresponding environmental releases. This model allows for evaluation of near-field chemical exposures and environmental releases from the use of consumer products for incorporation into LClA and other chemical assessments.