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Matrix Population Model for Estimating Effects from Time-Varying Aquatic Exposures: Technical Documentation
Thursby, G. Matrix Population Model for Estimating Effects from Time-Varying Aquatic Exposures: Technical Documentation. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-16/062, 2016.
Evaluation of different aquatic exposure scenarios is an integral part of EPA’s risk assessment process for the registration or re-registration of pesticides, but the Agency only uses a fraction of the available modeled exposure data. Several circumstances are presented within which population modeling results in different risk conclusions than assessments based on the traditional approach. The specific model herein is simple enough so that all toxicity parameters are derived from standard toxicity tests. The model successfully integrates acute and chronic toxicity data, and uses all available time-varying modeled exposure data. The report documents that population models hold great promise for integrating exposure, toxicity and life history information into meaningful measures of risk.
The Office of Pesticide Programs models daily aquatic pesticide exposure values for 30 years in its risk assessments. However, only a fraction of that information is typically used in these assessments. The population model employed herein is a deterministic, density-dependent periodic matrix model for integrating time-varying pesticide exposure effects on the marine invertebrate Americamysis bahia. The external exposure concentrations are converted to time-varying scaled internal concentrations by coupling a one-compartment toxicokinetics-toxicodynamics model with the matrix model. Several exposures scenarios (each with the same risk as determined by OPP’s traditional approach) were created within which population modeling documented different risk conclusions than assessments based on the traditional approach. Population modeling incorporates all available toxicological and exposure data, making a more complete assessment of the potential risk of time-varying aquatic concentrations.