COUPLING TOXICOKINETIC-TOXICODYNAMIC (TK-TD) AND POPULATION MODELS FOR ASSESSING AQUATIC ECOLOGICAL RISKS TO TIME-VARYING PESTICIDE EXPOSURES

摘要

Population modeling evaluations of pesticide exposure time series were compared to aspects of a currently used risk assessment process. The US Environmental Protection Agency’s Office of Pesticide Programs models daily aquatic pesticide exposure values for 30 years in its risk assessments, but does not routinely make full use of the information in those time series. We used mysid shrimp Americamysis bahia toxicity and demographic data to demonstrate the value of a toxicokinetic-toxicodynamic model coupled with a series of matrix population models in risk assessment refinements. This species is a small epibenthic marine crustacean routinely used in regulatory toxicity tests. We demonstrate how the model coupling can refine current risk assessments using only existing standard regulatory toxicity test results. Several exposure scenarios (each with the same initial risk characterization as determined by a more traditional organismal-based approach) were created within which population modeling documented different risks than assessments based on the traditional approach. We also present different acute and chronic toxicity data scenarios where TK-TD coupled with population modeling can distinguish different responses; responses that tradition risk evaluations are not designed to detect. Our results reinforce the benefits of this type of modeling in risk evaluations, especially related to time-varying exposure concentrations.