Standard aquatic exposure assessments conducted by US EPA for pesticides have been based on environmental fate data derived from laboratory studies. However, the behavior of chemicals in the environment is different because of simultaneous processes occurring in real world conditions that are not captured by controlled laboratory studies. This study demonstrates the value of using available field studies to parameterize environmental fate models in higher-tier refined exposure assessments. A water monitoring study was conducted to measure residues of fipronil and its metabolites in an on-site pond of an established golf course following fipronil applications on turf adjacent to the pond. In addition, an outdoor simulated pond study was conducted to characterize the fate of fipronil and its metabolites in aquatic environments. The PRZM and EXAMS models were used to simulate the fate and transport of fipronil and its major fiprole metabolites observed in the study. The models were parameterized using the data from the outdoor simulated pond study and some parameters were calibrated within their recommended limits. The simulation results from PRZM and EXAMS models showed good correspondence to observed data from the water monitoring study. The calibrated models were then run with long-term weather records to predict temporal distribution of fipronil and the total fiprole exposure concentrations. The results show that the aquatic exposure modeling parameterized using field studies can better represent the complex behavior of a chemical in environment and should be considered in higher-tier risk assessment.

Aquatic exposure model parameterization using outdoor simulated pond study

244th National Meeting (2012)

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