Indoor residential pesticide fate, transport, and exposure model

Abstract

A deeper understanding of the fate, transport, and exposure of indoor pesticides is needed, especially for application methods specific to indoor environments, such as perimeter and crack-and-crevice treatments. This study addresses this research need by investigating indoor dynamics of pesticides and estimating residential pesticide exposures. For four widely-used pesticides with diverse chemical properties, we refined and applied our multi-compartment indoor fate, transport, and exposure model to simulate time-dependent concentrations across multiple media, integrating exposures over 1- and 30-day periods. Our model shows that when pesticides are applied to floor edges, < 1 % of the total applied mass is transported from treated areas to air or untreated surfaces over 30 days of simulation. Because of limited measurement data for robust model validation, we compared our model’s estimates to those from the U.S. Environmental Protection Agency’s Standard Operating Procedures (SOPs) regulatory model. Comparison revealed that our model’s total exposure estimates are 2–5 orders of magnitude lower than those from the SOP model. Notably, even greater differences were observed for individual exposure routes, as the SOP model does not account for chemical properties but assumes that a fixed daily fraction of the applied mass is available for exposure. In contrast, our model accounts for chemical-specific fate and transport processes. This study highlights the critical role of incorporating chemical fate and transport in residential pesticide exposure assessments. However, monitoring studies are needed to validate our model estimates with measurements collected over time from indoor air and surfaces under known application methods and rates.