Modeling external exposure to pesticides in human populations: Developing an exposure scenario generator

Pesticides are a significant public health concern due to their widespread use. However, estimating population exposures remains challenging, given the need to integrate multiple exposure routes and scenarios. We developed the Pesticide Exposure Scenario Simulator (PESS) to estimate pesticide exposure across diverse population groups, including agricultural workers, residents living near treated fields, and individuals exposed through diet. PESS integrates three exposure modules (i.e., occupational, environmental, and dietary) to generate comprehensive distribution estimates. We applied PESS to assess exposure to three pesticides: endosulfan, mancozeb, and glyphosate, representing different authorization statuses, and compared the results against urinary biomonitoring data and literature sources. Occupational exposure estimates were significantly higher under low protection scenarios, ranging from 1000 to 100,000 µg/kg body weight/hour, with median values between 3000 and 10,000 µg/kg body weight/hour. High protection measures reduced exposure by approximately three orders of magnitude, yielding median values around 10 µg/kg body weight/hour. Environmental exposure estimates near treated fields (10 m) ranged from 1E-14-0.01 µg/kg body weight/hour, decreasing to 1E-14-1E-05 at 250 m, with median values between 1E-08 and 1E-07. Dietary exposure estimates for adults ranged from 1E-06-0.1 µg/kg body weight/day, with median values between 1E-04 and 0.0005. Exposure across routes was harmonized using a daily-event framework, where short-duration occupational and environmental exposures (1 h) were treated as single daily events due to rapid pesticide dissipation in the atmosphere, and thus considered equivalent to daily exposure. Dietary exposure was inherently expressed on a daily basis, ensuring consistency while preserving the event-based nature of non-dietary exposures. Protective equipment and application rates were key determinants of occupational exposure, while environmental exposures were primarily influenced by meteorological conditions, particularly wind speed. Dietary exposures showed lower variability in exposure values in comparison with other modules, reflecting differences in pesticide residues across food categories and age groups. These determinants are essential for accurate exposure assessments and highlight the need for integrated tools like PESS.