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Methodologies for estimating cumulative human exposures to current-use pyrethroid pesticides
Nicolle S Tulve1, Peter P Egeghy, Roy C Fortmann
1Office of Research and Development, National Exposure Research Laboratory, US EPA, MD-E205-04, Research Triangle Park, North Carolina 27711, USA. tulve.nicolle@epa.gov
This study compared three US Environmental Protection Agency (EPA) pesticide exposure assessment methods for children. The Standard Operating Procedures (SOPs) and SHEDS models showed strong correlations with urinary pesticide metabolites, indicating their reliability for exposure assessment.
Area of Science:
- Environmental Health
- Toxicology
- Risk Assessment
Background:
- Accurate estimation of residential pesticide exposure in children is crucial for public health and regulatory purposes.
- Existing methodologies, including Standard Operating Procedures (SOPs) and the Stochastic Human Exposure and Dose Simulation (SHEDS) model, are used by the US Environmental Protection Agency (EPA) for screening-level assessments.
- Validating these exposure models against biological markers, such as urinary metabolites, is essential for refining exposure estimates.
Purpose of the Study:
- To estimate cumulative residential pesticide exposures in young children using three distinct EPA methodologies.
- To compare the results from these methodologies with exposure estimates derived from measured urinary metabolite concentrations.
- To evaluate the performance of different approaches for estimating dermal pesticide exposure in children.
Main Methods:
- Estimated pesticide exposures (dermal, indirect ingestion) for nine children aged 4-6 years using EPA's SOPs, SHEDS, and the Draft Protocol for Measuring Children's Non-Occupational Exposure to Pesticides.
- Compared model-derived exposure estimates with concentrations of 3-phenoxybenzoic acid, a urinary pesticide metabolite.
- Analyzed various dermal exposure estimation approaches, identifying the most reasonable method.
Main Results:
- Dermal exposure estimates varied significantly across methodologies, with SOPs yielding lower estimates than SHEDS or the Draft Protocol.
- Indirect ingestion estimates also differed, with SOPs showing the lowest range and SHEDS the highest.
- Total absorbed dose estimates varied, but SHEDS and the Draft Protocol demonstrated strong positive correlations (R²=0.92 and R²=0.90, respectively) with measured urinary metabolites.
Conclusions:
- Both the SHEDS model and the Draft Protocol provide reasonable estimates of pesticide exposure and dose in children, supported by urinary metabolite data.
- The approach assuming even distribution of pesticide residue on the body appears most reasonable for dermal exposure estimation.
- Methodology selection should align with data availability and study objectives; further research is needed to optimize dermal exposure estimation for children.
