Characterizing Pyrethroid Pesticide Exposures in a Longitudinal Children’s Cohort Analyzing Household Dust and Urinary miRNA Biomarkers

Abstract

Pesticide exposures in agricultural regions can affect both farmworker and non-farmworker populations through cumulative occupational and residential pathways. Previous studies of the University of Washington Center for Child Environmental Health Risks Research (CHC) cohort in the Yakima Valley, Washington State, characterized OP exposure patterns across seasons and occupational groups and identified microRNAs as potential biomarkers of environmental pesticide exposure and early biological response. However, PT concentrations in household dust and their biological correlates remain comparatively understudied, particularly in the context PTs as a proposed substitute in the regulatory phase-out of OPs in the early 2000s. Understanding pyrethroid (PT) insecticide levels in household dust, the levels of co-exposure with organophosphates (OP), and their relationship with molecular biomarkers, contributes to building the exposure-response framework needed to evaluate cumulative pesticide burden in vulnerable populations.Methods: Using data from the CHC cohort, this study aims to characterize PT concentrations in household dust across two agricultural seasons and two study years (2005 and 2011), in farmworker (FW) and non-farmworker (NFW) households, and evaluated associations between household dust pesticide concentrations and urinary expression of ten candidate miRNAs in adults and children. Results: OP concentrations declined significantly between 2005 and 2011 consistent with phase-out policies, while PT concentrations showed no consistent temporal trend. Permethrin was the dominant PT compound, with concentrations similarly distributed across FW and NFW households. Across 130 compound-miRNA pairs evaluated, eight statistically significant inverse associations were identified, all indicating that higher household dust pesticide concentrations were associated with lower miRNA expression. Permethrin showed significant inverse associations with miR-320a, miR-133b, and miR-517b, while miR-223 was inversely associated with the reference dose-weighted sum of OPs; PT and OP associated miRNAs were non-overlapping. Conclusions: These findings characterize an underexplored component of the agricultural pesticide exposome in the CHC cohort, and indicate that household dust is a meaningful route of PT exposure in this agricultural community independent of occupational status, and that PT and OP compounds are associated with distinct urinary miRNA signatures, that may capture compound-class-specific molecular responses to residential pesticide burden, supporting the potential utility of miRNAs as biomarkers of pesticide-associated molecular responses.