Interpretation of Urinary Concentrations of Pyrethroid Metabolites in the Canadian Population in a Risk Context: Associated Factors and Comparison to Biomonitoring Equivalents

Abstract

Pyrethroids are extensively used in agricultural, commercial and residential pest control, and are implicated in adverse health outcomes in humans. We evaluated the associations between socio-demographic and dietary factors and urinary concentrations of pyrethroid metabolites in the Canadian general population using data collected under the Canadian Health Measures Survey (CHMS) cycles 1 and 2 (2007-11), and assessed the data in a risk context using the screening-level biomonitoring equivalents for 3-phenoxybenzoic acid (3-PBA), a common metabolite of several pyrethroids. Data from CHMS cycles 1 and 2 were combined for the analyses. Regression analysis revealed significant (p<0.05) age-dependent differences in the least-square geometric mean (LSGM) concentrations of the sum of all measured pyrethroid metabolites, or 3-PBA (LSGM for 20-39 years > 12-19 years). The concentrations were also associated with sex (females > males), country of birth (other than Canada > Canada), body mass index (normal weight > obese), season (fall > summer), use of home/yard pesticides or lice/flea control products (yes > no), and frequency of consumption of vegetables (high > low) and starchy roots (low > high). The geometric mean concentrations of 3-PBA for all age and sex groups from CHMS cycles 1 and 2 did not exceed the Tier 1 screening value of 1.7 µg/L based on the most stringent of the biomonitoring equivalents derived for the chronic dietary RfD (USEPA) and ADI (WHO/FAO/EC) suggesting that the cumulative exposures to pyrethroids in Canadians are low relative to guidance values, and existence of a margin of safety. Additional data on pyrethroid metabolites in Canadians from CHMS cycle 5 (2016-17) and cycle 6 (2018-19) will support an assessment of trends in exposure and future evaluation of risks.