Urinary concentrations of metabolites of pyrethroid insecticides in the general U.S. population: National Health and Nutrition Examination Survey 1999-2002

Abstract

Background: Pyrethroid insecticides are the most commonly used residential insecticides in the United States.

Objectives: Our objective was to assess human exposure via biomonitoring to pyrethroid insecticides in a representative sample of the general U.S. population >or= 6 years of age.

Methods: By using isotope-dilution high-performance liquid chromatography/electrospray chemical ionization/tandem mass spectrometry, we measured five urinary metabolites of pyrethroid insecticides in 5,046 samples collected as a part of the 1999-2002 National Health and Nutrition Examination Survey (NHANES). Univariate, multivariate, and Pearson correlation analyses were performed using SUDAAN and SAS software, incorporating the appropriate sample weights into the analyses. Multivariate analyses included age, sex, race/ethnicity, creatinine, fasting status, and urine collection time as covariates.

Results: We detected 3-phenoxybenzoic acid (3PBA), a metabolite common to many pyrethroid insecticides, in more than 70% of the samples. The least-squares geometric mean (LSGM) concentration (corrected for covariates) of 3PBA and the frequency of detection increased from 1999-2000 (0.292 ng/mL) to 2001-2002 (0.318 ng/mL) but not significantly. Non-Hispanic blacks had significantly higher LSGM 3PBA concentrations than did non-Hispanic whites and Mexican Americans in the 2001-2002 survey period and in the combined 4-year survey periods but not in the 1999-2000 survey period. Children had significantly higher LSGM concentrations of 3PBA than did adolescents in both NHANES periods and than adults in NHANES 1999-2000. Cis- and trans-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid were highly correlated with each other and with 3PBA, suggesting that urinary 3PBA was derived primarily from exposure to permethrin, cypermethrin, or their degradates.

Conclusions: Pyrethroid insecticide exposure in the U.S. population is widespread, and the presence of its metabolites in the urine of U.S. residents indicates that children may have higher exposures than adolescents and adults.

Figure 1

General metabolism of both type I and type II pyrethroid insecticides. Type I insecticides have an R₂ substitution of H, and type II insecticides have an R₂ substitution of CN (cyano group).

Figure 2

Pyrethroid metabolites measured in NHANES 1999–2002.

Figure 3

LSGM concentrations of age (A), sample collection time (B), and race (C: MA, Mexican American; NHB, non-Hispanic black; NHW, non-Hispanic white). *p < 0.05. **0.05 < p < 0.1.