Environmental exposure to pyrethroid pesticides in a nationally representative sample of U.S. adults and children: The National Health and Nutrition Examination Survey 2007-2012

Abstract

Pyrethroids are an important class of insecticides, and thousands of tons of these compounds are used in the United States every year. This study characterized exposures to pyrethroids and assessed demographic, socioeconomic, and lifestyle factors that modulate pyrethroid exposure using data from the National Health and Nutrition Examination Survey (NHANES) 2007-2012, a nationally representative survey of the non-institutionalized population of the United States. Urinary levels of commonly used biomarkers of pyrethroid exposure, including 3-phenoxybenzoic acid (3-PBA), 4-fluoro-3-phenoxybenzoic acid (F-PBA), and cis-dibromovinyl-dimethylcyclopropane carboxylic acid (DBCA), were determined by liquid chromatography-tandem mass spectrometry. The detection rate of 3-PBA, a nonspecific metabolite of several pyrethroids, was 78.1% in adults (N = 5233) and 79.3% in children (N = 2295). The detection rates of all other pyrethroid metabolites were <10%. The median urinary level of 3-PBA in adults was 0.47 μg/L (interquartile range, 0.14-1.22 μg/L). For children, the median urinary level was 0.49 μg/L (interquartile range, 0.17-1.29 μg/L). Age, gender, family income-to-poverty ratio (PIR), levels of physical activity, alcohol intake, and body mass index were associated with 3-PBA levels in adults. In children, age, gender, race/ethnicity, and PIR were associated with 3-PBA levels. 3-PBA levels also differed significantly across NHANES cycles, with higher levels observed in NHANES 2011-2012. Geometric mean 3-PBA levels in U.S. adults were 0.41 μg/L in NHANES 2007-2008, 0.41 μg/L in NHANES 2009-2010, and 0.66 μg/L in NHANES 2011-2012. In U.S. children, geometric mean 3-PBA levels were 0.40 μg/L in NHANES 2007-2008, 0.46 μg/L in NHANES 2009-2010, and 0.70 μg/L in NHANES 2011-2012. These results demonstrate that pyrethroid exposures remain a current environmental health concern and lay the foundation for further preclinical and epidemiological studies assessing human health risks associated with pyrethroids.

Keywords: Human exposure; Pesticides; Pyrethroids; U.S. population.

Figure 1.

Names and structure of pyrethroid pesticides used in U.S. agriculture and the corresponding metabolites analyzed by NHANES 2007-2012. In addition, d-phenothrin (not shown), a pyrethroid pesticide used in residential applications, forms the nonspecific pyrethroid metabolite 3-PBA.

Figure 2.

Geometric mean levels of 3-PBA differ significantly across the three NHANES cycles investigated for (A) adults and (B) children in the NHANES 2011-2012 population. This difference was statistically significant for 3-PBA levels expressed as μg/L (P <0.0001 for both U.S. adults and children; Tables S8 and S9) and μg/g creatinine (P <0.0001 for both U.S. adults and children; Tables S3 and S6). (C) In contrast, the estimated use of relevant pyrethroid pesticides did not show a clear increase in the period from 2007 to 2012. The low and high use estimates are the sum of use data of γ- and λ-cyhalothrin, cypermethrin, deltamethrin, esfenvalerate, fenpropathrin, τ-fluvalinate, permethrin, and tralomethrin calculated on a molar basis (Σpyrethroids). These pyrethroids are metabolized to 3-PBA, and their use data are available from the USGS (USGS). (D) Estimated agricultural uses of cyfluthrin and deltamethrin are lower compared to the total estimated uses of pyrethroids that are metabolized to 3-PBA. These estimates are consistent with the low detection rate of F-PBA, a specific metabolite of cyfluthrin, and DBCA, a specific metabolite of deltamethrin (see text for details).