Immunochemical analysis of 3-phenoxybenzoic acid, a biomarker of forestry worker exposure to pyrethroid insecticides

Pyrethroid insecticides widely used in forestry, agricultural, industrial, and residential applications have potential for human exposure. Short sample preparation time and sensitive, economical high-throughput assays are needed for biomonitoring studies that analyze a large number of samples. An enzyme-linked immunosorbent assay (ELISA) was used for determining 3-phenoxybenzoic acid (3-PBA), a general urinary biomarker of exposure to some pyrethroid insecticides. A mixed-mode solid-phase extraction reduced interferences from acid hydrolyzed urine and gave 110 ± 6% recoveries from spiked samples. The method limit of quantification was 2 μg/L. Urine samples were collected from forestry workers that harvest pine cone seeds where pyrethroid insecticides were applied at ten different orchards. At least four samples for each worker were collected in a 1-week period. The 3-PBA in workers classified as high, low, or no exposure based on job analysis over all sampling days was 6.40 ± 9.60 (n = 200), 5.27 ± 5.39 (n = 52), and 3.56 ± 2.64 ng/mL (n = 34), respectively. Pair-wise comparison of the differences in least squares means of 3-PBA concentrations among groups only showed a significant difference between high and no exposure. Although this difference was not significant when 3-PBA excretion was normalized by creatinine excretion, the general trend was still apparent. No significant differences were observed among days or orchards. This ELISA method using a 96-well plate was performed as a high-throughput tool for analyzing around 300 urine samples measured in triplicate to provide data for workers exposure assessment.