UC Davis

Pyrethroids are neurotoxic insecticides that exert their effects by prolonging the open time of sodium channels, which increases the duration of neuronal excitation. α-cypermethrin (αCM) is derived from the 8-stereoisomers that together make up the pyrethroid cypermethrin, which is one of the most common pyrethroids being used in agriculture throughout the world. The objective of this study was to characterize the occupational exposure to αCM in a cohort of Egyptian agriculture workers (n=37) before, during and after 6-10 consecutive days of application of αCM to cotton fields. Daily spot urine specimens were collected and analyzed by GC-MS NCI for the αCM metabolites 3-phenoxybenzoic acid (3-PBA) and cis-3-(2',2'-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis-DCCA). Prior to αCM application, median urinary levels of 3-PBA (4.59nmol/g creatinine) were greater than cis-DCCA (0.33nmole/g creatinine) demonstrating low background exposures to pyrethroids. During the application period for αCM, median urinary levels of both biomarkers increased (13.44nmol 3-PBA/g creatinine and 7.76nmol cis-DCCA/g creatinine) and ranged from 2.3-93.96nmol 3-PBA/g creatinine and 0.09-90.94nmol cis-DCCA/g creatinine, demonstrating that workers had a wide range of exposures to αCM. The data also demonstrate that pesticide applicators had greater exposures to αCM than workers who play a supporting role in the seasonal application of pesticides on the cotton crop. Urinary cis-DCCA and 3-PBA concentrations were elevated at 7-11 days after the cessation of αCM application, compared to baseline levels. This study is the first to use these biomarkers to quantify occupational exposures specifically to αCM. This urinary biomarker data will be useful for estimating daily internal dose, comparing exposures across job categories within the Egyptian pesticide application teams, and for modeling human exposures to αCM.