Time courses and variability of pyrethroid biomarkers of exposure in a group of agricultural workers in Quebec, Canada

Purpose Cypermethrin is a pyrethroid pesticide widely used in agriculture. Exposure can be assessed through biomonitoring. However, interpretation of results requires a proper knowledge of the toxicokinetics of the exposure biomarkers of interest. This study aimed at characterizing typical urinary time courses of biomarkers of exposure to cypermethrin in farm workers in Quebec following an exposure episode, distribution of values and variability, and predictors of elevated excretion levels. Methods Workers provided total voids before seasonal spraying and during three consecutive days following an exposure period. Personal factors, professional tasks, and exposure conditions were documented by questionnaire. The urinary metabolites cis - and trans -3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acids (DCCA) and 3-phenoxybenzoic acid (3-PBA) were quantified. Results Time courses showed significant variations of metabolite levels through time, although a clear profile typical of an acute exposure episode was not observed for several workers. However, maximum urinary levels in most exposed workers were generally reached 18–32 h following the onset of an exposure episode. Group comparison showed that applicators had higher excretions than workers performing inspection, harvest, or weeding. Conclusions Time-dependent variations in excretions indicate the importance of serial urinary collections for a proper interpretation of a worker exposure pattern. In the context of group comparison, the alternative based on observed time courses and peak levels in most exposed workers would be the collection of urine samples prior to an exposure episode, at the end-of-shift after exposure onset and following morning void. When spot samples can only be collected for population exposure assessment, Monte Carlo simulations showed that iterative random selection of single urinary values from individual time courses observed in this study to predict distribution of values in the group of workers converged to similar central tendencies.