Assessment of Exposure to Pyrethroids and Pyrethrins in a Rural Population of the Montérégie Area, Quebec, Canada

Abstract

Pesticide use remains a preoccupation of the population and public health authorities given its possible impact on health. Pyrethroids can be listed among the widely used pesticides. The general population is potentially chronically exposed to pyrethroids mainly through food intake, but acute or sporadic exposures can also occur by other routes. Although pyrethroids are considered among the least toxic pesticides, their neurotoxic properties can affect humans, but current exposure levels in the population of Quebec are not known. The study thus aimed at assessing pyrethroid exposure in a rural, agricultural population during summer through measurements of urinary biomarkers. A total of 163 volunteers, 49 children and 114 adults, living in the Montérégie area of Quebec, participated in the study, which took place from June to August 2006, the period of intensive application of pesticides. Participants were asked to collect all their micturitions from 6 p.m. until the next morning, including first morning void, and to fill out a questionnaire to document factors that could potentially contribute to exposure. A gas-chromatography mass-spectrometry method was used to quantify six urinary metabolites resulting from pyrethroid biotransformation: cis- and trans-2,2-(dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (cDCCA and tDCCA), 3-phenoxybenzoic acid (PBA), chrysanthemum dicarboxylic acid (CDCA), cis-2,2-(dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid (DBCA) and 4-fluoro-3-phenoxybenzoic acid (FPBA). Distributions of amounts of the six metabolites excreted per unit of body weight, during a standardized 12-hr period, followed the same decreasing pattern in adults and in children: tDCCA > PBA > cDCCA > CDCA > DBCA > FPBA. No statistically significant difference was observed between the two groups, but amounts of metabolites varied greatly among individuals, suggesting important interindividual variations in the absorbed doses of these compounds. No consistent associations were observed between the excretion of correlated metabolites and the various factors documented by questionnaire (personal factors, life habits, sources of exposure). Comparison of the current data with those observed in an urban population of the same province during the summer of 2005 suggests a greater summertime exposure to some pyrethroids in the rural population.