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.

Keywords:

• biological monitoring
• biomarkers
• human exposure
• pesticides
• pyrethroids

ACKNOWLEDGMENTS

The authors are very grateful to Drs. A. Charette and W. Lin for the synthesis of CDCA. We also address our gratitude to all the participants and to the team of the Agence de la santé et des services sociaux de la Montérégie for its contribution and help with the field work.

This study was funded by the Institute national de santé publique du Québec. The protocol of this study, requiring the enrollment of humans, as well as the questionnaires and the consent forms, were approved by the Human Research Ethics Committee of the Faculty of Medicine of the Université de Montréal prior to the onset of the study.

Notes

^A Defined as 3 times the standard deviation from 10 replicates of blanks spiked with pyrethroid metabolites levels ranging between 4 and 10 times the instrumental limit of detection, which was estimated to 3 times the signal to noise ratio.

^B Defined as 3.3 times the detection limit.

^C Precision for a given batch of analysis (same day, same calibration).

^D Essentially equivalent to the reproducibility except over a longer period of time (different days and different calibrations).

^E Percent recovery of pyrethroid metabolites using blank urine with low, medium, and high specific gravity spiked with 0.5 μg/L of standard.

^A This information was not available for all the participants. The % was thus calculated on the basis of the total number of answers for this factor.

^B Highest educational level indicated for the child sample applies to the conserting parent.

^A Incomplete urine voids were excluded.

^A Incomplete urine voids were excluded.

^A Children had statistically significantly higher biomarker levels than adults.

^B NS = non significant, with p>0.05 and no trend.

^C NS for all metabolites = nonsignificant association for the four main pyrethroid metabolites (tDCCA, cDCCA, PBA and CDCA) with p > 0.05 and no trend.

^D Effect contrary to what is expected, i.e., the group that answered positively to being exposed to the factor showed lower biomarker levels.

^E Includes fruit picking, the visit to a botanical garden, a greenhouse, a farm, or any other public place where pesticides can be used.

^F Insufficient power (n too small: ⩽ 8) to draw conclusions.

^G The group of participants who answered “Yes” had higher biomarker levels than the group that answered “No.”

^H Analysis was conducted according to two subgroups only to ensure a sufficient sample size in each group.

^I Individuals eating >4 portions of fruits and vegetables per day exhibited higher levels of this biomarker than those eating 1–4 portions of fruits per day.

^A Without excluding participants with incomplete urine collections.

^B Reference 23.

^C Reference 6.