[Comparison of the urinary excretion of biomarkers of exposure to pyrethroids and pyrethrins between residents of urban and rural areas of the province of Quebec, Canada].

BACKGROUND

Residents of rural (agricultural) areas are often suspected of being exposed to higher levels of pesticides than residents of urban areas. However, only a limited number of studies have specifically evaluated the impact of the geographical area of residence on pyrethroid and pyrethrin exposure in the general population. This study aimed at comparing the levels of biomarkers of exposure between an urban and rural, adult and children, population of the Province of Quebec, Canada.

METHODS

A total of 154 urban (Montreal) and 154 rural (Monteregie) participants provided a complete overnight timed-urine collection and filled a self-administered questionnaire. Urine samples were analyzed for pyrethroid and pyrethrin metabolites: cis- and trans-dichloro- and cis-dibromo- vinyldimethylcyclopropane carboxylic acids, phenoxy- and fluorophenoxy-benzoic acids and chrysanthemum dicarboxylic acid. Amounts of metabolites (pmol/12h par kilogram body weight) and their frequency of detection in the two populations were compared and interpreted with the help of the answers gathered by questionnaire.

RESULTS

Adults and children from the rural area tended to excrete higher levels of the main urinary metabolites, the cis- and trans-dichlorovinyldimethylcyclopropane carboxylic acids and the phenoxybenzoic acid, than those living in the urban area. When the adults and children were combined, this difference was statistically significant for the phenoxybenzoic acid (p=0.020), marginally significant for the trans-dichlorovinyldimethylcyclopropane carboxylic acid (p=0.053) and nonsignificant for the cis-dichlorovinyldimethylcyclopropane carboxylic acid (p=0.158). The chrysanthemum dicarboxylic acid, the fluorophenoxybenzoic acid and the dibromovinyldimethylcyclopropane carboxylic acid were detected in much lower proportion but, in the case of the fluorophenoxybenzoic acid, the relative frequency of detection was statistically significantly higher (p<0.001) in the rural population.

CONCLUSION

The presence of a baseline level of biomarkers in the urban and rural population confirms the ubiquity of pyrethroids and pyrethrins in the environment. However, in the rural adult and infantile population under study, other factors possibly contributed to slightly increase exposure compared to the urban population, namely the use of mosquito repellents and household insecticides as reported by questionnaire.