Développement d'outils de surveillance biologique pour l'évaluation des risques à la santé des travailleurs en arboriculture et en viticulture exposés aux fongicides
Several workers use captan and folpet as fungicides in agriculture, but their exposure has yet to be measured specifically and precisely. Biomonitoring is an excellent tool for this purpose since it allows to quantify internal exposure. However, the majority of toxicological data on these fungicides come from animal studies and data in humans are limited. The aim of this project was thus to develop biological monitoring tools in order to assess exposure to captan and folpet in humans. In this perspective, the project was divided into three complementary parts: i) to develop specific and accurate analytical methods in order to quantify captan and folpet metabolites in urine and blood, namely tetrahydrophthalimide (THPI) for captan and phthalimide (PI) and phthalic acid for folpet; ii) to determine the toxicokinetics of the two fungicides in humans by exposing volunteers acutely to low-doses of captan or folpet by oral and dermal routes under semi-controlled conditions and by quantifying the biomarkers in plasma and urine, except phthalic acid which was only measured in urine; iii) to validate the use of the selected biomarkers of exposure to captan and folpet and estimate actual exposures of workers and main exposure routes to these fungicide in the context of a field biomonitoring study in farmers during treatment and harvest activities over seven consecutive days. This study showed that THPI and PI are both valid and specific biomarkers of exposure to captan and folpet, respectively, in humans. Indeed, the developed methods for these two metabolites are accurate showing more sensitive detection limits than those reported in the literature, good recovery rate (90% for THPI and 75% for PI), linearity (R2>0.99) and stability (RSD<15% for intra-and inter-day precision and accuracy). They allowed determining the kinetic profiles of the two metabolites in healthy volunteers and in workers. These profiles indicate a rapid elimination of both metabolites, since the urinary elimination half-life of THPI was 11.7 h and 18.7 h following an oral and dermal absorption, respectively, and 27.3 h and 28.8 h for PI. They also evidence a low dermal absorption for both fungicides when oral and dermal route are compared. In addition, parallel profiles were observed between PI and phthalic acid, but the administrated dose of folpet was mostly recovered as phthalic acid rather than PI. As for the study of farmers, it showed that the dermal route was the main route of exposure. It also pointed out that it is important 1) to perform 24-h complete urine collections rather than collect spot urines, 2) to measure several metabolites to better assess actual exposure, and 3) to rely on the toxicokinetics to help interpret biomonitoring data. Overall, knowledge acquired from this study may be applied to other fungicides or even to other substances.
Captan Folpet THPI PI Biomonitoring Phthalic acid Kinetics Human data Field workers