Pesticide residue transfer in Thai farmer families: using structural equation modelling to determine exposure pathways

Use of pesticides in agriculture may lead to downstream exposure of farmers' families to pesticide residues inadvertently taken home. Identification of the independent contribution of different exposure pathways from the farmer to their children can provide clear targets to reduce exposure of farmers' children. Individual contribution of different pesticide transfer exposure pathways was investigated using structural equation modelling methods, and describe its benefits compared to standard multiple regression. 72 Thai families, consisting of a farmer, spouse and a child, participated in this study. Family members completed a questionnaire and self-collected three spot morning urine samples in the spraying season. Urine samples were analysed for DEP, DETP, DEDTP, DMP, DMTP and DMDTP. A path model was developed based on an a priori hypothesized framework to examine the individual contribution of different exposure pathways that may directly or indirectly affect transfer of pesticide residues from farmers to their children. Transfer from the farmer to the child occurs indirectly; primarily through transfer to the spouse in the first instance, but also through contamination of the home environment. Clear targets for interventions are directly the reduction of farmers' take-home exposures, and indirectly by frequent cleaning of the home to avoid build-up of pesticide residues.