Estimation of glyphosate biological half-life among farmers and residents in Thailand

Abstract

Glyphosate is a widely used herbicide worldwide. Research on human health effects has been limited and the toxicokinetics of glyphosate have not been widely examined. This research aimed to study the excretion profile and half-life of glyphosate in farmers and residents who use glyphosate to control weeds in their agricultural fields and near their households, respectively. Multiple spot urine samples per day were collected from the participants for 3 consecutive days after spraying glyphosate. The participants were interviewed about general characteristics, planting activities, glyphosate use, and their health problems related to glyphosate use. Glyphosate concentrations in urine samples were determined by HPLC with a fluorescence detector. The average age of residents (56.4 years) was significantly higher than that of farmers (45.5 years). The glyphosate excretion profile of most participants showed a gradual decline in glyphosate concentrations, but with or without additional exposures some of the profiles showed a jagged pattern of decline. The average urinary half-life of glyphosate in all participants was 24.58 h (95% CI: 18.43–30.73) and 20.95 h (95%CI: 16.85–25.05) for creatinine adjusted and non-adjusted measurements, respectively. The urinary glyphosate half-life measurements among the residents and farmers were not significantly different.