Urine glyphosate level as a quantitative biomarker of oral exposure

Background: Since the classification of glyphosate as a Group 2A substance "probably carcinogenic to humans" by the IARC in 2015, human health concerns have been raised regarding the exposure of operators, bystanders, and consumers. Urine measurement studies have been conducted, but since toxicokinetic data on glyphosate in humans is lacking, a meaningful interpretation of this data regarding exposure is not possible. Objective: This study aims to determine the fraction of glyphosate and AMPA excretion in urine after consuming ordinary food with glyphosate residue, to estimate dietary glyphosate intake. Methods: Twelve participants consumed a test meal with a known amount of glyphosate residue and a small amount of AMPA. Urinary excretion was examined for the next 48 h. Results: Only 1% of the glyphosate dose was excreted in urine. The urinary data indicated the elimination halflife was 9 h. For AMPA, 23% of the dose was excreted in urine, assuming that no metabolism of glyphosate to AMPA occurred. If all of the excreted AMPA was a glyphosate metabolite, this corresponds to 0.3% of the glyphosate dose on a molar basis. Conclusion: This study provides a basis for estimating oral glyphosate intake using urinary biomonitoring data.