Abstract
Organophosphorus pesticides are the most used pesticides in the United States. Most organophosphorus pesticides are composed of a phosphate (or phosphorothioate or phosphorodithioate) moiety and a variable organic group. Organophosphorus pesticides are scrutinized by regulatory bodies and agencies because of their toxicity or suspected carcinogenicity. Upon exposure, organophosphorus pesticides and their metabolites eliminate in urine; these urinary biomarkers are useful to evaluate human exposure. We developed a method using stable isotope dilution, ion chromatography tandem mass spectrometry for quantification in urine of 6 O,O-dialkylphosphates, metabolites of organophosphorus insecticides, and glyphosate, the most used herbicide in the United States. With simple and minimal sample preparation, the analytical method is selective and sensitive (limits of detection are 0.2-0.8 μg/L), accurate (>85%) and precise (relative standard deviation <20%), depending on the analyte. To assess the suitability of the method in real exposure scenarios, we analyzed samples collected anonymously from subjects with suspected exposure to pesticides (n = 40) or who had been on an organic diet (n = 50). We detected glyphosate in 80% of subjects reporting an organic diet and in 78% of those with suspected glyphosate exposure; concentrations ranged from <0.2 to 28.6 μg/L. Median concentrations were 0.39 μg/L for the organic diet group and 0.40 μg/L for individuals with suspected exposure. Interestingly, interquartile ranges were considerably higher among those reporting pesticide exposure (0.63 μg/L) than those consuming organic diets (0.42 μg/L). These data suggest that the method meets typical validation benchmark values and is sensitive to investigate background exposures in the general population.