Urinary concentrations and determinants of glyphosate and glufosinate in pregnant Canadian participants in the MIREC study

Background: Glyphosate is the most widely applied herbicide in agriculture. Glufosinate is a broad spectrum herbicide used to manage glyphosate-resistant weeds. Despite the widespread use of these herbicides, bio-monitoring data - which inform risk assessment and management - are sparse. Objectives: To identify determinants of urinary concentrations of these herbicides and their metabolites in pregnancy. Methods: We measured urinary concentrations of glyphosate, glufosinate, and their primary metabolites ami-nomethylphosphonic acid (AMPA) and 3-methylphosphinicopropionic acid (3-MPPA) in a single spot urine specimen collected during the first trimester of pregnancy from the Maternal-Infant Research on Environmental Chemicals (MIREC) study. MIREC recruited about 2000 pregnant women from 10 Canadian cities between 2008 and 2011. We used UItra-Performance Liquid Chromatography coupled to tandem mass spectrometry (UPLC-MS/ MS) with sensitive limits of detection to quantify analyte concentrations. We examined urinary concentrations according to maternal sociodemographics, sample collection characteristics, reported pesticide use, and con-sumption of fruits, vegetables, legumes, and grain products. We used ANOVA models with specific gravity -standardized chemical concentrations as the dependent variable to determine associations with maternal and sample determinants. Results: Among women with biobanked urine samples (n = 1829-1854), 74% and 72% had detectable con-centrations of glyphosate and AMPA, respectively. In contrast, one and six percent of women had detectable concentrations of glufosinate and 3-MPPA, respectively. The specific gravity-standardized geometric mean (95% CI) concentrations of glyphosate and AMPA were 0.112 (0.099-0.127) mu g/L and 0.159 (0.147-0.172) mu g/L, respectively. We observed a dose-response relationship between consumption of whole grain bread and higher urinary glyphosate concentrations. Season of urine collection and self-reported pesticide use were not associated with increased concentrations of any analyte. Conclusions: We detected glyphosate and AMPA in the majority of pregnant women from this predominantly urban Canadian cohort. Diet was a probable route of exposure.

Automated summary

This study aimed to identify determinants of urinary concentrations of the herbicides glyphosate and glufosinate and their metabolites in pregnancy. The results showed that the majority of pregnant women had detectable concentrations of glyphosate and its metabolite, while the detection rates of glufosinate and its metabolite were relatively low. The consumption of grain products showed a dose-response relationship with glyphosate concentration, indicating diet as the main route of exposure.