Widespread occurrence of glyphosate and aminomethylphosphonic acid in indoor dust from urban homes across the United States and its contribution to human exposure.

Glyphosate is the most widely used herbicide worldwide, with concerns over human exposure and potential health risks. Nevertheless, little is known about the sources of human exposure to glyphosate and its degradation product, aminomethylphosphonic acid (AMPA). In this study, we measured glyphosate and AMPA in 99 indoor dust samples collected from urban homes in sixteen states in the USA. Glyphosate and AMPA were detected in all samples at geometric mean (GM) concentrations of 193 and 30.8 ng/g, respectively. We found a strong and significant positive correlation between glyphosate and AMPA concentrations (r = 0.70, p < 0.01), indicating that the latter mainly originated from glyphosate. The concentrations of glyphosate (r = 0.40, p < 0.01) and AMPA (r = 0.33, p < 0.01) in indoor dust were significantly correlated with the county-wide agricultural usage of this herbicide. Human exposure to glyphosate and AMPA through dust ingestion were in the ranges of 0.05-0.85 and 0.01-0.14 ng/kg body weight (BW)/day, respectively, for various age groups, which were more than two orders of magnitude below the acceptable daily intake for glyphosate (500 μg/kg BW/day). Further studies are needed to identify the sources and health outcomes of human exposure to glyphosate.