Abstract
We determined glyphosate and its degradation product, aminomethylphosphonic acid (AMPA), in paired urine and feces of humans (N = 14), cats (N = 10) and dogs (N = 21). The geometric mean (GM) concentrations of ∑Gly (sum of glyphosate and AMPA) in urine of humans, cats, and dogs were 0.89, 33.2, and 8.38 ng/mL, respectively, whereas those in corresponding feces were 304, 1290, and 424 ng/g dry weight (dw), respectively. The concentrations of glyphosate and AMPA were positively correlated in both urine and feces (R: 0.64-0.79, p < 0.001), indicating co-exposure to these chemicals. Furthermore, the target analyte concentrations measured in paired urine and feces were significantly correlated (R: 0.72-0.75, p < 0.001). The fecal excretion rates of ∑Gly (GM: 130-3350 ng/kg body weight (BW)/day) in humans and pets were 4-7 times higher than the corresponding urinary excretion rates (GM: 20.9-930 ng/kg BW/day), emphasizing that glyphosate and AMPA are predominantly excreted in feces. The cumulative daily intakes (CDI) of glyphosate and AMPA were estimated based on urinary and fecal excretion rates. The GM CDI of ∑Gly were 170, 4840, and 2410 ng/kg BW/day for humans, cats, and dogs, respectively, which were at least two orders of magnitude below the acceptable daily intake (ADI) of glyphosate (0.5 mg/kg BW/day). This study provides an important insight into exposure to and excretion of glyphosate in humans and companion animals.