Glyphosate is an active ingredient of the most widely used herbicide Roundup. Human exposure to glyphosate among the participants has increased by 500 percent in the past two decades. In the years of 1993-1996, only 12 percent of participants had detectable levels of glyphosate in their urine. By 2013-2016, this number increased to 70 percent. The researchers also found a thirteen-times increase in glyphosate concentrations between the two collection periods.

Although glyphosate was designed to kill weeds, it also kills susceptible bacteria that have biochemical pathways similar to plants and weeds. Glyphosate impacts the intestinal microbiome through the residues from spraying, since glyphosate was shown to have negative effects on the composition of the intestinal flora of glyphosate from contaminated food. Even at incredibly low environmental concentrations (0.1 ppb) glyphosate had an impact on rat gut microbiome composition. In particular, it lowered the diversity of many of the beneficial microorganisms in experimental rats which enabled the proliferation of opportunistic E. Coli strains. These gut microbiome disturbances showed a substantial overlap with those associated with liver dysfunction in other studies. Several studies have also proposed that it may be a cause of autism through its impact on the gut microbiota.