(Beyond Pesticides, January 13, 2026) An important study in Nature Microbiology challenges the entrenched assumption in the chemical industry and among regulators that synthetic chemicals can be targeted for specific uses and have limited effects beyond those uses. The categorization of chemicals into pharmaceuticals, pesticides, and industrial chemicals masks their commonalities and combined potential for deep harm to biological systems. In particular, the effects of the onslaught of xenobiotics (not naturally produced) on human gut microbiota are of increasing concern.

The study, by an international team including researchers at the National Institute of Environmental Health Sciences, Cambridge University, and Heinrich Heine University in Germany, tested a set of xenobiotics, including pharmaceutical, pesticide, and industrial compounds, against 22 human gut bacteria. Using both in silico (computers) and in vitro (laboratory experiments), they found 168 chemicals that exerted inhibitory effects on the gut bacteria. Most of these interactions had not been previously reported. Of the xenobiotic categories, fungicides and industrial chemicals were the most influential.

The researchers note that the “pervasive use” of synthetic chemicals “and environmental persistence have led to pollution levels exceeding the planetary boundary for stable and resilient Earth systems” [emphasis added] and that “safety assessments for these chemicals currently do not consider the human gut microbiome.” Given the powerful and accumulating evidence that gut microbiota interact with every human physiological system (see Beyond Pesticides’ coverage here and here), a crucial priority for regulators must be to incorporate consideration of the microbiome into safety research and policies. Currently, the authors observe, there are no available population cohort data that track both chemical exposure and microbiome dynamics.