Researchers at the University of Cambridge report that 168 widely used industrial and agricultural chemicals slowed or stopped the growth of bacteria commonly found in a healthy human gut in laboratory experiments, raising questions about whether routine chemical exposure could affect the microbiome and, in some cases, antibiotic resistance.
Scientists at the University of Cambridge report that a large laboratory screen found 168 human-made chemicals that can harm bacteria commonly found in a healthy human gut.
According to the research team, the study tested 1,076 chemical contaminants against 22 species of gut bacteria under controlled lab conditions. The chemicals that inhibited bacterial growth included pesticides—such as herbicides and insecticides used on crops—as well as industrial chemicals used in products such as flame retardants and plastics.
The researchers said many of the chemicals identified are ones people may encounter through everyday exposure, including food, drinking water and the environment, and that most were not previously thought to affect gut bacteria.
The team also highlighted a potential link to antibiotic resistance. In the experiments, some bacteria altered how they functioned to survive chemical stress, and in certain cases this adaptation was associated with resistance to the antibiotic ciprofloxacin. The researchers cautioned that it is not yet clear whether the same changes occur in the human body.
Dr. Indra Roux of Cambridge’s MRC Toxicology Unit, the study’s first author, said the results suggest some substances designed to act on specific targets—such as insects or fungi—can also affect gut microbes. “We were surprised that some of these chemicals had such strong effects,” Roux said, adding that some industrial chemicals “weren’t thought to affect living organisms at all, but they do.”
Professor Kiran Patil, the senior author, said the scale of the dataset allowed the team to build a machine learning model intended to help predict whether chemicals already in use—or still in development—might inhibit gut bacteria, with the longer-term aim of supporting the design of chemicals that are “safe by design.”
Another researcher involved in the work, Dr. Stephan Kamrad, said safety assessments for new chemicals should consider potential effects on gut bacteria, which may be exposed via food and water.
The researchers emphasized that real-world exposure remains a major uncertainty: while they believe gut bacteria are likely to encounter many of the chemicals tested, the concentrations that reach the gut are not well established and monitoring studies would be needed to assess risk. Patil said more real-world exposure data will be important to determine whether similar effects occur in people.
In the meantime, the Cambridge team said steps that may reduce exposure to some chemical pollutants include washing fruits and vegetables before eating and avoiding pesticide use in home gardens.
