Glyphosate, common pesticides damage human DNA at low doses

Listen to the audio version of this article (generated by AI).

Several common pesticides, including the controversial herbicide glyphosate, cause genetic damage to people’s cells at very low exposure levels, according to a new study. Such cellular changes, often referred to as “genotoxicity,” are linked to cancer.

The findings suggest that current pesticide testing and regulation are not fully capturing how pesticides may harm people. 

The new study, published in the Annals of Global Health journal, tested 10 pesticides that people are exposed to and found that eight damaged or altered the DNA in human cells. For the weedkiller glyphosate, the researchers saw cell damage at the lowest levels tested, suggesting that there is almost no safe level of human exposure. It was the first time several of the pesticides were tested for impacts on DNA and the first study to confirm certain mixtures of the pesticides were toxic to cells as well. A mixture of glyphosate, the insecticide acetamiprid and the fungicide fluopyram, for example, damaged cells at the lowest dose tested. 

“Low-dose testing in toxicology is fundamental and often effects of low doses are underestimated simply because they are not studied,” said senior author Daniele Mandrioli, a researcher and secretary general at Collegium Ramazzini, adding that many pesticides are assumed non-toxic to DNA based on industry studies rather than having been tested by independent labs.

“Low-dose testing in toxicology is fundamental and often effects of low doses are underestimated simply because they are not studied.” – Daniele Mandrioli, Collegium Ramazzini

The study prioritized 10 pesticides to test based on previous European Union research on more than 200 pesticides. Mandrioli and colleagues focused on the 10 that were of most concern based on the previous exposure and health data.

In addition to glyphosate, three additional insecticides, three fungicides, and a chemical that boosts the potency of insecticides were all toxic to cells when tested individually. All eight are registered for use in the US. 

For some of the pesticides, including cyprodinil and deltamethrin, it was the first time they were shown to damage cells. 

The study highlights “the need for further research on human cells and incorporating lower‑dose concentration ranges in risk assessment studies,” the authors wrote. 

Glyphosate controversy 

The study comes a month after the US Supreme Court ruled in favor of the former Monsanto company in a case over Roundup, one of the company’s glyphosate-based herbicides. The court said that the US Environmental Protection Agency’s (EPA) regulatory authority over pesticides preempts state claims that a company failed to warn users of certain product risks when the EPA itself has not required such warnings. Bayer, which now owns Monsanto, has spent the last decade fighting more than 100,000 lawsuits filed by people who developed non-Hodgkin lymphoma they blamed on exposure to glyphosate-based weedkillers.

The EPA has “repeatedly concluded that glyphosate is not likely to cause cancer, [and] … has not required a cancer warning on Roundup’s label,” the court wrote. 

However, glyphosate has been scientifically linked to cancer in multiple studies, and was classified as a probable human carcinogen by an arm of the World Health Organization in 2015.

In a statement to The New Lede, Bayer said the new study “was not conducted with the same rigor as studies submitted to regulatory agencies such as the Environmental Protection Agency, the European Food Safety Authority and others who review and assess these products.”

“In short, assessments by regulatory authorities do not support the conclusions of this study, nor does the weight of scientific evidence,” the statement said. 

Luoping Zhang, a researcher and adjunct professor of toxicology at the University of California, Berkeley, said “the science is pretty clear” on glyphosate’s ability to cause genetic damage in exposed humans and in human cells. 

She pointed to two recent US studies — one that looked at pesticide applicators and another that looked at farmers — that found that the herbicide can alter or damage human cells. 

“Substances that are capable of breaking DNA in human cell lines are generally more likely to induce cancer or cause reproductive [and] developmental toxicity,” Mandrioli said. “This is why there is no safe threshold for genotoxic chemicals.”

Featured image: James Baltz/Unsplash +