International Agency for Research on Cancer

By Carey Gillam

New research by top US government scientists has found that people exposed to the widely used weed killing chemical glyphosate have biomarkers in their urine linked to the development of cancer and other diseases.

The study, published last week in the Journal of the National Cancer Institute, measured glyphosate levels in the urine of farmers and other study participants and determined that the presence of the pesticide was associated with signs of a reaction in the body called oxidative stress, a condition that causes damage to DNA. Oxidative stress is considered by health experts as a key characteristic of carcinogens.

The authors of the paper – 10 scientists with the National Institutes of Health and two from the Centers for Disease Control and Prevention (CDC) – concluded that their study “contributes to the weight of evidence supporting an association between glyphosate exposure and oxidative stress in humans.” They also noted that “accumulating evidence supports the role of oxidative stress in the pathogenesis of hematologic cancers,” such as lymphoma, myeloma and leukemia.

“Oxidative stress is not something you want to have,” said Linda Birnbaum, a toxicologist and former director of the National Institute for Environmental Health Sciences. “This study increases our understanding that glyphosate has the potential to cause cancer.”

The study findings come after the CDC reported last year that more than 80% of urine samples drawn from children and adults contained glyphosate. The CDC reported that out of 2,310 urine samples taken from a group of Americans intended to be representative of the US population, 1,885 were laced with detectable traces of glyphosate.

Glyphosate is the most heavily applied herbicide in history, both in the US and globally. One of the best-known glyphosate-based products is Monsanto’s Roundup weedkiller. Roundup has been used by farmers as well as consumers for more than 40 years. Monsanto has always assured the public and regulators that exposure to the weed killer does not pose a threat to human health, but many independent scientists say there is a wealth of evidence to contradict those assurances.

People are exposed to glyphosate by using products made with the chemical and also by eating food and drinking water contaminated with the pesticide. Scientists have found glyphosate residues in an array of popular foods and in waterways across the US.

Notably, in the new paper, the NIH and CDC scientists said that while their study focused on farmers who were exposed to glyphosate when they sprayed it on fields, they saw similar results in “non-farmers.”

The findings suggest “these effects may apply more broadly to the general population who are primarily exposed through ingestion of contaminated food and water or residential applications,” the study authors wrote.

The study is so significant that it warrants regulatory attention, said some independent scientists.

“This is a top level team of investigators and a highly credible study to which regulators need to pay attention,” said Phil Landrigan, a pediatrician and epidemiologist who worked for years at the CDC and the Environmental Protection Agency (EPA) and now directs the Program for Global Public Health and the Common Good at Boston College.

Michael Antoniou, a scientist with the department of medical and molecular genetics at King’s College in London who has been researching glyphosate for years, said the results were “worrying,” with “major health implications.”