Obscure Toxic Pesticide Found in 4 out of 5 People Tested

Four in five people may contain traces of a potentially dangerous pesticide in their urine, a new study warns.

The pesticide in question is chlormequat, an agricultural chemical that has been shown to damage reproductive health and fetal development in animals and may cause similar problems in humans, particularly children. However, the extent of these health impacts is still poorly understood.

In the U.S., chlormequat can be used only on ornamental plants, not food crops. However, since 2018 the Environmental Protection Agency has permitted the presence of chlormequat residues on imported oats and other foods.

“Chlormequat is primarily used on grain crops like oats, wheat and barley,” Alexis Temkin, a senior toxicologist at the nonprofit Environmental Working Group (EWG) and lead author on the study, told Newsweek. “[However,] in the U.S. only imported varieties of these crops are allowed to have chlormequat residues.”

In a recent study published in the Journal of Exposure Science and Environmental Epidemiology, Temkin and her EWG colleagues investigated the prevalence of this chemical—which the EWG has described as “toxic”—in oat-based food products as well as its presence in human urine.

“Testing of oat-based products found chlormequat in 92 percent on nonorganic samples and only low levels on one of eight organic foods,” Temkin said. “EWG also tested nine wheat-based products and only found chlormequat in two products at low levels.”

To test for the prevalence of this compound in humans, the team took urine samples from 96 individuals in the U.S. between 2017 and 2023 and tested them for the presence of chlormequat.

“Our findings show that of the people we tested, 80 percent of them were exposed to chlormequat and that samples collected in 2023 had more detections and at higher concentrations,” Temkin said.

She went on: “While this was just a pilot study, and not necessarily indicative of the general population, given that chlormequat is prevalent in popular oat-based products, these types of foods are likely a major source of exposure for the general public.”

Because of the effects of this compound on fertility and development in animal studies, the prevalence of chlormequat in human food and urine “raises alarm bells” and requires further investigation, Temkin said.

“Understanding these potential risks is urgently needed,” she said. The U.S. Department of Agriculture and the Food and Drug Administration “should be testing grains for chlormequat as part of annual pesticide monitoring,” she added.

“The Environmental Protection Agency needs to fully consider the potential risks to children’s health from chlormequat exposure and reconsider their recent decisions to allow chlormequat to be present in children’s foods,” Temkin said.