“The IARC is like a bible in the field … It’s long been recognized as the only agency that looks at environmental chemicals and their carcinogenicity,” says Alex Lu, an associate professor of environmental-exposure biology at Harvard. The 2014 IARC finding, he says, “was a huge deal because everyone is exposed to a little bit of [glyphosate] because it’s so widely used.”

Indeed, glyphosate, available to consumers as the weed killer Roundup, is the most widely used herbicide in the United States. Its use globally continues to grow. And it isn’t only a weed killer; it’s also sprayed on some grain crops before harvest to accelerate drying. Those treated grains then make their way into breakfast foods, containing trace amounts—which the FDA contends are safe—of the herbicide. (Monsanto, Roundup’s manufacturer, did not respond to a request for comment.)

The debate around glyphosate is focused on just how much should be allowed into food. Advocacy organizations such as the EWG and the Alliance for Natural Health disagree with U.S. regulatory bodies’ established risk guidelines for the herbicide. “The concern about glyphosate is long-term exposure,” Naidenko says. “Most health agencies would say a single portion does not cause deleterious effects. But think about eating popular foods such as oatmeal every day, or almost every day—that’s when … such amounts of glyphosate might pose health harm.”

And so the controversy continues. In 2016, the U.S. Department of Agriculture, or USDA, collaborated with the EPA to begin testing residue of glyphosate on corn. However, a year later the project was quietly dumped. In a statement made to the environmental blog EcoWatch, the USDA acknowledged its change of plans, stating that it switched gears to testing honey, which comes in contact with 100 different herbicides. Glyphosate would not be included in the test as it requires a different methodology.

The safety of glyphosate remains contentious within international regulatory bodies, as well. Debates have recently raged in Germany and Argentina. A year after the IARC labeled glyphosate a probable carcinogen, WHO—which, again, oversees the IARC—collaborated with the UN’s Food and Agriculture Organization and directly contradicted the IARC’s findings. Glyphosate, says the report, “is unlikely to pose a carcinogenic risk to humans from exposure through the diet.” The following year, the European Chemicals Agency declared it would not be classifying glyphosate as a carcinogen.

Lu remains dubious about both the FDA and WHO’s declarations that glyphosate is likely not carcinogenic. Part of the problem, he says, is that the herbicide has long been used with little information—and it’s only starting to trickle in now. “The reason that the IARC took so long is because of lack of data,” he says. “They had to weigh the validity [of the risk] before coming to the conclusion.”