For many people, a toasted bagel topped with honey might sound like a healthy breakfast choice. Others might prefer a bowl of oatmeal or cornflakes or a hot plate of scrambled eggs. Few would likely welcome a dose of weed killer that has been linked to cancer in their morning meal.

Yet that is exactly what private laboratory tests in the United States started showing with alarming frequency in 2014: residues of the world’s most widely used herbicide were making their way into American meals.

Testing since then, by both private and public researchers, has shown glyphosate residues not only in bagels, honey, and oatmeal but also in a wide array of products that commonly line grocery store shelves, including flour, eggs, cookies, cereal and cereal bars, soy sauce, beer, and infant formula.

Indeed, glyphosate residues are so pervasive that they’ve been found in human urine. Livestock are also consuming these residues in grains used to make their feed, including corn, soy, alfalfa and wheat.

Glyphosate residues have been detected in bread samples in the United Kingdom for years, as well as in shipments of wheat leaving the United States for overseas markets. “Americans are consuming glyphosate in common foods on a daily basis,” the Alliance for Natural Health said in its April 2016 report, which revealed glyphosate residues detected in eggs and coffee creamer, bagels and oatmeal.

In North Dakota, an agronomist at the state university, Joel Ransom, became so curious about glyphosate residue that in 2014 he ran his own tests on flour samples from the region. North Dakota grows much of America’s hard red spring wheat, a type that is considered the aristocrat of wheat and carries the highest protein content of all classes of American wheat.

It is used to make some of the world’s finest yeast breads, hard rolls, and bagels. But growing the wheat and bringing a healthy crop to harvest is not always easy in a state known for cold and damp conditions. To make harvesting the crop easier, many North Dakota farmers spray their wheat crops directly with glyphosate to help dry the plants a week or so before they roll out their combines. The practice is also common in Saskatchewan, across the border in Canada. So when Ransom ran his tests on flour samples from the area, including flour from Canada, he expected to find some samples with glyphosate. He certainly did not expect all of them to have glyphosate residues. But they did.

Since at least the 1960s, world food and health experts have sought to gauge how much of a pesticide can be ingested on a daily basis—an “acceptable daily intake” (ADI)—over a lifetime without any noteworthy health risk.

The United States allows among the highest levels of glyphosate residues, which critics say underscores the level of influence Monsanto has with regulators. The EPA even has gone so far as to say that safety margins called for by law to protect children from pesticide exposures could be reduced when it comes to glyphosate.

The Food Quality Protection Act calls for the EPA to use an extra tenfold (10X) safety factor when assessing exposure risk and establishing allowable levels for pesticide residues in food, unless the EPA determines the extra margin is not necessary to protect infants and young children because the substance in question is so safe. That’s exactly what the regulatory agency decided with glyphosate, saying it had adequate data to show that the extra margin of safety for glyphosate could be eliminated.

Even with the EPA’s generous allowances for glyphosate residues, many of the various individuals and organizations doing their own testing have found levels that exceed the tolerances, though many tests do show residues falling within the allowed thresholds.

Still, critics say even residues that the EPA says are at safe levels may in fact be harmful to human health when consumed meal after meal, day after day. They believe that the EPA’s analysis is outdated and not sufficient to protect people from the pervasiveness of many pesticides, such as glyphosate, that are often combined in food.

The private and nonprofit attempts to test foods for glyphosate residues were well under way when the World Health Organization’s cancer experts made their March 2015 decision to classify glyphosate as a probable human carcinogen. But testing efforts doubled after that, in large part because WHO’s decision didn’t stand alone; rather, it added to warnings that many scientists had been making for years.

It’s not just glyphosate residues that people worry about, of course. Fears about a range of chemical residues in food have been growing in recent years. Pesticide residues can be found in everything from mushrooms to potatoes and grapes to green beans.

One sample of strawberries examined by the USDA in an annual testing program found residues of twenty pesticides in the berries. In fact, roughly 85 percent of more than 10,000 food samples tested by the USDA in 2015 carried pesticide residues.

Most of those foods were fruits and vegetables, both fresh and processed—foods consumers generally consider healthy. Residue levels higher than what the government allows have been found in spinach, strawberries, grapes, green beans, tomatoes, cucumbers, and watermelon.

Even residues of chemicals long banned in the United States were found as recently as 2015, including residues of DDT or its metabolites found in spinach and potatoes. U.S. regulators have also reported finding illegally high levels of the neonicotinoid insecticide thiamethoxam in rice.

The USDA asserts that all these pesticide residues are nothing for people to worry about. The agency states that “residues found in agricultural products sampled are at levels that do not pose risk to consumers’ health and are safe.” But many scientists say there is little to no data to back up that claim. The animal studies the regulators rely on to set the allowable pesticide levels are typically conducted by, or on behalf of, the pesticide companies and look only at the effects of one pesticide at a time.

Regulators do not have sufficient research regarding how consuming residues of multiple types of pesticides affects us over the long term, and government assurances of safety are simply false, say the skeptical scientists.

“We don’t know if you eat an apple that has multiple residues every day what will be the consequences twenty years down the road,” said Chensheng Lu, associate professor of environmental exposure biology at the Harvard T.H. Chan School of Public Health. “They want to assure everybody that this is safe, but the science is quite inadequate. This is a big issue.”