Some products made by cereal and snack manufacturing company General Mills are contaminated with “troubling” levels of glyphosate, a cancer-causing ingredient found in the popular weedkiller Roundup, according to a report published yesterday by the Environmental Working Group (EWG), a nonprofit watchdog group.

The report asserts that popular cereals like Honey Nut Cheerios and Multi Grain Cheerios contain an ingredient that’s been tied to cancer.

“As these latest tests show, a box of Cheerios or other oat-based foods on store shelves today almost certainly comes with a dose of a cancer-causing weedkiller,” said EWG vice president for science investigations Olga Naidenko, PhD, in a press release.

The level of glyphosate detected in 21 oat-based snack and cereal products was higher than what EWG scientists recommend for children. Scientists say that glyphosate gets into these foods because the weedkiller Roundup, produced by Bayer-Monsanto, is used on or near oats and other crops grown for food.

“The only way to quickly remove this cancer-causing weedkiller from foods marketed to children is for companies like General Mills and Quaker to use oats from farmers who do not use glyphosate as a desiccant,” the analysis says.

This latest warning follows two other rounds of testing done in July and October of last year. All three rounds of testing confirmed that popular oat-based cereals and snacks currently found on grocery store shelves contained “levels of glyphosate consistently above EWG’s children’s health benchmark,” the report notes.

In the new analysis, the General Mills products with the highest glyphosate levels were Honey Nut Cheerios Medley Crunch and Cheerios. The EWG’s “health benchmark” for children is 160 parts per billion glyphosate; that’s the upper level considered “protective for children’s health with an adequate margin of safety.” . Honey Nut Cheerios Medley Crunch had 833 ppb and Cheerios had 729 ppb, the new report says.

Glyphosate has been labeled as “possibly carcinogenic to humans” by the World Health Organization since 2015. It was labeled a known carcinogen in 2017 by California’s Office of Environmental Health Hazard Assessment.

Bayer-Monsato has been sued multiple times by customers who used Roundup in their yards for years and subsequently developed cancer. Since August, three California juries have awarded plaintiffs $2.2 billion in lawsuits against Bayer-Monsanto.

In a statement provided to Health, General Mills said that the company’s top priority is food safety.  “Most crops grown in fields use some form of pesticides and trace amounts are found in the majority of food we all eat,” the statement reads. “Experts at the FDA and EPA determine the safe levels for food products. These are very strict rules that we follow as do farmers who grow crops. We continue to work closely with farmers, our suppliers and conservation organizations to minimize the use of pesticides on the ingredients we use in our foods.”

What is glyphosate?

Glyphosate (sold under the brand name Roundup) is an herbicide, which is another term for a chemical that kills weeds. First registered for use in the United States in 1974, glyphosate has become one of the most popular herbicides in the country, according to Oregon State University’s National Pesticide Information Center.

You can be exposed to glyphosate by breathing it or absorbing it through your eyes while using Roundup. If you don’t wash your hands after using it, you could swallow some of it by eating or smoking after spraying plants with it. Additionally, you can come into contact with it by touching plants that have just been sprayed with the weedkiller. It won’t easily pass through your skin.

Here’s how glyphosate ends up in food products: Farmers who grow non-organic products use Roundup to kill weeds on their farms, then companies like General Mills buy contaminated food products from those farmers.

Glyphosate’s potential to harm has been controversial for some time. Studies conducted by regulatory agencies around the world have concluded that the ingredient likely doesn’t cause cancer—for example, the EPA has said glyphosate poses no risk to human health. But scientists at the International Agency for Research on Cancer, a division of the World Health Organization, have said glyphosate is “probably carcinogenic to humans.”

What does this mean for your grocery list?

While Cheerios haven’t been deemed unsafe by the FDA, Health contributing nutrition editor Cynthia Sass, RD, provides some tips for being extra careful in light of this new analysis.

For example, it might be worth your while to pick up organic alternatives to cereals and snack bars made by companies that use conventionally grown ingredients. “If you’ve already been feeding your kids these cereals, or eating them yourself, take action in positive ways,” Sass says. “First, switch to organic cereal,” Sass says.

Of course, the price tags on organic products can make them out of reach for many consumers. “To save money on organic cereals, look for organic store brands, and go to the websites of organic brands to find coupons,” Sass recommends.

However, it’s important to note that even some organic brands contain glyphosate. “While organic farming prohibits the use of glyphosate, it can end up in organic brands because the chemical is able to bind to water and soil and travel through the air or streams to nearby organic farms,” Sass explains.

For this reason, Sass recommends protesting the use of glyphosate in the United States, by using social media or signing petitions. “Take action,” she says. “Most changes to the food system stem from consumer demand. Let companies and the FDA know you don’t want glyphosate in your food. What you don’t buy sends a strong message and can trigger large companies to make changes.”