New tests reveal popular cereals and snack foods could have potentially harmful levels of the same chemical found in weed killer.

The chemical is called glyphosate, and some reports say it may cause cancer. Of the 21 General Mills products examined by the Environmental Working Group, the highest levels of glyphosate were found in Honey Nut Cheerios Medley Crunch, which had more than five times what the advocacy group believes is a safe level. Original Cheerios had more than four-and-a-half times what the group considers safe.

The products are considered safe under EPA standards. "CBS This Morning" reached out to the EPA and FDA, but did not hear back.

General Mills said in a statement that "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."

Bayer, the maker of Roundup weed killer, told CBS News that the glyphosate levels in the report are "far below the established safety standards."

"An adult would have to eat 158 pounds of the oat-based food every day for the rest of their life to reach the strict limits set by the EPA," Bayer said in a statement. "The group behind the new report has a long history of spreading misinformation about pesticide residues. The reality is that regulatory authorities have strict rules when it comes to pesticide residues and the levels in this report are far below the established safety standards."

Dr. David Agus, a cancer specialist, joined "CBS This Morning" Thursday to sort out the claims. He said that "we just don't know" exactly how glyphosate will impact the human body in the long run.

"The problem is when you eat something, say, glyphosate, there's a 10, 20-year lag before disease and the intervention."

Agus explained that glyphosate emerged in the 1960s as a pipe cleaner, and then started being used as a weed killer. But in the 1990s, "usage went through the roof."

When asked if he'd willingly put the chemical in his own body, Agus said that he "certainly wouldn't."

"It can kill bacteria in your G.I. tract, it can disrupt your endocrine system, and there's reasonable data that it can increase risk of lymphoma. So based on all of those, it's probably not good," he said, adding that it can also disrupt our cells and hormone levels.

And he said the chemical is more prevalent in our food than ever. "In the last couple of years, more and more farms across the world are using it to kill all of their crops right before harvest so it's easier to harvest," he said. "So the levels have gone up dramatically in the last decade." Agus added that the urine of most Americans contains glyphosate.

As a result, Agus believes it's important for farmers to seek an alternative — and for society to incentivize other options. "The farmer who doesn't use glyphosate is at a competitive disadvantage to his or her neighbor who does use it. So we have to figure out better and safer ways of doing it."

About 10 years ago, the EPA raised the level of glyphosate allowed in food.

For details on Bayer's position on glyphosate, visit here.

EDITOR'S NOTE: Dr. Agus should have referred to EPA, rather than FDA, regulations in the discussion in this report.