It's not news that there's glyphosate in our food system. Glyphosate is the most widely used herbicide in the world and has been classified by the World Health Organization (WHO) as a "probable carcinogenic," although the organization isn't sure that humans ingest enough of it to be harmful. The question is, how much can we ingest before it becomes harmful?

No one really knows. In 2008, the Environmental Protection Agency (EPA) set a legal limit for glyphosate on oats at 30 parts per million, and more recently, the Environmental Working Group (EWG) set a health benchmark for safety, at 160 parts per billion. EWG has since done two rounds of independent testing on foods that contain oats. Results from the first round of testing on granola, instant oats, snack bars, oat breakfast cereals and whole oats — some conventional, some organic — found that the many of the products had levels of glyphosate residue that were over EWG's health benchmark for safety. (Within that link above, you'll find a more nuanced explanation of how EWG set its recommended levels, based on the work of California and the EPA.)

Of the 45 conventional foods tested, 43 of them tested positive for glyphosate residue and 31 of them exceeded EWG's health benchmark. Of the 16 organic products tested, five of them tested positive for glyphosate residue, but none of them exceeded EWG's benchmark.

EWG also commissioned a second set of tests of oat-based products, this time on products frequently eaten by children. The EPA's legal limit for glyphosate residue on oats doesn't differentiate between children and adults, and what may be safe for an adult may not be safe for a developing child. Roundup for Breakfast, Part 2, was released this week. This time, EWG found that all 28 products tested contained traces of glyphosate and 26 of them contained levels higher than its benchmark.

All of the products in round two came from Quaker oat products or Cheerios products — oatmeals, breakfast cereals, breakfast bars and granola snack bars. Full results can be found on the EWG website from that link in the previous graph.

How much is too much?

child, granola bar The EPA sets the same safety limit for glyphosate residue in foods for adults and kids. Some parents may want to limit the amount their kids are ingesting, though. (Photo: moreimages/Shutterstock)

EWG points out that the standards set in 2008 by the EPA were set before various findings about the carcinogenic nature of glyphosate were released, before California added it to its own list of chemicals known to cause cancer, and well before a jury awarded millions of dollars to a man diagnosed with a deadly cancer after he sued Monsanto. He had used Roundup weed killer for years in his job. In the 10 years since the EPA standards were set, much has been learned, but there are still so many questions about glyphosate's safety. (At the end of 2017, the EPA did release a draft on the Human Health and Ecological Risk Assessments for Glyphosate, but no official announcement has been made of any revised standards based on the draft.)

In 2016, the Federal Drug Administration (FDA) said it would begin testing for glyphosate in certain foods. EWG reports that both oats and wheat — "two main crops where glyphosate is used as a pre-harvest drying agent" — were left out of the testing. Of the crops tested, glyphosate was detected on 63 percent of corn samples and 67 percent of soybean samples.

Dizzy yet? This is a lot of information about a lot of tests with conflicting conclusions that consumers are supposed to sift through. And after sifting though it all, there's still no concrete answer to the question, "How much is too much?"

For those who want to choose their foods with an abundance of caution, information like this provided by EWG is helpful. Choosing organic foods is helpful, too, because although traces of glyphosate have been found in organic foods (even though glyphosate isn't legally allowed to be used on organics), organics end up with the lowest trace amounts.

Glyphosate Residue Free certification

Organics are one way to limit exposure to glyphosate residue, and combing through the findings of organizations like EWG on specific products are another. There's a third way. There's a Glyphosate Residue Free certification (which is not associated with EWG) that's starting to show up on some products. The certification is on a handful of products at the moment, most recently showing up on Foodstirs Modern Baking mixes, but as consumers become more aware (and perhaps more confused) about glyphosate, they can look for the certification on more products.

Robin Shreeves ( @rshreeves ) focuses on food from a family perspective from her home base in New Jersey.

There's a lot of glyphosate in kids' cereals
All of the oat-based cereals tested by EWG had traces of what the World Health Organization has named a "probable carcinogen."