A number of popular breakfast cereals, generally considered to be healthy for you, have been shown to contain harmful levels of a weed killer linked to cancer, a new study finds.

The lab work and analysis by the non-profit Environmental Working Group (EWG) found trace amounts of glyphosate in a number of products including Cheerios and Quaker Oats granola bars.

Glyphosate is the active chemical ingredient in Monsanto's Roundup weed killer.

Last week, a jury awarded $289 million to a former school groundskeeper who claimed Monsanto's popular Roundup weed killer contributed to his terminal cancer.

Scientists tested 29 products and found that almost three-quarters of the samples they tested contained higher levels of glyphosate than deemed safe, according to the report.

“That does not mean, ‘Stop eating this bowl of Cheerios right now!’ But then when you think about how people eat these oats,” Olga Naidenko, senior science adviser at EWG told Mother Jones. "That’s when those numbers start to come into concern.”

Glyphosate is the most widely used herbicide in the country due to the widespread adoption of GMOs. According to the IARC, the herbicide has additional chemical ingredients that are "probably carcinogenic to humans.

Monsanto (which is now owned by Bayer) said on Monday it planned to challenge the verdict on the grounds that the judge should have barred scientific evidence.

"More than 800 scientific studies, the US EPA, the National Institutes of Health and regulators around the world have concluded that glyphosate is safe for use and does not cause cancer," said a company representative.

The full list of products tested and results from the EWG is available below:

Potentially unsafe levels of glyphosate

  • Back to Nature Classic Granola
  • Barbara's Multigrain Spoonfuls, Original, Cereal
  • Bob's Red Mill Steel Cut Oats
  • Cheerios Toasted Whole Grain Oat Cereal
  • Giant Instant Oatmeal Original Flavor
  • Great Value Original Instant Oatmeal
  • Kellogg’s Cracklin’ Oat Bran oat cereal
  • Lucky Charms (without marshmallows)
  • Market Pantry Instant Oatmeal, Strawberries & Cream
  • Nature Valley Crunchy Granola Bars, Oats 'n Honey
  • Nature Valley Granola Protein Oats 'n Honey
  • Quaker Dinosaur Eggs, Brown Sugar, Instant Oatmeal
  • Quaker Old Fashioned Oats
  • Quaker Simply Granola Oats, Honey, Raisin and Almonds
  • Quaker Steel Cut Oats
  • Umpqua Oats, Maple Pecan

Safe levels of glyphosate

  • Back to Nature Banana Walnut Granola Clusters
  • Bob's Red Mill Organic Old Fashioned Rolled Oats
  • Kellogg’s Nutrigrain Soft Baked Breakfast Bars, Strawberry
  • KIND Vanilla, Blueberry Clusters with Flax Seeds
  • Nature's Path Organic Old Fashioned Organic Oats
  • Whole Foods Bulk Bin conventional rolled oats

No glyphosate detected

  • 365 Organic Old-Fashioned Rolled Oats
  • Cascadian Farm Organic Harvest Berry, granola bar
  • Kashi Heart to Heart Organic Honey Toasted cereal
  • Nature's Path Organic Honey Almond granola
  • Simple Truth Organic Instant Oatmeal, Original
Glyphosate Was Found on Most Samples of Oat-Based Foods
Type of Food Product Name Glyphosate (ppb)*
Sample 1 Sample 2 Sample 3
Granola Nature's Path Organic Honey Almond granola ND** ND  
Back to Nature Classic Granola 620 170  
Quaker Simply Granola Oats, Honey, Raisins & Almonds 430 400  
Back to Nature Banana Walnut Granola Clusters 30 30 340
Nature Valley Granola Protein Oats 'n Honey 220 170  
KIND Vanilla, Blueberry Clusters with Flax Seeds 50 60  
Instant Oats Giant Instant Oatmeal, Original Flavor 760    
Simple Truth Organic Instant Oatmeal, Original ND ND  
Quaker Dinosaur Eggs, Brown Sugar, Instant Oatmeal 620 780  
Great Value Original Instant Oatmeal 450    
Umpqua Oats, Maple Pecan 220 220  
Market Pantry Instant Oatmeal, Strawberries & Cream 120 520  
Oat Breakfast Cereal Kashi Heart to Heart Organic Honey Toasted cereal ND ND  
Cheerios Toasted Whole Grain Oat Cereal 490 470 530
Lucky Charms**** 400 230  
Barbara's Multigrain Spoonfuls, Original, Cereal 340 300  
Kellogg’s Cracklin’ Oat Bran oat cereal 250 120  
Snack Bar Cascadian Farm Organic Harvest Berry, granola bar ND ND  
KIND Oats & Honey with Toasted Coconut ND 120  
Nature Valley Crunchy Granola Bars, Oats 'n Honey 340 120  
Quaker Chewy Chocolate Chip granola bar 120 160  
Kellogg’s Nutrigrain Soft Baked Breakfast Bars, Strawberry 30 80  
Whole Oats 365 Organic Old-Fashioned Rolled Oats ND ND  
Quaker Steel Cut Oats 530 290  
Quaker Old Fashioned Oats 390 1100 1300
Bob's Red Mill Steel Cut Oats 300 ND  
Nature's Path Organic Old Fashioned Organic Oats 30 20  
Whole Foods Bulk Bin conventional rolled oats 10 40  
Bob's Red Mill Organic Old Fashioned Rolled Oats (4 samples tested) ND 10 20, 20***

Source: EWG, from tests by Eurofin Analytical Laboratories

*EWG's child-protective health benchmark for daily exposure to glyphosate in food is 160 ppb.

** ND = none detected

*** Two product samples tested both had 20 ppb glyphosate concentration.

**** Lucky Charms Frosted Toasted Oat Cereal with Marshmallows. Marshmallows were manually removed from the samples prior to shipping to the lab and testing for glyphosate.