WASHINGTON, D.C. (CBSNEWS.COM) – Two months after releasing an alarming report on herbicides in cereals and other food marketed to children, an environmental advocacy group is back with additional findings. This time, tests detected trace amounts of glyphosate — the active ingredient in Monsanto’s weed killer Roundup — in all of the nearly 30 samples of oat-based cereal and snack bars tested.

All of the samples tested within range of limits deemed acceptable by the U.S. Environmental Protection Agency and the U.S. Food and Drug Administration, and there’s widespread disagreement about what’s an acceptable amount of a chemical termed a “probable carcinogen” by the World Health Organization.

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The latest tests by the Environmental Working Group, or EWG, detected glyphosate in all 28 samples of products made with conventionally grown oats. All but two of the 28 samples had levels of glyphosate above EWG’s own health benchmark of 160 parts per billion.

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The products tested included 10 samples of different types of General Mills’ Cheerios and 18 samples of different Quaker brand products, including instant oatmeal, breakfast cereal and snack bars. The highest level of glyphosate found by the lab was 2,837 parts per billion in Quaker Oatmeal Squares breakfast cereal, the EWI said.

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