Why do the experts disagree about glyphosate?

By Bloom · · 4 min read

Glyphosate is the active ingredient in Roundup and the most widely used weed killer in the world. If you have read about it, you have probably seen two headlines that cannot both feel true: a World Health Organization agency calls it "probably carcinogenic", and the US Environmental Protection Agency says it is "not likely" to cause cancer. Both statements are accurate quotes. Here is what each agency looked at, what the courts have decided, and what testing has found in food and in people.

Two agencies, two different questions

In March 2015 the International Agency for Research on Cancer (IARC), part of the WHO, placed glyphosate in Group 2A, "probably carcinogenic to humans" [1]. It based this on limited evidence in humans (studies of non-Hodgkin lymphoma in people exposed to glyphosate, mostly through farm work), sufficient evidence in laboratory animals, and strong evidence that glyphosate can damage DNA and cause oxidative stress [1].

IARC rates hazard: whether a substance can cause cancer at some level of exposure. It does not say how likely that is at the amounts people actually meet.

Regulators rate risk: the chance of harm at real-world exposure. In its 2017 draft human health assessment, the EPA concluded that glyphosate is "not likely to be carcinogenic to humans" and found no other meaningful risks when it is used as the label directs [2]. In Europe, the European Chemicals Agency concluded in 2022 that glyphosate does not meet the criteria to be classified as a carcinogen, and the European Food Safety Authority (EFSA) found "no critical areas of concern" in July 2023 [3]. EFSA also listed issues it could not finalise, including the consumer dietary risk assessment [3]. The EU renewed glyphosate's approval for ten years in November 2023 [4].

So the agencies disagree, and part of the reason is that they answer different questions.

What the courts decided

In June 2022 a US federal appeals court, the Ninth Circuit, ruled that the EPA's conclusion that glyphosate is "not likely" to cause cancer was not supported by substantial evidence, because parts of the EPA's own analysis were inconsistent with it [5]. The court set aside the human health part of the EPA's 2020 interim decision, and in September 2022 the EPA withdrew the rest of that decision [6]. The EPA says it is updating its human health assessment and expects to finish in late 2026 [6].

In June 2026 the US Supreme Court ruled 7-2 in Monsanto Co. v. Durnell that federal pesticide law blocks state lawsuits claiming a product should have carried a cancer warning that the EPA did not require [7]. The ruling is about who controls pesticide labels. It does not decide whether glyphosate causes cancer.

How much reaches us

The best national data comes from the CDC. Its researchers measured glyphosate in urine from a nationally representative sample of Americans aged 6 and older in 2013-2014 and detected it in 81.2% of them [8]. Levels were higher in children aged 6 to 11 than in adults aged 20 to 59 [8]. Finding a chemical in urine shows exposure. On its own it does not show harm, and the study does not set a safe level.

What about oats?

Oats and oat cereals come up most often in this debate, and they are where official testing is thinnest. When the FDA ran a special glyphosate testing assignment in fiscal years 2016 and 2017, it tested corn, soybeans, milk and eggs, and found no residues above the legal limits [9][10]. Oats were not part of that assignment [9].

Most of what parents have read about oats comes from tests commissioned by the Environmental Working Group, an advocacy group. In October 2018, EWG had Anresco Laboratories in San Francisco test 28 samples of oat cereals, oatmeal and snack bars made with conventionally grown oats. All 28 contained glyphosate. The highest was 2,837 parts per billion (ppb) in Quaker Oatmeal Squares Honey Nut, and 26 of the 28 were above 160 ppb, a benchmark EWG set itself for children's daily intake [11].

Those numbers need two pieces of context. First, the legal limit the EPA sets for glyphosate on cereal grains, including oats, is 30 parts per million, which is 30,000 ppb [12]. Every result in EWG's tests was below it. EWG argues that this limit is too high for children; the EPA and the companies say products under it are safe [11]. Second, organic is not a guarantee of zero. In EWG's earlier round of tests in August 2018, about one third of the 16 products made with organic oats also contained glyphosate, at lower levels [11].

What we choose instead

Under USDA organic rules, crops sold as organic must be grown without synthetic substances unless they appear on a short approved list [13]. Glyphosate is not on that list; the only herbicides it allows are soap-based ones for roadsides and building edges, and mulches [14]. That is why, for oats, flour and other grains, every pick on Bloom is certified organic. It lowers the chance of glyphosate in the bowl. As EWG's own tests show, it does not rule it out.

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Sources

  1. International Agency for Research on Cancer. IARC Monographs Volume 112: Some Organophosphate Insecticides and Herbicides (evaluation March 2015) iarc.who.int
  2. US EPA. "EPA Releases Draft Risk Assessments for Glyphosate," December 2017 epa.gov
  3. European Food Safety Authority. "Glyphosate: no critical areas of concern; data gaps identified," 6 July 2023 efsa.europa.eu
  4. Commission Implementing Regulation (EU) 2023/2660 of 28 November 2023 renewing the approval of the active substance glyphosate eur-lex.europa.eu
  5. Natural Resources Defense Council v. EPA, 38 F.4th 34 (9th Cir. 2022), decided 17 June 2022 cdn.ca9.uscourts.gov
  6. US EPA. "Glyphosate" (registration review status, including the September 2022 withdrawal of the interim decision) epa.gov
  7. Monsanto Co. v. Durnell, No. 24-1068, US Supreme Court, decided 25 June 2026 supremecourt.gov
  8. Ospina M, Schütze A, Morales-Agudelo P, Vidal M, Wong L-Y, Calafat AM. "Exposure to glyphosate in the United States: Data from the 2013-2014 National Health and Nutrition Examination Survey." Environment International 170 (2022): 107620 doi.org
  9. US FDA. "FY 2016 Pesticide Analysis Demonstrates Consistent Trends Over Five Years," October 2018 fda.gov
  10. US FDA. "FY 2017 Pesticide Analysis Demonstrates Consistent Trends." fda.gov
  11. Environmental Working Group. "Roundup for Breakfast, Part 2: In New Tests, Weed Killer Found in All Kids' Cereals Sampled," October 2018 (tests by Anresco Laboratories; also reports the August 2018 round) ewg.org
  12. 40 CFR 180.364, Glyphosate; tolerances for residues ("Grain, cereal, group 15 except field corn, popcorn, rice, sweet corn, and wild rice": 30 ppm) ecfr.gov
  13. 7 CFR 205.105, Allowed and prohibited substances, methods, and ingredients in organic production and handling ecfr.gov
  14. 7 CFR 205.601(b), Synthetic substances allowed for use in organic crop production: herbicides and weed barriers ecfr.gov

Bloom explains labels, ingredients and certifications. Not medical advice; ask your paediatrician.