The short answer
IARC called glyphosate probably carcinogenic to humans in 2015. The EPA says it is not likely to be carcinogenic to humans. The gap comes from hazard versus risk, and it is the backdrop to the Prop 65 dispute.
Prop 65 is California's hazard-based warning law.
IARC calls glyphosate 'probably carcinogenic'; the EPA disagrees.
The EPA says IARC and the EPA ask different questions: hazard versus real-world risk.
The court history of the Prop 65 warning is not covered by the sources checked for this page.
Choose how you want to read this
The whole article, with every detail and caution.
When agencies disagree
Glyphosate is a widely used weedkiller. The hazard-versus-risk debate shows up clearly in how agencies describe it.
In March 2015, the International Agency for Research on Cancer (IARC) classified glyphosate as "probably carcinogenic to humans" (Group 2A). IARC based this on limited evidence in people, enough evidence in animal studies, and strong evidence of genotoxicity (damage to genes).
The U.S. EPA reached a different conclusion. It says glyphosate is "not likely to be carcinogenic to humans." The EPA explains that it looks at risk under real-world exposure, while IARC asks whether a substance can cause cancer under any conditions. See our page on glyphosate.
Where Prop 65 fits
Proposition 65 is California's warning law, run by the state's OEHHA. It is hazard-based. A warning on a label means a chemical is on the state list. It does not measure how likely harm is at the amount you meet.
The listing history and the court cases over the glyphosate warning are not described here. We could not confirm them in a source this site accepts. For current details, see OEHHA's Prop 65 pages. Note also that in 2022 a federal appeals court vacated part of the EPA's glyphosate human health decision, and the EPA withdrew its interim decision. The EPA says this does not by itself mean its scientific findings are wrong.
The bottom line
IARC and the EPA answer different questions, so their labels can differ. A Prop 65 warning is a hazard signal, not a personal risk estimate. If you use glyphosate products, ask your care team how an exposure like this fits with your other risks.
Sources
Common questions
Why was glyphosate listed under Prop 65?
IARC classified it as 'probably carcinogenic to humans' in 2015. California's Office of Environmental Health Hazard Assessment (OEHHA) keeps the Prop 65 list. This page has not confirmed the listing details in an approved source.
Why did courts block the warning?
We could not confirm the court rulings in a source we accept, so this page does not describe them. The EPA's position is that glyphosate is not likely to be carcinogenic to humans.
Is glyphosate still on the Prop 65 list?
We could not confirm the current status in an approved source. OEHHA's Prop 65 pages are the place to check.
What does this dispute show?
It highlights the tension when a hazard-based classification (IARC's) differs from a risk-based conclusion (the EPA's).
Questions to ask your doctor
Being prepared helps you get the most out of your appointments. Save or print these questions.
Tap a question to save it to your list (kept on this device).
Talk with a trained specialist or navigator
Cancer Explained provides educational guidance, but does not replace trained specialists, social workers, or your medical team.
Talk to a trained cancer information specialist
Free, confidential assistance from NCI Cancer Information Service via phone, chat, or email.
Contact your oncology team
Locate after-hours contact numbers, portal messages, or urgent triage phone lines.
Find a patient navigator
Get one-on-one help with appointments, logistics, translation, and care coordination.
Find a genetic counselor
Discuss inherited mutation risk, family history, and genetic testing options.
Find an oncology social worker
Access emotional counseling, family support groups, and mental health resources.
Find a financial navigator
Locate copay assistance foundations, grant programs, and lodging/travel support.
Find a clinical-trial specialist
Search matching studies and speak with NCI trial information specialists.
Plain-language explanation of the published sources cited on this page. AI-assisted, source-checked, not clinician-reviewed.
Last updated: 2026-08-11Next planned review: 2028-07-05
Review details and limits
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status — Source checked. This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
General education — varies by person. Answers genuinely differ between people. This page explains what commonly varies and points you to your care team for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
Words to know
Tap any term to see what it means.
Knowledge check
0 of 4 answered
This self-assessment checks understanding of educational content only. It is not medical advice.
How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
Read more about our editorial process, our use of AI, and our corrections policy.
Spotted a problem? Report an error — a factual mistake, broken or outdated source, confusing wording, or anything that seems unsafe. Please do not include names, medical record numbers, dates of birth, addresses, or other identifying medical information in your report.
After using this page, do you understand what to do next?
Anonymous — we only record the answer, never who gave it.