The short answer
The EU's CLP Regulation classifies carcinogens into Category 1A (known), 1B (presumed), and 2 (suspected). These carry hazard statements — 'May cause cancer' (H350) or 'Suspected of causing cancer' (H351) — and a health-hazard pictogram. It's Europe's version of a carcinogen label.
CLP is the EU's Classification, Labeling and Packaging Regulation.
Carcinogens are sorted into Category 1A, 1B, and 2.
1A = known human carcinogen; 1B = presumed; 2 = suspected.
Hazard statements: H350 'May cause cancer'; H351 'Suspected of causing cancer.'
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The full explanation.
Europe's carcinogen label
How does the EU officially decide that a chemical is a carcinogen, and how does it put that on a label? The answer is the CLP Regulation (Classification, Labeling and Packaging). It is Europe's answer to the hazard groups you have seen from IARC. The difference is simple. CLP is built straight into EU law and product labels.
Three categories
CLP sorts carcinogens into three categories, based on how strong the evidence is:
- Category 1A — Known to be carcinogenic to humans. The grade rests mostly on human evidence.
- Category 1B — Presumed to be carcinogenic to humans. It rests mostly on animal evidence.
- Category 2 — Suspected human carcinogen. The evidence is thinner or less convincing.
That may feel familiar. It broadly parallels the IARC groups. Category 1A and 1B resemble IARC Group 1 and 2A. Category 2 resembles Group 2B. They are separate systems, run by different bodies, so they do not always match exactly. But the logic under both is the same: grade by strength of evidence.
The hazard statements
CLP also attaches standard hazard statements. These are short, fixed phrases that appear on labels and safety data sheets:
- H350 — "May cause cancer" — for Category 1A and 1B carcinogens.
- H351 — "Suspected of causing cancer" — for Category 2 carcinogens.
The wording is deliberate. "May cause cancer" signals stronger evidence. "Suspected of causing cancer" signals more doubt. It is the same known-versus-suspected split, turned into standard label language.
The pictogram
Carcinogens also carry the health-hazard pictogram (GHS08). It is a white diamond with a red border, showing a silhouette with a starburst on the chest. Seeing it tells you a serious health hazard is involved, such as the risk of cancer.
Built on a global system
CLP is how the EU puts the Globally Harmonized System (GHS) into practice. GHS is a United Nations framework for classifying and labeling chemical hazards the same way in every country. That is why the pictograms and hazard statements look familiar on chemical products around the world, including in the US.
Why CLP matters beyond the label
CLP is not just about labels. A carcinogen classification under CLP feeds into the EU's other frameworks. It can flag a substance for REACH restrictions or for Substance of Very High Concern status. It also triggers tighter workplace protections. In the EU system, naming the hazard is the first domino, and it sets the other controls in motion.
The bottom line
CLP is the EU's official system for sorting carcinogens into Categories 1A, 1B, and 2. It labels them with hazard statements (H350 or H351) and the health-hazard pictogram. It is Europe's carcinogen label, and the trigger that switches on the rest of the EU's controls.
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Words to know
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Common questions
What are the CLP carcinogen categories?
Category 1A (known to be carcinogenic to humans, based on human evidence), Category 1B (presumed carcinogenic, based mainly on animal evidence), and Category 2 (suspected human carcinogen).
What do the hazard statements mean?
Category 1A and 1B carcinogens carry H350, 'May cause cancer.' Category 2 carcinogens carry H351, 'Suspected of causing cancer.' These standard phrases appear on labels and safety data sheets.
How does CLP relate to IARC?
Both classify hazard, and the categories are broadly parallel (1A/1B resemble IARC Group 1/2A; Category 2 resembles 2B). But they are separate systems run by different bodies, so they don't always match exactly.
What is GHS?
The Globally Harmonized System, a UN framework for classifying and labeling chemical hazards. CLP is how the EU implements GHS, which is why the pictograms look familiar worldwide.
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Sources last checked: 2026-08-11 what this meansLast updated: 2026-08-11Next planned review: 2028-07-05
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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. We do not employ clinicians and do not intend to — our work 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 checked line by line against the sources listed on it. That confirms the sources support what the page says. 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.
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