| Group 1 | Carcinogenic to humans | 135 agents |
|---|---|---|
| Group 2A | Probably carcinogenic to humans | 95 agents |
| Group 2B | Possibly carcinogenic to humans | 323 agents |
| Group 3 | Not classifiable as to its carcinogenicity to humans | 500 agents |
For definitions of these groups, please see the Preamble.
It is strongly recommended to consult the complete Monographs on these agents, the publication date, and the list of studies considered. Significant new information might support a different classification.
For agents that have not been classified, no determination of non-carcinogenicity or overall safety should be inferred.
- List of Classifications (optimized for the latest versions of the browsers Chrome and Mozilla Firefox)
- List of Classifications by cancer site (PDF file)
- French version of the List of classifications by cancer site, as hosted by Centre Léon Bérard
See Preventable Exposures Associated With Human Cancers (Cogliano et al., 2011)
Read the IARC Monographs Q&A for answers to commonly asked questions on the evaluation process.
Note: In September 2022, four additional individual Group 1 agents were created by splitting up some existing agent groupings because not all agents in the groups had the same cancer sites with sufficient and limited evidence for cancer in humans. Three strains of human papillomavirus (HPV) were split from a larger grouping of HPV strains. Ultraviolet (UV) radiation from welding was split from a broader category of UV radiation.
Note 2: In July 2023, an additional Group 1 agent was generated by creating an individual listing for uranium, which was previously listed without being named specifically as a member of the family, Radionuclides, alpha-particle-emitting, internally deposited (Group 1).
Although care was taken in preparing these lists, mistakes may be present.
If you find an error, please notify us at imo@iarc.who.int.Last update: 27 June 2025