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Agents Classified by the IARC Monographs, Volumes 1–133

Group 1 Carcinogenic to humans 126 agents
Group 2A Probably carcinogenic to humans  94 agents
Group 2B Possibly carcinogenic to humans 322 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.

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.

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: 5 May 2023