IARC group 1


IARC group 1 Carcinogens are substances, chemical mixtures, and exposure circumstances which have been classified as carcinogenic to humans by the International Agency for Research on Cancer. This category is used when there is sufficient evidence of carcinogenicity in humans. Exceptionally, an agent may be placed in this category when evidence of carcinogenicity in humans is less than sufficient, but when there is sufficient evidence of carcinogenicity in experimental animals and strong evidence in exposed humans that the agent acts through a relevant mechanism of carcinogenicity.
This list focuses on the hazard linked to the agents. This means that while carcinogens are capable of causing cancer, it does not take their risk into account, which is the probability of causing a cancer, given the level of exposure to this carcinogen.
The list is up to date as of January 2026, including all agents classified by Volumes 1–140 of the IARC Monographs.

Agents

CAS No.AgentVolumeVolume publication yearEvaluation yearAdditional information
Clonorchis sinensis 61, 100B20122009
Helicobacter pylori 61, 100B20122009
Opisthorchis viverrini 61, 100B20122009
Schistosoma haematobium 61, 100B20122009
Acheson process, occupational exposure associated with11120172014
Acid mists, strong inorganic54, 100F20122009
Alcoholic beverages44, 96, 100E20122009
Aluminium production34, Sup 7, 92, 100F20122009
Areca nut85, 100E20122009
Auramine productionSup 7, 99, 100F20122009
Automotive gasoline45, 138In prep.2025
Benzidine, dyes metabolized to99, 100F20122009
  • Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data
Betel quid with tobaccoSup 7, 85, 100E20122009
Betel quid without tobaccoSup 7, 85, 100E20122009
Coal gasificationSup 7, 92, 100F20122009
Coal, indoor emissions from household combustion of95, 100E20122009
Coke productionSup 7, 92, 100F20122009
Engine exhaust, diesel46, 10520142012
Epstein-Barr virus70, 100B20122009
Estrogen therapy, postmenopausal72, 100A20122008
  • There is "evidence suggesting lack of carcinogenicity" for estrogen-only menopausal therapy in humans and cancer of the colorectum. An inverse association has been observed between estrogen-only menopausal therapy and cancer of the colorectum.
    • Estrogen-progestogen menopausal therapy 72, 91, 100A20122008
    Estrogen-progestogen oral contraceptives 72, 91, 100A20122008
  • There is "evidence suggesting lack of carcinogenicity" for combined estrogen-progestogen oral contraceptives in humans and cancers of the endometrium, ovary, and colorectum. An inverse association has been observed between combined estrogen-progestogen oral contraceptives and cancers of the endometrium, ovary, and colorectum.
    • Firefighter 98, 1322023 online2022
    Fission products, including strontium-90100D20122009
    Fluoro-edenite fibrous amphibole11120172014
    Haematite mining 1, Sup 7, 100D20122009
    Hepatitis B virus 59, 100B20122009
    Hepatitis C virus 59, 100B20122009
    Hepatitis D virus 59, 139In prep.2025
    Human T-cell lymphotropic virus type I67, 100B20122009
    Human immunodeficiency virus type 1 67, 100B20122009
    Human papillomavirus type 1664, 90, 100B20122009
  • The HPV types that have been classified as carcinogenic to humans can differ by an order of magnitude in risk for cervical cancer
    • Human papillomavirus type 1864, 90, 100B20122009
  • The HPV types that have been classified as carcinogenic to humans can differ by an order of magnitude in risk for cervical cancer
    • Human papillomavirus type 3364, 90, 100B20122009
  • The HPV types that have been classified as carcinogenic to humans can differ by an order of magnitude in risk for cervical cancer
    • Human papillomavirus types 31, 35, 39, 45, 51, 52, 56, 58, 5964, 90, 100B20122009
  • The HPV types that have been classified as carcinogenic to humans can differ by an order of magnitude in risk for cervical cancer
    • Ionizing radiation 100D20122009
    Iron and steel founding 34, Sup 7, 100F20122009
    Isopropyl alcohol manufacture using strong acidsSup 7, 100F20122009
    Kaposi sarcoma herpesvirus70, 100B20122009
    Leather dust100C20122009
    MOPP and other combined chemotherapy including alkylating agentsSup 7, 100A20122008
    Magenta productionSup 7, 57, 99, 100F20122009
    Merkel cell polyomavirus 104, 139In prep.2025
    Mineral oils, untreated or mildly treated33, Sup 7, 100F20122009
    Neutron radiation75, 100D20122009
  • Overall evaluation upgraded to Group 1 with supporting evidence from other relevant data
    • Nickel compoundsSup 7, 49, 100C20122009
    Opium consumption1262021 online2020
    Outdoor air pollution10920162013
    Outdoor air pollution, particulate matter in10920162013
    Painter 47, 98, 100F20122009
    Phenacetin, analgesic mixtures containingSup 7, 100A20122008
    Polychlorinated biphenyls, dioxin-like, with a Toxicity Equivalency Factor according to WHO 10720162013
  • Overall evaluation upgraded to Group 1 with strong supporting evidence from other relevant data
    • Processed meat 11420182015
    Radioiodines, including iodine-13178, 100D20122009
    Radionuclides, alpha-particle-emitting, internally deposited78, 100D20122009
  • Specific radionuclides for which there is sufficient or limited evidence in humans are also listed individually as Group 1 agents
    • Radionuclides, beta-particle-emitting, internally deposited78, 100D20122009
  • Specific radionuclides for which there is sufficient evidence in humans are also listed individually as Group 1 agents
    • Rubber manufacturing industry28, Sup 7, 100F20122009
    Salted fish, Chinese-style56, 100E20122009
    Solar radiation 55, 100D20122009
    Soot 35, Sup 7, 92, 100F20122009
    Tobacco smoke, secondhand83, 100E20122009
    Tobacco smoking83, 100E20122009
    Tobacco, smokelessSup 7, 89, 100E20122009
    Ultraviolet radiation from welding 100D, 1182018 online2017
  • Volume 100D concluded that there is sufficient evidence for ocular melanoma in welders
  • Volume 118 concluded that ultraviolet emissions from welding are carcinogenic to humans
    • Ultraviolet radiation 55, 100D20122017
  • Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data
    • Ultraviolet-emitting tanning devices 100D20122009
    Welding fumes49, 1182018 online2017
    Wood dust62, 100C20122009
    X- and Gamma-Radiation75, 100D20122009
    Radon-222 and its decay products43, 78, 100D20122009
    4,4'-Methylenebis Sup 7, 57, 99, 100F20122009
  • Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data
    • Tacrolimus137In prep.2024
    Tamoxifen66, 100A20122008
  • There is "evidence suggesting lack of carcinogenicity" for tamoxifen in humans and cancer of the female breast. An inverse association has been observed between tamoxifen and cancer of the female breast.
    • 1,3-ButadieneSup 7, 54, 71, 97, 100F20122009
    Acrylonitrile19, Sup 7, 71, 1362025 online2024
    Radium-224 and its decay products78, 100D20122009
    Asbestos 14, Sup 7, 100C20122009
    • Mineral substances that contain asbestos should also be regarded as carcinogenic to humans
    • These CAS Nos are for substances that CAS does not treat in its regular CA index
    Polychlorinated biphenyls18, Sup 7, 10720162013
    Voriconazole137In prep.2024
    1--3--1-nitrosourea Sup 7, 100A20122008
    Radium-226 and its decay products78, 100D20122009
    AflatoxinsSup 7, 56, 82, 100F20122009
    Phosphorus-32, as phosphate78, 100D20122009
    Melphalan9, Sup 7, 100A20122008
    Silica dust, crystalline, in the form of quartz or cristobaliteSup 7, 68, 100C20122009
    Radium-228 and its decay products78, 100D20122009
    N'-Nitrosonornicotine and 4--1--1-butanone Sup 7, 89, 100E20122009
    • Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data
    2,3,7,8-Tetrachlorodibenzo-para-dioxinSup 7, 69, 100F20122009
    Chromium compoundsSup 7, 49, 100C20122009
    Methoxsalen plus ultraviolet A radiation24, Sup 7, 100A20122008
    Treosulfan26, Sup 7, 100A20122008
    Chlorambucil26, Sup 7, 100A20122008
    Aristolochic acid82, 100A20122008
  • Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data
    • Aristolochic acid, plants containing82, 100A20122008
    Etoposide76, 100A20122008
  • Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data
    • Etoposide in combination with cisplatin and bleomycin76, 100A20122008
    Perfluorooctanoic acid 110, 1352025 online2023
    Azathioprine26, Sup 7, 100A20122008
    Chlornaphazine4, Sup 7, 100A20122008
    FormaldehydeSup 7, 62, 88, 100F20122009

    		Cyclophosphamide26, Sup 7, 100A20122008
    Benzopyrene|BenzopyreneSup 7, 92, 100F20122009
    • Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data
    Sulfur mustard9, Sup 7, 100F20122009
    ThiotepaSup 7, 50, 100A20122008
    Bisether; chloromethyl methyl ether 4, Sup 7, 100F20122009
    Busulfan4, Sup 7, 100A20122008
    Diethylstilbestrol21, Sup 7, 100A20122008
    2,3,4,7,8-Pentachlorodibenzofuran100F20122009
    • Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data
    3,3',4,4',5-Pentachlorobiphenyl 100F20122009
  • See Polychlorinated biphenyls, dioxin-like, with a TEF according to WHO
    • Lindane11320182015
    Hydrochlorothiazide50, 108, 137In prep.2024
    Ciclosporin50, 100A20122008
    Phenacetin24, Sup 7, 100A20122008
    • Overall evaluation upgraded to Group 1 with supporting evidence from other relevant data
    Ethanol in alcoholic beverages96, 100E20122009
    Coal-tar pitch35, Sup 7, 100F20122009
    Erionite42, Sup 7, 100C20122009
    Shale oils35, Sup 7, 100F20122009
    Benzene29, Sup 7, 100F, 12020182017
    Plutonium78, 100D20122009
    Thorium-232 and its decay products78, 100D20122009
    Arsenic and inorganic arsenic compounds23, Sup 7, 100C20122009
    Beryllium and beryllium compoundsSup 7, 58, 100C20122009
    Cadmium and cadmium compounds58, 100C20122009
    Uranium, mixture of isotopes 78, 100D20122009
  • Uranium was listed as a Group 1 agent as a member of the family, Radionuclides, alpha-particle-emitting, internally deposited. There was limited evidence for the carcinogenicity of mixtures of uranium isotopes, with positive associations for lung cancer
    • Vinyl chlorideSup 7, 97, 100F20122009
    Acetaldehyde associated with consumption of alcoholic beverages100E20122009
    Ethylene oxideSup 7, 60, 97, 100F20122009
  • Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data
    • 1,2-Dichloropropane41, Sup 7, 71, 11020172014
    TrichloroethyleneSup 7, 63, 10620142012
    Coal-tar distillation92, 100F20122009
    Pentachlorophenol53, 71, 11720192016
    2-Naphthylamine4, Sup 7, 99, 100F20122009
    4-Aminobiphenyl1, Sup 7, 99, 100F20122009
    Benzidine29, Sup 7, 99, 100F20122009
    ortho-ToluidineSup 7, 77, 99, 100F20122009