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 (IARC). This category is used when there is sufficient evidence of carcinogenicity in humans. Exceptionally, an agent (chemical mixture) 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 (mixture) 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
+ Agents Classified by the IARC Monographs, Volumes 1–140CAS No.AgentVolumeVolume publication yearEvaluation yearAdditional informationClonorchis sinensis (infection with)61, 100B20122009Helicobacter pylori (infection with)61, 100B20122009Opisthorchis viverrini (infection with)61, 100B20122009Schistosoma haematobium (infection with)61, 100B20122009Acheson process, occupational exposure associated with11120172014Acid mists, strong inorganic54, 100F20122009Alcoholic beverages44, 96, 100E20122009Aluminium production34, Sup 7, 92, 100F20122009Areca nut85, 100E20122009Auramine productionSup 7, 99, 100F20122009Automotive gasoline45, 138In prep.2025Benzidine, dyes metabolized to99, 100F20122009Overall evaluation upgraded to Group 1 based on mechanistic and other relevant dataBetel quid with tobaccoSup 7, 85, 100E20122009Betel quid without tobaccoSup 7, 85, 100E20122009Coal gasificationSup 7, 92, 100F20122009Coal, indoor emissions from household combustion of95, 100E20122009Coke productionSup 7, 92, 100F20122009Engine exhaust, diesel46, 10520142012Epstein-Barr virus70, 100B20122009Estrogen therapy, postmenopausal72, 100A20122008There 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 (combined)72, 91, 100A20122008Estrogen-progestogen oral contraceptives (combined)72, 91, 100A20122008There 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 (occupational exposure as a)98, 1322023 online2022Fission products, including strontium-90100D20122009Fluoro-edenite fibrous amphibole11120172014Haematite mining (underground)1, Sup 7, 100D20122009Hepatitis B virus (chronic infection with)59, 100B20122009Hepatitis C virus (chronic infection with)59, 100B20122009Hepatitis D virus (HDV)59, 139In prep.2025Human T-cell lymphotropic virus type I67, 100B20122009Human immunodeficiency virus type 1 (infection with)67, 100B20122009Human papillomavirus (HPV) type 1664, 90, 100B20122009The HPV types that have been classified as carcinogenic to humans can differ by an order of magnitude in risk for cervical cancerHuman papillomavirus (HPV) type 1864, 90, 100B20122009The HPV types that have been classified as carcinogenic to humans can differ by an order of magnitude in risk for cervical cancerHuman papillomavirus (HPV) type 3364, 90, 100B20122009The HPV types that have been classified as carcinogenic to humans can differ by an order of magnitude in risk for cervical cancerHuman papillomavirus (HPV) types 31, 35, 39, 45, 51, 52, 56, 58, 5964, 90, 100B20122009The HPV types that have been classified as carcinogenic to humans can differ by an order of magnitude in risk for cervical cancerIonizing radiation (all types)100D20122009Iron and steel founding (occupational exposure during)34, Sup 7, 100F20122009Isopropyl alcohol manufacture using strong acidsSup 7, 100F20122009Kaposi sarcoma herpesvirus70, 100B20122009Leather dust100C20122009MOPP and other combined chemotherapy including alkylating agentsSup 7, 100A20122008Magenta productionSup 7, 57, 99, 100F20122009Merkel cell polyomavirus (MCPyV)104, 139In prep.2025Mineral oils, untreated or mildly treated33, Sup 7, 100F20122009Neutron radiation75, 100D20122009Overall evaluation upgraded to Group 1 with supporting evidence from other relevant dataNickel compoundsSup 7, 49, 100C20122009Opium consumption1262021 online2020Outdoor air pollution10920162013Outdoor air pollution, particulate matter in10920162013Painter (occupational exposure as a)47, 98, 100F20122009Phenacetin, analgesic mixtures containingSup 7, 100A20122008Polychlorinated biphenyls, dioxin-like, with a Toxicity Equivalency Factor (TEF) according to WHO (PCBs 77, 81, 105, 114, 118, 123, 126, 156, 157, 167, 169, 189)10720162013Overall evaluation upgraded to Group 1 with strong supporting evidence from other relevant dataProcessed meat (consumption of)11420182015Radioiodines, including iodine-13178, 100D20122009Radionuclides, alpha-particle-emitting, internally deposited78, 100D20122009Specific radionuclides for which there is sufficient or limited evidence in humans are also listed individually as Group 1 agentsRadionuclides, beta-particle-emitting, internally deposited78, 100D20122009Specific radionuclides for which there is sufficient evidence in humans are also listed individually as Group 1 agentsRubber manufacturing industry28, Sup 7, 100F20122009Salted fish, Chinese-style56, 100E20122009Solar radiation (see Ultraviolet radiation (wavelengths 100–400 nm, encompassing UVA, UVB, and UVC); Ultraviolet radiation from welding; and Ultraviolet-emitting tanning devices)55, 100D20122009Soot (as found in occupational exposure of chimney sweeps)35, Sup 7, 92, 100F20122009Tobacco smoke, secondhand83, 100E20122009Tobacco smoking83, 100E20122009Tobacco, smokelessSup 7, 89, 100E20122009Ultraviolet radiation from welding (see Ultraviolet radiation (wavelengths 100–400 nm, encompassing UVA, UVB, and UVC); Ultraviolet-emitting tanning devices; and Solar radiation)100D, 1182018 online2017Volume 100D concluded that there is sufficient evidence for ocular melanoma in welders Volume 118 concluded that ultraviolet emissions from welding are carcinogenic to humans (Group 1; there is sufficient evidence in humans for the carcinogenicity of ultraviolet radiation from welding)Ultraviolet radiation (wavelengths 100–400 nm, encompassing UVA, UVB, and UVC) (see Ultraviolet radiation from welding; Ultraviolet-emitting tanning devices; and Solar radiation)55, 100D20122017Overall evaluation upgraded to Group 1 based on mechanistic and other relevant dataUltraviolet-emitting tanning devices (see Ultraviolet radiation (wavelengths 100–400 nm, encompassing UVA, UVB, and UVC); Ultraviolet radiation from welding; and Solar radiation)100D20122009Welding fumes49, 1182018 online2017Wood dust62, 100C20122009X- and Gamma-Radiation75, 100D20122009Radon-222 and its decay products43, 78, 100D201220094,4'-Methylenebis(2-chloroaniline) (MOCA)Sup 7, 57, 99, 100F20122009Overall evaluation upgraded to Group 1 based on mechanistic and other relevant dataTacrolimus137In prep.2024Tamoxifen66, 100A20122008There 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, 100F20122009Acrylonitrile19, Sup 7, 71, 1362025 online2024Radium-224 and its decay products78, 100D20122009Asbestos (all forms, including actinolite, amosite, anthophyllite, chrysotile, crocidolite, tremolite)14, Sup 7, 100C20122009Mineral substances (e.g. talc or vermiculite) 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 indexPolychlorinated biphenyls18, Sup 7, 10720162013Voriconazole137In prep.20241-(2-Chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea (Methyl-CCNU) (Semustine)Sup 7, 100A20122008Radium-226 and its decay products78, 100D20122009AflatoxinsSup 7, 56, 82, 100F20122009Phosphorus-32, as phosphate78, 100D20122009Melphalan9, Sup 7, 100A20122008Silica dust, crystalline, in the form of quartz or cristobaliteSup 7, 68, 100C20122009Radium-228 and its decay products78, 100D20122009N'-Nitrosonornicotine (NNN) and 4-(N-Nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK)Sup 7, 89, 100E20122009Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data2,3,7,8-Tetrachlorodibenzo-para-dioxinSup 7, 69, 100F20122009Chromium (VI) compoundsSup 7, 49, 100C20122009Methoxsalen (8-methoxypsoralen) plus ultraviolet A radiation24, Sup 7, 100A20122008Treosulfan26, Sup 7, 100A20122008Chlorambucil26, Sup 7, 100A20122008Aristolochic acid82, 100A20122008Overall evaluation upgraded to Group 1 based on mechanistic and other relevant dataAristolochic acid, plants containing82, 100A20122008Etoposide76, 100A20122008Overall evaluation upgraded to Group 1 based on mechanistic and other relevant dataEtoposide in combination with cisplatin and bleomycin76, 100A20122008Perfluorooctanoic acid (PFOA)110, 1352025 online2023Azathioprine26, Sup 7, 100A20122008Chlornaphazine4, Sup 7, 100A20122008FormaldehydeSup 7, 62, 88, 100F20122009Cyclophosphamide26, Sup 7, 100A20122008Benzo[a]pyreneSup 7, 92, 100F20122009Overall evaluation upgraded to Group 1 based on mechanistic and other relevant dataSulfur mustard9, Sup 7, 100F20122009ThiotepaSup 7, 50, 100A20122008Bis(chloromethyl)ether; chloromethyl methyl ether (technical-grade)4, Sup 7, 100F20122009Busulfan4, Sup 7, 100A20122008Diethylstilbestrol21, Sup 7, 100A201220082,3,4,7,8-Pentachlorodibenzofuran100F20122009Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data3,3',4,4',5-Pentachlorobiphenyl (PCB-126)100F20122009See Polychlorinated biphenyls, dioxin-like, with a TEF according to WHOLindane11320182015Hydrochlorothiazide50, 108, 137In prep.2024Ciclosporin50, 100A20122008Phenacetin24, Sup 7, 100A20122008Overall evaluation upgraded to Group 1 with supporting evidence from other relevant dataEthanol in alcoholic beverages96, 100E20122009Coal-tar pitch35, Sup 7, 100F20122009Erionite42, Sup 7, 100C20122009Shale oils35, Sup 7, 100F20122009Benzene29, Sup 7, 100F, 12020182017Plutonium78, 100D20122009Thorium-232 and its decay products78, 100D20122009Arsenic and inorganic arsenic compounds23, Sup 7, 100C20122009Beryllium and beryllium compoundsSup 7, 58, 100C20122009Cadmium and cadmium compounds58, 100C20122009Uranium, mixture of isotopes (see Radionuclides, alpha-particle-emitting, internally deposited)78, 100D20122009Uranium 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 cancerVinyl chlorideSup 7, 97, 100F20122009Acetaldehyde associated with consumption of alcoholic beverages100E20122009Ethylene oxideSup 7, 60, 97, 100F20122009Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data1,2-Dichloropropane41, Sup 7, 71, 11020172014TrichloroethyleneSup 7, 63, 10620142012Coal-tar distillation92, 100F20122009Pentachlorophenol53, 71, 117201920162-Naphthylamine4, Sup 7, 99, 100F201220094-Aminobiphenyl1, Sup 7, 99, 100F20122009Benzidine29, Sup 7, 99, 100F20122009ortho-ToluidineSup 7, 77, 99, 100F20122009
See also IARC group 2A IARC group 2B IARC group 3
References
External links Description of the list of classifications , IARC