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
{| class="wikitable plainrowheaders sortable mw-datatable sticky-header"
|+ Agents Classified by the IARC Monographs, Volumes 1–140
|-
! scope="col" style="width:6.5em;" |CAS No.
! scope="col" |Agent
! scope="col" |Volume
! scope="col" |Volume publication year
! scope="col" |Evaluation year
! scope="col" style="width:15em;" |Additional information
|-
|
|Clonorchis sinensis (infection with)
|61, 100B
|2012
|2009
|
|-
|
|Helicobacter pylori (infection with)
|61, 100B
|2012
|2009
|
|-
|
|Opisthorchis viverrini (infection with)
|61, 100B
|2012
|2009
|
|-
|
|Schistosoma haematobium (infection with)
|61, 100B
|2012
|2009
|
|-
|
|Acheson process, occupational exposure associated with
|111
|2017
|2014
|
|-
|
|Acid mists, strong inorganic
|54, 100F
|2012
|2009
|
|-
|
|Alcoholic beverages
|44, 96, 100E
|2012
|2009
|
|-
|
|Aluminium production
|34, Sup 7, 92, 100F
|2012
|2009
|
|-
|
|Areca nut
|85, 100E
|2012
|2009
|
|-
|
|Auramine production
|Sup 7, 99, 100F
|2012
|2009
|
|-
|
|Automotive gasoline
|45, 138
|In prep.
|2025
|
|-
|
|Benzidine, dyes metabolized to
|99, 100F
|2012
|2009
|
- Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data
|-
|
|Betel quid with tobacco
|Sup 7, 85, 100E
|2012
|2009
|
|-
|
|Betel quid without tobacco
|Sup 7, 85, 100E
|2012
|2009
|
|-
|
|Coal gasification
|Sup 7, 92, 100F
|2012
|2009
|
|-
|
|Coal, indoor emissions from household combustion of
|95, 100E
|2012
|2009
|
|-
|
|Coke production
|Sup 7, 92, 100F
|2012
|2009
|
|-
|
|Engine exhaust, diesel
|46, 105
|2014
|2012
|
|-
|
|Epstein-Barr virus
|70, 100B
|2012
|2009
|
|-
|
|Estrogen therapy, postmenopausal
|72, 100A
|2012
|2008
|
- 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 (combined)
|72, 91, 100A
|2012
|2008
|
|-
|
|Estrogen-progestogen oral contraceptives (combined)
|72, 91, 100A
|2012
|2008
|
- 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 (occupational exposure as a)
|98, 132
|2023 online
|2022
|
|-
|
|Fission products, including strontium-90
|100D
|2012
|2009
|
|-
|
|Fluoro-edenite fibrous amphibole
|111
|2017
|2014
|
|-
|
|Haematite mining (underground)
|1, Sup 7, 100D
|2012
|2009
|
|-
|
|Hepatitis B virus (chronic infection with)
|59, 100B
|2012
|2009
|
|-
|
|Hepatitis C virus (chronic infection with)
|59, 100B
|2012
|2009
|
|-
|
|Hepatitis D virus (HDV)
|59, 139
|In prep.
|2025
|
|-
|
|Human T-cell lymphotropic virus type I
|67, 100B
|2012
|2009
|
|-
|
|Human immunodeficiency virus type 1 (infection with)
|67, 100B
|2012
|2009
|
|-
|
|Human papillomavirus (HPV) type 16
|64, 90, 100B
|2012
|2009
|
- 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 (HPV) type 18
|64, 90, 100B
|2012
|2009
|
- 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 (HPV) type 33
|64, 90, 100B
|2012
|2009
|
- 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 (HPV) types 31, 35, 39, 45, 51, 52, 56, 58, 59
|64, 90, 100B
|2012
|2009
|
- 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 (all types)
|100D
|2012
|2009
|
|-
|
|Iron and steel founding (occupational exposure during)
|34, Sup 7, 100F
|2012
|2009
|
|-
|
|Isopropyl alcohol manufacture using strong acids
|Sup 7, 100F
|2012
|2009
|
|-
|
|Kaposi sarcoma herpesvirus
|70, 100B
|2012
|2009
|
|-
|
|Leather dust
|100C
|2012
|2009
|
|-
|
|MOPP and other combined chemotherapy including alkylating agents
|Sup 7, 100A
|2012
|2008
|
|-
|
|Magenta production
|Sup 7, 57, 99, 100F
|2012
|2009
|
|-
|
|Merkel cell polyomavirus (MCPyV)
|104, 139
|In prep.
|2025
|
|-
|
|Mineral oils, untreated or mildly treated
|33, Sup 7, 100F
|2012
|2009
|
|-
|
|Neutron radiation
|75, 100D
|2012
|2009
|
- Overall evaluation upgraded to Group 1 with supporting evidence from other relevant data
|-
|
|Nickel compounds
|Sup 7, 49, 100C
|2012
|2009
|
|-
|
|Opium consumption
|126
|2021 online
|2020
|
|-
|
|Outdoor air pollution
|109
|2016
|2013
|
|-
|
|Outdoor air pollution, particulate matter in
|109
|2016
|2013
|
|-
|
|Painter (occupational exposure as a)
|47, 98, 100F
|2012
|2009
|
|-
|
|Phenacetin, analgesic mixtures containing
|Sup 7, 100A
|2012
|2008
|
|-
|
|Polychlorinated 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)
|107
|2016
|2013
|
- Overall evaluation upgraded to Group 1 with strong supporting evidence from other relevant data
|-
|
|Processed meat (consumption of)
|114
|2018
|2015
|
|-
|
|Radioiodines, including iodine-131
|78, 100D
|2012
|2009
|
|-
|
|Radionuclides, alpha-particle-emitting, internally deposited
|78, 100D
|2012
|2009
|
- 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 deposited
|78, 100D
|2012
|2009
|
- Specific radionuclides for which there is sufficient evidence in humans are also listed individually as Group 1 agents
|-
|
|Rubber manufacturing industry
|28, Sup 7, 100F
|2012
|2009
|
|-
|
|Salted fish, Chinese-style
|56, 100E
|2012
|2009
|
|-
|
|Solar radiation (see Ultraviolet radiation (wavelengths 100–400 nm, encompassing UVA, UVB, and UVC); Ultraviolet radiation from welding; and Ultraviolet-emitting tanning devices)
|55, 100D
|2012
|2009
|
|-
|
|Soot (as found in occupational exposure of chimney sweeps)
|35, Sup 7, 92, 100F
|2012
|2009
|
|-
|
|Tobacco smoke, secondhand
|83, 100E
|2012
|2009
|
|-
|
|Tobacco smoking
|83, 100E
|2012
|2009
|
|-
|
|Tobacco, smokeless
|Sup 7, 89, 100E
|2012
|2009
|
|-
|
|Ultraviolet radiation from welding (see Ultraviolet radiation (wavelengths 100–400 nm, encompassing UVA, UVB, and UVC); Ultraviolet-emitting tanning devices; and Solar radiation)
|100D, 118
|2018 online
|2017
|
- 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 (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, 100D
|2012
|2017
|
- Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data
|-
|
|Ultraviolet-emitting tanning devices (see Ultraviolet radiation (wavelengths 100–400 nm, encompassing UVA, UVB, and UVC); Ultraviolet radiation from welding; and Solar radiation)
|100D
|2012
|2009
|
|-
|
|Welding fumes
|49, 118
|2018 online
|2017
|
|-
|
|Wood dust
|62, 100C
|2012
|2009
|
|-
|
|X- and Gamma-Radiation
|75, 100D
|2012
|2009
|
|-
|
|Radon-222 and its decay products
|43, 78, 100D
|2012
|2009
|
|-
|
|4,4'-Methylenebis(2-chloroaniline) (MOCA)
|Sup 7, 57, 99, 100F
|2012
|2009
|
- Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data
|-
|
|Tacrolimus
|137
|In prep.
|2024
|
|-
|
|Tamoxifen
|66, 100A
|2012
|2008
|
- 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-Butadiene
|Sup 7, 54, 71, 97, 100F
|2012
|2009
|
|-
|
|Acrylonitrile
|19, Sup 7, 71, 136
|2025 online
|2024
|
|-
|
|Radium-224 and its decay products
|78, 100D
|2012
|2009
|
|-
|<br><br><br>
|Asbestos (all forms, including actinolite, amosite, anthophyllite, chrysotile, crocidolite, tremolite)
|14, Sup 7, 100C
|2012
|2009
|
- Mineral 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 index
|-
|
|Polychlorinated biphenyls
|18, Sup 7, 107
|2016
|2013
|
|-
|
|Voriconazole
|137
|In prep.
|2024
|
|-
|
|1-(2-Chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea (Methyl-CCNU) (Semustine)
|Sup 7, 100A
|2012
|2008
|
|-
|
|Radium-226 and its decay products
|78, 100D
|2012
|2009
|
|-
|
|Aflatoxins
|Sup 7, 56, 82, 100F
|2012
|2009
|
|-
|
|Phosphorus-32, as phosphate
|78, 100D
|2012
|2009
|
|-
|
|Melphalan
|9, Sup 7, 100A
|2012
|2008
|
|-
|
|Silica dust, crystalline, in the form of quartz or cristobalite
|Sup 7, 68, 100C
|2012
|2009
|
|-
|
|Radium-228 and its decay products
|78, 100D
|2012
|2009
|
|-
|<br>
|N'-Nitrosonornicotine (NNN) and 4-(N-Nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK)
|Sup 7, 89, 100E
|2012
|2009
|
- Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data
|-
|
|2,3,7,8-Tetrachlorodibenzo-para-dioxin
|Sup 7, 69, 100F
|2012
|2009
|
|-
|
|Chromium (VI) compounds
|Sup 7, 49, 100C
|2012
|2009
|
|-
|
|Methoxsalen (8-methoxypsoralen) plus ultraviolet A radiation
|24, Sup 7, 100A
|2012
|2008
|
|-
|
|Treosulfan
|26, Sup 7, 100A
|2012
|2008
|
|-
|
|Chlorambucil
|26, Sup 7, 100A
|2012
|2008
|
|-
|
|Aristolochic acid
|82, 100A
|2012
|2008
|
- Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data
|-
|
|Aristolochic acid, plants containing
|82, 100A
|2012
|2008
|
|-
|
|Etoposide
|76, 100A
|2012
|2008
|
- Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data
|-
|<br><br>
|Etoposide in combination with cisplatin and bleomycin
|76, 100A
|2012
|2008
|
|-
|
|Perfluorooctanoic acid (PFOA)
|110, 135
|2025 online
|2023
|
|-
|
|Azathioprine
|26, Sup 7, 100A
|2012
|2008
|
|-
|
|Chlornaphazine
|4, Sup 7, 100A
|2012
|2008
|
|-
|
|Formaldehyde
|Sup 7, 62, 88, 100F
|2012
|2009
|
|-
|<br>
|Cyclophosphamide
|26, Sup 7, 100A
|2012
|2008
|
|-
|
|[[Benzo(a)pyrene|Benzo<nowiki>[</nowiki>a<nowiki>]</nowiki>pyrene]]
|Sup 7, 92, 100F
|2012
|2009
|
- Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data
|-
|
|Sulfur mustard
|9, Sup 7, 100F
|2012
|2009
|
|-
|
|Thiotepa
|Sup 7, 50, 100A
|2012
|2008
|
|-
|<br>
|Bis(chloromethyl)ether; chloromethyl methyl ether (technical-grade)
|4, Sup 7, 100F
|2012
|2009
|
|-
|
|Busulfan
|4, Sup 7, 100A
|2012
|2008
|
|-
|
|Diethylstilbestrol
|21, Sup 7, 100A
|2012
|2008
|
|-
|
|2,3,4,7,8-Pentachlorodibenzofuran
|100F
|2012
|2009
|
- Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data
|-
|
|3,3',4,4',5-Pentachlorobiphenyl (PCB-126)
|100F
|2012
|2009
|
- See Polychlorinated biphenyls, dioxin-like, with a TEF according to WHO
|-
|
|Lindane
|113
|2018
|2015
|
|-
|
|Hydrochlorothiazide
|50, 108, 137
|In prep.
|2024
|
|-
|<br>
|Ciclosporin
|50, 100A
|2012
|2008
|
|-
|
|Phenacetin
|24, Sup 7, 100A
|2012
|2008
|
- Overall evaluation upgraded to Group 1 with supporting evidence from other relevant data
|-
|
|Ethanol in alcoholic beverages
|96, 100E
|2012
|2009
|
|-
|
|Coal-tar pitch
|35, Sup 7, 100F
|2012
|2009
|
|-
|
|Erionite
|42, Sup 7, 100C
|2012
|2009
|
|-
|
|Shale oils
|35, Sup 7, 100F
|2012
|2009
|
|-
|
|Benzene
|29, Sup 7, 100F, 120
|2018
|2017
|
|-
|
|Plutonium
|78, 100D
|2012
|2009
|
|-
|
|Thorium-232 and its decay products
|78, 100D
|2012
|2009
|
|-
|
|Arsenic and inorganic arsenic compounds
|23, Sup 7, 100C
|2012
|2009
|
|-
|
|Beryllium and beryllium compounds
|Sup 7, 58, 100C
|2012
|2009
|
|-
|
|Cadmium and cadmium compounds
|58, 100C
|2012
|2009
|
|-
|
|Uranium, mixture of isotopes (see Radionuclides, alpha-particle-emitting, internally deposited)
|78, 100D
|2012
|2009
|
- 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 chloride
|Sup 7, 97, 100F
|2012
|2009
|
|-
|
|Acetaldehyde associated with consumption of alcoholic beverages
|100E
|2012
|2009
|
|-
|
|Ethylene oxide
|Sup 7, 60, 97, 100F
|2012
|2009
|
- Overall evaluation upgraded to Group 1 based on mechanistic and other relevant data
|-
|
|1,2-Dichloropropane
|41, Sup 7, 71, 110
|2017
|2014
|
|-
|
|Trichloroethylene
|Sup 7, 63, 106
|2014
|2012
|
|-
|
|Coal-tar distillation
|92, 100F
|2012
|2009
|
|-
|
|Pentachlorophenol
|53, 71, 117
|2019
|2016
|
|-
|
|2-Naphthylamine
|4, Sup 7, 99, 100F
|2012
|2009
|
|-
|
|4-Aminobiphenyl
|1, Sup 7, 99, 100F
|2012
|2009
|
|-
|
|Benzidine
|29, Sup 7, 99, 100F
|2012
|2009
|
|-
|
|ortho-Toluidine
|Sup 7, 77, 99, 100F
|2012
|2009
|
|}
See also
- IARC group 2A
- IARC group 2B
- IARC group 3
References
External links
- Description of the list of classifications , IARC
- List of Classifications (latest version)
<!-- ** Agents Classified, (last updated on 7 April 2015) (((old version of the same thing from the previous link, so hide it))) -->
- List of Classifications by cancer sites with sufficient or limited evidence in humans, Volumes 1 to 124 (Last update: 8 July 2019)
- Agents Classified by the IARC Monographs, Volumes 1–123 (Last update: 25 March 2019)