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).^[1] 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.^[2] The list is up to date as of January 2024.^[3]

Agents

Infectious conditions

Viruses

• Human immunodeficiency virus type 1 (infection with)
• Human T-cell lymphotropic virus type I
• Human papillomavirus types 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, and 59
• Hepatitis B virus (chronic infection with)
• Hepatitis C virus (chronic infection with)
• Kaposi's sarcoma-associated herpesvirus
• Epstein–Barr virus

Bacterium

• Helicobacter pylori (infection with)

Worms

• Clonorchis sinensis (infection with)
• Opisthorchis viverrini (infection with)
• Schistosoma haematobium (infection with)

Chemical substances

• Acetaldehyde associated with consumption of alcoholic beverages^[4]
• Aflatoxins
• 4-Aminobiphenyl
• Aristolochic acids, and plants containing them
• Arsenic and inorganic arsenic compounds^{[note 1]}
• Asbestos (all forms, including actinolite, amosite, anthophyllite, chrysotile, crocidolite, tremolite)
• Azathioprine
• Benzene
• Benzidine, and dyes metabolized to
• Benzo[a]pyrene
• Beryllium and beryllium compounds^{[note 2]}
• 1,3-Butadiene
• 1,4-Butanediol dimethanesulfonate (Busulphan, Myleran)
• Cadmium and cadmium compounds^{[note 2]}
• Chlornapazine (N,N-Bis(2-chloroethyl)-2-naphthylamine)
• Chlorambucil
• Bis(chloromethyl)ether
• Chloromethyl methyl ether
• Chromium(VI) (Hexavalent chromium) compounds^{[note 2]}
• Ciclosporin
• Cyclophosphamide
• 1,2-Dichloropropane
• Diethylstilboestrol
• Erionite
• Ethylene oxide
• Etoposide alone, and in combination with cisplatin and bleomycin
• Fluoro-edenite fibrous amphibole
• Formaldehyde
• Gallium arsenide
• Lindane
• Melphalan
• Methoxsalen (8-Methoxypsoralen) plus ultraviolet A radiation
• 4,4'-Methylenebis(2-chloroaniline) (MOCA)
• MOPP and other combined chemotherapy including alkylating agents
• Mustard gas (Sulfur mustard)
• 2-Naphthylamine
• Nickel compounds^{[note 2]}
• 4-(N-Nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK)
• N-Nitrosonornicotine (NNN)
• 2,3,4,7,8-Pentachlorodibenzofuran
• 3,4,5,3’,4’-Pentachlorobiphenyl (PCB-126)
• Pentachlorophenol
• Perfuorooctanoic acid (PFOA), evaluated 2023
• Polychlorinated biphenyls
• Semustine [1-(2-Chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea, Methyl-CCNU]
• Silica dust, crystalline, in the form of quartz or cristobalite
• Tamoxifen^{[note 3]}
• 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD)
• Thiotepa (1,1',1"-Phosphinothioylidynetrisaziridine)
• Treosulfan
• Trichloroethylene
• o-Toluidine
• Vinyl chloride

Radiations and physical agents thereof

• Ionizing radiation (all types)
• Neutron radiation
• Phosphorus-32, as phosphate
• Plutonium
• Radioiodines, including iodine-131
• Nuclear fission products, including strontium-90
• Radionuclides, α-particle-emitting, internally deposited^{[note 4]}
• Radionuclides, β-particle-emitting, internally deposited^{[note 4]}
• Radium-224 and its decay products
• Radium-226 and its decay products
• Radium-228 and its decay products
• Radon-222 and its decay products
• Solar radiation
• Thorium-232 and its decay products
• Ultraviolet radiation (wavelengths 100-400 nm, encompassing UVA, UVB, and UVC)
• X-ray and gamma radiation

Complex mixtures/agents

• Aflatoxins (naturally occurring mixtures of)
• Outdoor air pollution
• Outdoor air pollution, particulate matter in
• Alcoholic beverages
• Areca nut, also known as betel nut
• Betel quid with or without tobacco
• Coal-tar pitch
• Coal-tars (see Coal-tar distillation)
• Engine exhaust, diesel^[5]
• Estrogen-progestogen menopausal therapy (combined)
• Estrogen-progestogen oral contraceptives (combined)^{[note 5]}
• Estrogen therapy, postmenopausal NB There is "evidence suggesting lack of carcinogenicity" for estrogen-only menopausal therapy in humans and colorectal cancer. An inverse association has been observed between estrogen-only menopausal therapy and cancer of the colorectum.
• Leather dust
• Mineral oils, untreated or mildly treated
• Phenacetin, analgesic mixtures containing
• Plants containing aristolochic acid
• 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)^{[note 6]}
• Processed meat (consumption of)^[6]
• Salted fish, Chinese-style
• Shale-oils
• Soot, as found in occupational exposure of chimney sweeps
• Wood dust

Exposure circumstances

• Acheson process, occupational exposure associated with
• Acid mists, strong inorganic
• Aluminium production
• Auramine production
• Boot and shoe manufacture and repair (see Leather dust, Benzene)
• Chimney sweeping (see Soot)
• Coal gasification
• Coal, indoor emissions from household combustion of
• Coal-tar distillation
• Coke production
• Firefighter (occupational exposure as a)
• Furniture and cabinet making (see Wood dust)
• Haematite mining (underground)
• Iron and steel founding (occupational exposure during)
• Isopropyl alcohol manufacture using strong acids
• Magenta production
• Opium consumption
• Painter (occupational exposure as a)
• Paving and roofing with coal-tar pitch (see Coal-tar pitch)
• Rubber manufacturing industry
• Tobacco, smokeless
• Tobacco smoke, second-hand
• Tobacco smoking
• Ultraviolet-emitting tanning devices
• Welding fumes and UV radiation