IARC group 1

Classification

IARC monographs

* Group 1: carcinogenic
* Group 2A: probably carcinogenic
* Group 2B: possibly carcinogenic
* Group 3: not classifiable
* Group 4: probably not carcinogenic

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

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### Infectious conditions

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#### Viruses

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* 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

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* Helicobacter pylori (infection with)

#### Worms

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

### Chemical substances

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* Acetaldehyde associated with consumption of alcoholic beverages[4]
* Acrylonitrile
* 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
* Ethanol in alcoholic beverages[4]
* 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
* Perfluorooctanoic 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
* hydrochlorothiazide[5][6]
* voriconazole[5][6]
* tacrolimus[5][6]

### Radiations and physical agents thereof

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* 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

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* 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[7]
* 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)[8]
* Salted fish, Chinese-style
* Shale-oils
* Soot, as found in occupational exposure of chimney sweeps
* Wood dust

### Exposure circumstances

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* 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

## See also

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* IARC group 2A
* IARC group 2B
* IARC group 3

## Notes

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1. ^ This evaluation applies to the group of compounds as a whole and not necessarily to all individual compounds within the group.
2. ^ a b c d Evaluated as a group.
3. ^ There is also conclusive evidence that this agent (tamoxifen) reduces the risk of contralateral breast cancer.
4. ^ a b Specific radionuclides for which there is sufficient evidence for carcinogenicity to humans are also listed individually as Group 1 agents.
5. ^ There is also convincing evidence in humans that these agents confer a protective effect against cancer in the endometrium and ovary.
6. ^ Overall evaluation upgraded to Group 1 with strong supporting evidence from other relevant data.

## References

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1. ^ "List of Classifications, Agents classified by the IARC Monographs, Volumes 1–124". IARC Monographs on the Evaluation of Risk to Humans. IARC. July 7, 2019. Retrieved July 14, 2019.
2. ^ "IARC monographs preamble (as amended in 2019)" (PDF). International Agency for Research on Cancer (IARC). Retrieved August 18, 2023. "A cancer hazard is an agent that is capable of causing cancer, whereas a cancer risk is an estimate of the probability that cancer will occur given some level of exposure to a cancer hazard."
3. ^ "List of Classifications – IARC Monographs on the Identification of Carcinogenic Hazards to Humans". monographs.iarc.who.int. Retrieved 2024-02-01.
4. ^ a b "IARC Strengthens Its Findings on Several Carcinogenic Personal Habits and Household Exposures" (Press release). International Agency for Research on Cancer (IARC). Retrieved August 1, 2014. "November 2, 2009 ‐‐ IARC has updated the cancer assessments of several personal habits and household exposures that cause cancer, including tobacco, areca nut, alcohol, and household coal smoke. The update was conducted with the advice of 30 scientists from 10 countries who met at IARC in October 2009. [...] The Working Group concluded that acetaldehyde associated with alcohol consumption is carcinogenic to humans (Group 1) and confirmed the classification in Group 1 of alcohol consumption and of ethanol in alcoholic beverages."
5. ^ a b c Cogliano VJ, Corsini E, Fournier A, Nelson HH, Sergi CM, Antunes AMM; et al. (2024-11-29). "Carcinogenicity of hydrochlorothiazide, voriconazole, and tacrolimus". The Lancet Oncology. 26 (1): 15–16\. doi:10.1016/S1470-2045(24)00685-5.`{{cite journal}}`: CS1 maint: multiple names: authors list (link)
6. ^ a b c "List of Classifications". IARC. Retrieved 2025-04-12.
7. ^ "IARC: Diesel Engine Exhaust Carcinogenic" (Press release). International Agency for Research on Cancer (IARC). Retrieved August 14, 2016. "June 12, 2012 ‐‐ After a week-long meeting of international experts, the International Agency for Research on Cancer (IARC), which is part of the World Health Organization (WHO), today classified diesel engine exhaust as carcinogenic to humans (Group 1), based on sufficient evidence that exposure is associated with an increased risk for lung cancer"
8. ^ "IARC Monographs evaluate consumption of red meat and processed meat" (PDF). Retrieved 26 October 2015.

## External links

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* Description of the list of classifications Archived 2013-07-28 at the Wayback Machine, IARC
* List of Classifications (latest version)
* 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)

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Cancer-causing materials and agents (carcinogens)

* Cancer
* Cancer cells

Prominent human carcinogens|

* Acetaldehyde
* Arsenic
* Asbestos
* Bacteria
* Helicobacter pylori
* Benzo[a]pyrene
* 1,3-Butadiene
* Diethylstilbestrol
* Formaldehyde
* Ionizing radiation (e.g., from isotopes of plutonium and radium)
* Tobacco smoke
* Ultraviolet light
* Viruses
* Epstein–Barr
* Hepatitis B
* Hepatitis C
* HPV

IARC lists|

* Group 1 (carcinogenic)
* Group 2A (probably carcinogenic)
* Group 2B (possibly carcinogenic)
* Group 3 (not classifiable)

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