List of Known Carcinogens That Cause Cancer in Humans

Author: Ian C. Langtree - Writer/Editor for Disabled World (DW)
Published: 2014/10/11 - Updated: 2025/03/22
Publication Type: Informative
Category Topic: Cancer - Tumors - Related Publications

Page Content: Synopsis - Introduction - Main - Insights, Updates

Synopsis: This information provides a comprehensive list of substances identified as known human carcinogens, including chemicals like benzene and formaldehyde, environmental exposures such as asbestos and radon, and lifestyle factors like tobacco smoke and alcohol consumption. Understanding these carcinogens is crucial for individuals, especially seniors and those with disabilities, as they may have increased vulnerability to environmental hazards or occupational exposures. By being informed about these risks, individuals can take proactive measures to reduce exposure, such as avoiding tobacco products, ensuring proper ventilation to mitigate radon accumulation, and using appropriate protective equipment when necessary - Disabled World (DW).

Defining Carcinogen

Carcinogen: A Carcinogen is defined as any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substances are considered carcinogens, but their carcinogenic activity is attributed to the radiation, for example, gamma rays and alpha particles, which they emit. Common examples of non-radioactive carcinogens are inhaled asbestos, certain dioxins, and tobacco smoke. Although the public generally associates carcinogenicity with synthetic chemicals, it is equally likely to arise in natural and synthetic substances. Carcinogens are not necessarily immediately toxic. Thus their effect can be insidious.

Introduction

Recently Added Carcinogens

Four substances have been added to the U.S. Department of Health and Human Services 14th Report on Carcinogens, a science-based document that identifies chemical, biological, and physical agents that are considered cancer hazards for people living in the United States. The new report now includes 243 listings.

Ortho-toluidine, used to make rubber chemicals, pesticides, and dyes have been reevaluated and are now listed as a known human carcinogen.

Three substances have been added as reasonably anticipated to be human carcinogens. These include:

1-bromopropane, used as a cleaning solvent and spray adhesive;
cumene used to make phenol and acetone, and also found in fuel products and tobacco smoke;
wood preservative mixture pentachlorophenol.

Main Content

"Identifying substances in our environment that can make people vulnerable to cancer will help in prevention efforts," said Linda Birnbaum, Ph.D., director of the National Institute of Environmental Health Sciences (NIEHS) and the National Toxicology Program (NTP). "This report provides a valuable resource for health regulatory and research agencies, and it empowers the public with information people can use to reduce exposure to cancer-causing substances."

The Report on Carcinogens is a congressionally mandated report prepared for the HHS Secretary by NTP. The report identifies agents, substances, mixtures, or exposures in two categories: known to be a human carcinogen and reasonably anticipated to be a human carcinogen.

A listing in the report indicates a cancer hazard but does not mean that a substance will cause cancer. Many factors, including the amount and duration of exposure and an individual's susceptibility to a substance, can affect whether a person will develop cancer.

Also see our list of List of Ingredients and Additives in Cigarettes.

Jump-To:

Carcinogenic to Humans - Full List
Known to be Human Carcinogens
Probably Carcinogenic to Humans
Reasonably Anticipated to be Human Carcinogens

Full List of Currently Known Human Carcinogens:
Group 1: Carcinogenic to humans
Acetaldehyde (from consuming alcoholic beverages) Acid mists, strong inorganic Aflatoxins Alcoholic beverages Aluminum production 4-Aminobiphenyl Areca nut Aristolochic acid (and plants containing it) Arsenic and inorganic arsenic compounds Asbestos (all forms) and mineral substances (such as talc or vermiculite) that contain asbestos Auramine production Azathioprine Benzene Benzidine and dyes metabolized to benzidine Benzo[a]pyrene Beryllium and beryllium compounds Betel quid, with or without tobacco Bis(chloromethyl)ether and chloromethyl methyl ether (technical-grade) Busulfan 1,3-Butadiene Cadmium and cadmium compounds Chlorambucil Chlornaphazine Chromium (VI) compounds Clonorchis sinensis (infection with) Coal, indoor emissions from household combustion Coal gasification Coal-tar distillation Coal-tar pitch Coke production Cyclophosphamide Cyclosporine Diethylstilbestrol Engine exhaust, diesel Epstein-Barr virus (infection with) Erionite Estrogen postmenopausal therapy Estrogen-progestogen postmenopausal therapy (combined) Estrogen-progestogen oral contraceptives (combined) (Note: There is also convincing evidence in humans that these agents confer a protective effect against cancer in the endometrium and ovary) Ethanol in alcoholic beverages Ethylene oxide Etoposide Etoposide in combination with cisplatin and bleomycin Fission products, including strontium-90 Formaldehyde Haematite mining (underground) Helicobacter pylori (infection with) Hepatitis B virus (chronic infection with) Hepatitis C virus (chronic infection with) Human immunodeficiency virus type 1 (HIV-1) (infection with) Human papillomavirus (HPV) types 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59 (infection with) (Note: The HPV types that have been classified as carcinogenic to humans can differ by order of magnitude in risk for cervical cancer) Human T-cell lymphotropic virus type I (HTLV-1) (infection with) Ionizing radiation (all types) Iron and steel founding (workplace exposure) Isopropyl alcohol manufacture using strong acids Kaposi sarcoma herpesvirus (KSHV)/human herpesvirus 8 (HHV-8) (infection with) Leather dust Magenta production Melphalan Methoxsalen (8-methoxypsoralen) plus ultraviolet A radiation 4,4'-Methylenebis(chloroaniline) (MOCA) Mineral oils, untreated or mildly treated MOPP and other combined chemotherapy, including alkylating agents 2-Naphthylamine Neutron radiation Nickel compounds N'-Nitrosonornicotine (NNN) and 4-(N-Nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK) Opisthorchis viverrini (liver fluke; infection with) Outdoor air pollution Painter (workplace exposure as a) 3,4,5,3',4'-Pentachlorobiphenyl (PCB-126) 2,3,4,7,8-Pentachlorodibenzofuran Phenacetin (and mixtures containing it) Phosphorus-32, as phosphate Plutonium Radioiodines, including iodine-131 Radionuclides, alpha-particle-emitting, internally deposited (Note: Specific radionuclides for which there is sufficient evidence for carcinogenicity to humans are also listed individually as Group 1 agents) Radionuclides, beta-particle-emitting, internally deposited (Note: Specific radionuclides for which there is sufficient evidence for carcinogenicity to humans are also listed individually as Group 1 agents) Radium-224 and its decay products Radium-226 and its decay products Radium-228 and its decay products Radon-222 and its decay products Rubber manufacturing industry Salted fish (Chinese-style) Schistosoma haematobium (flatworm; infection with) Semustine (methyl-CCNU) Shale oils Silica dust, crystalline, in the form of quartz or cristobalite Solar radiation Soot (as found in workplace exposure of chimney sweeps) Sulfur mustard Tamoxifen (Note: There is also conclusive evidence that tamoxifen reduces the risk of contralateral breast cancer in breast cancer patients) 2,3,7,8-Tetrachlorodibenzo-para-dioxin Thiotepa Thorium-232 and its decay products Tobacco, smokeless Tobacco smoke, secondhand Tobacco smoking ortho-Toluidine Treosulfan Ultraviolet (UV) radiation, including UVA, UVB, and UVC rays Ultraviolet-emitting tanning devices Vinyl chloride Wood dust X- and Gamma-radiation
National Toxicology Program 12th Report on Carcinogens "Known to be human carcinogens"
Aflatoxins Alcoholic beverage consumption 4-Aminobiphenyl Analgesic mixtures containing phenacetin Aristolochic acids Arsenic compounds, inorganic Asbestos Azathioprine Benzene Benzidine Beryllium and beryllium compounds 1,3-Butadiene 1,4-Butanediol dimethylsulfonate (busulfan, Myleran) Cadmium and cadmium compounds Chlorambucil 1-(2-Chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea (MeCCNU) bis(chloromethyl) ether and technical-grade chloromethyl methyl ether Chromium hexavalent compounds Coal tar pitches Coal tars Coke oven emissions Cyclophosphamide Cyclosporin A Diethylstilbestrol (DES) Dyes metabolized to benzidine Environmental tobacco smoke Erionite Estrogens, steroidal Ethylene oxide Formaldehyde Hepatitis B virus Hepatitis C virus Human papillomaviruses: some genital-mucosal types Melphalan Methoxsalen with ultraviolet A therapy (PUVA) Mineral oils (untreated and mildly treated) Mustard gas 2-Naphthylamine Neutrons Nickel compounds Oral tobacco products Radon Silica, crystalline (respirable size) Solar radiation Soots Strong inorganic acid mists containing sulfuric acid Sunlamps or sunbeds, exposure to Tamoxifen 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD); "dioxin" Thiotepa Thorium dioxide Tobacco smoking Vinyl chloride Ultraviolet radiation, broad spectrum UV radiation Wood dust X-radiation and gamma radiation
International Agency for Research on Cancer Group 2A: Probably carcinogenic to humans
Acrylamide Adriamycin (doxorubicin) Androgenic (anabolic) steroids Art glass, glass containers, and press ware (manufacture of) Azacitidine Biomass fuel (primarily wood), emissions from household combustion Bischloroethyl nitrosourea (BCNU) Captafol Carbon electrode manufacture Chloramphenicol alpha-Chlorinated toluenes (benzal chloride, benzo trichloride, benzyl chloride) and benzoyl chloride (combined exposures) 1-(2-Chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) 4-Chloro-ortho-toluidine Chlorozotocin Cisplatin Cobalt metal with tungsten carbide Creosotes Cyclopenta[cd]pyrene Dibenz[a,h]anthracene Dibenzo[a,l]pyrene Diethyl sulfate Dimethylcarbamoyl chloride 1,2-Dimethylhydrazine Dimethyl sulfate Epichlorohydrin Ethyl carbamate (urethane) Ethylene dibromide N-Ethyl-N-nitrosourea Frying, emissions from high-temperature Glycidol Hairdresser or barber (workplace exposure as) Human papillomavirus (HPV) type 68 (infection with) Indium phosphide IQ (2-Amino-3-methylimidazo[4,5-f]quinoline) Lead compounds, inorganic Mate, hot 5-Methoxypsoralen Methyl methanesulfonate N-Methyl-N-nitro-N-nitrosoguanidine (MNNG) N-Methyl-N-nitrosourea Nitrate or nitrite (ingested) under conditions that result in endogenous nitrosation Nitrogen mustard N-Nitrosodiethylamine N-Nitrosodimethylamine 2-Nitrotoluene Non-arsenical insecticides (workplace exposures in spraying and application of) Petroleum refining (workplace exposures in) Polychlorinated biphenyls (PCBs) Procarbazine hydrochloride Shiftwork that involves circadian disruption Styrene-7,8-oxide Teniposide Tetrachloroethylene (perchloroethylene) Trichloroethylene 1,2,3-Trichloropropane Tris(2,3-dibromopropyl) phosphate Vinyl bromide (Note: For practical purposes, vinyl bromide should be considered to act similarly to the human carcinogen vinyl chloride.) Vinyl fluoride (Note: For practical purposes, vinyl fluoride should be considered to act similarly to the human carcinogen vinyl chloride.)
National Toxicology Program 12th Report on Carcinogens "Reasonably anticipated to be human carcinogens"
Acetaldehyde 2-Acetylaminofluorene Acrylamide Acrylonitrile Adriamycin (doxorubicin hydrochloride) 2-Aminoanthraquinone o-Aminoazotoluene 1-Amino-2,4-dibromoanthraquinone 1-Amino-2-methylanthraquinone 2-Amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) 2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) 2-Amino-3-methylimidazo[4,5-f]quinoline (IQ) 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) Amitrole o-Anisidine hydrochloride Azacitidine (5-Azacytidine, 5-AzaC) Benz[a]anthracene Benzo[b]fluoranthene Benzo[j]fluoranthene Benzo[k]fluoranthene Benzo[a]pyrene Benzotrichloride Bromodichloromethane 2, 2-bis-(bromoethyl)-1,3-propanediol (technical grade) Butylated hydroxyanisole (BHA) Captafol Carbon tetrachloride Ceramic fibers (respirable size) Chloramphenicol Chlorendic acid Chlorinated paraffins (C₁₂, 60% chlorine) 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea Bis(chloroethyl) nitrosourea Chloroform 3-Chloro-2-methylpropene 4-Chloro-o-phenylenediamine Chloroprene p-Chloro-o-toluidine and p-chloro-o-toluidine hydrochloride Chlorozotocin C.I. basic red 9 monohydrochloride Cisplatin Cobalt sulfate Cobalt-tungsten carbide: powders and hard metals p-Cresidine Cupferron Dacarbazine Danthron (1,8-dihydroxyanthraquinone) 2,4-Diaminoanisole sulfate 2,4-Diaminotoluene Diazoaminobenzene Dibenz[a,h]acridine Dibenz[a,j]acridine Dibenz[a,h]anthracene 7H-Dibenzo[c,g]carbazole Dibenzo[a,e]pyrene Dibenzo[a,h]pyrene Dibenzo[a,i]pyrene Dibenzo[a,l]pyrene 1,2-Dibromo-3-chloropropane 1,2-Dibromoethane (ethylene dibromide) 2,3-Dibromo-1-propanol Tris (2,3-dibromopropyl) phosphate 1,4-Dichlorobenzene 3,3'-Dichlorobenzidine and 3,3'-dichlorobenzidine dihydrochloride Dichlorodiphenyltrichloroethane (DDT) 1,2-Dichloroethane (ethylene dichloride) Dichloromethane (methylene chloride) 1,3-Dichloropropene (technical grade) Diepoxybutane Diesel exhaust particulates Diethyl sulfate Diglycidyl resorcinol ether 3,3'-Dimethoxybenzidine 4-Dimethylaminoazobenzene 3,3'-Dimethylbenzidine Dimethylcarbamoyl chloride 1,1-Dimethylhydrazine Dimethyl sulfate Dimethylvinyl chloride 1,6-Dinitropyrene 1,8-Dinitropyrene 1,4-Dioxane Disperse blue 1 Dyes metabolized to 3,3'-dimethoxybenzidine Dyes metabolized to 3,3'-dimethylbenzidine Epichlorohydrin Ethylene thiourea Di(2-ethylhexyl) phthalate Ethyl methanesulfonate Furan Glass wool fibers (inhalable) Glycidol Hexachlorobenzene Hexachlorocyclohexane isomers Hexachloroethane Hexamethylphosphoramide Hydrazine and hydrazine sulfate Hydrazobenzene Indeno[1,2,3-cd]pyrene Iron dextran complex Isoprene Kepone (chlordecone) Lead and lead compounds Lindane and other hexachlorocyclohexane isomers 2-Methylaziridine (propylenimine) 5-Methylchrysene 4,4'-Methylenebis(2-chloroaniline) 4-4'-Methylenebis(N,N-dimethyl)benzenamine 4,4'-Methylenedianiline and its dihydrochloride salt Methyleugenol Methyl methanesulfonate N-methyl-N'-nitro-N-nitrosoguanidine Metronidazole Michler's ketone [4,4'-(dimethylamino) benzophenone] Mirex Naphthalene Nickel (metallic) Nitrilotriacetic acid o-Nitroanisole Nitrobenzene 6-Nitrochrysene Nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether) Nitrogen mustard hydrochloride Nitromethane 2-Nitropropane 1-Nitropyrene 4-Nitropyrene N-nitrosodi-n-butylamine N-nitrosodiethanolamine N-nitrosodiethylamine N-nitrosodimethylamine N-nitrosodi-n-propylamine N-nitroso-N-ethylurea 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone N-nitroso-N-methylurea N-nitrosomethylvinylamine N-nitrosomorpholine N-nitrosonornicotine N-nitrosopiperidine N-nitrosopyrrolidine N-nitrososarcosine o-Nitrotoluene Norethisterone Ochratoxin A 4,4'-Oxydianiline Oxymetholone Phenacetin Phenazopyridine hydrochloride Phenolphthalein Phenoxybenzamine hydrochloride Phenytoin Polybrominated biphenyls (PBBs) Polychlorinated biphenyls (PCBs) Polycyclic aromatic hydrocarbons (PAHs) Procarbazine hydrochloride Progesterone 1,3-Propane sultone beta-Propiolactone Propylene oxide Propylthiouracil Reserpine Riddelliine Safrole Selenium sulfide Streptozotocin Styrene Styrene-7,8-oxide Sulfallate Tetrachloroethylene (perchloroethylene) Tetrafluoroethylene Tetranitromethane Thioacetamide 4,4'-Thiodianaline Thiourea Toluene diisocyanate o-Toluidine and o-toluidine hydrochloride Toxaphene Trichloroethylene 2,4,6-Trichlorophenol 1,2,3-Trichloropropane Ultraviolet A radiation Ultraviolet B radiation Ultraviolet C radiation Urethane Vinyl bromide 4-Vinyl-1-cyclohexene diepoxide Vinyl fluoride

Substance Added as a Known Human Carcinogen

Since 1983, ortho-toluidine has been listed in the Report on Carcinogens as reasonably anticipated to be a human carcinogen. However, new cancer studies led NTP to reevaluate and reclassify ortho-toluidine. It is now added to the category of known human carcinogen, based on studies in humans showing it causes urinary bladder cancer. Ortho-toluidine is a synthetic chemical produced in other countries and imported into the United States by several companies in high volumes. It is primarily used to make rubber chemicals, pesticides, and dyes. It is also used in some consumer and medical products. People are mainly exposed through the workplace by skin contact and inhalation when using ortho-toluidine. People can also be exposed outside the workplace through sources such as tobacco smoke.

3 Substances Added to the New Report as Reasonably Anticipated to Be a Human Carcinogen

The chemical 1-bromopropane is a colorless pale yellow liquid used as a solvent in many commercial industries. It is used as a cleaner for optics, electronics, and metals and a solvent for aerosol-applied adhesives such as those used in foam cushion manufacturing. It is also used in dry cleaning and solvent sprays for aircraft maintenance. Workers in certain occupations may be more exposed to 1-bromopropane than the general population. No human studies were identified that evaluated the relationship between human cancer and exposure specifically to 1-bromopropane. However, inhalation exposure to 1-bromopropane in rodents caused tumors in several organs, including the skin, lungs, and large intestine.
Cumene is a flammable, volatile liquid with a gasoline-like odor. It is a natural component of coal tar and petroleum in tobacco smoke. It is used primarily to make acetone and phenol. People are mainly exposed to cumene through the environment and workplaces that use or produce cumene. It can be found in emissions from petroleum products. Inhalation exposure to cumene caused lung tumors in male and female mice and liver tumors in female mice. No human studies were identified that looked at the relationship between human cancer and exposure specifically to cumene.
Pentachlorophenol and by-products of its synthesis are complex mixtures of chemicals used as wood preservatives. Because virtually everyone exposed to pentachlorophenol is also exposed to its synthesis by-products, they were evaluated together. In the United States, pentachlorophenol has been regulated since the 1980s as a restricted-use pesticide. It is used industrially for treating utility poles, wood pilings, fence posts, and lumber or timber for construction. Most exposure has occurred in settings where workers treat or come in contact with treated lumber. People may also be exposed to this mixture from breathing contaminated air, dust, or contact with contaminated soil. Exposure to this mixture was associated with an increased risk of non-Hodgkin lymphoma in human studies. It also caused tumors in the liver and other organs in mice.

References

International Agency for Research on Cancer (IARC). Agents Classified by the IARC Monographs, Volumes 1 - 100. 2011.
US Department of Health and Human Services. Public Health Service, National Toxicology Program. Report on Carcinogens, Twelfth Edition. 2011.
List of Ingredients and Additives in Cigarettes - Disabled World - https://www.disabled-world.com/medical/pharmaceutical/addiction/cigarette-ingredients.php

Insights, Analysis, and Developments

Editorial Note: Awareness of known carcinogens is a vital component of public health. As research continues to uncover the links between various substances and cancer, it becomes increasingly important for regulatory bodies to update safety guidelines and for individuals to stay informed. This collective vigilance empowers society to make informed choices, potentially reducing the incidence of cancer and promoting overall well-being - Disabled World (DW).

Ian C. Langtree Author Credentials: Ian is the founder and Editor-in-Chief of Disabled World, a leading resource for news and information on disability issues. With a global perspective shaped by years of travel and lived experience, Ian is a committed proponent of the Social Model of Disability-a transformative framework developed by disabled activists in the 1970s that emphasizes dismantling societal barriers rather than focusing solely on individual impairments. His work reflects a deep commitment to disability rights, accessibility, and social inclusion. To learn more about Ian's background, expertise, and accomplishments, visit his full biography.