The list of 116 things that cause cancer – and how to use it

Sales of bacon and sausages fell by £3m in UK supermarkets in just two weeks following the World Health Organization’s announcement that processed meats are “definite” carcinogens.

The International Agency for Research on Cancer (IARC), the specialized cancer agency of the World Health Organization, placed processed meats in the same category as smoking, asbestos and plutonium. But, shocking as that sounds, it does not mean that the risk of cancer is elevated to the same level by all these substances or processes.

Justin Davies, Consultant Colorectal Surgeon at Addenbrooke’s Hospital, Cambridge and Clinical Adviser at Check4Cancer, explains: “Knowledge is one of the keys to fighting or avoiding cancer; if we know what to avoid, we have the potential to reduce our risk. This list can help us towards that goal, but it needs to be understood in context. While all the substances in the Group 1 category have been shown to be carcinogens, they are not necessarily equal in terms of their potency, or the risks they pose. To understand the level of risk, we need to consider each item individually. There is no safe level for smoking, for example, which tops the list as the world’s number one carcinogen. But – as with alcohol, which is also on the list – the increase in cancer risk from consumption of processed meat is directly related to intake. Moderate and infrequent consumption of processed meats such as bacon and sausages represents a very small increase in risk – although for those already at elevated risk of colorectal cancer, cutting these out completely may well be the desirable option.”

Experts concluded that each 50g portion of processed meat eaten daily increases the risk of colorectal cancer by 18%. Processed meat refers to meat that has been transformed through salting, curing, fermentation, smoking or other processes to enhance flavour or improve preservation. Examples of processed meat include hot dogs (frankfurters), ham, sausages, bacon, corned beef, and biltong or beef jerky as well as canned meat and meat-based preparations and sauces.

Below is IARC’s full Group 1 list – the things it says are definitely carcinogenic (red meat is not on this list, because it is only classified as a “probable” cause of cancer. The IARC splits these into three categories: “Carcinogenic exposure circumstances”, “Carcinogenic mixtures” and “Carcinogenic agents and groups of agents”. Tobacco smoking, the number one cause of cancer is first on the list, accounting for around 70% of global cancer deaths. Processed meats appear at No.39 in the list, and last in the “Carcinogenic mixtures” section.

Carcinogenic exposure circumstances

  1. Tobacco smoking
  2. Sunlamps and sunbeds
  3. Aluminium production
  4. Arsenic in drinking water
  5. Auramine production
  6. Boot and shoe manufacture and repair
  7. Chimney sweeping
  8. Coal gasification
  9. Coal tar distillation
  10. Coke (fuel) production
  11. Furniture and cabinet making
  12. Haematite mining (underground) with exposure to radon
  13. Secondhand smoke
  14. Iron and steel founding
  15. Isopropanol manufacture (strong-acid process)
  16. Magenta dye manufacturing
  17. Occupational exposure as a painter
  18. Paving and roofing with coal-tar pitch
  19. Rubber industry
  20. Occupational exposure of strong inorganic acid mists containing sulphuric acid

Carcinogenic mixtures

  1. Naturally occurring mixtures of aflatoxins (produced by funghi)
  2. Alcoholic beverages
  3. Areca nut - often chewed with betel leaf
  4. Betel quid without tobacco
  5. Betel quid with tobacco
  6. Coal tar pitches
  7. Coal tars
  8. Indoor emissions from household combustion of coal
  9. Diesel exhaust
  10. Mineral oils, untreated and mildly treated
  11. Phenacetin, a pain and fever reducing drug
  12. Plants containing aristolochic acid (used in Chinese herbal medicine)
  13. Polychlorinated biphenyls (PCBs) - widely used in electrical equipment in the past, banned in many countries in the 1970s
  14. Chinese-style salted fish
  15. Shale oils
  16. Soots
  17. Smokeless tobacco products
  18. Wood dust
  19. Processed meat

Carcinogenic agents and groups of agents

  1. Acetaldehyde
  2. 4-Aminobiphenyl
  3. Aristolochic acids and plants containing them
  4. Asbestos
  5. Arsenic and arsenic compounds
  6. Azathioprine
  7. Benzene
  8. Benzidine
  9. Benzo[a]pyrene
  10. Beryllium and beryllium compounds
  11. Chlornapazine (N,N-Bis(2-chloroethyl)-2-naphthylamine)
  12. Bis(chloromethyl)ether
  13. Chloromethyl methyl ether
  14. 1,3-Butadiene
  15. 1,4-Butanediol dimethanesulfonate (Busulphan, Myleran)
  16. Cadmium and cadmium compounds
  17. Chlorambucil
  18. Methyl-CCNU (1-(2-Chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea; Semustine)
  19. Chromium(VI) compounds
  20. Ciclosporin
  21. Contraceptives, hormonal, combined forms (those containing both oestrogen and a progestogen)
  22. Contraceptives, oral, sequential forms of hormonal contraception (a period of oestrogen-only followed by a period of both oestrogen and a progestogen)
  23. Cyclophosphamide
  24. Diethylstilboestrol
  25. Dyes metabolized to benzidine
  26. Epstein-Barr virus
  27. Oestrogens, nonsteroidal
  28. Oestrogens, steroidal
  29. Oestrogen therapy, postmenopausal
  30. Ethanol in alcoholic beverages
  31. Erionite
  32. Ethylene oxide
  33. Etoposide alone and in combination with cisplatin and bleomycin
  34. Formaldehyde
  35. Gallium arsenide
  36. Helicobacter pylori (infection with)
  37. Hepatitis B virus (chronic infection with)
  38. Hepatitis C virus (chronic infection with)
  39. Herbal remedies containing plant species of the genus Aristolochia
  40. Human immunodeficiency virus type 1 (infection with)
  41. Human papillomavirus type 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59 and 66
  42. Human T-cell lymphotropic virus type-I
  43. Melphalan
  44. Methoxsalen (8-Methoxypsoralen) plus ultraviolet A-radiation
  45. 4,4’-methylene-bis(2-chloroaniline) (MOCA)
  46. MOPP and other combined chemotherapy including alkylating agents
  47. Mustard gas (sulphur mustard)
  48. 2-Naphthylamine
  49. Neutron radiation
  50. Nickel compounds
  51. 4-(N-Nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK)
  52. N-Nitrosonornicotine (NNN)
  53. Opisthorchis viverrini (infection with)
  54. Outdoor air pollution
  55. Particulate matter in outdoor air pollution
  56. Phosphorus-32, as phosphate
  57. Plutonium-239 and its decay products (may contain plutonium-240 and other isotopes), as aerosols
  58. Radioiodines, short-lived isotopes, including iodine-131, from atomic reactor accidents and nuclear weapons detonation (exposure during childhood)
  59. Radionuclides, α-particle-emitting, internally deposited
  60. Radionuclides, β-particle-emitting, internally deposited
  61. Radium-224 and its decay products
  62. Radium-226 and its decay products
  63. Radium-228 and its decay products
  64. Radon-222 and its decay products
  65. Schistosoma haematobium (infection with)
  66. Silica, crystalline (inhaled in the form of quartz or cristobalite from occupational sources)
  67. Solar radiation
  68. Talc containing asbestiform fibres
  69. Tamoxifen
  70. 2,3,7,8-tetrachlorodibenzo-para-dioxin
  71. Thiotepa (1,1’,1”-phosphinothioylidynetrisaziridine)
  72. Thorium-232 and its decay products, administered intravenously as a colloidal dispersion of thorium-232 dioxide
  73. Treosulfan
  74. Ortho-toluidine
  75. Vinyl chloride
  76. Ultraviolet radiation
  77. X-radiation and gamma radiation