The situations described in this section are those where there is a proven cancer risk: an increased incidence of cancer has clearly been associated with exposure to a known carcinogen.
What is a carcinogen?
A carcinogen is a substance that causes cancer in the body. Many carcinogens are well known and exposure is preventable, such as chemicals in asbestos or tobacco smoke. Some are less well recognised, such as alcohol.
Below is a list of situations where there is a proven cancer risk:
People smoking tobacco |
Situation |
People smoking tobacco |
Exposure |
Active smokers |
Carcinogen |
Tobacco smoke, being a mixture containing polycytic aromatic hydrocarbons and the nitrosated derivatives of nicotine and nor-nicotine. |
Principal route of exposure |
Inhalation |
Target organ (or tumour type) |
Lung, oral cavity, naso-oro & hypopharynx, nasal cavity & paranasal sinuses, larynx, stomach, esophagus, pancreas, liver, kidney, ureter, urinary bladder, uterine cervix & bone marrow |
Comment |
Major preventable cause of malignant disease |
People who previously smoked tobacco |
Situation |
People who previously smoked tobacco |
Exposure |
Ex-smokers |
Carcinogen |
Tobacco smoke, being a mixture containing polycytic aromatic hydrocarbons and the nitrosated derivatives of nicotine and nor-nicotine. |
Principal route of exposure |
Previous inhalation |
Target organ (or tumour type) |
Lung, oral cavity, naso-oro & hypopharynx, nasal cavity & paranasal sinuses, larynx, stomach, esophagus, pancreas, liver, kidney, ureter, urinary bladder, uterine cervix & bone marrow |
Comment |
Risk is reduced by comparison with continued smoking
|
Using smokeless tobacco |
Situation |
Using smokeless tobacco |
Exposure |
Users of snuff, chewing tobacco and snus |
Carcinogen |
Tobacco-related nitrosamines |
Principal route of exposure |
Oral |
Target organ (or tumour type) |
Oral cavity, pancreas |
Comment |
Animal data establish role of nitrosamines |
Tanning through sunlamps and solaria |
Situation |
Tanning through sunlamps and solaria |
Exposure |
Persons using the appliances |
Carcinogen |
Ultraviolet radiation
|
Principal route of exposure |
Irradiation |
Target organ (or tumour type) |
Skin |
Comment |
Sunlamp data plus carcinogenic hazard established in relation to solar irradiation |
Local atmospheric pollution from point sources of industrial emissions |
Situation |
Local atmospheric pollution from point sources of industrial emissions |
Exposure |
Residents of particular local communities |
Carcinogen |
Multiple, often unspecified, and including particulate matter, from petrochemical, steel and other industry, mainly involving sites in Europe and the United States.
|
Principal route of exposure |
Inhalation |
Target organ (or tumour type) |
Lung, bladder (limited evidence) |
Comment |
Increased risk of lung cancer was consistently observed in cohort and case control studies. Evidence is limited in relation to bladder cancer as most studies have been of employees with potentially high exposure to outdoor air pollution rather than residents. |
General outdoor air pollution |
Situation |
Whole population
|
Exposure |
Worst for residents exposed to high traffic corridors with heavy diesel emissions |
Carcinogen |
Pollutants include
- Diesel exhaust
- Polycyclic aromatic hydrocarbons
- Benzene
- Formaldehyde - Particulate matter
|
Principal route of exposure |
Inhalation |
Target organ (or tumour type) |
Lung, bladder (limited evidence) |
Comment |
Evidence is limited in relation to bladder cancer as most studies have been of employees with potentially high exposure to outdoor air pollution rather than residents. Air quality monitoring and quantitative assessment is required to adequately characterise risk in differing locations. |
Treatment with certain therapeutic drugs |
Situation |
Treatment with certain therapeutic drugs |
Exposure |
Patients receiving relevant drugs/treatments |
Carcinogen |
Phenacetin-containing analgesics
Diethylstilboestrol
Cyclophosphamide & other cytotoxic drugs (including combinations)
Combined estrogen-progestogen contraceptives
|
Principal route of exposure |
Therapeutic administration |
Target organ (or tumour type) |
Target organ/tumor types specific for particular drug and include leukaemia and cancers of breast, liver, kidney and multiple other sites |
Comment |
Listed agents exemplify, but do not include all therapeutic drugs in the highest IARC/NTP category. Risk-benefit consideration are relevant; some drugs listed are used because of clear benefit despite a recognized hazard |
Drinking alcoholic beverages |
Situation |
Drinking alcoholic beverages |
Exposure |
Consumers of alcoholic beverages, and particularly those who smoke. |
Carcinogen |
Alcoholic beverages; (no class of drink is more markedly implicated than others) |
Principal route of exposure |
Oral |
Target organ (or tumour type) |
Oral cavity, esophagus, liver, breast |
Comment |
No particular category of beverage (beer, wine or spirits) is most strongly implicated. |
Occupational cancer attributable to specific agents |
Situation |
Occupational cancer attributable to specific agents |
Exposure |
Workers handling, or having contact with, particular chemicals or radiation |
Carcinogen |
Soot and tar
Benzo[a]pyrene
Vinyl chloride
Ionizing radiation Radon
Benzene
Cr VI , Ni, As & Cd compounds
TCDD
Formaldehyde
|
Principal route of exposure |
Dermal, inhalation |
Target organ (or tumour type) |
Target organ depends on the agent: most commonly lung, urinary bladder and skin; all sites combined for TCDD |
Comment |
Agents listed are only a subset of known occupational carcinogens. Agents listed are implicated in a non-occupational environmental context addressed in Inferred risks. |
Deliberate exposure to sunlight |
Situation |
Deliberate exposure to sunlight |
Exposure |
White skinned populations |
Carcinogen |
Solar radiation; broad spectrum ultraviolet radiation |
Principal route of exposure |
Irradiation |
Target organ (or tumour type) |
Skin (cutaneous melanoma, squamous cell carcinoma, basal call carcinoma) |
Comment |
Account must also be taken of the beneficial effects of sunlight in relation to vitamin D. |
Particular work environments or job classifications |
Situation |
Particular work environments or job classifications |
Exposure |
Workers eg. work as a painter and work in the rubber industry; environments associated with aluminium production, coke production, furniture & cabinet making; iron & steel founding |
Carcinogen |
Some chemicals implicated (eg exposure to polycyclic aromatic hydrocarbons or aromatic amines) but causality not established because of complex exposures. |
Principal route of exposure |
Inhalation, and in some instances, dermal |
Target organ (or tumour type) |
Lung and other sites |
Comment |
By comparison with occupational cancers caused by particular agents, specific causative agents have not been identified in relation to the work environments listed.
|
Residing near point sources of recognised carcinogens causing extreme local pollution |
Situation |
Residing near point sources of recognised carcinogens causing extreme local pollution |
Exposure |
Relevant local populations |
Carcinogen |
Asbestos
Coke oven and iron foundry emissions
Arsenic, cadmium and nickels compounds
|
Principal route of exposure |
Inhalation in all cases |
Target organ (or tumour type) |
Lung and other sites depending on pollutant |
Comment |
Studies indicate increased cancer risk in local populations, though some studies fail to establish carcinogenic risk in this context. |
Passive smoking |
Situation |
People smoking tobacco |
Exposure |
Children & adults in smoker household; persons exposed as a consequence of smoking in the workplace and other environments |
Carcinogen |
Tobacco smoke passively inhaled |
Principal route of exposure |
Inhalation |
Target organ (or tumour type) |
Lung. Some evidence regarding larynx and other sites |
Comment |
Some inferences in relation to target organs apart from lung (eg. larynx) |
Drinking water contamination from industrial sources of arsenic |
Situation |
Drinking water contamination from industrial sources of arsenic |
Exposure |
Surrounding communities |
Carcinogen |
Arsenic compounds |
Principal route of exposure |
Ingestion |
Target organ (or tumour type) |
Urinary bladder & others |
Comment |
Many relevant studies do not established increased incidence of cancer despite clear evidence of relevant exposure. |
Residential exposure to radon |
Situation |
Residential exposure to radon |
Exposure |
Occupants of particular houses |
Carcinogen |
Radon |
Principal route of exposure |
Inhalation and irradiation (Yes: studies involving home exposure indicate causality) |
Target organ (or tumour type) |
Lung |
Comment |
Carcinogenic hazard established primarily by occupational studies but residential risk is specifically recognised. |
This information is based on peer review research published in the journal: B.W. Stewart, Banding carcinogenic risks in developed countries: A procedural basis for qualitative assessment, Mutat. Res.: Rev. Mutat. Res. (2008), doi:10.1016/j.mrrev.2007.11.007.