Proven risk

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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 Asbestos 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.

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