Enviromental Causes

Your risk of cancer can increase through exposure to cancer causing agents. These agents may be biological (specific viruses or bacteria), physical (ultraviolet light, x-rays) or chemical. Only a minor fraction of chemicals cause cancer and these are referred to as ‘carcinogens'.

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.

As distinct from lifestyle choices (choosing to smoke, drink alcohol or engage in deliberate sun exposure), exposure to carcinogens may occur outside your control. Exposure may occur in the workplace, or in the wider environment through air, water or soil pollution. You may also be exposed to particular chemicals through the use of consumer products.

Involuntary exposure to carcinogens often comes to the public’s attention through reports in the media concerning particular issues (use of herbicides, contaminants of food, hazards associated with cosmetics etc). However, in all such instances, the level of cancer risk is rarely made clear. Such reports can cause alarm and confusion, even though there may be no risk or minimal risk.

To assist the public, media and health professionals, a method of classifying the level of carcinogenic risk associated with exposure to known, probable and possible carcinogens has been developed, by categorising each agent and the circumstances under which exposure occurs.

In the five tables below are more than 60 possible cancer-causing agents and situations of exposure. These are reviewed and ranked in one of five risk bands - Proven, Likely, Inferred, Unknown or Unlikely.

*Carcinogen – any substance which tends to produce a cancer in a body.

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.

Banding carcinogenic risks in developed countries: A procedural basis for qualitative assessment

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Proven risk

Proven risks of cancer are situations in which an increased incidence of cancer has clearly been associated with exposure to a known carcinogen. Some examples include:

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Likely risk

Likely risks of cancer involve exposure to a known carcinogen or an agent considered to be a probable carcinogen. Some examples include:

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Inferred risk

Inferred risks of cancer involve exposure to an agent that may be carcinogenic, though the evidence comes primarily from laboratory studies involving animals. Some examples include:

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Unknown carcinogenic risk

Unknown carcinogenic risk of cancer involves exposure to an agent that is a probable carcinogen or may be carcinogenic. There is greater uncertainty because of the method of exposure. Some examples include:

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Unlikely risk

Unlikely risk of cancer involves exposure to an agent that may be carcinogenic or where there is little evidence to suggest the agent is carcinogenic. There is also inadequate evidence that the method of exposure would have a carcinogenic effect. Some examples include: