The World Health Organisation (WHO) says that at least one third of cancers are preventable; therefore, avoiding exposure to known carcinogens (cancer causing substances) and making healthy lifestyle choices that help reduce risk can be effective measures to prevent cancer.

diets high in fruits and vegetables may help protect against many cancers

Some cancers (for example bowel or breast) can be prevented by detecting early stages tumours, which can then be removed.

Other cancers caused by viruses can be prevented by vaccines. These include liver cancer caused by hepatitis B and C and cervical cancer, as well as some head and neck cancers caused by the human papilloma virus.

While there are limited opportunities to prevent cancers caused by inherited risk factors, knowledge of a person’s risk can lead to improved health outcomes.

Known cancer risk factors

The link between cancer and a number of risk factors has been well-established. WHO lists the following factors that are known to cause or increase the risk of cancer:

Lifestyle related factors:

  • Tobacco use
  • Physical inactivity, dietary factors, obesity and being overweight
  • Alcohol use

Environmental factors:

  • Infections
  • Environmental pollution
  • Occupational carcinogens
  • Radiation, including exposure to sunlight

Preventing lifestyle related cancers

Individual lifestyle choices have been identified as key to reducing cancer incidence. As a consequence, many public health programs focus on encouraging behavioural change and providing information on cancer prevention and lifestyle choices.

Tobacco use is the single greatest avoidable risk factor for cancer mortality worldwide, causing an estimated 22% of cancer deaths per year. Many programs provide support for those wishing to quit smoking and many countries have put in place legislative measures to prevent second hand exposure.

A link has been established between overweight and obesity and many types of cancer. Various cancer types are attributable to the joint effect of diet, obesity and physical inactivity, particularly in high-income countries.

cancer-risk-and-chromium

Regular exercise and activity as well as healthy diets high in fruits and vegetables may help protect against many cancers. On the other hand, excess consumption of red and preserved meat may be associated with an increased risk of bowel (colorectal) cancer.

Alcohol use is a risk factor for many cancer types including cancer of the oral cavity, pharynx, larynx, oesophagus, liver, bowel and breast. Risk of cancer has been proven to increase with the amount of alcohol consumed thus abstaining or limiting alcohol use may help reduce the risk.

Preventing cancers caused by environmental factors

Avoiding exposure to infectious agents, carcinogenic substances, pollutants and radiation is the most effective way to lower cancer risk.

Infectious agents are responsible for almost 22% of cancer deaths in the developing world and 6% in industrialised countries. Preventive measures include vaccination and prevention of infection and infestation.

According to WHO and the International Agency for Research on Cancer, environmental pollution of air, water and soil with carcinogenic chemicals accounts for 1–4% of all cancers. Exposure to carcinogenic chemicals in the environment can occur through drinking water or pollution of indoor and ambient air. Measures to reduce risk of cancers caused by environmental factors include the establishment of government agencies, for example the Unites States Environmental Protection Agency, to monitor and regulate pollutants in the environment.

environmental pollution of air, water and soil with carcinogenic chemicals accounts for 1–4% of all cancers

More than 40 agents, mixtures and exposure circumstances in the working environment are carcinogenic to humans and are classified as occupational carcinogens. It is well documented that occupational carcinogens are causally related to cancer of the lung, bladder, larynx and skin and to leukaemia and nasopharyngeal cancer.

Knowledge on radiation risk has been mainly acquired from epidemiological studies after exposure. Ionizing radiation is carcinogenic to humans and can cause leukaemia and a number of solid tumours. Residential exposure to radon gas from soil and building materials is estimated to cause between 3% and 14% of all lung cancers.

Ultraviolet (UV) radiation and exposure to sun can cause skin cancer, including basal cell carcinoma, squamous cell carcinoma and melanoma. Avoiding excessive exposure, use of sunscreen and protective clothing are effective preventive measures.

Early diagnosis and cancer screening

Some preventative measures are focused on early detection of cancer. For example, in Australia national screening programs are available for bowel, breast and cervical cancer.
WHO recommends national cancer prevention programs to reduce the number of cancer cases and deaths, and to improve quality of life of patients.

Further reading

This limited collection of articles published across CANCERRESEARCH sites explores many aspects of cancer prevention in more detail. If you have any questions or concerns, please discuss these with your health care provider.

What causes cancer: bad luck or external factors?

A study published in Science in early 2015 reported that most cancers aren’t preventable and are simply a case of “bad luck”. A year on, however, and a study published in Nature has come to the opposite conclusion: that external factors such as tobacco, sunlight and human papilloma virus play a greater part in whether or not a person gets cancer. So what does cause cancer: bad luck, or avoidable lifestyle choices and environmental factors?

Lynch syndrome – a common cancer risk explained

Lynch syndrome is a common, inherited condition that affects thousands of Australians and greatly increases the risk of developing cancer. Yet 95% of those who have it don’t know about it.

Interactive body map – what causes cancer?

There’s abundant advice out there on what you should or shouldn’t eat, drink, swallow, or stand next to, to avoid cancer. But it’s often lacking in evidence, and the jumble of messages can be confusing.

The body map published in The Conversation brings together the evidence on proven cancer causes. Using credible scientific sources it answers questions about whether alcohol, red meat or sun exposure increase your cancer risk.

Unproven cancer risks distract focus from real cause: lifestyle

According to a review of global evidence by an Australian cancer researcher, the fixation on potentially cancer-causing chemicals in the air, food and consumer products is diverting attention from the real risks.

Cancer risk and red meat: what the who report really said

On 26 October 2015, the cancer arm of the World Health Organization released its evaluation on how likely red and processed meats are to cause cancer.
The verdict?
Consumption of processed meat is classified within group 1 – alongside known carcinogens including asbestos, tobacco, arsenic and alcohol. It causes bowel cancer and is implicated in stomach cancer.