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What Causes Lung Cancer?

The cause of every type of cancer is still not fully understood.

However, it is increasingly thought that changes in the genes that program cell functions become faulty. This results in abnormal cell growth and/or multiplication.

It now appears that in many types of cancers, external influences – such as lifestyle, diet, chemicals and environment – may trigger these faulty genes into action.

In the case of lung cancer, several external influences (or risk factors) have been identified as having a strong link to the development of tumour growth in the lungs.

Risk factors for lung cancer include1:

  • Tobacco smoke
  • Passive smoking: long term exposure to breathing in the air of smokers in your household/workplace.
  • Chemical substances: found within cigarettes and other smoking substances, such as pipes and cigars. Some of these chemicals are also found in cannabis (marijuana).
  • Environmental factors: exposure to air pollution, such as chemical, radiation leaks and radon exposure.
  • Occupational exposure such as asbestos (a recognised cause of mesothelioma, which is not strictly a lung cancer, but rather a cancer of the membranes which surround the lungs) and diesel exhaust.
  • Age
  • Family history of lung cancer
  • Previous lung diseases

While tobacco smoking is the largest signal cause of lung cancer, people who have never smoked can be diagnosed with lung cancer.

The risk of developing lung cancer decreases in people who stop smoking, but they are still at higher risk than people who have never smoked.

For information and support to try and stop smoking click here


  1. Cancer Australia 2011. Investigating symptoms of lung cancer: a guide for GPs