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Causes - Lung cancer

Most cases of lung cancer are caused by smoking, although people who have never smoked can also develop the condition.


Smoking cigarettes is the single biggest risk factor for lung cancer. It's responsible for more than 7 out of 10 cases.

Tobacco smoke contains more than 60 different toxic substances, which are known to be carcinogenic (cancer-producing).

If you smoke more than 25 cigarettes a day, you are 25 times more likely to get lung cancer than someone who does not smoke.

Frequent exposure to other people’s tobacco smoke (passive smoking) can also increase your risk of developing lung cancer.

While smoking cigarettes is the biggest risk factor, using other types of tobacco products can also increase your risk of developing lung cancer and other types of cancer, such as oesophageal cancer and mouth cancer.

These products include:

  • cigars
  • pipe tobacco
  • snuff (a powdered form of tobacco)
  • chewing tobacco

Smoking cannabis may also increase the risk of developing lung cancer. Most people who smoke cannabis mix it with tobacco. While they tend to smoke less tobacco than people who smoke regular cigarettes, they usually inhale more deeply and hold the smoke in their lungs for longer.


Radon is a natural radioactive gas that comes from tiny amounts of uranium present in all rocks and soils. It can sometimes be found in buildings.

If radon is breathed in, it can damage your lungs, particularly if you smoke. Radon gas causes a small number of lung cancer deaths in England.

Occupational exposure and pollution

Exposure to certain chemicals and substances which are used in several occupations and industries may increase your risk of developing lung cancer. These chemicals and substances include:

  • arsenic
  • asbestos
  • beryllium
  • cadmium
  • coal and coke fumes
  • silica
  • nickel

Find out more about asbestosis and silicosis.

Research has also found that frequently being exposed to diesel fumes over many years increases your risk of developing lung cancer.

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Page last reviewed: 01 November 2022
Next review due: 01 November 2025