Lung cancer - Causes 

Causes of lung cancer 

Smoking

Smoking cigarettes is the single biggest risk factor for lung cancer. It is responsible for about 90% of all cases.

Tobacco smoke contains more than 60 different toxic substances, which can lead to the development of cancer. These substances 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 a non-smoker.

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 has also been linked to an increased risk of lung cancer. Most cannabis smokers mix their cannabis with tobacco. While they tend to smoke less than tobacco smokers, they usually inhale more deeply and hold the smoke in their lungs for longer.

One researcher has estimated that smoking four joints (homemade cigarettes mixed with cannabis) may be as damaging to the lungs as smoking 20 cigarettes.

Even smoking cannabis without mixing it with tobacco is potentially dangerous. This is because cannabis also contains substances that can cause cancer.

Passive smoking

Even if you do not smoke, frequent exposure to other people’s tobacco smoke (passive smoking) can increase your risk of developing lung cancer.
For example, research has found that non-smoking women who share their house with a smoking partner are 25% more likely to develop lung cancer than non-smoking women who live with a non-smoking partner.

Radon

Radon is a naturally occurring radioactive gas that can seep up from the ground into buildings. If radon is breathed in, it can damage your lungs, particularly if you are a smoker. Radon is estimated to be responsible for about 3% of all lung cancer deaths in England.

Occupational exposure

Exposure to certain chemicals and substances that are used in several occupations and industries has been linked to a slightly higher risk of developing lung cancer. These chemicals and substances include arsenic, asbestos, beryllium, cadmium, coal and coke fumes, silica and nickel.

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Last reviewed: 11/11/2011

Next review due: 11/11/2013

How does cancer begin?

The body is made up of millions of different types of cells. Cancer happens when some of the cells multiply in an abnormal way. When cancer affects organs and solid tissues, it causes a growth called a tumour to form. Cancer can occur in any part of the body where the cells multiply abnormally.

How does cancer spread?

If it is not treated, cancer can quickly grow and spread, either in the skin or the blood, or to other parts of the body. This usually happens through the lymphatic system.
If the cancer reaches your lymphatic system, it can spread to any other part of your body, including your bones, blood and organs.

Lung cancer myths and facts

We separate the fact from the fiction about lung cancer and its link with smoking and other risk factors.

Lung cancer: are you at risk?

The facts about lung cancer, including how to tell if you're at risk, even if you don't smoke, and what you can do to prevent the disease