Risk factors and causes of lung cancer

Smoking cigarettes is the main cause of lung cancer. However, people who don’t smoke can still develop lung cancer.

If someone stops smoking, their risk of developing lung cancer falls quickly. Within 15 years, it will be similar to that of non-smokers.

Breathing in other people’s smoke (passive smoking) slightly increases the risk of getting lung cancer.

Lung cancer is more common in older people. There may also be a slightly greater risk of developing lung cancer if a close family member has had lung cancer. People who have had radiotherapy to the chest in the past also have a slightly increased risk.

There are environmental factors that may increase the risk of lung cancer. These are being exposed to:

  • High concentrations of radon gas, which is found naturally in some areas of the country. 
  • Asbestos, which was used in certain jobs, such as the building industry. Its use is now banned in the UK.

Risks of developing lung cancer

Lung cancer is the second most common cancer diagnosed in the UK. About 43,500 people are diagnosed with it each year.

Smoking is the cause of most lung cancers. There are also other risk factors that can increase the chances of developing lung cancer.

Having a particular risk factor doesn’t mean you will definitely get cancer. And sometimes people without any known risk factors can develop cancer.


Smoking

Smoking tobacco is the cause of most lung cancers and the biggest risk factor.

The more you smoke (this includes cigarettes, cigars and pipes), the greater your risk. Around 90% of people (9 out of 10) who get lung cancer are smokers or ex-smokers. Starting smoking at a young age means the risk is higher.

Because more men used to smoke than women, lung cancer is still more common in men. But the number of men with lung cancer in the UK has fallen, while in women the number has increased due to more women smoking.

People who do not smoke can also develop lung cancer, but their risk is much lower. About 10–15% of people (around 1 in 10) who get lung cancer have never have smoked.

Lung cancer in smokers and non-smokers
Lung cancer in smokers and non-smokers

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When people stop smoking, their risk of lung cancer falls quickly. After about 15 years it’s almost the same as a non-smoker.

Passive smoking

Breathing in other people’s cigarette smoke (passive smoking) can slightly increase the risk of lung cancer. But it’s still much lower than if you smoke yourself.


Age

Lung cancer is more common in older people. About 80% of lung cancers (8 in 10) are diagnosed in people over 60. It’s rare in people under 40.


Radon gas

In certain parts of the UK, a natural gas called radon can pass from the soil into the foundations of buildings. Exposure to high levels of radon can increase the risk of developing lung cancer, but particularly if you smoke as well.


Asbestos

People who have been in prolonged or close contact with asbestos, previously used in building industries, have a higher risk of lung cancer. The risk is greater if they smoke.

Exposure to asbestos also increases the risk of mesothelioma, a cancer of the membranes that cover the lungs (the pleura). If you have worked with asbestos and have lung cancer or mesothelioma, you may be able to claim compensation.

We have more information on financial help and compensation for mesothelioma.


Previous cancer treatment

People who have had radiotherapy to the chest to treat lymphoma or testicular cancer that has spread have a slightly increased risk of lung cancer. The risk is greater if they smoke.

But for these people, the risk of developing lung cancer is far outweighed by the benefits of their cancer treatment.


Lowered immunity

Having a lowered immunity as a result of illness or treatment can increase the risk of lung cancer. People with HIV and AIDS have a lowered immune system and also people who take drugs called immunosuppressants after an organ transplant.


Family risk

People with a close relative who had lung cancer may have a slightly increased risk.

If you’re concerned about a family history of lung cancer, you may find it helpful to read our section on cancer genetics. You can also talk to your GP.


Other causes

Contact with certain chemicals and substances, usually through work, can rarely cause lung cancer.

Recent research has shown that air pollution can cause lung cancer. But it’s difficult to know the risk for individuals as it depends on the air quality where they live and how much pollution they are exposed to. For most people the risk is very slight compared to smoking, which is a major risk factor.

Lung cancer is not infectious and can’t be passed on to other people.