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Causes of Lung Cancer

This page presents information on lung cancer causes including smoking, radon gas, industrial carcinogens, air pollution, physical activity, previous cancer treatment, diet and alcohol and other factors.

A study published in December 2011 estimated that, in the UK, around 91% of lung cancers in men and more than 86% in women are linked to lifestyle and environmental factors - the majority of these caused by smoking.


Around 86% of lung cancer deaths in the UK are caused by tobacco smoking. Overall, tobacco smoking is estimated to be responsible for more than a quarter of cancer deaths in the UK, that is, around 43,000 deaths in 2009.  Tobacco smoke is estimated to have caused around 60,000 cases of cancer in the UK in 2010.

Radon gas

Radon is considered to be the second largest cause of lung cancer after tobacco. A naturally occurring radioactive gas, radon is a known human carcinogen and increased risks of lung cancer were first observed in uranium miners with high radon exposure levels. Radon can also accumulate in homes and other buildings. Much lower exposure to radon multiplies the risk of lung cancer for both smokers and non-smokers by the same amount, but its effect is much greater for smokers as their risk of lung cancer is already much higher. Other sources of radiation exposure contributing to the burden of lung cancer include radiotherapy (which was estimated to cause around 320 cases of lung cancer in the UK in 2010), diagnostic radiation (around 125 cases) and natural (background) radiation (around 85 cases).

Industrial exposure

Several industrial carcinogens, for example, arsenic and polycyclic hydrocarbons as well as some occupations including non-ferrous metal production and painting, have been linked to lung cancer.  Diesel exhaust was classified as a cause of lung cancer by the International Agency for Research on Cancer (IARC) in June 2012, following a review of evidence mainly from highly-exposed workers.  IARC cited a study of diesel exhaust exposure in miners, which showed risk of lung cancer was increased approximately three times in those most heavily exposed. The large American prospective Agricultural Health Study Exposure suggests that exposure to herbicides and insecticides increases lung cancer risk. Occupational exposure to silica can result in silicosis with an increased risk for lung cancer, but without silicosis there is no increased risk. The body of evidence supports an increased risk of lung cancer with exposure to asbestos in non-smokers, and that risks are especially high in those who smoke, who also have past exposure to asbestos. It has been estimated that around 21% of lung cancers in men in the UK and around 4% in women are linked to occupational exposures. Around 40% of the total occupation-attributable cases were caused by asbestos, around 17% by silica and around 13% by diesel engine exhaust.

Air pollution

Outdoor air pollution is also thought to make a small contribution to the lung cancer burden. In urban areas, traffic fumes are the main source of outdoor exposure. Use of solid fuel in the home for cooking or heating has been associated with an increased risk.


Family history

A family history of lung cancer in a first-degree relative is associated with a two-fold increased risk, independent of smoking.  If both cancers are diagnosed before the age of 60, the risk ratio is almost five-fold. The association between family history and risk may be stronger in black individuals than white.


Physical activity

People who participate in higher levels of recreational physical activity have a lower risk of lung cancer.

Previous cancer treatment

Treatment for Hodgkin’s lymphoma increases lung cancer risk by 2.6-7-fold. Risk ratios are higher in smokers than non-smokers and with radiotherapy compared to chemotherapy. Increased risk of lung cancer has also been shown after treatment for non-Hodgkin’s lymphoma, and up to 30 years after diagnosis with testicular cancer, which is linked to radiation to the chest as part of the treatment.

Diet, supplements and alcohol

A diet rich in vegetables has been associated with a reduced risk of lung cancer, but the protective effect may be limited to smokers:  however, evidence remains mixed. Higher fruit consumption has also been associated with a small reduction in risk.  The role of dietary vitamin C is as yet unclear and there is a suggestion that it may be a marker for other protective dietary factors.  A higher intake of beta-cryptoxanthin may be associated with a reduced risk.  Both vitamin C and beta-cryptoxanthin are found in brightly coloured fruit. Higher intakes of selenium, copper and zinc have all been associated with a reduced risk. The close association between smoking and alcohol intake is a possible confounding factor in studies of lung cancer risk and alcohol and no strong link has been established. 

Other risk factors

Significant increases in risk of lung cancer have been reported in people with HIV and AIDS even after accounting for smoking, although one study showed an association in men only. 

People with antibodies to Chlamydia pneumoniae have an increase in risk.  Chlamydia pneumoniae is an infectious bacteria associated with a number of diseases including pneumonia. An increased risk of lung cancer has been shown in people with systemic lupus erythematosus, and Klinefelter syndrome, in both cases less than two-fold. A systematic review of published studies showed that risk of lung cancer is almost doubled for people with a previous diagnosis of tuberculosis (TB), after taking into account smoking history.

*note: statistics on this page are sourced from http://www.cancerresearchuk.org

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