6.3 Risk factors

Table 6.2 Risk factors for lung cancer, by direction of association and strength of evidence

Increases risk

Decreases risk

Convincing or probable

Tobacco smoking and involuntary (passive) smoking1





Ionizing radiation2


Arsenic and arsenic compounds; asbestos; beryllium and beryllium compounds; cadmium and cadmium compounds; chromium compounds; nickel compounds; silica dust; and polycyclic aromatic hydrocarbons (PAHs)3-7


Employment as a painter8


Beta-carotene supplements9,10


History of tuberculosis11


Indoor emissions from household combustion of coal1,12


Low socio-economic status13


Family history of lung cancer14,15



Physical activity18,25


Non-starchy or cruciferous vegetables18,26

Low body fatness/leanness18

Flavonoids from foods27

Infection with chlamydia pneumoniae or Helicobacter pylori19,20

Green tea28

Occupational exposure to diesel motor exhaust or organic dust21,22

Employment in cotton textile and agriculture industries29

Hormone replacement therapy23,24

Aspirin and other non-steroidal anti-inflammatory drugs30


1 Secretan et al., 2009; 2 El Ghissassi et al., 2009; 3 Celik et al., 2008; 4 Baan et al., 2009; 5 Lacasse et al., 2009; 6 Straif et al., 2009;

7 main route of exposure is occupational; 8 Guha et al., 2010; 9 in current smokers; 10 Tanvetyanon and Bepler, 2008; 11 Liang et al., 2009; 12 Hosgood et al., 2010; 13 Sidorchuk et al., 2009; 14 one or more relative(s) with lung cancer; 15 Lissowska et al., 2010;

16 Uehara and Kiyohara, 2010; 17 Tang et al., 2010; 18 World Cancer Research Fund / American Institute for Cancer Research, 2007;

19 Zhan et al., 2011; 20 Zhuo et al., 2009; 21 Olsson et al., 2011; 22 Peters et al., 2011; 23 in non-smoking women; 24 Greiser et al., 2010; 25 International Agency for Research on Cancer, 2002; 26 Lam et al., 2009; 27 Tang et al., 2009a; 28 Tang et al., 2009b;

29 Lenters et al., 2010; 30 Bosetti et al., 2006

Smoking is the principal cause of lung cancer (Table 6.2). In populations with prolonged cigarette use, 90% of lung cancer cases are due to cigarette smoking (International Agency for Research on Cancer, 2004b). Risk increases with younger age at smoking commencement and longer duration of smoking. Stopping smoking, at any age but particularly so before middle age, avoids most of the subsequent risk (Peto et al., 2000). In addition, involuntary exposure to tobacco smoke (passive smoking) is a cause of lung cancer in those who have never smoked. The consistent relationship between higher lung cancer risk and lower socio-economic status probably reflects social class variations in tobacco exposure.

The chances of developing lung cancer are increased in those exposed to radon, ionizing radiation and a variety of chemicals and compounds. Various lifestyle factors (such as alcohol intake, physical activity, leanness and aspects of diet) may be related to lung cancer, but it is not always possible to rule out the possibility that the associations are due to a residual effect of smoking. 

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