• ‘Cigarette smoking is an established cause of cancer at multiple anatomic sites and is the single largest preventable cause of cancer in the EU. It is the main cause of lung cancer, responsible for eight in ten lung cancers.’

• ‘The major cause of lung cancer is tobacco smoking […], which is responsible for 80–85% of lung cancer cases worldwide.’

• ‘Smoking is the main cause of lung cancer. It is estimated that over 90 per cent of cases among men and over 80 per cent among women worldwide are attributable to tobacco use. Passive smoking is also a cause of lung cancer.’

Cigarette smoking:

• ‘Based on solid evidence, cigarette smoking causes lung cancer. The risks of lung cancer associated with cigarette smoking are dose-dependent and increase markedly according to the number of cigarettes smoked per day and the number of years smoked. On average, current smokers have approximately 20 times the risk of lung cancer compared with non-smokers.’
• ‘Magnitude of Effect: Increased risk, very large.’

Exposure to second-hand smoke:

• ‘Based on solid evidence, exposure to second-hand smoke is an established cause of lung cancer.’
• ‘Magnitude of Effect: Increased risk, small magnitude.’

• ‘Smoking is by far the leading risk factor for lung cancer. About 80% of lung cancer deaths are thought to result from smoking, and this number is probably even higher for SCLC.’

•  ‘Occupational exposure to asbestos, crystalline silica, radon, mixtures of polycyclic aromatic hydrocarbons and heavy metals are associated with an increased risk of lung cancer.’

• ‘Based on solid evidence, workplace exposure to asbestos, arsenic, beryllium, cadmium, chromium, and nickel increases lung cancer incidence and mortality.’
• ‘Magnitude of Effect: Increased risk, large magnitude (more than fivefold).’

• ‘Air pollution (indoor and outdoor) is a major environmental risk for health in Europe, and a known cause of cancer, in particular of the lung.’

• ‘Indoor air pollution from household combustion of solid fuel and cooking fumes in poorly ventilated homes was established as a lung carcinogen.’
• ‘Outdoor air pollution […] has been classified by the IARC Monographs as carcinogenic to humans (Group 1).’^a

• Exposure to indoor air pollution from wood and coal burning for cooking and heating are associated with an increased risk of lung cancer.

• ‘Based on solid evidence, exposure to outdoor air pollution, specifically small particles, increases lung cancer incidence and mortality.
• ’‘Magnitude of Effect: Increased risk, compared with the lowest exposure categories, those in the highest exposure categories have approximately a 40% increased risk of lung cancer.’

• ‘Arsenic and inorganic arsenic compounds is carcinogenic to humans (Group 1).’^a

• There is strong evidence that:
  ‘Drinking water containing arsenic increases the risk of lung cancer.’

• ‘The major cause of lung cancer is tobacco smoking. Other causes of lung cancer include asbestos, silica, several heavy metals, radon, and indoor and outdoor air pollution.’

• ‘Occupational exposure to asbestos, crystalline silica, radon, mixtures of polycyclic aromatic hydrocarbons and heavy metals are associated with an increased risk of lung cancer.’

• ‘Based on solid evidence, indoor exposure to radon increases lung cancer incidence and mortality, particularly among cigarette smokers.’
• ‘Magnitude of Effect: Increased risk that follows a dose-response gradient, with small increases in risk for levels experienced in most at-risk homes to greater increases in risk for high-level exposures.’

• High-dose β-carotene supplements increase the risk of lung cancer among people exposed to tobacco.

There is strong evidence that:

• ‘In current and former smokers, taking high-dose beta-carotene supplements increases the risk of lung cancer.’

There is limited evidence that:

• ‘Consuming red meat, processed meat and alcoholic drinks increases the risk of lung cancer.’
• ‘In current smokers and former smokers, consuming vegetables and fruit decreases the risk of lung cancer.’
• ‘Consuming foods containing retinol, beta-carotene or carotenoids decreases the risk of lung cancer.’
• ‘In current smokers, consuming foods containing vitamin C decreases the risk of lung cancer.’
• ‘In people who have never smoked, consuming foods containing isoflavones (constituent of plants with oestrogen-like properties) decreases the risk of lung cancer.’

• ‘Based on equivocal evidence, the observed inverse associations between lung cancer and dietary factors, such as fruit and vegetable consumption, are difficult to disentangle from cigarette smoking.’
• ‘Magnitude of Effect: Inverse association, moderate magnitude, but difficult to determine if true cause-effect association or due to confounding by cigarette smoking.’

There is limited evidence that:

• ‘Being physically active decreases the risk of lung cancer.'

• ‘Based on equivocal evidence, the observed inverse associations between lung cancer and higher levels of physical activity are difficult to disentangle from cigarette smoking.’
• ‘Magnitude of Effect: Inverse association, moderate magnitude, but difficult to determine if true cause-effect association or due to confounding by cigarette smoking.’