The main cause of lung cancer is smoking, although non-smokers can also develop the condition. Smoking and other risk factors for lung cancer are described below.

• Smoking is the cause of lung cancer in more than 90% of cases and is the single biggest risk factor for lung cancer. There are more than 60 different toxins in tobacco smoke that can cause cancer and these are referred to as carcinogens.

Although tobacco smoking is the main risk factor for lung cancer, other tobacco products such as pipe tobacco, cigars, chewing tobacco and snuff can also raise the risk of lung cancer and other forms of cancer such as mouth cancer and esophageal cancer.

• Smoking cannabis can also raise the risk of lung cancer. According to estimates, four cannabis joints (joints contain a mixture of cannabis and tobacco) can damage the lungs as much as 20 tobacco cigarettes.
• Passive smoking can also increase the risk of lung cancer. Research has shown that women who do not smoke, but share their home environment with a smoker are at a 25% greater risk of developing the condition than a female non-smoker who lives with a non-smoking partner.
• Radon, a radioactive gas found in rocks and soil, can cause damage to the lungs and in England, radon is thought to account for around 3% of deaths caused by lung cancer.
• Occupational exposure to certain substances has been associated with an increased risk of lung cancer. Examples include asbestos, arsenic, cadmium, coal, coke, beryllium, silica and nickel.