About eight out of every 10 lung cancer cases are caused by smoking. A proportion of people who develop lung cancer have never been smokers. Some lung cancer in those who have never smoked (about 10%), is caused by exposure to environmental tobacco smoke, either in the workplace – particularly the hospitality or entertainment industries – and/or at home. Lung cancer may be caused by certain workplace chemicals such as asbestos and also by atmospheric pollution. In some cases of lung cancer in those who have never smoked, no specific cause is evident. Cigarette smoking remains one of the leading causes of lung and other cancers, is responsible for at least 1 in 10 cancer cases overall and causes 1 in 5 cancer deaths.