Tobacco smoking is the number one cause of lung cancer; in fact, it is the number one known cause of cancer generally. Nothing else comes close. For comparison, a study in the Lancet, a top medical journal, estimated that smoking accounts for 86 per cent of lung cancer deaths in developed countries, while air pollution accounts for just three per cent. This means that smoking kills almost 30 times more people from lung cancer than air pollution does. While many studies have found that air pollution, such as diesel particles, can increase the risk of cancer, the effect is not experienced by the whole community, but specifically involves transport workers and other people whose jobs mean that they spend a lot of time driving diesel vehicles. Indoor air pollution, from coal-burning stoves or cooking fumes, can also cause lung cancer. Whether wood smoke causes cancer is not clear. Apart from cancer, air pollutants generally cause a range of respiratory diseases and it is good health practice to avoid repeated and long-term exposure.