[Passive smoking and risk of cancer]

During the last two decades there have been frequent discussions as to whether passive smoking causes cancer, or not. It is difficult to carry out satisfactory studies on this issue, partially because any increased risk of cancer seems modest. The tobacco industry has not only attempted to make the public aware of studies which conclude that passive smoking is harmless, but it has also tried to keep alive the discussion as to whether exposure to passive smoking is harmful, or not. A large number of studies has been carried out on the possible impact passive smoking may have on the risk of lung cancer, and it seems justifiable to conclude that passive smoking does increase the risk of this type of cancer. For other types of cancer too few studies have been performed to draw any firm conclusions.