Increased incidence of lung and skin cancer in Finnish silicotic patients.

Cancer incidence during 1953 to 1991 in 811 Finnish silicotic patients diagnosed between 1936 and 1977 was evaluated. In comparison with the general population, excesses were observed for all cancers (standardized incidence ratio, 1.7 [95% confidence interval, 1.4 to 1.9]), all lung cancers (2.9 [2.4 to 3.5]), squamous cell lung cancers (3.3 [2.3 to 4.5]), and skin cancers: melanoma (3.0 [0.8 to 7.6]) and nonmelanoma (2.9 [1.2 to 6.1]). Confounding by tobacco smoking did not explain the lung cancer increment. The consistency of the association between silicosis and lung cancer across a large number of studies suggests that silicosis represents a direct or indirect lung cancer hazard. The skin cancer excess, a relatively novel finding, may be explained either by carcinogens in foundries, or silica-induced lowering of immunocompetence, which would lead to a more pronounced effect of solar ultraviolet radiation.