Mortality among silicotics in Genoa, Italy, from 1961 to 1987.

A historical cohort mortality study conducted among 515 silicotic subjects revealed higher than expected risks for all causes [standardized mortality ratio (SMR) 1.89], respiratory tract diseases (SMR 8.89), silicotuberculosis (SMR 27.00), respiratory tract cancers (SMR 3.14), and lung cancer (SMR 3.50). Mortality from cardiovascular diseases was lower than that expected (SMR 0.51). Lung cancer risk increased with duration of occupational exposure (SMR 2.80, 2.99, and 5.02 for 14, 15-29, and 30 years of employment, respectively). Lung cancer risk was higher for the silicotics without tuberculosis (SMR 3.72) than for those with tuberculosis (SMR 2.83). Indirect adjustment for smoking habits, including number of cigarettes smoked per day, showed that smoking would have been responsible for a maximum risk of 1.77. Thus smoking may have explained 50% of the observed excess mortality from lung cancer.