Epidemiologic studies of occupational and environmental exposures and cancer of the lung

• In order to study the importance of some less well-known occupational exposures and environmental factors in lung cancer etiology, a series of investigations were conducted in the Latium region of Italy, which includes the city of Rome. Five historical cohort studies were carried out on various occupational groups: power plant workers and merchant seamen with potential exposure to asbestos occupations with exposure to silica dust (silicotics receiving a disability compensation), and occupations withexposure to sulphuric acid mist (soap production workers) and to engine exhaust (taxi drivers). In addition, a case-control study evaluated lung cancer risk among ceramic workers exposed to silica dust, and a correlation study compared lung cancer mortality rates in areas with distinct geological features as a proxy of radon exposure in dwellings. Finally, time trends and geographical differences in lung cancer mortality rates in Italy not due to active smoking (background rates) were estimated to obtain an overall view of the aggregate effect of other factors than active smoking.More or less clearly increased risks of lung cancer mortality were observed in the cohorts of power plant workers (SMR=ol. 8, 95% cr~D.77-3.5;9D~ cr~o.ss-3.2), and merchant seamen (SMR~1.7, 95~ CI=l.l-2. 5) 1 probably mainly due to asbestos. An excess lung cancer risk was detected among ceramic workers (OR=2. 0, 95% CI=l.l-3.5); those ceramic workers with silicosis showed an even higher relative risk (0R=3. 9, 95% CI=l. 8-8.3) . Subjects receiving a disability pension for silicosis in the region were also found to have an increased risk of lung cancer (MOR=1.5; 95% CI=l.l-1.9). There was a suggestion of excess risk of lung cancer among workers in the production of soap (SMR=1.7; 95%CI~D.55-3.9; 90~ CI~0.73-3.6), although the limited size of the study precludes any definitive conclusion. Taxi drivers in Rome also appeared to have a slightly increased risk of lung cancer (SMR~1.2, 95~ CI~D.97-1.5), especially those enrolled more recently (SMR~1.4, 95~ CI~l.02-1.9)After adjustment for smoking and urbanization, the ecologic study showed a 20% increase in mortality rates for lung cancer in an area with a higher level of background radiation. Indoor radon exposure may be suggested as a potentially important risk factor for lung cancer in that area.When differences of time and place in lung cancer death rates not attributable to active smoking were studied, all calculations indicated that the estimated background rates increased in Italy from the period 1956-58 to the period 1987-1989, especially in males. Higher background rates were observed in heavily urbanized areas than in rural areas.The overwhelming role in cigarette smoking is well recognized but various environmental factors also play an important role in causing lung cancer. These factors should not be neglected in public health efforts to reduce the risk of lung cancer, especially as they may at times be easier to reduce or eliminate than smoking.

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