Sauna, dust and migration as risk factors in lung cancer among smoking and non-smoking males in Finland.

To study possible causes of the high lung cancer incidence among Finnish males, the Finnish Cancer Registry and the Cancer Registry of Norway in 1962 performed a population survey covering smoking habits, occupational and residential history and, in Finland, sauna habits. The cohort of 4,475 Finnish men has now been followed up for incidence of lung cancer in 1964-1979. The relative importance of 3 factors--sauna baths, occupational exposure to dust, and migration to urban areas--was studied in different smoking categories. Among smokers of greater than or equal to 25 g/day, takers of frequent saunas (more than once a week) displayed some excess risk (RR 1.7). In smokers an increased risk was also found among those exposed to dust (RR 1.3), and those who had migrated to urban areas (RR 1.8, when compared to native urban population). Dust exposure and migration factors act synergistically with smoking. Migration was the only factor apart from smoking to show a substantial population-attributable risk, which amounted to 10%.