Lung cancer in males an epidemiological study in northern Sweden with special regard to smoking and occupation

Abstract: In a case-control study comprising 589 cases of male lung cancer in northern Sweden longitudinal data concerning occupations, employments and smoking habits were collected by questionnaires.Pipe smoking was as common as cigarette smoking and gave very similar relative risk. The pipe smoking cases, however, had significantly higher mean age and mean smoking years at the time of diagnosis than the cigarette smoking cases. In ex- smokers, the relative risk gradually decreased from 5 years after smoking cessation but this decrease was much less pronounced in ex-pipe smokers than in ex-cigarette smokers. High relative risks were obtained for small cell and squamous cell carcinomas. For adenocarcinoma the relative risk was considerably lower but still significantly increased. The population etiologic fraction attributable to smoking was about 80% in this series.Some occupational groups (underground miners, copper smelter workers, electricians and plumbers) exposed to previously known lung carcinogenic agents had considerably increased odds ratios, which persisted after adjustment for smoking. A slightly elevated odds ratio was observed in a group of blue collar workers potentially exposed to lung carcinogenic agents but this elevation generally disappeared after adjustment for smoking. For two specific subgroups, asphalt and concrete workers and pulp workers, the overrisk persisted after adjustment for smoking. Farmers and foresters had strikingly low odds ratios, which could only partly be explained by their more moderate smoking habits. The population etiologic fraction attributable to occupation was in the reported material assessed to 9 per cent.Professional drivers had higher average tobacco consumption than non-drivers, which explained the slightly increased crude odds ratio found for the occupational group as a whole. Smoking drivers in an upper age group (70 and over), however, had a high relative risk of lung cancer, while in a lower age group (under 70) no significant increase was found. The results in the older age group suggested a multiplicative effect between smoking and the occupational exposure.The study clearly verified the increased lung cancer risk in underground miners. An obvious dose-response relation was found with high risk after long time exposure. All analyses concerning underground miners suggested an interaction of a multiplicative type between underground mining and smoking in the causation of lung cancer. The cases of small cell carcinoma among the underground miners had shorter average latency time and in contrast to the other part of the material, shorter average age than the cases with epidermoid cancer.