Cancers of the lip and oropharynx in different social and occupational groups in Finland.

Social status and occupation-specific risks of cancers of the lip, tongue, mouth and pharynx were studied in a nationwide series of 2369 men and 809 women diagnosed in Finland in 1971-1985 and recorded in the files of the Finnish Cancer Registry. Codes for social status (four classes) and occupation (336 categories) were drawn from the files of the 1970 Population Census. The standardised incidence rates (SIR) were defined as the ratios of observed and expected numbers of cases, the expected ones being based on the sex, age, site and calendar period-specific incidence rates in the Finnish population. The SIR of lip cancer in the lowest social class was five times that of the highest one, thus indicating the effects of social class differences in smoking habits. The effect of outdoor work on the development of lip cancer was also strongly supported by this study. The social class-adjusted SIR for fisherman was 2.7 (95% C.I. 1.3-5.0), for forestry managers 2.2 (1.2-3.6), for timber workers 1.9 (1.2-2.9) and for farmers 1.8 (1.2-2.6). For cancers of the oral cavity and pharynx there was no clear correlation with social class. However, the SIR for these cancers among farmers was significantly reduced. The occupation-specific SIRs pointed more to alcohol than smoking aetiology. In the case of cancer of the tongue, no aetiological clues whatsoever could be found. The role of direct occupational factors in the aetiology of any of these cancers seemed to be minimal.