To understand the reasons for underreporting of occupational
cancers, we investigated cases' perceptions of the causes of
cancer. As part of a case-control study in the province of British Columbia, Canada, 105
bladder cancer cases, 48
nasal cancer cases, 51
mesothelioma cases, and 159 population-based controls (frequency matched to cases on age and sex) were interviewed using structured questions about their smoking, medical, residential, occupational, and
carcinogen exposure histories. We asked cases what they thought caused their disease, and asked population controls about their understanding of the etiologies of the three
cancers. Most cases and controls (69%) indicated that they had "no idea" about causes, with the exception that the majority of
mesothelioma cases (70%) recognized
asbestos as a cause. Smoking was perceived as a cause of
bladder cancer by 21 percent of cases. Many cases knew about the
asbestos and smoking etiologies from discussions with their physicians. Chemicals were commonly cited as causes of nasal and
bladder cancer, but very few specific known or probable
carcinogens for these sites were named. Cases (12%) more frequently than controls (2%) thought prior disease or
trauma was a cause for all three types of
cancer. Other etiologic factors less frequently listed by subjects included environmental pollution, hereditary factors, drugs, and radiation. Most cases recognized the major cause of
mesothelioma, but few subjects knew about lifestyle or occupational causes of
bladder cancer or
nasal cancer, suggesting that education about the multiple
cancer risks of smoking and about occupational
carcinogens needs to be improved.