Laryngeal and hypopharyngeal cancers and occupational exposure to formaldehyde and various dusts: a case-control study in France

Objectives-A case-control study was conducted in France to assess possible associations between occupational exposures and squamous cell carcinomas of the larynx and hypopharynx. Methods-The study was restricted to men, and included 201 hypopharyngeal ca ncers, 296 laryngeal cancers, and 296 controls (patients with other tumour sites). Detailed information on smoking, alcohol consumption, and lifetime occupational history was collected. Occupational exposure to seven substanc es (formaldehyde, leather dust, wood dust, flour dust, coal dust, silica du st, and textile dust) was assessed with a job exposure matrix. Exposure var iables used in the analysis were probability, duration, and cumulative leve l of exposure. Odds ratios (ORs) with their 95% confidence intervals (95% C Is) were estimated by unconditional logistic regression, and were adjusted for major confounding factors (age, smoking, alcohol, and when relevant oth er occupational exposures). Results-Hypopharyngeal cancer was found to be associated with exposure to c oal dust (OR 2.31, 95% CI 1.21 to 4.40), with a significant rise in risk wi th probability (p<0.005 for trend) and level (p<0.007 for trend) of exposur e. Exposure to coal dust was also associated with an increased risk of lary ngeal cancer (OR 1.67, 95% CI 0.92 to 3.02), but no dose-response pattern w as found. A significant relation, limited to hypopharyngeal cancer, was fou nd with the probability of exposure to formaldehyde (p<0.005 for trend),wit h a fourfold risk for the highest category (OR 3.78,95% CI 1.50 to 9.49). W hen subjects exposed to formaldehyde with a low probability were excluded, the risk also increased with duration (p<0.04) and cumulative level of expo sure (p<0.14). No significant association was found for any other substance . Conclusion-These results indicate that exposure to formaldehyde and coal du st may increase the risk of hypopharyngeal cancer.