Wood dust exposure and squamous cell cancers of the upper respiratory tract.

While it is well-accepted that exposure to hardwood dust increases the risk of sinonasal adenocarcinoma, it is still not clear to what extent wood dust exposure increases the risk of sinonasal squamous cell carcinoma or whether such exposure is also associated with adjacent upper respiratory sites. These questions were addressed using data from two population-based case-control studies in Washington State in 1979-1987. After control for major risk factors, employment in wood-related occupations was most strongly associated with nasal cancer, especially when analysis was restricted to long-term employment 15 or more years before diagnosis (odds ratio = 7.3; 95% confidence interval 1.4-34.2). Although the overall risk for the nasopharynx was only slightly elevated, similar analysis restrictions increased the odds ratio to 4.2 (95% confidence interval 0.4-26.6). There was little indication of increased risk for the oropharynx or larynx. Although based on small numbers, these findings suggest that exposure to softwood dust increases the risk of both sinonasal and nasopharyngeal squamous cell cancers.