Introduction The ambiguity in carcinogenicity of softwood dust intrigued the current study to explore stronger evidence on risk of nasal cancer attributable to lifetime cumulative exposure (CE) to softwood-predominated mixed wood dust across broad wood-processing industries in four Nordic countries.

Method A population-based case-control study was conducted on all male cases with nasal adenocarcinoma (393 cases), other types of nasal cancer (2446), and nasopharyngeal cancer (1747) diagnosed in Finland, Sweden, Norway, and Iceland between1961 and 2005. For each case, five male controls, who were alive at the time of diagnosis of the case (index date), were randomly selected, matched by birth-year and country. CEs to wood dust and formaldehyde before the index date were quantified with job-exposure matrix based on occupational titles derived from population censuses.

Results Hazard ratios (HRs) and 95% confidence intervals (CIs) for the CE of wood dust were estimated by conditional logistic regression, adjusted for CE to formaldehyde. There was an increasing risk of nasal adenocarcinoma related to wood dust exposure. The HR in the highest CE category of wood dust (≥ 28.82 mg/m³-years) was 16.5 (95% CI: 5.05–54.1). Neither non-adenocarcinoma of the nose nor nasopharyngeal cancer could be linked to wood dust exposure.

Conclusion Lifetime CE to softwood-predominated mixed wood dusts is strongly linked to risk of nasal adenocarcinoma but not other types of nasal or nasopharyngeal cancer.