Nested case-control study of lung cancer among pulp and paper workers in relation to exposure to dusts.

BACKGROUND Numerous studies have indicated an increased risk of lung cancer in pulp and paper industry workers. In a 1990 survey, standardized mortality ratio (SMR) was found to be 122 (95% CI:96-153) for lung cancer in Polish male workers in the pulp and paper industry, and 166 (95% CI:95-270) among workers engaged in paper production. METHODS A nested case-control design within a cohort of pulp and paper workers was applied. Seventy-nine lung cancer cases and 237 "healthy" controls were selected from the cohort of 10,460 workers employed during the years 1968-1990, and observed until the end of 1995. Based on personnel files, occupational exposure was reconstructed by experts. Using a questionnaire, data on smoking habits were collected. ORs unadjusted and adjusted for smoking were calculated applying the model of conditional logistic regression. RESULTS Occupational exposure to inorganic dusts (kaolin, lime, cement, brick, grindstone) adjusted for smoking was a significant lung cancer risk factor, with a 4.0-fold risk (95% CI:1.3-12.6), and a dose-response by cumulative dose index. Among organic dusts only wood dust increased albeit insignificantly the risk for those exposed (adjusted for smoking OR = 2.1, 95% CI:0.9-4.9), but without dose-response relationship. CONCLUSIONS Exposure to occupational dust with relatively low content of silica, but at high concentrations may be considered as a factor increasing lung cancer risk. However, the observation made in this study should be viewed with caution as it was based on a small number of cases, and further evidence is needed to confirm or refute the authors' hypothesis.