Lung Function Among Workers in the Soft Tissue Paper-Producing Industry: Discussion
For FVC, a dose-dependent decrease from 105.4 to 96.9% predicted in the subgroup with highest cumulative dust exposure was observed (Table 3), This effect was also found with relation to cumulative fiber exposure (105.4% predicted and 97.1% predicted). The parameter estimates with relation to dust-years and fiber-years (Table 4) show clear dose-response relationships that are more pronounced compared to FEV1.
FEV1%FVC did not change significantly in the subgroups with different exposure intensity. The relation of both parameters slightly increased with increasing exposure intensity without reaching statistical significance (Tables 3, 4).
The prevalence of FVC < 80% predicted rose with increasing cumulative dose from 1.0% (reference) to 15.3% (dust) and 15.0% (fibers) in the subgroup with the highest cumulative exposure (Table 3). The odds ratios increased significantly for cumulative dust exposure from 9.3 (< 25 dust-years) to 11.7 (25 to 100 dust-years) to 16.3 (> 100 dust-years) and for cumulative fiber exposure from 11.4 (< 3 fiber-years) to 17.4 (> 3 fiber-years) [Table 4].
Smoking habits had no significant effects on FVC, FEV1%FVC, and the prevalence of FVC < 80% predicted, but a significant effect on FEVX (p = 0.0001) [Table 4]. Mean values of former smokers were similar to those of nonsmokers (106.7% predicted vs 105.9% predicted) [Table 3]. Animal experiments suggest that cellulose fibers have a long biopersistence at least in rat lungs and can cause slight interstitial fibrosis, fiber-associated granulomata, alveolar histiocytosis, alveolar lipopro-teinosis, as well as alveolar cell-type hyperplasia. Therefore, impaired lung function could be expected to be a plausible adverse effect after occupational soft tissue fiber and/or dust exposure. However, scientific reports on lung function analysis in soft tissue workers are contradictory and inconsistent. This might be due to small study groups and considerably differing exposure intensities. Cross-sectional studies in soft-tissue paper-producing factories with high exposure described a high prevalence of respiratory symptoms, and a decreased lung function in workers with at least 10 years of exposure to concentrations of paper dust > 5 mg/m. In low-dose exposed workers, no adverse effects on lung function could be detected.