Airway inflammation in paper mill workers

Paper mill workers are exposed to culturable microorganisms (MOs). We hypothesized that inflammatory airway response could be detected in sputum of nonsymptomatic workers. From four paper mills, we included 29 healthy nonsmoking men. Workers exposed to high levels of MOs (HMOE, n = 17) were compared with workers exposed to low levels of MO (LMOE, n = 12). A reference group of 22 healthy, nonsmoking, nonexposed (NE) men were also included. We performed differential cell counts of induced sputum, studied gene expressions of isolated sputum macrophages and analyzed inflammatory parameters, including matrix metalloproteinases. Sputum from HMOE workers had a significantly higher percentage of neutrophils than that from LMOE workers (P < 0.05) and NE controls (P < 0.001). There was also an increased gene expression of different pro-inflammatory cytokines, interleukin-6, tumor necrosis factor-alpha, and macrophage inflammatory protein-1beta in isolated airway macrophages and increased levels of total matrix metalloprotease-9 activity in induced sputum from the HMOE group. Our findings indicate that paper industry workers exposed to MOs develop subclinical airway inflammation.