Inflammatory cell response in bronchoalveolar lavage fluid after nitrogen dioxide exposure of healthy subjects: a dose-response study.

The combination of environmental chamber exposure and bronchoalveolar lavage (BAL) was used to study the effects of the common air pollutant nitrogen dioxide (NO2). Eighteen healthy nonsmokers were exposed to NO2 during 20 min in an exposure chamber during light bicycle ergometer work. All subjects were examined with BAL at least 3 wks before exposure, as a reference. The subjects were re-examined with BAL, in groups of eight, 24 h after exposure to 4, 7 and 10 mg NO2.m.3 (2.25, 4.0 and 5.5 ppm), respectively. An inflammatory cell response was found after exposure to all concentrations. An increase in the number of lymphocytes in BAL fluid was observed after 7 and 10 mg.m.3 (p less than 0.05 and 0.02, respectively). An increase in the number of mast cells, that appears to be dose-dependent, was found after exposure to all concentrations. The proportion of lysozyme positive alveolar macrophages was elevated after exposure to 7 mg.m.3. The inflammatory mediators fibronectin, hyaluronan, angiotensin converting enzyme (ACE) and beta 2-microglobulin were unchanged by exposure. Due to the findings of inflammatory cell changes far below the peak exposure limits for work places in industrialized countries, 9-18 mg.m.3, the safety of these limits is questioned. Studies are in progress in our laboratory using BAL to evaluate the effects of repeated NO2 exposure.