EFFECTS OF NITROGEN-DIOXIDE EXPOSURE ON HUMAN HOST-DEFENSE

Nitrogen dioxide (NO2) exposure has been linked with increased respira tory illness and infection. The objective of this study was to determi ne whether exposure at peak indoor levels causes airway inflammation o r impairs local or systemic host defense in humans either immediately or 18 h after exposure. In an initial phase, 12 volunteers were expose d to purified air or a targeted concentration of 2.0 ppm NO2 for 6 h, with inter mittent exercise, and underwent bronchoalveolar lavage (BAL ) 18 h after exposure, in a second phase, 12 volunteers participated i n an identical exposure protocol but BAL was performed immediately aft er exposure. Eighteen hours after exposure to NO2, polymorphonuclear l eukocytes recovered by BAL increased from 2.2 +/- 0.3 to 3.1 +/- 0.4% (p = .005) and small decreases were found in the percentage of blood C D8(+) T lymphocytes (p =.01) and in blood T lymphocytes expressing nei ther CD4 nor CD8 (p =.03). These variables were not significantly diff erent immediately after NO2 exposure. Nitrogen dioxide exposure did no t alter lymphocyte subsets in BAL or alveolar macrophage function at e ither time point. Exposure to 2.0 ppm NO2 for 6 h with exercise causes airway inflammation and may alter blood lymphocyte populations 18 h a fter exposure.