Bronchoalveolar mastocytosis and lymphocytosis after nitrogen dioxide exposure in man: a time-kinetic study

The combination of environmental chamber exposure and bronchoalveolar lavage (BAL) was used to study the time-course of the cell response in the human lung to nitrogen dioxide (NO2). Healthy subjects were exposed for 20 min to 7 mg NO2.m-3 (4 ppm), a concentration which occurs indoors in industries and is below the peak exposure limit for work places in most countries, 10 mg.m-3 (5.5 ppm). BAL was performed in all subjects several weeks before exposure and 4, 8, 24 and 72 h after exposure, in eight subjects at each time. Mastocytosis and lymphocytosis were found in BAL fluid 4-24 h after exposure, with normalization after 72 h. A mild increase in lysozyme positive macrophages was found 24-72 h after exposure. The time-course of the human pulmonary cell response to NO2, demonstrated in BAL fluid, represents a new and previously not reported finding after exposure to this common air pollutant. Our findings are diverging from results obtained in animal studies, using approximately the same NO2 concentrations, indicating that the results from the animal studies may not be transferable to man.