Nitrogen dioxide (NO2) is a ubiquitous air pollutant. Previous research suggests that individuals with allergic asthma may develop adverse responses when exposed to ambient concentrations of NO2. This project consisted of two controlled exposure experiments that compared the lung function and airway inflammatory effects of three-hour exposure to filtered air and 0.40 ppm NO2 with and without allergen challenge in individuals with allergic asthma [house dust mite (HDM) allergen]. The first experiment investigated whether NO2 exposure would decrease lung function and induce non-allergic airway inflammation, compared to filtered air exposure. The second used the same protocols, but the subjects also underwent an allergen challenge to investigate whether NO2 exposure would increase both allergen-induced decrements in lung function and increases in airway inflammation, compared to filtered air exposure. In experiment one, the NO2 exposure induced a significant decrease in lung function at six-hour post exposure, but had no significant change on airway inflammation indicating that three-hour exposure to a high ambient level of NO2 does not induce non-allergic airway inflammation in allergic asthmatic individuals. In experiment two, while exposure to NO2 did not significantly affect lung function following HDM allergen on a group basis, three individual subjects had substantial HDM allergen-induced decrements in lung function suggesting individual differences in susceptibility. Exposure to NO2 and HDM allergen resulted in a significant decrease in allergic inflammatory cells (eosinophils) at six-hour post-exposure, but no significant effect on other indices of airway inflammation.
These results indicate that in many individuals with allergic asthma, a three-hour exposure to a high ambient concentration of NO2 in conjunction with allergen exposure does not affect allergen-induced changes in lung function or airway inflammation. However, there appears to be a subset of individuals with allergic asthma in whom NO2 exposure increases allergen-induced decrements in lung function.
Colin Solomon received his Ph.D. in physiology from the University of Queensland, Australia. He is an assistant professor in the Department of Medicine at the University of California at San Francisco. Dr. Solomon investigates the mechanisms of toxin-induced (gas and particle) airway inflammation in humans using controlled exposure experiments.
John R. Balmes received his M.D. from the Mount Sinai School of Medicine. He is a professor in the Department of Medicine at the University of California at San Francisco, Chief of the Division of Occupational and Environmental Medicine at San Francisco General Hospital, and Director of the Northern California Center for Occupational and Environmental Health. Dr. Balmes investigates the effects of various air pollutants on airway inflammation and respiratory health in humans using controlled human exposure and epidemiologic studies.
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