Biological effects of inhaled nitrogen dioxide in healthy human subjects

Abstract

Purpose

Several epidemiological studies indicate that inhaled nitrogen dioxide (NO₂) at low concentrations have been statistically associated with adverse health effects. However, these results are not reflected by exposure studies in humans. The aim of the study was to assess the acute functional and cellular responses to different NO₂ concentrations in healthy human subjects with various techniques.

Methods

Twenty-five subjects were exposed for 3 h to NO₂ concentrations 0, 0.1, 0.5, and 1.5 ppm in a randomized crossover study design during 4 consecutive weeks. In each subject, lung function, diffusion capacity and exhaled nitric oxide were measured and inflammation markers were assessed in blood, nasal secretions, induced sputum and exhaled breath condensate.

Results

From all lung function indices under consideration, only intrathoracic gas volume was borderline significantly increased after 0.5 ppm (p = 0.048) compared to 0.1 ppm NO₂. Regarding the cellular effect parameters, the macrophage concentration in induced sputum decreased with increasing NO₂ concentration, although these changes were only borderline significant (p = 0.05).

Conclusion

These results do not suggest a considerable acute adverse response in human subjects after 3 h of exposure to NO₂ in the NO₂ concentration range investigated in this study.

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