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Short-Term Exposure to Ozone and Levels of Exhaled Nitric Oxide

Modig, Larsa; Dahgam, Santoshb; Olsson, Davida; Nyberg, Fredrikb,c; Wass, Kristinab; Forsberg, Bertila; Olin, Anna-Carinb

doi: 10.1097/EDE.0000000000000002
Air Pollution

Background: Adverse effects of air pollution include respiratory inflammation. A few epidemiologic studies have shown elevations in the fraction of exhaled nitric oxide, a marker of airway inflammation, after exposure to traffic-related pollutants.

Methods: We examined whether short-term exposures to ozone (O3), oxides of nitrogen (NOx), or particulate matter <10 μm (PM10) were associated with proximal and distal airway inflammation. The study included 5841 randomly selected Swedish adults from 25 to 75 years of age. Fraction of exhaled nitrogen was measured at two flow rates: 50 ml/s representing the proximal airways and 270 ml/s representing the distal airways. Air pollution data were obtained from an urban monitoring site. We applied linear regression to estimate short-term associations of O3, NOx, and PM10 with fractions of exhaled NO at 50 and 270 ml/s.

Results: An interquartile range increase in 120-hour average O3 levels was associated with a 5.1% (95% confidence interval = 1.7% to 8.5%) higher level of fraction of exhaled NO at 270 ml/s and 3.6% (−0.4% to 3.4%) higher level of the fraction of exhaled NO at 50 ml/s. For NOx, a small effect was seen for the 24-hour average on the fraction of exhaled NO at 270 ml/s, while for PM10 no clear effects were seen. There was a tendency for a weaker effect of ozone and a stronger effect of NOx in subjects with asthma.

Conclusions: Exposure to O3 was associated with a marker of distal airway inflammation, while the association was less obvious for inflammation of the proximal airways.

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From the aOccupational and Environmental Medicine, Department of Public Health and Clinical Medicine, University of Umeå, Umeå, Sweden; bOccupational and Environmental Medicine, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden; and cAstraZeneca R&D, Mölndal, Sweden.

A.-C.O. received 4000 US$ from Aerocrine in lecture fees. The other authors have no conflicts to report.

Supplemental digital content is available through direct URL citations in the HTML and PDF versions of this article ( This content is not peer-reviewed or copy-edited; it is the sole responsibility of the author.

Correspondence: Lars Modig, Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine, University of Umeå, SE-90187 Umeå, Sweden. E-mail:

© 2014 by Lippincott Williams & Wilkins, Inc