Combined atmospheric oxidant capacity and increased levels of exhaled nitric oxide

Abstract

Nitrogen dioxide and ozone are two interrelated oxidative pollutants in the atmosphere. Few studies have evaluated the health effects of combined oxidant capacity (Ox). We investigated the short-term effects of Ox on fractional exhaled nitric oxide (FeNO), a well-established biomarker for airway inflammation, in a group of chronic obstructive pulmonary disease patients. Real-time concentrations of Ox were obtained by calculating directly the sum of nitrogen dioxide and ozone. Linear mixed-effect models were applied to explore the acute effects of Ox on FeNO levels. Short-term exposure to Ox was significantly associated with elevated FeNO. This effect was strongest in the first 24 h after exposure, and was robust to the adjustment of PM2.5. A 10 μg m−3 increase in 24 h average concentrations of Ox was associated with 4.28% (95% confidence interval: 1.19%, 7.37%) increase in FeNO. The effect estimates were statistically significant only among males, elders, and those with body mass index ≥24 kg m−2, a comorbidity, higher educational attainment, or moderate airflow limitation. This analysis demonstrated an independent effect of Ox on respiratory inflammation, and suggested that a single metric Ox might serve as a preferable indicator of atmospheric oxidative capacity in further air pollution epidemiological studies.