Comparisons of combined oxidant capacity and redox-weighted oxidant capacity in their association with increasing levels of FeNO

Abstract

BackgroundSome ozone (O3) and nitrogen dioxides (NO2) health effects studies use Ox (sum value) as a surrogate. However, little is known about how this related to Oxwt (weighted value). ObjectiveWe investigated the effects of redox-weighted oxidant capacity (Oxwt) on fractional exhaled nitric oxide (FeNO), a biomarker of airway inflammation, in a set of chronic obstructive pulmonary disease (COPD) patients. We also compare combined oxidant capacity (Ox) and Oxwt in their associations with increasing levels of FeNO. MethodsWe measured FeNO values in 600 participants who have COPD at Shanghai Pulmonary Hospital. Ox was calculated directly by the sum of O3 and NO2. The redox-weighted oxidant capacity was calculated by denoting Oxwt as the weighted average of redox potentials. We applied generalized additive models (GAM) to investigate the impacts of Ox and Oxwt on FeNO levels, respectively. We fitted the same models for the influence of O3 and NO2 individually and jointly on FeNO levels to compare the result of Ox and Oxwt. ResultsOxwt were significantly linked with FeNO levels. The impact was robustest in current day after exposure, and were closely linked with the adjustment of PM2.5. A 10 μg m−3 increase in average Oxwt concentrations was linked to 0.88 (95% CI: −1.46, 3.28) increase, whereas a 10 μg m−3 increase in average Ox concentration was linked to 0.62 (95% CI: −0.79, 2.07) increase in FeNO. In two-pollutant models, an increase of 10 μg m−3 in average O3 concentrations with adjustment of NO2 was associated with 0.57 (95% CI: −1.26, 2.01) increase in FeNO. The impact estimates of Ox and Oxwt were statistically significant among males, non-smoking and elders who age above 65 years old. ConclusionsThis analysis demonstrated that Oxwt is used as a better indicator of atmospheric oxidative capacity as a proxy of O3 and NO2 in further epidemiological studies.