Short-term association of environmental exposures with nitric oxide concentration in exhaled air

Background: Fractional exhaled nitric oxide (FeNO) is a biomarker of type-2 lung inflammation. Previous studies reported an association between particulate matter (PM) exposure and FeNO, while the association with ambient air temperature is unclear. Aim: To evaluate the short-term association of PM₁₀ concentrations and air temperature with FeNO among subjects with/without chronic respiratory diseases. Methods: 605 healthy controls and 412 cases (rhinitis, asthma, chronic bronchitis) aged 20-70 years, who participated in the GEIRD multicenter case-control study on respiratory health in Verona between 2008 and 2014 were involved. Residential addresses collected during clinical interviews were geocoded, and daily PM₁₀ concentrations and air temperature were assigned at each location in the frame of the BIGEPI project. Mean PM₁₀ concentrations and air temperature were calculated for lag 0-1 days before FeNO measurement and considered short-term exposure indicators in the analysis. Associations were assessed using multiple linear regression of FeNO adjusted for sex, age, case-control status, BMI, smoking, atopy, and seasonality (quadratic function of day of the year). Results: Mean±SD PM₁₀ concentration and temperature were 38.5±18.6 μg/m³ and 14.0±7.7 °C, respectively. FeNO levels were higher for both cases and controls during spring/summer (p<0.001). A 10 μg/m³ increase in PM₁₀ concentrations was associated with a 3% increase in FeNO at lag 0-1 (RR: 1.03, 95%CI:1.00-1.06); no significant association was found with air temperature (RR: 0.88, 95%CI: 0.76-1.02 per 10 °C). Conclusion: Seasonality and PM₁₀ concentrations at the time of measurement seem to influence FeNO levels.