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 MeanąSD PM10 concentration and temperature were 38.5ą18.6 ?g/m3 and 14.0ą7.7 °C, respectively. FeNO levels were higher for both cases and controls during spring/summer (p<0.001). A 10 ?g/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.