Associations between air pollutants and peak expiratory flow and fractional exhaled nitric oxide in students

BACKGROUND: Studies on the effects of outdoor air pollution on the respiratory health of students in tropical countries such as Malaysia are limited. OBJECTIVE: To assess associations between outdoor air pollutants and peak expiratory flow (PEF) and fractional exhaled nitric oxide (FeNO). METHOD: PEF and FeNO levels of 487 students recruited in Melaka and Putrajaya, Malaysia, were measured in April and June 2014. Multiple linear regression with mutual adjustment was used to analyse the associations between exposure to air pollution and health. RESULTS: PEF was significantly associated with ozone for 1-day exposure (beta = -13.3 l/min, 95% CI -22.7 to -3.8), carbon monoxide for 2-day exposure (beta =-57.2 l/min, 95% CI -90.7 to -23.7) and particulate matter <= 10 mu m in diameter for 3-day exposure (beta =-6.0 l/min, 95% CI -9.2 to -2.8) and 7-day exposure (beta = -8.6 l/min, 95% CI -13.0 to -4.1). Stratified analysis showed that associations between PEF and outdoor air pollutant exposures were similar in students with and without elevated FeNO levels. CONCLUSION: Outdoor air pollution in Malaysia may cause airway obstruction unrelated to eosinophilic airway inflammation among students as measured using FeNO.