Methods: In a pilot randomized controlled trial, 25 children with asthma aged 6-10 years were enrolled from 3 urban U.S. schools and randomized to the air cleaner (n=13, 9 classrooms) and control group (n=12, 9 classrooms). Classroom air pollutant measurements and spirometry were completed at baseline and twice after randomization. Asthma symptoms were surveyed every 3 months.
Results: At baseline, classroom levels of fine particulate matter (PM2.5), black carbon (BC), and nitrogen dioxide were 6.1 μg/m3, 0.43 μg/m3, and 13.6 ppb, respectively. The air cleaner intervention decreased PM2.5 levels by up to 2.3 μg/m3 (95% confidence interval (CI): -3.5, -1.0; p=0.003) and BC levels by 0.17 μg/m3 (95% CI: -0.32, -0.03; p=0.03). These reductions corresponded to a 49% decrease in PM2.5 and 58% decrease in BC concentrations. Nitrogen dioxide levels remained unchanged. Among spirometry findings, the air cleaner intervention improved peak expiratory flow by up to 16% (or 0.5 L/s; 95% CI: 0.1, 0.8; p=0.03). There was suggestive evidence of greater decreases in asthma symptoms in the air cleaner group.
Conclusions: In our pilot classroom-based air cleaner intervention, significant reductions were observed in particulate pollutants. Further large-scale studies are needed to comprehensively evaluate the effectiveness of school-based environmental interventions in reducing asthma morbidity in children.