Pulmonary Benefits of Intervention with HEPA Air Purifier in Schoolchildren: A Double-Blind Crossover Study

Background: The protective effect of air purifiers on the respiratory system of healthy children remains unclear so far. Method: We designed an air purifier intervention crossover study among 125 schoolchildren aged 9–12 years in a boarding school in Beijing, China. The indoor and outdoor PM10, PM2.5, and PM1 concentrations were monitored, and a total of 30 indices, including respiratory symptoms, pulmonary functions, inflammation, and oxidative stress indicators, were analyzed. We used the logistic mixed-effects model and the linear mixed-effects model to evaluate the correlation between exposure (intervention and time-weighted PM concentration) and effects (indicators). Findings: The findings showed that the air purifier intervention was associated with a 13.29% decrease in runny nose, 11.05% decrease in FeNO, 12.03% decrease in EBC IL-1β, and 4.2% decrease in IL-6. The patterns of associations with each 10 µg/m3 decrease in the PM10, PM2.5, and PM1 concentrations were consistent with those for filter intervention. Moreover, lower PM2.5 and PM1 were associated with lower EBC MCP-1, 5.47% and 13.56%, respectively. The pulmonary function indices were negatively associated with the intervention and PM. Interpretation: We screened out some sensitive indices (FeNO, IL-6, IL-1β, MCP-1) related to respiratory symptoms and inflammation, which could reflect the early abnormal response of the respiratory system under short-term PM exposure. Our findings suggested that air purifiers have a protective effect on children’s respiratory system. Funding: This work was supported by the National research program for key issues in air pollution control, China (Grant No. DQGG0405). Declaration of Interest: None to declare. Ethical Approval: The study was approved by the Ethics Review Committee of National Institute of Environmental Health, Chinese Center for Disease Control and Prevention (No. 201803) and the Biomedical Ethics Committee of Peking University (No. IRB00001052-18089). Parents and schoolchildren were informed about the study beforehand, and all the participants and their parents signed the informed consent.