Indoor air pollution is associated with numerous adverse health outcomes. Air purifiers are widely used to reduce indoor air pollutants. Ionization air purifiers are becoming increasingly popular for their low power consumption and noise, yet its health effects remain unclear. This randomized, double-blind crossover study is conducted to explore the cardiorespiratory effects of ionization air purification among 44 children in Beijing. Real or sham purification was performed in classrooms for 5 weekdays. Size-fractionated particulate matter (PM), black carbon (BC), ozone (O3), and negative air ions (NAI) were monitored, and cardiorespiratory functions were measured. Mixed-effect models were used to establish associations between exposures and health parameters. Real purification significantly decreased PM and BC, e.g. PM0.5, PM2.5, PM10 and BC were dereased by 48%, 44%, 34% and 50% respectively. O3 levels were unchanged, while NAI was increased from 12 to 12,997 cm-3. Real purification was associated with a 4.4% increase in forced exhaled volume in 1 second (FEV1) and a 14.7% decrease in exhaled nitrogen oxide (FeNO). However, heart rate variability (HRV) was altered negatively. Interaction effects of NAI and PM were observed only on HRV, and alterations in HRV were greater with high NAI. Ionization air purifier could bring substantial respiratory benefits, however, the potential negative effects on HRV need further investigation.

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Numerous research has explored the associations of outdoor or indoor fine particulate matter (PM2.5) and health effects; however, few studies compared the effects of indoor PM2.5 originated from outdoor (PM2.5,os) and indoor sources (PM2.5,is). To assess the associations of PM2.5,os and PM2.5,is with cardiopulmonary function in patients with chronic obstructive pulmonary disease (COPD) and healthy elderly adults, blood pressure (BP) and pulmonary function were repeatedly examined in 43 COPD patients and their 32 healthy spouses in Beijing, China. Iron was used as tracer element to separate PM2.5,os and PM2.5,is. Mixed‐effects models were applied to assess the associations of PM2.5,os or PM2.5,is and health effects after controlling for potential confounders. There was a reduction in forced expiratory volume in first second (FEV1) in COPD patients associated with PM2.5,is during the heating season. PM2.5,os was positively associated with diastolic BP (DBP) in healthy elderly adults during the heating season. There was a reduction in peak expiratory flow (PEF) in healthy elderly adults associated with PM2.5,os during the non‐heating season. Exposure to indoor‐ and outdoor‐originated PM2.5 had different health effects on cardiopulmonary function in different populations. The results provide supporting evidence for improving indoor air quality to promote public health among susceptible population.

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