Cardiopulmonary Benefits of Reducing Indoor Particles of Outdoor Origin

A Randomized, Double-Blind Crossover Trial of Air Purifiers

Renjie Chen, PHD; Ang Zhao, MS; Honglei Chen, PHD; Zhuohui Zhao, PHD; Jing Cai, PHD; Cuicui Wang, MS; Changyuan Yang, MS; Huichu Li, MS; Xiaohui Xu, PHD; Sandie Ha, PHD; Tiantian Li, PHD; Haidong Kan, PHD


J Am Coll Cardiol. 2015;65(21):2279-2287. 

In This Article

Abstract and Introduction


Background Indoor exposure to fine particulate matter (PM2.5) from outdoor sources is a major health concern, especially in highly polluted developing countries such as China. Few studies have evaluated the effectiveness of indoor air purification on the improvement of cardiopulmonary health in these areas.

Objectives This study sought to evaluate whether a short-term indoor air purifier intervention improves cardiopulmonary health.

Methods We conducted a randomized, double-blind crossover trial among 35 healthy college students in Shanghai, China, in 2014. These students lived in dormitories that were randomized into 2 groups and alternated the use of true or sham air purifiers for 48 h with a 2-week washout interval. We measured 14 circulating biomarkers of inflammation, coagulation, and vasoconstriction; lung function; blood pressure (BP); and fractional exhaled nitric. We applied linear mixed-effect models to evaluate the effect of the intervention on health outcome variables.

Results On average, air purification resulted in a 57% reduction in PM2.5 concentration, from 96.2 to 41.3 μg/m3, within hours of operation. Air purification was significantly associated with decreases in geometric means of several circulating inflammatory and thrombogenic biomarkers, including 17.5% in monocyte chemoattractant protein-1, 68.1% in interleukin-1β, 32.8% in myeloperoxidase, and 64.9% in soluble CD40 ligand. Furthermore, systolic BP, diastolic BP, and fractional exhaled nitrous oxide were significantly decreased by 2.7%, 4.8%, and 17.0% in geometric mean, respectively. The impacts on lung function and vasoconstriction biomarkers were beneficial but not statistically significant.

Conclusions This intervention study demonstrated clear cardiopulmonary benefits of indoor air purification among young, healthy adults in a Chinese city with severe ambient particulate air pollution. (Intervention Study on the Health Impact of Air Filters in Chinese Adults; NCT02239744) (J Am Coll Cardiol 2015;65:2279–87) © 2015 by the American College of Cardiology Foundation.


Numerous studies have demonstrated that ambient fine particulate (particulate matter with an aerodynamic diameter <2.5 μm, PM2.5) air pollution is significantly associated with increased cardiopulmonary morbidity and mortality.[1,2] Furthermore, PM2.5 may exacerbate cardiopulmonary symptoms, sometimes even within hours of exposure, and may result in serious adverse outcomes, such as chronic obstructive pulmonary disease,[3] myocardial infarction,[4] heart failure,[5] fatal arrhythmias,[6] sudden cardiac arrest,[7] and stroke.[8] The underlying biological mechanisms for these associations are not yet well understood, although there are hypotheses that implicate inflammation, impaired lung function, oxidative stress, increased arterial blood pressure (BP), endothelial dysfunction, blood coagulation, arterial vasoconstriction, and altered cardiac autonomic function.[1]

China has one of the highest levels of ambient PM2.5 in the world. It was estimated that ambient PM2.5 contributed to more than 1.2 million deaths and a loss of 24 million healthy years in China and ranked fourth among all contributions to the health burden.[9] Outdoor PM2.5 can penetrate indoors. In China, urban residents on average spend 87% of their time indoors, and this percentage may be even higher for vulnerable subgroups, such as young children and the elderly population.[10] Therefore, it is critically important to identify ways to effectively reduce indoor exposure to PM2.5 of outdoor origin. Unlike the outdoor environment, a substantial reduction of PM2.5 can be achieved in the indoor environment simply by using air filters, cleaners, or purifiers. Indeed, several previous studies suggest potential benefits of indoor use of air filters on cardiopulmonary health.[11–14] However, these studies were conducted in less polluted countries, and empirical evidence from China is lacking.

Therefore, we conducted a randomized, double-blind crossover study to examine whether short-term use of air purifiers improves cardiopulmonary health among healthy young adults in Shanghai, the largest city in China. We chose circulating biomarkers and lung function as the primary endpoints because they have been consistently associated with air pollution in observational studies.[15–17] The secondary endpoints included BP and indicators of respiratory inflammation.