Intervention Study on the Health Impact of Air Filters in Chinese Adults

Cardiopulmonary Benefits of Reducing Indoor Particles of Outdoor Origin: a Randomized Double-blind Crossover Trial of Air Purifiers

This study aimed to evaluate whether a short-term indoor air purifier intervention improves cardiopulmonary health based on a randomized double-blind crossover trial

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 two groups and alternated the use of true or sham air purifiers for 48 hours with a 2-week wash-out interval.All participants and research staff were blinded to the group assignment. We requested all participants to stay in their dormitory room with the windows/doors closed throughout each 48-hour intervention period. We delivered foods and drinks to each room during the intervention period. All interventions started at 8 a.m. to avoid issues related to diurnal variation. We evaluated health endpoints and drew blood immediately after the completion of each 48-hour intervention. We measured 14 circulating biomarkers of inflammation, coagulation and vasoconstriction, lung function, blood pressure (BP), and fractional exhaled nitric oxide (FeNO).

air pollution, air purification, intervention, randomized controlled trial, cardiovascular health, pulmonary health

This group of subjects used an intervention of sham air purifiers under the same conditions with true purifiers with the only difference being removal of the filter gauze in the sham purifiers.

The 10 dormitory rooms were randomized into two groups of 5 rooms each. One group used an air purifier placed in the center of the room for 48 hours corresponding to one weekend, followed by a 2-week washout period, and another 48 hours of using a sham air purifier under the same conditions. The other group simply reversed the order in which the real and sham air purifiers were used. All rooms used the same qualified air purifiers (model FAP04, 3M Filtrete), with the only difference being removal of the filter gauze in the sham purifiers. The air pollution auto-sensing feature of air purifiers was disabled in both groups. All participants and research staff were blinded to the group assignment. We requested all participants to stay in their dormitory room with the windows/doors closed throughout each 48-hour intervention period.

Peripheral blood samples (5 ml) were drawn by a nurse, separated into serum and plasma, and stored at -80 ℃ within 30 minutes. We measured the levels of 14 circulating biomarkers: (1) 8 biomarkers of inflammation, including C-reactive protein (CRP), fibrinogen, P-selection, monocyte chemoattractant protein-1 (MCP-1), interleukin-1b, interleukin-6, tumor necrosis factor-α (TNF-α) and myeloperoxidase; (2) 4 biomarkers of coagulation, including soluble CD40 ligand (sCD40L), plasminogen activator inhibitor-1, tissue plasminogen activator and D-Dimer; and (3) 2 biomarkers of vasoconstriction, including endothelin-1 and angiotensin-converting enzyme.

Blood samples were drawn within one hour after the intervention, and lab analysis was completed in the next 10 days

A respiratory physician measured forced vital capacity, forced expiratory volume in 1 second and peak expiratory flow of each participant using the JAEGER Masterlab equipment (Würzburg, Germany) that meets the American Thoracic Society criteria. The volume signal was calibrated at least once on a testing day with a 3.0 L syringe connected to the pneumotachograph in accordance with the manufacturers' recommendations. We instructed participants to perform at least three forced expiratory lung function maneuvers in order to obtain a minimum of two acceptable and reproducible values, and we recorded the best results.

After sitting in a quiet room for at least 5 min, participants had their left upper arm BP measured by trained technicians using a mercury sphygmomanometer at least three times with 2-min minimum intervals between measurements. The second and third sets of readings were averaged to obtain systolic BP and diastolic BP. Pulse pressure was calculated as the difference between systolic BP and diastolic BP. If the differences among the three measurements were bigger than 5 mmHg, a new round of measurements were arranged.

FeNO is an established biomarker of respiratory inflammation, and has been widely used in epidemiological studies because of its high sensitivity, specificity and non-invasive nature. We measured FeNO levels using a portable NIOX MINO machine (Aerocrine AB, Solna, Sweden) according to standardized procedures by the American Thoracic Society and the European Respiratory Society.

Inclusion Criteria: Healthy college students aged between 18 and 26 All the subjects should stay indoor almost the entire time, and stayed within the central urban area of shanghai during the wash-out period. Exclusion Criteria: current smokers or ever smokers chronic respiratory diseases chronic cardiovascular diseases acute infections medication use in recent one month

Chen R, Zhao A, Chen H, Zhao Z, Cai J, Wang C, Yang C, Li H, Xu X, Ha S, Li T, Kan H. Cardiopulmonary benefits of reducing indoor particles of outdoor origin: a randomized, double-blind crossover trial of air purifiers. J Am Coll Cardiol. 2015 Jun 2;65(21):2279-87. doi: 10.1016/j.jacc.2015.03.553.