Cardiopulmonary benefits of reducing indoor particles of outdoor origin: a randomized, double-blind crossover trial of air purifiers

Abstract

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).

Keywords: air pollution; air purification; cardiovascular health; intervention; pulmonary health; randomized controlled trial.

Copyright © 2015 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1. The Time-Varying PM2.5 Concentration in Outdoor Air, Sham-Purified Indoor Air, and True-Purified Indoor Air

The hourly concentrations in sham-purified air and true-purified air are the arithmetic averages of measurements in all dormitory rooms for a group. The hourly concentrations in outdoor air was measured on the rooftop of one dormitory building. PM2.5 = particulate matter <2.5 μm in aerodynamic diameter.

Central Illustration. Percent change in PM2.5 and Associated Cardiopulmonary Health Indicators Comparing the True-Purified Air Scenario to the Sham-Purified Air Scenario

Differentiated colors represent different indicators of exposure and health: green = PM2.5, red = blood inflammation, gray = blood coagulation, blue = vasoconstriction, purple = lung function, yellow = blood pressure, and orange = respiratory inflammation. ACE = angiotensin-converting enzyme; CRP = C-reactive protein; FeNO = Fractional exhaled nitric oxide; FEV1 = forced expiratory volume in 1 s; FVC = forced vital capacity; MCP-1 = monocyte chemoattractant protein-1; PAI-1 = plasminogen activator inhibitor-1; PEF = peak expiratory flow; PM2.5 = particulate matter <2.5 μm in aerodynamic diameter; sCD40L = soluble CD40 ligand; TNF-α = tumor necrosis factor-α; t-PA = tissue plasminogen activator.