Reducing personal exposure to particulate air pollution improves cardiovascular health in patients with coronary heart disease

Abstract

Background: Air pollution exposure increases cardiovascular morbidity and mortality and is a major global public health concern.

Objectives: We investigated the benefits of reducing personal exposure to urban air pollution in patients with coronary heart disease.

Methods: In an open randomized crossover trial, 98 patients with coronary heart disease walked on a predefined route in central Beijing, China, under different conditions: once while using a highly efficient face mask, and once while not using the mask. Symptoms, exercise, personal air pollution exposure, blood pressure, heart rate, and 12-lead electrocardiography were monitored throughout the 24-hr study period.

Results: Ambient air pollutants were dominated by fine and ultrafine particulate matter (PM) that was present at high levels [74 μg/m³ for PM(2.5) (PM with aerodynamic diamater <2.5 µm)]. Consistent with traffic-derived sources, this PM contained organic carbon and polycyclic aromatic hydrocarbons and was highly oxidizing, generating large amounts of free radicals. The face mask was well tolerated, and its use was associated with decreased self-reported symptoms and reduced maximal ST segment depression (-142 vs. -156 μV, p = 0.046) over the 24-hr period. When the face mask was used during the prescribed walk, mean arterial pressure was lower (93 ± 10 vs. 96 ± 10 mmHg, p = 0.025) and heart rate variability increased (high-frequency power: 54 vs. 40 msec², p = 0.005; high-frequency normalized power: 23.5 vs. 20.5 msec, p = 0.001; root mean square successive differences: 16.7 vs. 14.8 msec, p = 0.007). However, mask use did not appear to influence heart rate or energy expenditure.

Conclusions: Reducing personal exposure to air pollution using a highly efficient face mask appeared to reduce symptoms and improve a range of cardiovascular health measures in patients with coronary heart disease. Such interventions to reduce personal exposure to PM air pollution have the potential to reduce the incidence of cardiovascular events in this highly susceptible population.

Trial registration: ClinicalTrials.gov NCT00809653.

Figure 1

Self-reported symptoms of well-being in the presence or absence of the face mask. *p < 0.05.

Figure 2

(A) Representative filter samples collected showing contribution by mass of the three size fractions averaged over 3 days. (B) Estimated contribution of each size fraction collected on filters by particle number. (C) Oxidative potential of the collected Beijing PM (1 mg/mL) using EPR to assess oxygen-centered free radical generation, compared with NIST diesel exhaust PM (10 μg/mL) and urban dust (1 mg/mL) and the prooxidant positive control (pyrogallol 100 μM) as described previously (Miller et al. 2009). Data are mean ± SD (n = 2–4).