Altered Heart-Rate Variability in Asthmatic and Healthy Volunteers Exposed to Concentrated Ambient Coarse Particles

Abstract

Twelve mildly asthmatic and four healthy adults were exposed to filtered air (FA) and concentrated ambient coarse particles (CCP) supplied to a whole-body exposure chamber via a coarse particle concentrator with 15 parallel virtual impactors. Exposures were conducted in a Los Angeles suburb with high levels of motor-vehicle pollution and lasted 2 h with intermittent exercise. Mean CCP concentration was 157 μ g/m ³ (range: 56–218 μ g/m³) measured by continuous monitoring with a tapered-element oscillating microbalance (TEOM). On average, 80% of mass was coarse (2.5–10 μ m aerodynamic diameter) and the rest < 2.5 μ m. Relative to FA, CCP exposure did not significantly alter respiratory symptoms, spirometry, arterial oxygen saturation, or airway inflammation according to exhaled nitric oxide and total and differential cell counts of induced sputum. After CCP exposure, Holter electrocardiograms showed small (p <. 05) increases in heart rate and decreases in heart-rate variability, which were larger in healthy than in asthmatic subjects. Cardiac ectopy did not increase. In conclusion, acute exposure to elevated concentrations of ambient coarse particles elicited no obvious pulmonary effects but appeared to alter the autonomic nervous system of the heart in adult volunteers.

Supported by Southern California Particle Center and Supersite (U.S. Environmental Protection Agency R827352-01-0) and the California Air Resources Board (53-4507-8360. Additional support was provided by the U.S. EPA (R826708-01-0) and NIEHS (1PO1ES09581-01). This article has not been reviewed by these agencies and the contents do not necessarily reflect the views and policies of the agencies. The mention of trade names and commercial products does not constitute endorsement or recommendation for use.