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Duanping Liao, MD, Ph.D. One hypothesis is that inhalation of particulate air pollution may trigger an inflammatory response in the lung, followed by the release of chemical mediators that affect autonomic nervous system control of the heart beat. Previous research has found little evidence of pollution effects on the oxygen carrying capacity of the blood, but observed that a small elevation in pulse rate was associated with a rise in PM10 levels. The medical and biological relevance of this effect is unclear. Advance: Dr. Liao and his colleagues examined associations between particulate matter, ozone, carbon monoxide, nitrogen dioxide, and sulfur dioxide and cardiac autonomic control. They calculated particulate matter and gaseous pollutants as 24-hour averages and ozone exposure as an 8-hour average. Their findings suggest that higher ambient air pollutant concentrations are associated with decreased autonomic cardiac control especially among subjects with existing cardiovascular disease. Implication: The strongest association was found with particulate matter which is a "complex mixture of suspended particles that vary in size and composition." The levels of exposure documented in this study were far below current EPA standards, yet still produced adverse effects on cardiac autonomic control. This study adds to the body of evidence suggesting a link between particulate matter exposure and adverse cardiac outcomes. The decrease in heart rate variability associated with the exposures in this study suggests that such exposures may increase the risk of acute cardiovascular disease events. Citation: Liao D, Duan Y, Whitsel EA, Zheng ZJ, Heiss G, Chinchilli VM, Lin HM. Association of higher levels of ambient criteria pollutants with impaired cardiac autonomic control: a population-based study. Am J Epidemiol. 2004 Apr 15;159(8):768-77. |
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