January 21, 2010 — Particulate air pollution increases the risk for myocardial infarction, and lowering indoor particulate air pollution levels by using ordinary high-efficiency particulate air (HEPA) filtration improves 2 markers of cardiovascular risk: microvascular endothelial function and systemic inflammation.

Ryan W. Allen, PhD, and colleagues from Simon Fraser University in Burnaby, British Columbia, Canada, studied healthy adults living in a small community where wood-burning stoves are the main sources of pollution. The report published January 21 in the American Journal of Respiratory and Critical Care Medicine.  The researchers found that a HEPA filter significantly improved endothelial function and reduced inflammation in these participants. Whether this might translate into fewer heart attacks is not yet known.

“Our main objectives were to evaluate the potential for a simple intervention to improve indoor air quality and reduce pollution-related cardiovascular health risks and to better understand the mechanisms that contribute to air pollution-related cardiovascular health problems,” Dr. Allen said in a news release.  The connection between particulate air pollution and cardiovascular morbidity is suspected to involve endothelial dysfunction, inflammation, and oxidative stress.

The researchers recruited 45 adults from 25 homes. Each participant’s home was monitored for 2 consecutive 7-day periods, during which time HEPA filters were operated in the main activity room and in each participant’s bedroom. HEPA filters were operated normally during one 7-day period and without the internal filters in place during the other (ie, control) period.  The primary outcome was the reactive hyperemia index, an indicator of microvascular endothelial function that marks an early stage in the atherosclerotic process and predicts cardiovascular morbidity and mortality. A reduced reactive hyperemia index indicates that blood vessels have an impaired response to changes in blood flow.

“Exploratory” endpoints were markers of oxidative stress (malondialdehyde, 8-iso-prostaglandin F2-alpha) and of inflammation (C-reactive protein, interleukin-6, and band cell counts).
The researchers found that the air filters increased participants’ reactive hyperemia index by 9.4% and decreased C-reactive protein by 32.6% but did not affect oxidative stress markers. Indoor fine-particle concentrations decreased by more than 60%.

“Our results support the hypothesis that systemic inflammation and impaired endothelial function, both predictors of cardiovascular morbidity, can be favorably influenced by a reduction of particle concentration and add to a growing body of evidence linking short-term exposure to particulate matter with a systemic inflammatory response,” Dr. Allen said.

Am J Respir Crit Care Med
 http://ajrccm.atsjournals.org/cgi/content/abstract/201010-1572OCv1