Even healthy people exposed to ultrafine particulate pollution associated with traffic and fossil-fuel combustion for just two hours show changes in heart rhythm and evidence of clot formation that may herald the potential for serious cardiac events, according to research from the Environmental Protection Agency.
The study was published in the American Thoracic Society's American Journal of Respiratory and Critical Care Medicine.
"We wanted to look at the specific effects that these ultrafine particles have on healthy individuals as these particles are deposited more deeply and with greater efficiency into the lower respiratory tract and may have effects beyond the pulmonary system," said lead author of the study, James Samet, Ph.D. senior principal investigator with the clinical research branch of the National Health and Environmental Effects Research Laboratory, of the EPA.
Dr. Samet and colleagues exposed 19 healthy 18-to-35 year-old volunteers to the concentrated levels of ambient ultrafine particles from Chapel Hill, North Carolina. The subjects exercised intermittently in a sealed chamber while breathing either filtered air or air containing particulate matter concentrated to about 20 times the ambient levels, which is on par with the ambient concentrations in heavily polluted cities such as Mexico City or Beijing. They then compared the effects of each exposure on markers of coagulation,lung inflammation, pulmonary function andcardiac electrophysiology
"We discovered that there was little to no inflammatory response to speak of in the lungs and airways," said Dr. Samet. "But there were prothrombotic and cardiovascular effects that include evidence of alterations in autonomic cardiovascular control and cardiac repolarization."
Specifically, there were changes in the subject's QT interval, which is represented by the sharp spike and following hump on an EKG. The QT interval is the time during which the heart cells "recover" their polarization after having discharged during the contraction phase, in preparation for the next beat. Changes in the QT interval indicate a change in heart rhythm that may be too subtle to detect by pulse rate variability alone.