Inhalation of ultrafine particulate found in fossil-fuel combustion can change heart rhythm, by spending even two hours in traffic, increase the risk of serious cardiac events, a new study claims.
Environmental Protection Agency research checked the hearts of 19 healthy 18-to-35 year-old volunteers from Chapel Hill, North Carolina, who were exposed to the concentrated levels of ambient ultrafine particles, to reach the conclusion.
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, said: "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."he 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
The researchers noted 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.
Samet said: "We discovered that there was little to no inflammatory response to speak of in the lungs and airways.
"But there were prothrombotic and cardiovascular effects that include evidence of alterations in autonomic cardiovascular control and cardiac repolarization."
He concluded: "This study provides additional evidence that exposure to the smallest particles in the ambient air is associated with a disregulation of cardiac rhythm as well as prothrombotic effects that may be of significant concern, especially for susceptible individuals.
"Additional studies are underway to confirm these findings and expand our mechanistic understanding of the cellular and molecular events that underlie the adverse health effects of exposure to ambient particulate matter."
The study has been published in the American Thoracic Society's American Journal of Respiratory and Critical Care Medicine.