A new study has found that exposure to air pollution from diesel exhaust could worsen the conditions of people with heart disease. VOA's Jessica Berman reports that experts say the study adds to scientific evidence that urban air pollution is harmful to human health.
The latest study led by British cardiologist Nicholas Mills looked at the effects of diesel exhaust on 20 men with heart disease.
The participants had had heart attacks three years before the study, but all had been successfully treated and in were in stable condition. At the time of the study, none suffered from chest pain or abnormal heart rhythms.
Under carefully controlled conditions, Mills says the men were exposed for one hour to diluted diesel exhaust, during which time they exercised moderately and rested. "This is exposure designed to mimic the sort of exposure you might encounter in heavy traffic," he said.
In other words, the fine-particled soot spewed from the tail pipes of trucks, buses and cars in many densely populated cities around the world.
The men then exercised and rested in filtered air.
During two sessions, researchers electrically monitored the amount of stress on the participants' hearts, and they measured levels of a so-called guardian protein known as t-PA that circulates through the blood stream, helping to prevent blood clots.
Investigators found that inhalation of diesel exhaust caused a three-fold increase in stress on the heart during exercise, compared to exposure to filtered air. And the body's ability to release t-PA was reduced by one-third, a situation that could potentially put heart patients at greater risk of stroke.
The results of the study by Dr. Mills and colleagues at the University of Edinburgh and researchers in Sweden are published in the New England Journal of Medicine. The researchers have studied the effects of air pollution on health for several years.
Other studies have noted an increase in the number of hospital admissions with rising levels of air pollution. The World Health Organization estimates air pollution is responsible for 800-thousand deaths each year.
Murray Mittleman is a professor of medicine at the Harvard School of Medicine in Massachusetts. Mittleman says the latest research may explain the results of an important study out of Germany. "It builds on other work that just being exposed to traffic, riding in traffic - whether you were driving a car or a passenger, or on a bus, say - there was a higher risk of heart attack in the one to two hours following that," he said.
In an editorial in the New England Journal, Mittleman wrote that people with heart conditions should not take home the wrong message from the study, that they should stop exercising because they live near a polluted area. "I would not avoid it for this risk. Nonetheless, if you have a better option, the idea of staying away from vigorous exercise in close proximity to traffic is a much better idea," he said.
That is because the evidence also shows that exercise is a critical factor in preventing heart disease.