ORLANDO, Florida, November 10, 2003 (ENS) – When the concentration of airborne particulate matter from diesel exhaust increases, the incidence of heart attacks shoots up, according to new research presented Sunday at the American Heart Association's Scientific Sessions 2003. On days with high air pollution, the risk is greater for tobacco smokers than for nonsmokers, a team of French researchers has found.
"Smokers are more sensitive to air pollution, as far as their risk for heart attacks," said study author Yves Cottin, M.D., Ph.D., of the cardiology department at the University of Dijon in Burgundy, France.
"When fine particles of less than 10 micrometers (µm), which are mainly attributable to diesel exhaust, exceeded 25 micrograms (µg) per cubic meter, hospital admissions for heart attack rose by 91 percent in the general population and even more in current smokers," Dr. Cottin said.
Cottin and his team examined data collected from 322 patients hospitalized for heart attack from the greater Dijon area during the period January 2001 to December 2002. Forty-two percent were smokers.
The researchers compared the daily incidence of heart attack with the average daily concentrations in the air of particles smaller than 10µm (PM10). They also measured average levels of ozone, sulfur dioxide, nitrogen dioxide and carbon monoxide.
Researchers included the ATMO index, widely used in France as a daily overall indicator of air quality. The index ranges from one to 10, where one indicates very good and 10 very poor. It is calculated via the daily monitoring of four pollutants, both gases and particles - nitrogen dioxide, sulfur dioxide, ozone and PM10.
While the pollution level rose to six or higher only about five percent of the time, or about 18 days a year, heart attacks were 161 percent more likely to occur in the general population and 250 percent more likely in smokers during those high pollution days.
When considered separately, ozone, sulfur dioxide and nitrogen dioxide did not cause measurable adversel effects, Cottin said. But the team found that increased particulate matter increased the risk of heart attack, even at levels lower than current national standards.
"This is yet another strong case against smoking, and a warning for high risk people to stay indoors, or refrain from strenuous activities during peak air pollution periods. Doctors could even consider increasing heart disease treatment during those high risk pollution times," Cottin said.
Studies are under way to follow up with the patients who had heart attacks during the study period to analyze any differences that might exist between heart attacks people have during peak air pollution times versus cleaner air days.
The risks may be similar in other cities around the world, Cottin said, but the data needs confirmation in different geographic areas.