Exposure to particulate matter -- the tiny particles emitted by automobiles, especially diesel vehicles -- is probably the cause for their increased mortality, Dr. H.-Erich Wichmann, director of the Institute of Epidemiology of the GSF-National Research Center for Environment and Health in Neuherberg, Germany, told Reuters Health.

Most studies on the health effects of pollution have focused on short-term exposure, Wichmann and his team note in the September issue of Epidemiology.

To better understand the relationship between long-term exposure to pollution and mortality, the researchers looked at roughly 4,800 women who had participated in studies of women's health during the 1980s and 1990s, when they were 50 to 59 years old.

This allowed the investigators to study the effects of 10 to 20 years of pollution exposure, which they estimated by determining how far the women lived from major roads and the amount of nitrogen dioxide and particulate matter measured by nearby air monitoring stations.

During the follow-up period, 8 percent of the women died, 3 percent from cardiopulmonary causes.

According to the team, women who lived within a 50-meter radius of a busy road were 70 percent more likely to die due to cardiopulmonary causes.

There is not much that people living close to heavy traffic can do to reduce their exposure to particulate matter, Wichmann noted in an interview, as the pollutant also finds its way indoors.

"The only effective measure is to reduce the concentration of these particles, and especially for Germany, the most effective way would be to use particle traps for diesel cars," he added.

There has been discussion of requiring traps on newly built cars, he said, and to truly reduce the particulate matter it would also be necessary to retro-fit old cars with the traps as well.

SOURCE: Epidemiology, September 2006.