MONDAY, April 11 (HealthDay News) -- A special exhaust filter for diesel engines cuts emissions of heart-harmful microscopic particles by 98 percent, which could lead to fewer deaths from cardiovascular disease, a new study suggests.

The very tiny particles found in diesel engine exhaust are associated with a slice of the heart disease caused by air pollution, but "if we use these particle traps on diesel engines, then we could significantly reduce the harmful effects of air pollution," said co-senior study author Dr. David E. Newby of the British Heart Foundation.

The study, funded by grants from heart and lung foundations in Britain and Sweden, is published in the April 11 online edition of Circulation.

According to the World Health Organization, air pollution -- including pollution from diesel engines -- is a major contributor to 800,000 premature deaths each year around the world.

The filtered exhaust, however, appeared to spare the hearts and lungs of those breathing it, with test subjects experiencing better blood vessel health and more protection against blood clots than those exposed to regular diesel exhaust, according to the team led by Newby, who is also the John Wheatley Chair of Cardiology at the University of Edinburgh in Scotland.

For the three-way double-blind study, Newby's team randomly assigned 19 healthy nonsmoking men to breathe filtered air, unfiltered diesel-engine exhaust and filtered diesel-engine exhaust -- that is, exhaust after it passed through the particle trap. (To make the exhaust safe to breathe, 90 percent was shunted away and the rest mixed with filtered air.)

The men inhaled each gas for one hour and at the same time, alternated moderate 15-minute bouts of exercise with 15 minutes of rest. The sessions were at least a week apart.

The researchers found the particle trap removed some 98 percent of all particles in the diesel exhaust and 99.8 percent of the smallest and most damaging particles. The trap tested by the researchers was made by Johnson Matthey, Inc.; however, the researchers received no funding from the company.

In addition, when compared with filtered air, direct diesel exhaust reduced the ability of blood vessels to dilate in the six to eight hours after exposure. Moreover, men breathing filtered air had a greater release of a compound in the body that dissolves blood clots than did men breathing unfiltered diesel exhaust.

This compound, called tissue plasminogen activator, is one way the body helps prevent heart attacks and strokes, the researchers noted.

Another test for blood clotting showed that breathing unfiltered diesel exhaust increased clotting, compared with both filtered air and trap-filtered diesel exhaust. In fact, there was no difference in clotting ability between those who inhaled filtered diesel exhaust and filtered air, the researchers found.

Martin Lassen, director of business development at Johnson Matthey, Inc., which makes the diesel particle trap, said the particle trap for trucks would cost an additional $5,000 to $7,000 per vehicle. For cars, the cost would be under $2,000.

"In addition, the filter has no effect on fuel economy," Lassen added.

Dr. Robert D. Brook, an associate professor of medicine in the cardiovascular medicine division at the University of Michigan and co-author of an accompanying journal editorial, said that "these findings strongly support the concept that reducing the particulate pollution associated with diesel, and likely other combustion sources of air pollution, can lead to substantial improvements in cardiovascular health."

In addition, the results also support the 2007 regulations for diesel particle traps in U.S. vehicles and also the retro-fitting of the existing fleet to protect the public health, Brook said. Starting with the 2007 model year, pollution from trucks and buses had to be reduced by more than 90 percent, according to the U.S. Environmental Protection Agency.

"The findings also suggest that it is principally the particles, rather than the gaseous pollutants, involved in triggering adverse cardiovascular health responses to brief diesel air pollution," he added.

"Even brief exposure to particulate matter air pollution can rapidly trigger -- within hours -- adverse cardiovascular health responses capable or promoting an acute event such as heart attack or stroke in susceptible people. Available technology of particle traps appear capable of substantially reducing this risk," Brook said.

More information

For more information on air pollution, visit the U.S. National Library of Medicine.