The study did not address how the particles trigger heart attacks. Other studies have shown that the particles, small enough to bypass the body's defenses and get into the lungs and other tissue, cause inflammation and blood clotting. These symptoms may contribute to heart attacks by blocking flow of blood through the heart, some researchers say. Still other studies have shown that the particles may create electrical reactions that affect the nervous system. PM-2.5 particles are light enough to travel long distances and infest air that's typically clean.
Air conditioning helps to filter it out of the indoors.
Researchers noted that Boston does not have excessive pollution and meets federal air quality standards, so the risk could be even worse in high-pollution cities such as Houston and Los Angeles. The Environmental Protection Agency's air quality standards, last updated in 1997, have been challenged in court in part because no one has pinpointed why pollution particles pose a health risk. The study could be used to encourage the EPA to consider stricter air standards, said Dr. Jonathan Samet, chairman of the department of epidemiology at Johns Hopkins University, who was not involved in the study. All Rights Reserved. Join or start this discussion Get personalized traffic reports.