Striking at the heart

exposure to elevated levels of fine particles from automobiles for just two hours raises the likelihood of heart attack according to a recent study in the journal Circulation.

Murray Mittleman, director of cardiovascular epidemiology at Boston's Beth Israel Deaconess Medical Centre, us , who led the study said previous studies linked exposure to particulate air pollution to heightened risk of cardiovascular diseases, but the new study is the first to look at short-term effects of air pollution on the risk of heart attack.

This type of pollution is produced by combustion processes in automobile engines, power plants, refineries and smelters, added Douglas Dockery, professor of environmental epidemiology at the Harvard School of Public Health, usa . These particles are less than 2.5 micrometers (25/10,000th of a millimeter) in size. Dockery said larger particles such as airborne dust and debris from farming, construction work and mining are far less likely to trigger a heart attack.

These particles are so small that after being inhaled, they can evade the normal defense mechanisms in the lungs and penetrate deeply into the lung's air sacs and their presence there can 'trigger a systemic inflammatory response that can be detected as high levels of a certain protein associated with an increase in heart attack risk', say researchers.

They have tracked pollution levels in the Boston region and interviewed 722 people about four days after they entered area hospitals with a heart attack in 1995 and 1996 for the study. They found that the patients experienced a 48 per cent rise in heart attack risk in the two hours after exposure to high levels of this type of invisible air pollutants. The patients experienced an increased risk even 24 hours after exposure. High amounts of fine particulate air pollution are present typically during very hot, hazy summer days, according to Mittleman.