Pollution, heart disease linked
2002-07-30 12:23
Washington - Air pollution worsens heart disease by cutting off circulation to the heart, Finnish researchers reported on Monday in a study that helps explain why polluted environments aggravate not only asthma but heart conditions.
The US Environmental Protection Agency estimates that 60 000 people a year die in the United States alone from particulate air pollution - the kind caused when small particles of smoke pervade the air.
Dr Juha Pekkanen of the National Public Health Institute in Kuopio, Finland, and colleagues looked specifically at pollution coming from factory smokestacks and the tailpipes of some diesel-powered buses and trucks.
Heart disease patients exposed to such pollution were about three times more likely to have ischemia - decreased blood flow to the heart - while exercising after being exposed to such pollution, as compared with when they exercised after breathing in cleaner air, they reported.
Writing in this week's online issue of Circulation, published by the American Heart Association, the researchers said they could measure clear changes in oxygen supply to the heart using electrocardiograms (ECG).
They studied 45 heart disease patients, nearly half of them women, all living within an area in Helsinki where air pollution could be easily measured.
Twice a week for six weeks the researchers gave the volunteers an exercise test, and charted their findings against readings of extremely fine particles in the air locally.
Two days after breathing in polluted air, the volunteers had "significantly elevated" levels of ischemia, Pekkanen and colleagues wrote.
Ischemia is often painless, but is a sign of serious heart disease. The pollution may either be helping clumps of artery-clogging plaque break off - causing heart attacks and strokes - or it could be causing dangerous heart rhythms, or both, the researchers said.
Heart rate also increased after exposure to pollution - from an average of 61 beats per minute to 90.
Problem 'pervasive and growing'
The study helps explain why pollution can affect heart disease, Dr Murray Mittleman, director of cardiovascular epidemiology at Harvard University and Beth Israel Deaconess Medical Centre in Boston, and colleagues said in a commentary.
Mittleman and colleagues cited studies that showed health risks from particle-containing air pollution were notable not only in the expected cities, such as Los Angeles and Houston, but in "cities that are considered to have relatively clean air, such as Boston, Seattle and Minneapolis".
Researchers reported in Circulation earlier this year that fine particles, when inhaled, can stay in the system for hours, travelling in the blood to various organs.
Those particles can disrupt the heart's activity, interfering with its rhythm and tightening arteries.
"The problem with particulate air pollution is pervasive and growing," they wrote. Mittleman said that on days when pollution levels were high, many people would be better off exercising indoors - something many authorities already recommend in daily air quality reports.
Mittleman noted a number of holes in the study. For one, the original study was supposed to include volunteers in Germany and the Netherlands, but not enough of those patients had enough measurable ischemia to be used in the study.