For the first time, the American Heart Association now says air
pollution increases the risk of stroke, heart attack, and other cardiovascular
problems. Air pollution has long been thought to cause these types of issues,
but only recently has scientific evidence supported this theory.
Air pollution such as fine particles emitted by diesel engines,
power plants, and industrial activity are particularly dangerous. The American
Cancer Society has determined and accepted that the risk of death from a
cardiovascular event increases by 12% for every increase of 10 micrograms of
fine particle pollutants per cubic meter of air.
Most deaths caused by air pollution are due to heart attacks and
other events that cause blockage of arteries. Recent studies have also
suggested that deaths from other causes like heart failure and heart rhythm
abnormalities also rise as pollutant levels increase. 
Those at risk of heart problems would be well advised to remain
indoors when air pollution levels are high. Also, the use of air purifiers
should be considered to help remove contaminants inside the home.