Atmospheric pollution affects the normal breathing functions. Exposure to atmospheric pollution causes decreased oxygen supply to the heart muscle during exercise in those with heart problems. There have been many studies linking exposure to air pollution with both heart disease and lung problems.But a study from North Carolina is the first to show how pollution can restrict the oxygen supply to the heart during exercise.
A group of 40 heart patients, whose average age was 65, exercised on a treadmill while being monitored on an electrocardiogram. Exposure to both fine (diameter less than 2.5 micrometers) and ultra-fine (diameter less than 1 micrometer) particles reduced the oxygen supply to the heart muscle during exercise by a factor of about three. Such pollution is linked with the exhaust coming out of factory smokestacks, and with diesel vehicle fumes.
It's not clear whether these findings also extend to healthy people. However, if you have heart problems you are probably better off exercising in an air-conditioned gym than in the outdoors - especially on a hazy day.