Try a morning workout if you exercise outdoors.
"Exercise early in the day when ozone is low," says Edelman. Breathing heavily for that cardio workout draws air—and pollution—deeper into the lungs. A pre-rush hour sweat is better than waiting until later as the afternoon can be trouble, especially in warmer months when temperature, the sun's greatest intensity, and exhaust from mid-day traffic combine to up the ozone. Avoiding rush-hour traffic will save you a dose of other air pollutants as well.
[Want an "ideal" heart? Read the American Heart Association's list of the 7 most important factors for long life.]