And when we exercise heavily, we breathe mostly through the mouth, bypassing the body's first line of defense against pollution, the nose. People who already are especially vulnerable to air pollution are even more vulnerable when exercising or engaging in strenuous work. Those with heart and lung disease. Be especially conscious of smog levels during warm weather. Since sunlight and time are necessary for ozone smog formation, the highest levels of ozone typically occur during the afternoon.
Air quality is reported as a percentage of the federal health standard for a pollutant.
If the current index is above 100, air pollution exceeds the level considered safe. At ozone smog levels above 100, children, asthmatics and other sensitive groups should limit strenuous exercise. Even otherwise healthy people should consider limiting vigorous exercise when ozone levels are at or above the health standard. Do avoid midday or afternoon exercise, and avoid strenuous outdoor work, if possible, when ozone smog or other pollution levels are high. Do make sure teachers, coaches and recreation officials know about air pollution and act accordingly.