An endurance athlete can process as much as twenty times the normal intake. Mouth breathing during exercise bypasses the nasal passages, the body's natural air filter. These facts mean that when we exercise in polluted air, we increase our contact with the pollutants, and increase our vulnerability to health damage. The interaction between air pollution and exercise is so strong that health scientists typically use exercising volunteers in their research. Research has found that air pollution can reduce breathing ability, cause chest pain, coughing, wheezing and other physical irritation.
Air pollution can interfere with the workings of the lungs, heart and other organs.
It can aggravate asthma and other chronic lung and heart diseases, can weaken the lung's defenses against infection and may cause lung diseases. In pregnant women the fetus is especially vulnerable to the effects of the mother's inhalation of carbon monoxide. The news isn't all bad. Be especially conscious of smog levels during warm weather. In warm areas, smog can be a problem at any time of the year.