Evaluation for compliance with the new PM 2.5 is ongoing. Since then, photochemical smog has been observed frequently in many other cities as well. Health effects - Ozone and other photochemical oxidants such as peroxyacyl nitrates and aldehydes are associated with health effects in humans. Peroxyacyl nitrates and aldehydes cause the eye irritation that is characteristic of photochemical pollution. Exposure to O3 can cause coughing, chest pain, and throat irritation.
Ozone can also increase susceptibility to respiratory infections.
In addition, ozone impairs normal functioning of the lungs and reduces the ability to perform physical exercise. Recent studies also suggest that even at lower ozone concentrations some healthy individuals engaged in moderate exercise for six to eight hours may experience symptoms. All of these effects are more severe in individuals with sensitive respiratory systems. In particular, studies show that exposure to moderate levels may impair the ability of individuals with asthma or respiratory disease to engage in normal daily activities. The potential chronic effects of repeated exposure to ozone are of even greater concern.