Mostly from a few industrial facilities, but also from the sanding or wearing away of old lead-based paint. Nitrogen dioxide Irritates the nose and throat, especially in people with asthma. Appears to increase susceptibility to respiratory infections. When nitrogen dioxide reaches unhealthy levels, children and people with respiratory disease are most at risk. Power plants, large industrial facilities, and motor vehicles.
Ozone Irritates the lungs and breathing passages, causing coughing and pain in the chest and throat.
Increases susceptibility to respiratory infections and reduces the ability to exercise. Effects are more severe in people with asthma and other respiratory ailments. Long-term exposure may lead to scarring of lung tissue and lowered lung efficiency. When ozone reaches unhealthy levels, children and people with asthma are most at risk. Ozone does not come directly from tailpipes or smokestacks.