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1. Where do the pollutants that form ozone come from?

Pollutants that contribute to ground-level ozone formation come from many different types of sources. As you learned, these pollutants are NOx and VOCs. In the DFW region, pollution from cars and trucks, or on-road vehicles, contribute approximately 45 percent of the NOx pollution that leads to ozone formation.

2. Why do we care about the ozone?

The EPA sets federal standards for air pollutants according to health-based criteria. When levels are near or above the National Ambient Air Quality Standards, an ozone watch or warning is issued. The EPA has established levels at which ozone is unhealthy for humans. Ozone irritates the lining of the lungs, can aggravate respiratory conditions, and can make breathing more difficult for some people such as young children, seniors, asthma sufferers, and those with respiratory diseases. The watch and warning system using the Air Quality Index (AQI) colors, was developed to notify citizens that ozone concentrations are close to exceeding or do exceed healthy levels of ozone and that outside activities might be unhealthy for sensitive groups. For most of the population, exposure for long periods of time to higher ozone levels indicated by the color purple on the AQI are unhealthy.