Ozone Categories

Why are such measurements important?  The most widespread pollution problems are with ozone, so let's use it as an example.  The Environmental Protection Agency measures each metropolitan area's ozone levels over time.  If the levels are too high, the city has not attained the legal standard and is ranked in one of six "ozone nonattainment" categories specified in the Clean Air Act.

States with cities in nonattainment must submit plans showing how they will try to solve their air-quality problems.  These plans often include encouraging or mandating alternative transportation fuels.  Areas that meet the standard but are close to nonattainment (near-nonattainment areas) are also planning to reduce ozone to ensure they never move into the nonattainment category. 

Two areas in Texas are considered near-nonattainment areas:  Victoria and Corpus Christi. Three areas that are nearing acceptable limits have created voluntary plans to reduce emissions called Early Action Compacts. These areas are Austin, San Antonio, and North East Texas.