Introduction to Air Quality

Air quality affects all of those living in the San Antonio region in one way or another. It concerns most citizens by way of health effects. The air quality issue for the San Antonio region has been that of ground-level ozone.  Ground-level ozone is created when light winds, heat, and sunshine together with an adequate combination of pollutants (nitrogen oxides and volatile organic compounds); cause a chemical reaction that produces ozone pollution. Vehicle use contributes greatly to our ground level ozone issue.

In addition, it affects transportation planning. The Clean Air Act (CAA) requires the Environmental Protection Agency (EPA) to set air quality standards referred to as the National Ambient Air Quality Standards (NAAQS) to protect both public health and the public welfare (crops and vegetation) as ground-level ozone affects both.  If an area is in compliance with the NAAQS, than it is considered in “attainment”, whereas, if it is producing more pollution than the NAAQS allow for it is deemed “nonattainment”.

If an area is deemed nonattainment, then the EPA requires MPO’s utilize Transportation Conformity as a means to ensure that transportation activities will worsen existing violations, not cause new air quality violations, or delay timely attainment of the NAAQS. Conformity applies to Metropolitan Transportation Plans (MTP), Transportation Improvement Programs (TIP) and highway and transit projects funded or approved by the Federal Highway Administration (FHWA) and the Federal Transit Authority (FTA). Transportation conformity requirements ensure that federal funds go to transportation activities that are consistent with an area's air quality goals.

Currently we are in attainment for ground-level ozone, however, due to the EPA lowering the NAAQS threshold we are close to being declared nonattainment for ground-level ozone.

The links to the left provide additional information regarding each of the issues outlined above.