San Antonio Missions National Historical Park is within one of
16 air quality districts in Texas. The Clean Air Act, amended in
1990, provides that emission sources must comply with air
quality standards and regulations that have been established by
federal, state, and county regulatory agencies. San Antonio is a
Class II area as it relates to the Clean Air Act, meaning that
it is in an area with less ozone depletion potential than a
Class I area. Area air quality is considered good, except for
ground-level ozone during the hot season (May through October).
Ozone levels recorded in the San Antonio region have been
elevated often enough that it is considered a “near
nonattainment area,” (high risk for violation of federal air
quality standards), and is expected to be designated
nonattainment in the near future. The park does not monitor air
quality since this data is readily available from the Texas
Commission on Environmental Quality and the Alamo Area Council
of Governments. These agencies operate numerous a