The National Ambient Air Quality Standards (NAAQS) are established under the Clean Air Act. The U.S. Environmental Protection Agency (EPA) is charged with setting the NAAQS values to protect public health and welfare. Those values are set based on scientific knowledge and are reviewed every five years to integrate the most recent data on the health effects from each pollutant.
The Texas Commission on Environmental Quality (TCEQ) collects and evaluates data from available air quality monitors in the state, and then works with the EPA to designate areas in Texas that are either in compliance or out of compliance with the NAAQS. If the air quality in a geographic area meets or is better than the NAAQS, it is called an attainment area; areas that do not meet the NAAQS are called nonattainment areas.
When an area is designated as nonattainment for a given NAAQS, the TCEQ works with regional planning entities such as the Houston-Galveston Area Council to draft a plan known as a State Implementation Plan (SIP) to reduce air pollution. The state-level plan, which must be approved by the EPA, outlines the measures that the nonattainment areas will take to improve air quality so that attainment can be achieved. Once a nonattainment area meets the standards, EPA will designate the area as a “maintenance area.”