Air Quality Standards

How can you tell if the air is clean? You can always look out the window, but that doesn’t tell you much. Under the Clean Air Act, Congress directed the Environmental Protection Agency (EPA) to set national standards that would help determine air quality.

The National Ambient Air Quality Standards (NAAQS) established benchmarks for six major pollutants: particulate matter, sulfur dioxide, ozone, nitrogen dioxide, carbon monoxide and lead. They are the yardstick by which the U.S. measures the success or failure of its efforts to maintain clean air.

Two types of standards are included in the NAAQS. Primary standards define the levels of air quality needed for the protection of public health, including the health of particularly sensitive people like asthmatics, children and the elderly. Secondary standards define the levels needed to safeguard the public welfare; they deal with matters of visibility and the prevention of harm to animals, crops, vegetation and buildings.

Regions of the country that fail to meet the standards are designated as “nonattainment areas” and are required to design and carry out plans to achieve the mandated levels. The EPA reviews the standards every five years and updates them as necessary. A list of the primary and secondary standards is found at NAAQS.

Because more than half the power TVA produces is generated by burning fossil fuels—coal, oil and gas—the corporation has a special responsibility to help the Tennessee Valley meet these air quality standards. To read about emissions from TVA plants and the measures TVA is taking to control them, select the name of a plant or a pollutant from the menu at right.

Toxics Release Inventory

Another assessment of air quality is provided by the Toxics Release Inventory (TRI), which is based on a list of chemicals that the EPA has identified as potentially hazardous to human health. TVA is required to report annually on the amounts of TRI chemicals released by its fossil-fuel plants (those that burn coal or oil). For information on the TRI, including frequently asked questions and emissions statistics for all of TVA’s fossil plants, see Toxics Release Inventory.