The last post explained the broad ambient air protection inherent in the Clean Air Act and the NAAQS, and this post builds on that information. 

In addition to the national ambient air quality standards as enforced by SIPs or FIPs, states also must enforce New Source Performance Standards, or "NSPS," National Emission Standards for Hazardous Air Pollutants, or "NESHAPS," and New Automobile Standards. NSPS apply to specific categories of pollutants that must be regulated if emitted from new stationary, or industrial, sources. Under this program, new pollution sources are even allowed to offset permitted emissions by reducing emissions from old sources in some circumstances. Under the NESHAP, the source of the pollution is irrelevant. States can regulate in many ways to protect human health from hazardous substances, like arsenic, asbestos, benzene, beryllium, and mercury. Because of the New Automobile Standards, new cars have to meet tailpipe emission standards, which call for a 90% reduction in emissions.

In addition to the regulatory controls SIPs provide to bring nonattainment regions into compliance with the NAAQs, states must also prevent attainment regions from deteriorating into nonattainment regions. To achieve this goal, states must designate each air quality control region or portion thereof as either attainment or nonattainment for each criteria pollutant. If a new pollution source wants to emit any pollution into a region classified as attainment, then the new source must obtain a Prevention of Significant Deterioration, or "PSD," permit. PSD permits have successfully prevented attainment regions from earning a nonattainment classification across the country.

As you can see, the state and federal clean air laws are quite complex.  We have only just scratched the surface with this introductory overview of the Clean Air Act.  Let us know if you want to learn more about how the law protects the air we breathe.