| OCR Text |
Show 2 of both S02 and NOx to existing utility sources for the purpose of reducing acid precipitation. The CAAAs also require control of 189 hazardous air pollutants (HAPs) from all sources, and require states to move more quickly to improve ambient air quality, both as a means of reducing risks to human. health. Although the CAAAs have affected a much larger range of sources and pollutants than previous legislation, and have made some significant changes to the traditional approaches to regulating air pollution control, the CAAAs' provisions relating to NOx control are relatively straightforward. Pollution control regulations for individual sources can take two primary approaches: setting limits on the amount of a pollutant that can be emitted, leaving the method of achieving these limits to the individual sources; or mandating the use of a particular control technology to ensure a certain percentage reduction in emissions. The first approach is "emissions-based," and the second is "technology-based." In addition to these approaches, agencies can also create regulations using two other approaches: "stack emission" regulation, which specifies technologies or emission limits at a particular source; or the setting of ambient pollutant levels, which specifies a certain level of pollutant in the environment of interest. The second "other" approach can lead to ' "stack emissionu regulations, or to total mass emissions designed to prevent sources from emitting pollutants in such quantities that the desired ambient pollutant levels are exceeded. The CAAAs incorporate to some degree each of these concepts into the NOx control provisions of the CAAAs. The acid rain provisions of the CAAAs are set forth in Title IV, and specify NOx emission limits for utility boilers. However, Title IV also bases the emission limits on a certain technology, giving the final regulation a combined "emission-based" and "technology-based" twist. NO x emissions are also subject to limitation under Title I, which is concerned with attaining ambient air quality. Title I can require sources to c'ontrol NOx emissions to achieve air quality standards for both nitrogen dioxide (N02) and for ozone (03). Thus, Title IV is an example of the "stack emission" control strategy for a specific group of sources, while Title I is base~ on ·ambient air quality which implies control of all sources in a given area. Other differences between the two provisions and the implications for control technology requirements are discussed in the following sections. |
