2008 Ozone National Ambient Air Quality Standard (NAAQS)

0.060 to 0.070 ppm, based on this reconsideration of the evidence available at the time the last standard was set. Today’s proposed rule also includes a separate secondary NAAQS, for which this RIA provides only qualitative analysis due to the limited nature of available EPA guidance for attaining this standard This supplement to the RIA contains an updated illustrative analysis of the potential costs and human health and welfare benefits of nationally attaining a new primary ozone standard. The basis for this updated economic analysis is the RIA published in March 2008 with a few significant changes. These changes reflect the more stringent range of options being proposed by the Administrator. It also reflects some significant methodological improvements to air pollution benefits estimation, which EPA has adopted since the ozone standard was last promulgated. These significant changes include the following: � In March 2008, the Administrator lowered the primary ozone NAAQS from 0.084 ppm to 0.075 ppm. The RIA which accompanied that rule analyzed a less stringent alternative standard of 0.079 ppm, and two more stringent standards of 0.065 and 0.070 ppm. This RIA supplement presents an analysis of three alternative standard