1. Because, in 2009, the District of Columbia Court of Appeals rejected EPA’s prior effort to keep the PM2.5 standard at 15 ug/m3.
2. Because, as I have previously noted, the Court of Appeals pretty much told EPA that it could not ignore the advice of its Clean Air Science Advisory Committee in setting the NAAQS.
3. Because the CASAC basically advised EPA to set a standard of 12-13 ug/m3.
4. Because the Court of Appeals recently affirmed EPA’s revised NOx NAAQS, in part because EPA had relied on CASAC in setting the new NOx NAAQS.
Bottom line? If you know anyone who wants to wager that the new PM2.5 NAAQS will be overturned, have them contact me; I have a bridge to sell them.
In terms of the details, final non-attainment designations will be made by December 2014 and states will have to attain the new standards by 2020. EPA currently projects that only 7 counties in California will still be in non-attainment at that point, largely due to reductions in PM resulting from other EPA rules, such as the utility MACT rule. However, EPA had previously also been relying on the Cross-State Air Pollution Rule, or CSAPR. While the Bush EPA Clean Air Interstate Rule remains in effect for now, EPA is going to have to get the D.C. Circuit decision vacating CSAPR reversed or promulgate a new rule that can withstand judicial review.