EPA’s judicial winning streak continues. Today, the D.C. Circuit Court of Appeals affirmed EPA’s regulations lowering the PM 2.5 National Ambient Air Quality Standard from 15.0 ug/m3 to 12.0 ug/m3. This was not a close case or a difficult decision. Indeed, as we had previously pointed out, the D.C. Circuit had previously rejected EPA’s decision to keep the NAAQS at 15 ug/m3 and EPA’s Clean Air Science Advisory Committee had supported lowering the NAAQS to 12 ug/m3 or 13ug/m3. Given the courts’ deference in recent years to EPA technical decisions supported by CASAC, this outcome was not a surprise.

As per usual, the Court noted that it “exercise[s] great deference when we evaluate claims about competing bodies of scientific research.” In light of that deference, the Court’s conclusion was “brief”:

Petitioners simply have not identified any way in which EPA jumped the rails of reasonableness in examining the science.

The Court’s opinion also addressed two other issues of some importance. First, it affirmed EPA’s decision to eliminate the use of spatial averaging in determining NAAQS compliance. The petitioners argued that EPA had not justified its decision to change its policy. To the Court, this asked the wrong question:

When EPA revises the level of the NAAQS, this Court does “not ask why the prior NAAQS once was ‘requisite’ but is no longer up to the task.” … Rather, the only inquiry is “whether EPA’s proposed NAAQS is ‘requisite.’” In other words, we do not assign “presumptive validity” to the prior NAAQS; the question is whether EPA reasonably explains the current standards.

Finally, petitioners challenged EPA’s decision to require near-road monitoring of NAAQS compliance in certain heavily populated urban areas. The Court’s answer was simple. The NAAQS is supposed to protect everyone – even those living near roadways. End of story.

Whether EPA’s decision to lower the NAAQS was right – and the evidence to me suggests that it was – it was always sufficiently on track to survive judicial review. The Supreme Court is going to have no interest in any appeal here.