Whenever someone asks why greenhouse gases are regulated under the Clean Air Act the automatic answer is “because the Supreme Court said so in Massachusetts v. EPA.”  While that is true, it takes additional steps to explain why greenhouse gas (GHG) emissions from stationary sources are regulated under the Clean Air Act.  After all Massachusetts v. EPA was a case involving mobile sources under Title II of the Clean Air Act and not stationary sources under Title I of the Clean Air Act.  Ultimately, the answer is found in the EPA’s regulatory definition of a regulated new source review pollutant.  As defined in the code of federal regulations, a regulated NSR pollutant is a 1) a criteria pollutant for which a NAAQS has been established, 2) a pollutant subject to a standard under Clean Air Act Section 111 (new source performance standards, NSPS), 3) a pollutant regulated under Title VI (stratospheric ozone protection),  and 4) ” any pollutant that otherwise is subject to regulation under the Act.”

The Supreme Court in Massachusetts v. EPA required EPA to determine under CAA Section 202(a) whether GHGs from automobiles caused or contributed to air pollution which endangered public health or welfare.  On December 9, 2009, EPA determined that six individual GHGs and classes of GHGs endangered human health and welfare, and determined that automobiles released four of these six GHGs.   Pursuant to this determination, EPA promulgated light duty truck standards and heavy duty truck standards in May of 2010 and August of 2011, respectively.  Having passed these standards, GHGs were now “pollutant[s] subject to regulation under the Act” and now subject to regulation under NSR.  That being said, these standards were written to cover production years 2012-2016 for light duty vehicles and 2014-2018 for heavy duty trucks.  Presumably, if these standards were not extended or not rewritten to include GHGs, GHGs would no longer be regulated under NSR.

If you have followed recent US EPA proposed regulations, you may remember that EPA has proposed new source performance standards (NSPS) for utilities that cover GHGs (see our recent blog entry).  While, arguably, the best demonstrated technology standard for NSPS is not extremely onerous, promulgating a NSPS that regulates GHGs provides yet another hook for EPA to regulate GHGs since the definition of a regulated NSR pollutant includes a pollutant subject to Clean Air Act Section 111 (NSPS).  In other words, EPA appears to be reinforcing its authority to regulate GHGs under NSR.

Disclaimer: This article cannot, and does not, create any attorney/client or consultant/client relationship.