On April 4, 2013, EPA Region 6 issued a letter that followed from lengthy debate between TCEQ and EPA regarding which agency has authority to permit non-greenhouse gas ("non-GHG") emissions above prevention of significant deterioration ("PSD") significance levels when PSD review is triggered solely by GHG emissions.

EPA had initially asserted that it in those instances EPA should permit GHG emissions as well as non-GHG emissions above PSD significance levels. In response to EPA’s request for TCEQ to explain its rationale for asserting authority to permit such non-GHG emissions, TCEQ issued a letterdated February 13, 2013 in which TCEQ explained the legal basis for its position. In EPA Region 6’s April 4, 2013 response letter, EPA stated that, based upon the representations in TCEQ’s letter, "the EPA has no objection to the TCEQ’s proposal to issue PSD permits for such sources that emit non-GHG pollutants when such pollutants are increased in amounts that equal or exceed the PSD significance levels."