On December 6, 2019 the EPA released a final rule establishing state implementation plan (SIP) requirements for areas that fail to meet the the 2015 national ambient air quality standards (NAAQS) for ozone. Ozone, a pollutant that causes numerous respiratory illnesses, results from reactions between nitrogen oxides (NOx) and volatile organic compounds (VOCs), which are emitted by cars, and stationary sources such as power plants, industrial boilers, refineries and chemical plants.
For each air pollutant such as ozone that the EPA deems dangerous to public health, the Clean Air Act requires the agency to set nationally uniform ambient concentration limits, or NAAQS, that are protect the public. (The EPA did this in 2015 when it tightened the acceptable ambient levels of ground-level ozone from 75 parts per a billion (ppb) to 70 ppb. Although there was speculation that the Trump Administration would roll this back, the Administration ultimately decided to defend the 2015 ozone NAAQS in a court challenge to their stringency recently argued before the U.S. Court of Appeals for the D.C. Circuit.)
Once the NAAQS are set the EPA sets standards for, and each state must create, state implementation plans that provide for “implementation, maintenance, and enforcement” of the NAAQS in each air quality control region within their borders. Prior to the end of the Obama Administration, in November 2016, the EPA solicited public comment on proposed revisions to federal requirements for these SIPs. This final rule responds to those comments and finalizes specific CAA requirements for the content of nonattainment area SIPs for the 2015 ozone NAAQS.
According to the EPA, the SIP requirements contained in this final rule largely mirror the SIP requirements for nonattainment areas that were in effect for the prior, 2008 ozone NAAQS, with a few key revisions.
- First, the new rule requires states to consider how pollution sources within state boundaries but outside of nonattainment areas could impact the emissions levels of ozone within nonattainment areas, and if necessary, requires them to implement control measures for these sources.
- Second, whereas the rule for complying with the 2008 NAAQS required States to show actual emissions reductions using emissions inventory data and demonstrate compliance with control measures required in their plans, the new rule only requires demonstration of control measures. Other parts of the CAA still require States to determine if nonattainment areas have achieved actual reductions, but they are not required to submit these determinations to the EPA.
- Third, the new rule updates various deadline and timing requirements for SIPs and providers further guidance on optional trading programs for NOx and VOC.
Although the EPA explored the idea of changing the nonattainment area classification scheme, it has announced that it will pursue those revisions in a separate future rulemaking.
The final rule went into effect on February 4, 2019.