The U.S. Circuit Court of Appeals for the District of Columbia on August 23 ruled in favor of Obama administration ground-level ozone thresholds. The rules set the highest acceptable level under the Clean Air Act at 70 parts per billion. Ozone contributes to smog, which can lead to severe breathing problems for children and people with asthma.
The three-judge panel rejected claims from industry and conservative states that the National Ambient Air Quality Standards for ozone are impossible to achieve. The plaintiffs argued that 70 ppb is less than the naturally occurring background levels of ozone in some areas of the U.S. and it is therefore unfair to classify them as “nonattainment areas” subject to stricter permitting requirements. The court also rejected a grandfathering provision that allowed some sources in the middle of a permitting process to continue operating under an earlier, less stringent ozone threshold.
Critics of the standard waited to file suit while the Trump administration spent more than a year considering whether to scrap the Obama-era rule and revert to more lenient ozone limits. In a surprise move, the Trump EPA agreed to defend the 70-ppb limit.