Nitrogen Oxide (NOx) is a very reactive, brown-hued gas commonly produced when fuels are burned at high temperature by motor vehicles, chemical plants, etc. Industries will often intentionally oxidize NOx to produce lacquers, dies, and Nitric Acid, which is basic component in both fertilizers and explosives. When NOx is released into the atmosphere as an industrial byproduct, the results contribute substantially to smog, ozone depletion, and acid rain. More directly, exposure to NOx by humans can result in respiratory difficulty and eye, nose, and throat irritation. It is these risks that puts NOx in the ambit of the Clean Air Act (CAA), and subject to the National Ambient Air Quality Standard (NAAQS).
In 2010, pursuant to the NAAQS, the EPA set a one-hour standard for nitrogen dioxide (NO2) at 100 parts per billion (ppb), a standard that was re-affirmed in 2018 when the EPA determined no further update was needed.
According to a suit filed by the Center for Biodiversity (CBD) and the Sierra Club about a year ago, the EPA violated provisions 108 and 109 of the CAA, which essentially require the EPA to re-evaluate potentially harmful gasses, like NOx, every five years. The suit was prompted by the plaintiffs arguing that the EPA’s delay is more than a mere ministerial lapse, and that there has been undeniable evidence of NOx posing more of a risk of lung and heart disease, diabetes, birth problems, cancer and death, as well as harms to water, soil and the environment.
Now, after a year of litigation and negotiation, the EPA has entered into a court decree with CBD and Sierra, calling for a comprehensive, integrated assessment of the risks posed by NOx by 2026, and a formal review of the NOx NAAQS by 2028.
Environmental groups, while satisfied that results have been achieved, feel all they have ‘won’ is forcing the EPA to do what it was already required to do.