April 25, 2018
EPA is poised to formally publish a final decision to leave its primary air quality standards for nitrogen oxides (NOx) unchanged, ending a review process that began six years ago according to a April 17, 2018 Greenwire report.
The standards, intended to protect public health with an adequate margin of safety, will remain in their existing form.
University of Colorado (Boulder)
The one-hour standard remains at 100 parts per billion, while the annual benchmark, based on an average of yearly NOx concentrations, stays at 53 ppb, according to the notice set for publication in the Federal Register.
Administrator Scott Pruitt had signed off on the decision earlier this month, in accordance with a deadline set last year in a settlement to a lawsuit brought by two environmental groups.
The annual standard has not changed since first promulgated in 1971; EPA added the hourly standard in 2010 as a way of addressing short-term elevated levels near roadways.
Following legal challenges brought by industry groups, the U.S. Court of Appeals for the District of Columbia Circuit upheld the hourly standard in 2012.
Nitrogen oxides, with nitrogen dioxide serving as a regulatory placeholder for the broad class of gases, are a major ingredient in smog. On their own, they can irritate the eyes, nose and throat.
Under the Clean Air Act, EPA is supposed to review its standards for NOx and five other “criteria” pollutants every five years to determine whether they are adequate in light of what’s known about their health and ecological effects.
The agency is in the midst of a review of the secondary “public welfare” standards for NOx, sulfur dioxide and particulate matter that is scheduled to conclude in 2022, according to a schedule released last year.
What this means to you
EPA is poised to formally publish a final decision to leave its primary air quality standards for nitrogen oxides (NOx) unchanged. The one-hour standard remains at 100 parts per billion, while the annual benchmark, based on an average of yearly NOx concentrations, stays at 53 ppb.
MIRATECH can help
Contact MIRATECH for answers to stationary engine NOx emission control questions.