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EPA Proposes Regulatory Options for Maintaining NOx Air Quality Standards

Release Date: 02/15/2005
Contact Information:

Contact: John Millett 202-564-7842 / [email protected]


(Washington, D.C.-- 02/15/05) On Feb. 14, 2005, EPA proposed three regulatory options to maintain air quality in areas that meet national air quality standards for nitrogen dioxide (NO2). The Clean Air Act's Prevention of Significant Deterioration (PSD) program for NOx uses "increments" to limit the amount of air quality deterioration that may occur in any given area of the country. For this purpose, ambient concentrations of NO2 are measured in micrograms per cubic meter. New and modified industrial facilities must evaluate the impact of their emissions of nitrogen oxides (NOx) in a clean air area to demonstrate that they will not cause or contribute to a violation of any national ambient air quality standard or degrade the air beyond the level allowed by PSD increments for NOx. To ensure that air quality does not deteriorate in PSD areas, states and tribes issue Clean Air Act permits requiring proposed new and expanded facilities to install state-of-the-art air pollution controls. While the PSD program is intended to maintain air quality, numerous other Clean Air Act regulations on stationary and mobile sources have reduced and will further reduce NOx emissions in the United States.

Today's action proposes the three following options:

1. To retain the existing increments NOx measured as nitrogen dioxide (NO2) in the ambient air as established in October 1988;
2. To allow states that choose to implement an interstate cap and trade program for sources of NOx to rely on the benefits of that program in place of the existing increments to prevent significant deterioration of NO2 air quality; or
3. To allow states to adopt their own planning strategies and implement these in lieu of the NO2 increment system if they show that PSD for NOx is satisfied through some combination of state and federal emissions controls that have been or will be adopted.

NOx is a precursor to the formation of ground-level ozone and fine particle pollution. At elevated levels these polluants can have significant health effects aggravating heart and lung conditions, increasing susceptibility to respiratory illnesses, damaging lungs. Fine particles are also associated with premature death. In additional these pollutants have negative environmental impacts including vegatation damage, acid deposition, and visibility impairment.

Under the current PSD program for NOx and in conjunction with numerous other air pollution control programs and regulations on industries and vehicles NOx emissions in the United States have fallen from 25.1 million tons per year in 1990 to 20.5 million tons in 2003, according to EPA's most recent air emissions trends report: https://www.epa.gov/airtrends/econ-emissions.html .

In addition, ozone levels have decreased over the past 10 to 25 years. In 2003, the improved air quality resulted mainly from favorable weather conditions and continuing reductions in emissions, according to EPA's most recent ozone air quality trends report: https://www.epa.gov/airtrends/ozone.html . Several future regulations on industry, power plants and vehicles are expected to further reduce NOx emissions and help prevent the formation of ground-level ozone. Information on these future regulations is available online at: https://www.epa.gov/cleanair2004/ .

EPA will accept comment on this proposal for 60 days following publication in the Federal Register. For further information and a pre-publication copy of the proposed rule, visit: https://www.epa.gov/nsr/actions.html .


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