Implications of the Proposed 1-hour NO2 Ambient Air Quality Standard

In June of 2009, USEPA proposed to revise the ambient air quality standards for nitrogen dioxide (NO2) to include a new 1-hour standard (Federal Register, 2009) along with the original annual average national ambient air quality standard (NAAQS). The current annual average standard is 53 ppb (or 100 μg/m3). The proposed 1-hour NO2 NAAQS ranged from 80 to 100 ppb (151 to 189 μg/m3). The rationale for the addition of a 1- hour NO2 standard is scientific evidence linking short-term NO2 exposures with increased respiratory effects, especially in people with asthma. According to the USEPA, these effects can lead to increased visits to emergency rooms and hospital admissions for respiratory illnesses, particularly in at-risk populations, such as children, the elderly, and asthmatics. Some states, such as New Jersey, already had short-term NO2 air quality criteria; however, as an NAAQS, issues of background concentration and attainment status will become important. In addition, with USEPA's recent concern about air quality impacts during startup and shutdown SU/SD) conditions, and under malfunctions, the new short-term NO2 NAAQS is likely to have far-reaching implications. On January 22, 2010, EPA finalized the regulation, setting a new 1-hour NAAQS for NO2 at 100 ppb, and retaining the annual primary and secondary standards (USEPA, 2010a).A major component of air permitting is demonstrating that a proposed facility or modification complies with all the applicable ambient air quality standards and criteria. This demonstration is accomplished with the application of air dispersion modeling following standard procedures published by the USEPA and state and local air quality management agencies. This paper discusses the compliance implications of adding this new 1-hour NO2 standard to the permitting of a number of different NO2 emission source types from an air quality modeling perspective. The various source types will include combustion sources typically found at wastewater treatment plants and other municipal facilities, such as diesel generators, gas-fired turbines, flares, emergency and blackstart engine generators, Using previously performed dispersion modeling analyses for these various NO2 emissions sources which had been shown to comply with the annual NO2 NAAQS, these analyses will be revisited to determine whether the same sources will be able to comply the new 1-hour NO2 NAAQS.