Posts Tagged ‘air quality standards’

EPA Issues New Short-term NO2 National Ambient Air Quality Standard

Thursday, February 4th, 2010

by Phil DeVita

On January 22, 2010, the Environmental Protection Agency (EPA) strengthened the primary national ambient air quality standard (NAAQS) for nitrogen dioxide (NO2) by adding a 1-hour NO2standard of 100 ppb.  The EPA administration is retaining the current annual standard of 53 ppb.

The EPA decided the existing annual standard does not provide sufficient protection of public health in the short-term period and believes the new standard will protect against adverse health effects associated with short-term exposure near roadways and urban areas. Current scientific evidence suggests short-term exposures to peak NO2 concentrations correlates with adverse respiratory effects to sensitive populations (i.e., children and the elderly) leading to increased visits to emergency rooms.

Currently, all areas of the U.S. comply with the existing annual NO2 standard.  EPA will designate attainment and non-attainment areas for the new standard by January 2012.  Over the last 30 years, annual NO2 concentrations have continued to decrease.  This decline is mainly attributed to more efficient automobile engines due to the implementation of emission standards for light-duty vehicles.  With the phasing in of emission standards for heavy duty engines in newer vehicles, we should continue to see decreases in NO2 emissions in the future.

Studies have shown that NO2 concentrations are typically higher near roadways when compared to existing monitor locations maintained by state agencies.  Concentrations in heavy traffic areas can be as much as two times greater than residential areas.  As part of this action, EPA is requiring changes to the monitoring network to protect the public health from high short-term concentrations near major roadways, urban areas (i.e., areas with a population greater than 1 million people), and in communities vulnerable to NO2related health effects. These new monitoring and reporting requirements will begin by January 1, 2013.  Once these new monitors are in place, EPA at their discretion could re-designate attainments areas in 2016 or 2017.

The new short-term standard will affect all types of emission sources including aviation, mobile sources, and fossil fuel combustion sources.  For new projects subject to the National Environmental Policy Act (NEPA) and located in a NO2 non-attainment region, general conformity determinations will need to demonstrate project emissions will not exceed the new standards prior to receiving federal funding.  This may subject some sources to additional mitigation measures and could require a source to obtain emissions offsets.   In addition to NEPA review, a project may also need to demonstrate compliance with the new standard in order to receive approval under a state environmental policy act or an air quality permit.   One way of addressing compliance with the standard is conducting air dispersion modeling.  Air dispersion modeling is typically used by new or existing facilities to demonstrate compliance with the NAAQS.   Moving forward, dispersion modeling could be an effective tool many sources will utilize in demonstrating compliance with the new standard.