Posts Tagged ‘ambient air quality’

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.

Proposed Air Quality Standards for Sulfur Dioxide

Wednesday, December 9th, 2009

by Phil DeVita

For the first time since 1971, the Environmental Protection Agency (EPA) has proposed to revise the National Ambient Air Quality Standards for sulfur dioxide (SO2).  The proposal calls for a new 1-hour standard.  The current SO2 standard consists of a primary 24-hour and annual standard.  There is also a secondary 3-hour standard.  The primary standards were set to protect the public health including the health of the sensitive population (e.g. asthmatics, children, and the elderly).  The secondary standard was established to address public welfare and the environment.  Recent health studies have linked short-term (e.g. ranging from 5 minutes to 24-hours) SO2 exposures to adverse respiratory effects including increased asthma symptoms and bronchoconstriction.

The EPA is currently taking comments on the new 1-hour standard ranging from 50 and 100 parts per billion (ppb).  Since the revised standard would be more protective, the EPA is proposing to revoke the current 24-hour and annual standard.  The current proposal only addresses the primary standards.  EPA will address the secondary standard (e.g. 3-hour) under a second proposal in 2011.  The current and proposed SO2 standards are presented in the following tables.

Current Standards

Averaging Time

Primary Standards

Secondary Standards

3-Hour

none

500 ppb

24-Hour

140 ppb

none

Annual

30 ppb

none

Proposed Standards

Averaging Time

Primary Standards

Secondary Standards

1-Hour

(50 to 100 ppb)

none

3-Hour

none

500 ppb

24-Hour

Revoke

none

Annual

Revoke

None

EPA is also proposing changes to the monitoring requirements for SO2.  Monitors would be placed in urban areas and areas with high SO2 emission levels.  The proposal includes changing the Air Quality Index (AQI) to reflect the new standards thereby improving states’ abilities to alert the public when short-term levels may affect their health.

The public comment period is open for 60 days after the proposal is published in the Federal Register.  EPA will hold a public hearing on January 5, 2010 in Atlanta.   EPA must issue a final decision by June 2, 2010.

The proposed SO2 revision comes off the heels of EPA’s recent proposal to revise the nitrogen dioxide (NO2) standard.  EPA is proposing to include a new 1-hour NO2 standard ranging from 80-100 ppb while also soliciting comments as low as 65 ppb and  up to 150 ppb.  The proposal would retain the current annual standard of 53 ppb.  The comment period has closed on the NO2 standard and EPA must issue a final decision by January 22, 2010.

These proposed standards will affect all types of emission sources, including aviation.  For areas in non-attainment and maintenance regions, general conformity determinations will need to demonstrate that project emissions will not exceed these standards prior to FAA approving federal funding.