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EPA Proposes Revisions to Air Quality Index for Particle Pollution

Release Date: 01/15/2009
Contact Information: Cathy Milbourn, (202) 564-4355 /7849/

(01/15/09) EPA is proposing to update its Air Quality Index (AQI) to reflect the latest standards for fine particle pollution. The proposal also would set a “significant harm” level, which states use in developing emergency episode plans. Fine particle pollution is also known as fine particulate matter, or PM 2.5.

Under the proposed changes, the AQI would reach “code orange” – unhealthy for sensitive groups – when particle pollution levels reach 35.5 micrograms per cubic meter of air (ug/m3). The changes also would mean air quality reaches the “unhealthy” category at a lower particle pollution level.

These proposed changes likely would not have a noticeable impact on daily air quality forecasts. States have been voluntarily forecasting code orange when particle pollution reaches 35 ug/m3, the same level as the revised daily health standard. EPA revised this standard in September 2006.

The proposed rule also would set a significant harm level equal to an AQI value of 500. States use these levels in air quality emergency episode plans, which set procedures for delivering information to potentially affected citizens and for reducing emissions from sources in the area that are potentially contributing to harmful PM 2.5 levels. EPA is seeking comment on its proposal for setting the 500 AQI level.

The AQI is EPA’s color-coded tool for communicating air quality to the public. An AQI value of 50, for example, represents good air quality with little potential to affect public health, while an AQI value over 300 represents hazardous air quality. AQI reporting is required in cities of 350,000 and larger; however, more than 300 cities voluntarily issue air quality forecasts as a public health service.

EPA will take comment for 60 days after the proposal is published in the Federal Register and will hold a public hearing on March 5, 2009, at the Intercontinental Dallas, 15201 Dallas Parkway, Addison, Texas.

In addition, EPA will host a blog to provide the public additional avenues for discussing this proposal. Comments to the blog will not be considered official comments for the record; however, the blog will provide readers with easy links for submitting official comments. The blog will open the week of March 2, 2009, the same week as the public hearing. EPA will notify the public about how to participate in the blog and how to be notified when the blog is open.

For more information about the AQI proposal: