Monday, February 9, 2009

EPA Air Quality Index AQI for PM2.5 - New Significant Harm Level

On January 15, 2009 EPA proposed to revise its Air Quality Index (AQI) to update the values States use to report daily concentrations for fine particle matter (also known as PM2.5) to reflect changes to the fine particle standard made in 2006. The Agency also proposed to set a “significant harm level” (SHL) equal to the proposed AQI value of 500.

The AQI is EPA’s color-coded tool for communicating air quality to the public; values range from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health concern.

The proposed changes to AQI values include:

  • Setting a PM2.5 AQI value of 100 (anything above 100 is unhealthy for sensitive groups) at 35 ug/m3, which is equal to the 24-hour PM2.5 standard.
  • Setting an AQI of 150 (above 150 is unhealthy) would be set at 55 ug/m3
  • The proposed rule would retain the current AQI values of 200, 300, 400 and 500 at their current levels.

EPA also is proposing to set a Significant Harm Level (SHL) for PM2.5 equal to the proposed AQI value of 500, which is 500 ug/m3. An SHL is a factor used in designing air pollution Emergency Episode Plans, which are required for certain areas of the country. These plans are used to establish procedures for delivering timely information to citizens potentially affected by elevated PM2.5 levels, and to curtail emissions from sources in the area that are potentially contributing to harmful PM2.5 levels.

For further information contact Caltha LLP at
Caltha LLP Website

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