New Standards, New AQI

On March 12, 2008, EPA announced that the 8-hour ozone standard had been lowered to 75 ppb. In October 2006, EPA lowered the 24-hour fine particle standard to 35 micrograms per cubic meter (ug/m3). These changes have prompted the Department to amend the Air Quality Index (AQI).

DNR's air quality map displays the same colors for AQI it has used in the past, but the colors better reflect the current air quality standards for ozone and fine particles. When pollutant levels exceed the revised standards, the AQI becomes orange, unhealthy for sensitive individuals. The concentration ranges in each AQI level have been lowered proportionally. These ranges match the criteria the Department uses for calling air quality advisories and watches.

In addition to changing the AQI calculation, we have changed the units for several pollutants from parts per million (ppm) to parts per billion (ppb). This means that results will be in whole numbers rather than in decimals. For example, an ozone concentration of 0.075 ppm will be reported as 75 ppb.

• More information on the changes

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