Why are the AQI calculations for ozone and fine particles being changed now?
Ozone When EPA changed the ozone standard, the federal rule included a requirement to change the AQI concentration ranges. Agencies that report AQI were encouraged to time the change so that the data from the entire monitoring season are calculated using the revised ranges. In Wisconsin, the official monitoring season begins on April 15. Monitoring sites begin operating in advance of the April 15 season so April 1 was chosen as an implementation date. Fine Particles The federal regulation that lowered the air quality standard for fine particles did not address the update to the AQI. At that time, EPA expected that they would have a separate proposal out for public comment within a couple of months. In February 2007, EPA shared the concentration ranges under consideration; however, the proposed rule has been delayed. Agencies were encouraged to use the revised standard in their forecasting activities. During 2007, DNR used the revised standard in their decisions about issuing watches or
