No Modeling Required for Annual PM10 NAAQS

January 2, 2007

On October 17, 2006, EPA revoked the annual National Ambient Air Quality Standard (NAAQS) for particulate matter with an aerodynamic diameter less than or equal to 10 microns (PM10). This EPA action became effective on December 18, 2006. The department is in the process of adopting this NAAQS change into Iowa administrative code.

Since Iowa statute does not allow state air quality rules to be more stringent than federal regulations, it is no longer necessary to conduct dispersion modeling to demonstrate attainment with the annual PM10 NAAQS. Industries and their consultants do not need to submit modeling for the annual PM10 NAAQS.

The level and form of the 24-hour PM10 NAAQS were not changed in the NAAQS revision. Modeling requirements for the 24-hour PM10 NAAQS remain unchanged.

Modeling questions related to the annual PM10 NAAQS should be directed to the Air Quality Bureau's Modeling Group by calling (515) 242-5100.