This month, the Environmental Protection Agency (EPA)  issued draft guidance proposed for updating the tools state regulators use to evaluate air pollution impacts from industrial facilities as part of the permitting process.

The draft guidance (RIN:2060-ZA24) updates the significant impact levels state regulators use during the prevention of significant deterioration permitting process to measure the impact expanded emissions will have on ambient concentrations of ozone and fine particulate matter. Significant impact levels are tools state regulators can use to determine whether any given industrial facility's emissions would have a negative impact on compliance with the national ambient air quality standards during the permitting review process.

The EPA updated its significant impact levels using a new air quality variability approach that it says produces values that are more universally applicable.

The revised significant impact levels recommended by the EPA would be 1.2 micrograms per cubic meter under the daily fine particulate matter standards, 0.2 micrograms per cubic meter under the annual particulate matter standards and 1.0 part per billion under the 8-hour ozone standards.