WASHINGTON (CN) – The Environmental Protection Agency has set thresholds defining how far air quality around the country strayed from the 2008 National Ambient Air Quality Standards for ozone.
The degree to which an area is out of compliance increases the number and severity of control measures states must bring to bear to mitigate poor air quality and the amount of time they have to do so. The five classifications, in increasing order of severity, are: marginal; moderate; serious; severe and extreme.
The classifications are based on the percentage by which air quality in regulated pollutants exceeds the attainment standard set in 2008. For instance, “extreme” areas are those where measured ozone parts per million in an average one hour period are 133 percent above the NAAQS while “marginal” areas are less than one percent off the standard.
Areas designated as “extreme” have 20 years from December 31 of the year they are classified to reach attainment status, while “marginal” areas have just 3 years.
Only two areas nationally are classified as “extreme” while 36 are ranked as “marginal,” three are “moderate,” two are “serious” and three are “severe.”
The new designation thresholds are effective July 20.
Click the document icon for this regulation and others.