West Michigan ozone nonattainment actions

After the USEPA sets a new ozone standard the USEPA and EGLE work together to determine whether areas are in attainment or nonattainment (see What are the different types of area designations? below) If an area had air quality measurements of high ozone for three or more years, EGLE and USEPA staff review further data to determine if the area should be considered nonattainment. Nonattainment is based on a review of air quality measurements, emissions information, computer air modeling results which provide insight to the dispersion of air pollution, and weather patterns.

The area will have one of three types of designations. Initial designations consist of classifications for areas in attainment, nonattainment, and unclassifiable, defined below. After initial designations USEPA reviews nonattainment areas after a set number of years to reassess if an area needs to be reclassified to a higher degree of nonattainment (see Are there different degrees of nonattainment areas? below).

Attainment is a term for areas that are meeting the air quality standards. The monitoring data for attainment areas shows over a long period of time that pollutant concentrations are at or below the federal air quality standard at the time of initial designations. Additionally, nonattainment areas can come back into attainment through what is referred to as redesignation (see What does it mean if an area redesignates to attainment? below).

Nonattainment is a term applied to an area that has pollutant concentrations above federal air quality standards over a long period of time. An area may also be considered nonattainment if pollution from that area is contributing to poor air quality in another area. Unclassifiable is a term used when an areas status is not able to be determined after evaluating available information. Unclassifiable designations are used when there is not an ozone monitor present in the area (see How are locations of ozone monitors decided? above)