Summary

Description

A design value is a statistic that describes the air quality status of a given location relative to the level of the National Ambient Air Quality Standards (NAAQS). Design values are defined to be consistent with the individual NAAQS as described in CFR Part 50. They are typically used to designate and classify nonattainment areas, as well as to assess progress towards meeting the NAAQS. To view a list of areas designated nonattainment, see EPA's Green Book site. Design values are computed and published annually by EPA's Office of Air Quality Planning and Standards and reviewed in conjunction with the EPA Regional Offices. Some of these design values can change after the date of publication for a variety of reasons, including but not limited to: 1) EPA agreement that certain data were influenced by exceptional events and therefore not subject for comparison with the NAAQS, 2) States retroactively entering or changing erroneous data based on later findings, and/or 3) notification of a monitoring issue (e.g. network design, site combination, change in the regulatory status of a monitor) that would prompt a revision.