This web service contains layers which depict Design Values for the following criteria air pollutants: Lead (Pb), Annual and Daily Fine Particulate Matter (PM2.5), Particulate Matter (PM10), Carbon Monoxide (CO2), Sulfur Dioxide (SO2), Ozone (O3), and Nitrogen Dioxide (NO2). 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). This GIS dataset includes design values for individual monitoring sites, counties, and nonattainment areas, where applicable. Design values are defined to be consistent with the individual NAAQS as described in CFR Part 50. Design values are typically used to designate and classify nonattainment areas, as well as to assess progress towards meeting the NAAQS. 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. The information contained in this web service is intended for informational use only and does not constitute a regulatory determination by EPA as whether an area has attained a NAAQS. The information set forth in this report has no regulatory effect. To have regulatory effect, a final EPA determination as to whether an area has attained a NAAQS or attained a NAAQS as of its applicable attainment date can be accomplished only after rulemaking that provides an opportunity for notice and comment. No such determination for regulatory purposes exists in the absence of such rulemaking.