This polygon shapefile shows designated areas for particulate matter < 10 microns according to the 24-Hour National Ambient Air Quality Standards (NAAQS). This category of particle pollution measurement monitors inhalable coarse particles, such as those found near roadways and dusty industries, that are larger than 2.5 micrometers and smaller than 10 micrometers in diameter. A geographic area that meets or does better than the primary standard is called an attainment area; areas that don't meet the primary standard are called nonattainment areas. These standards are part of the Clean Air Act. See Code of Federal Regulations, Section 40 Part 81 (40CFR81.305) for detailed information about Ambient Air Quality Standards. Each designation and classification area has an associated date field that represents the "effective" date of the action as published in 40CFR81.305. Projection: Teale Albers, NAD83.This data set is intended to help provide the public with information to determine whether or not air quality within a given area is healthy. Once designations take effect, they also become an important component of state, tribal and local governments' efforts to control coarse particulate matter pollution.