National Ambient Air Quality Standards (NAAQS)
EPA-established limits on concentrations of six criteria pollutants that must be met nationwide to protect public health and the environment.
Detailed Explanation
The National Ambient Air Quality Standards are pollutant concentration limits established by the EPA under the Clean Air Act. NAAQS exist for six criteria pollutants: carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter (PM2.5 and PM10), and sulfur dioxide. There are two types of NAAQS: primary standards, which are set to protect public health with an adequate margin of safety (including the health of sensitive populations), and secondary standards, which are set to protect public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings. The EPA periodically reviews and may revise these standards based on the latest scientific evidence. The most recent significant revision came in 2024, when the annual PM2.5 standard was tightened from 12 to 9 micrograms per cubic meter. When an area fails to meet a NAAQS, it is designated as a "nonattainment area" and must develop a state implementation plan to bring pollution levels into compliance. NAAQS are the regulatory backbone of air quality management in the United States and directly influence the AQI scale. AirHistory's data reflects the outcomes of these standards — cities in attainment areas generally score higher Air Quality Grades.
Related Terms
Criteria Pollutants
The six common air pollutants regulated by the EPA under the Clean Air Act: ozone, PM2.5, PM10, CO, NO2, and SO2.
Clean Air Act
The primary federal law governing air quality in the United States, first enacted in 1963 and significantly amended in 1970 and 1990.
Nonattainment Area
A geographic area that fails to meet one or more National Ambient Air Quality Standards for a criteria pollutant.
EPA Air Quality System (AQS)
The EPA's national database of ambient air quality data collected from monitoring stations across the United States.
Frequently Asked Questions
EPA-established limits on concentrations of six criteria pollutants that must be met nationwide to protect public health and the environment.
The National Ambient Air Quality Standards are pollutant concentration limits established by the EPA under the Clean Air Act. NAAQS exist for six criteria pollutants: carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter (PM2.5 and PM10), and sulfur dioxide. There are two types of NAAQS: primary standards, which are set to protect public health with an adequate margin of safety (including the health of sensitive populations), and secondary standards, which are set to protect public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings.