How are criteria pollutants and National Ambient Air Quality Standards related?

Criteria pollutants are a set of air pollutants that cause smog, acid rain, and other health hazards. The six criteria pollutants are particulate matter, ozone, sulfur dioxide, nitrogen dioxide, carbon monoxide, and lead. Using health-based data, EPA has established national ambient air quality standards (NAAQS) for the six criteria pollutants. The standards are the levels to which criteria pollutant emissions are limited to in given time periods.