National Emissions Standards for Hazardous Air Pollutants
Emissions standards set by EPA for an air pollutant not covered by NAAQS that may cause an increase in fatalities or in serious, irreversible, or incapacitating illness. Primary standards are designed to protect human health, secondary standards to protect public welfare (e.g. building facades, visibility, crops, and domestic animals).
Selected National Emissions Standards for Hazardous Air Pollutants links: