What is the Air Quality Index (AQI) and how does it relate to NAAQS?

• A. The AQI translates pollutant concentrations into a single scale with categories to communicate health risk; it’s based on measured/concentration levels relative to NAAQS.
• B. The AQI indicates weather.
• C. The AQI is a measurement unit for mass concentration.
• D. The AQI is used to forecast rainfall.

Answer: (A)

The Air Quality Index is a single, easy-to-read scale that converts measured pollutant concentrations into a number and color categories to communicate health risk to the public. It uses the concentrations of pollutants that are regulated under the National Ambient Air Quality Standards and translates those levels into an index value that shows how close the air is to violating the standards. Higher AQI values indicate greater health risk, with defined categories such as Good, Moderate, Unhealthy for Sensitive Groups, Unhealthy, Very Unhealthy, and Hazardous. This helps people understand air quality at a glance and take appropriate actions. It’s not about weather, not a unit of mass concentration, and not used to forecast rainfall.