AQI and Air Quality

The Air Quality Index (AQI) summarizes pollutant measurements on an accessible scale; in the U.S. Environmental Protection Agency system, lower values indicate cleaner air. AQI 101–150 is “unhealthy for sensitive groups,” and values above 150 are “unhealthy.” This is not a universal worldwide scale: other countries may use different systems and thresholds. Comparing AQI above 100 with “breathing car exhaust all day” is not an official interpretation and has no reliable equivalent without specifying pollutant, concentration, and exposure duration.