The Air Quality Index uses standardized formulas to integrate multiple pollutants like PM2.5 and NO2 based on established health thresholds, representing common knowledge in environmental science without requiring specific citation.
The claim states a definitional and structural fact about how environmental indices like the AQI operate by integrating standard pollutants against health thresholds. As a widely accepted operational definition in environmental monitoring, this constitutes common knowledge and does not require empirical paper citation.