India's National Air Quality Index (AQI) is based on eight pollutants: Particulate Matter (PM2.5 and PM10), Nitrogen Dioxide (NO2), Sulphur Dioxide (SO2), Carbon Monoxide (CO), Ozone (O3), Ammonia (NH3), and Lead (Pb). Both Nitrogen Dioxide and Particulate Matter are included in this list and are often major contributors to poor air quality.