AQI: Why Sept 2020 was worse than last 2 years

Delhi recorded only eight “satisfactory” air quality days and 22 “moderate” ones this September, with a monthly average Air Quality Index (AQI) of 118. An analysis of the September data of the last three years showed that there were fewer “satisfactory” air days this year than in the last two years, with a higher average AQI level as well.