Delhi recorded its worst air quality for December this year since 2018 with an average AQI of 349, as per official data. In December 2018, Delhi witnessed average Air Quality Index (AQI) of 360, an official said. The December average was 337 in 2019, 332 in 2020, 336 in 2021, 319 in 2022, 348 in 2023 and 294 in 2024.