New Delhi: Delhi’s average AQI of 167.2 this month is the lowest Oct reading ever, thanks to a confluence of favourable factors, such as excess rainfall, a late Diwali and a low contribution of stubble burning to the emission load so far.The AQI of 167.2 has happened after years of breaching 200 on the AQI scale — 223 in 2025, 234 in 2024, 219 in 2023, 210 in 2022. In 2021, the average Oct AQI was 173, which is still a few notches higher than this Oct.Data from Central Pollution Control Board shows that the average AQI was 265 in 2020, 234 in 2019, 269 in 2018, 285 in 2017, 271 in 2016 and 264 in 2015.However, the average PM2.5 and PM10 levels are still higher than the national standard. The PM2.5 concentration this month is 70.5 micrograms per cubic metre, when the daily national ambient air quality standard is 60 micrograms per cubic metre. It is also 4.7 times higher than WHO’s daily safe limit of 15 micrograms per cubic metre for PM2.5.The PM10 level this Oct reached 175.8 micrograms per cubic metre when the daily national ambient air quality standard of 100 micrograms per cubic metre. It was 3.8 times higher than WHO’s safe limit of 45 micrograms per cubic metre.After moderate to heavy rainfall in Delhi and its adjoining areas, the air quality improved from 222 in the poor category Thursday to 60 in the satisfactory range Friday. It was also the cleanest Oct day in four years. A lower AQI than this in Oct was last recorded on Oct 11, 2022, when the reading was 44.This month, Delhi recorded five poor days, three satisfactory days and 22 moderate days.Anumita Roychowdhury, executive director-research and advocacy, Centre for Science and Environment, sounded caution while explaining the reasons for the lower AQI. The excess rainfall throughout the month scrubbed ambient particulates while also aiding dispersion, she said. “This minimised the transboundary smoke contribution from regional farm stubble burning. Also this time, Diwali firecracker emissions are not impacting Oct’s air quality. While this drop offers relief, the improvement is largely meteorology-driven,” Roychowdhury said.She added that as winter approaches, dropping temperatures and atmospheric inversion will require rigorous ground-level action focused on transport, waste burning and industrial emission sources.Sunil Dahiya, the founder of the think tank Envirocatalyst, said: “Measures taken across sectors might have led to a reduction…. But the major factor is driven by meteorology.”
