Due to the cleanest monsoon in the last four years, pre-winter pollution in Delhi recorded cleaner this year, CSE (Centre for Science and Environment) said on Friday.

The CSE in its analyses on air pollution said pollution build -up well synchronized across the Indo-Gangetic Plain and this demands regional action and demanded for making short-term emergency measures more robust, and also push for deeper system changes to reduce traffic volumes, eliminate waste burning, ban dirty industrial fuels, and implement stringent dust control measures especially in the construction sector.

According to the CSE report on air pollution, the extraordinarily wet monsoon season has also translated into the cleanest monsoon season for Delhi in the last four years.

“The city-wide average for the monsoon this year stood at 41 microgramme per cubic metre (ug/m3), with 96 days meeting the 24-hour standard for PM2.5. There was a progressive increase in the number of cleaner days with an average 6 per cent annual improvement since 2018. In Delhi, Dr Karni Singh Shooting Range recorded the lowest seasonal average of 33 ug/m3, while the National Stadium had 100 days that met the daily standard. Anand Vihar, with a seasonal average of 61 ug/m3 had lesser number of days – 54 -- meeting the standard and was the worst hotspot in the city,” the Delhi based think-tank said, adding, “The start of the monsoon’s retreat date almost perfectly coincides with the start of bad air days in Delhi.”

Anumita Roychowdhury, executive director, research and advocacy, CSE:  “The 2021 winter is starting with a cleaner threshold compared to the previous years, largely due to the intense and prolonged effect of the monsoons. While winter pollution cannot be predicted at this moment, the evidence of rising summer pollution in 2021 despite the lockdown and the evidence of a synchronised effect of winter pollution across the Indo-Gangetic Plain add to our concern.

How soon and intensely the winter pollution will hit us will depend on the scale and speed of action across the region and leveraging it for more sustained air quality gains.”

 CSE also said summer pollution is also increasing. Comparing summer 2020 pollution data with 2021, it said the advantage of improved air quality during the summer of 2020 due to the lockdown was lost in the 2021 summer, with the seasonal average climbing to 79 ug/m3 and the number of days meeting the standard plummeting to 51 (from 90 in 2020). “In fact, PM2.5 levels this summer have almost returned to the 2019 levels despite the partial lockdowns,” it said.

“The first phase of winter smog is often triggered by large-scale stubble burning in the region. The contribution of farm stubble fire this year started roughly around October 10, the same time as in 2018 and 2020. Peak contribution this year so far was registered on October 16 when 14 percent of Delhi’s PM2.5 was attributed to stubble fire smoke (according to SAFAR).

Heavy rains in the following days washed out the first build-up of the season. The smoke season generally peaks around the cusp of October and November, with contribution spiking to over 40 per cent on the worst days,”CSE added.