The good news is pollution levels in the Delhi NCR region since September 2019 are lower than in 2018 thanks to the weather and advance action that prevented severely polluted days in the region, finds a Centre for Science and Environment (CSE) analysis.
All that changed on Diwali night which ushered in the season's first severe pollution peak due to the bursting of firecrackers. From a very clean afternoon, the change to severe pollution levels after 10 pm was drastic. There was a 10-fold jump in PM 2.5 concentration between 5 pm and 1 am due to firecrackers. It undid the comparatively cleaner trend from September 15 to October 27.
CSE analysed the Central Pollution Control Board's (CPCB)'s real time data from Delhi and towns in the NCR including Gurugram, Faridabad, Noida and Ghaziabad to find PM 2.5 concentrations levels to assess the trend during Diwali, the weekly trend before Diwali, and the overall trend since September 15.
"While winter conditions are yet to set in and the weather during the period of analysis (September 15 to October 27) has remained relatively favourable (including a delayed monsoon), several ongoing systemic actions and preventive emergency measures had also contributed to prevent an early onset of very poor and severe pollution in Delhi-NCR. The scenario changed on Diwali night," says Anumita Roychowdhury, executive director-research and advocacy, CSE.
In 2019, there have been days with lower wind speeds than in 2018, yet pollution has not exceeded 2018 levels. Even on days with better wind conditions in 2018 leading to Diwali, pollution was higher compared to 2019 - this shows overall pollution load in the city in 2018 must have been higher.
Ghaziabad was the first town in the NCR to experience the season's first 24-hour average severe pollution on Diwali. The air in the other cities and towns is also expected to follow suit post Diwali. In 2018, Diwali occurred on November 7, 10 days later than this year. Says Roychowdhury: "It is absolutely necessary that action is now stepped up to ensure that Delhi and NCR do not plunge into a prolonged smog episode this winter."
She suggests steps to enforce emergency action on industrial pollution, waste burning and dust generators with strong deterrence and zero tolerance across Delhi and NCR. There is a need to step up longer term systemic action to eliminate dirty industrial fuels, up-scale public transport, and minimise waste burning and dust generation for sustained air quality impact.