Pollution levels in Delhi-NCR high after Diwali

Despite cracker ban, the 24-hour average level of PM2.5 during Diwali and the morning after has been 397 mg per cubic metre, which is 6.6 times higher than the standards

By Shambhavi Shukla
Published: Friday 20 October 2017

The SO2 levels increased by more than three times in several locations, which is a direct indication of impact of Diwali crackers. Credit: PixabayAn analysis by the Centre for Science and Environment (CSE) has shown that despite the cracker ban, air pollution levels breached the emergency standards on Diwali night. But it is also clear that without the ban on the sale of firecrackers, the levels would have been far worse. Calm wind and more moisture in the air on the post-Diwali morning worsened the pollution build-up.

Releasing the analysis, Anumita Roychowdhury, executive director, research and advocacy, CSE, said: “It is clear that the Delhi-NCR region requires a longer term and systemic action than a one-off ban. The Supreme Court has already ordered a phase down strategy with the help of regulation of chemicals, standards, reduced quantum of crackers, controlled bursting of crackers through community events and locational controls. This must be implemented without delay for a longer term solution to the problem.”

Roychowdhury added, “Delhi and NCR cannot continue to remain on emergency mode all the time to address this public health crisis. This demands longer term strategy to control pollution from continuous sources, including motor vehicles and industry, while curbing episodic pollution from firecrackers and farm fires. A comprehensive action plan must combine short and long-term strategies for vehicles, industry, waste burning and construction activities for more sustained and longer term gains.”

Key highlights

CSE tracked hourly data from about 13 air quality monitoring stations of the Central Pollution Control Board, Delhi Pollution Control Committee and India Meteorological Department to track the changes in air quality during Diwali. The findings are indicative as this analysis faced data quality challenges. For instance, the Mandir Marg station is showing a constant reading from 12 pm onwards. Siri Fort, on the other hand, has stopped giving data since yesterday. While Punjabi Bagh and ITO have stopped giving data since 12 pm, the data for R K Puram is not available from midnight to 3am in the morning. The data for Faridabad is not available since 10pm of October 19. Moreover, direct comparison with 2016 Diwali has been difficult as data from all stations are not available for both the years.

Air quality hits emergency level: Despite the cracker ban the 24-hour average level of PM2.5 during Diwali and the morning after (12 pm - 12 am), October 19-20) has been 397 microgramme per cubic metre (mg / cu m). This is 6.6 times higher than the standards and more than two times higher than the levels of pre-Diwali day when the 24-hour average was 184 microgramme per cu m.

PM2.5 level of 2017 Diwali is lower than that in 2016 Diwali: CSE could compare only four stations (Mandir Marg, Punjabi Bagh, Anand Vihar and R K Puram) to get an indicative idea about the trend. This shows a reduction of 29.5 per cent in 24-hour average PM2.5  levels (12 am - 12 pm) this year. The average PM2.5 concentration in these four stations has reduced from 325 microgramme per cu m in 2016 to 229 microgramme per cu m this year. This estimate may change if more stations are added.

Pre-Diwali level this year much cleaner than previous year: This year pre-Diwali pollution has been lower than the pre-Diwali pollution of 2016. Last year the pre-Diwali pollution had already hit the severe level (4.9 times the standard) whereas this year, it remained within very poor category (2.9 times higher than the standard). Other steps, including closure of Badarpur Power Station and conventional brick kilns, and stronger action on trucks as part of the graded response action plan contributed to this trend.

Night-time pollution three to four times higher than day-time pollution in Delhi and NCR towns: During the day (about 13 hour average—6am to 7pm), the levels in Delhi and NCR towns of Gurugram and Ghaziabad were in very poor category (Delhi—139 microgramme per cu m; Gurugram—121 microgramme per cu m; and Gaziabad—142 microgramme per cu m). However, during Diwali night (about 12 hour average—7pm to 7am) the levels in Delhi, Gurugram and Gaziabad were in emergency level. (Delhi—548 microgramm per cu m; Gurugram—382 microgramme per cu m; Ghaziabad—501 microgramem per cu m).

SO2 levels increased dramatically during the night of Diwali (10pm-3am): The SO2 levels, which otherwise remain very low in the region, increased by more than three times in several locations, including RK Puram, Shadipur and Punjabi Bagh. During pre-Diwali (October 17-18), the SO2 levels in Delhi were less than 50 microgramme per cu m, but on Diwali night the hourly levels increased alarmingly to 183 microgramme per cum. This is a direct indicator of impact of Diwali crackers.

The emergency condition has prevailed until 10am on October 20: The levels have started to decrease thereafter but are still in 'severe' category. Many stations such as Shadipur, DTU, Dwarka, Lodhi Road, RK Puram, North campus and CRRI Mathura Road have observed peaking of pollution with the hourly levels staying above 500-1100 microgramme per cu m between 12am and 6am.

Overall, since October 1, PM2.5 levels have remained at poor level until October 7. Thereafter, it increased to very poor category. This also coincides with the starting of farm fires. However, on Diwali night and the morning after the region has experienced severe and emergency level.

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