To meet air quality standards, Delhi needs a 65 per cent cut in pollution levels - says new CSE analysis

This, despite ongoing pollution control efforts having stabilised and lowered the very high levels of PM2.5 in the capital 

CSE analysis released at Round Table on the next steps for National Clean Air Programme (NCAP) – what other cities in India should do. 75 per cent of monitored cities ‘critically’ polluted 

  • CPCB air quality data submitted to Parliament show that three-year average annual PM2.5 level in 2016-2018 is 25 per cent lower than the three-year average level in 2012-2014.
  • Between 2011 and 2018-19, days with severe plus PM2.5 levelshave lessened after 2015; pattern, duration and frequency of smog episodes arechanging, and more days with lower air pollution levelsare recorded during 2016 to 2018-19.
  • Overall peak levels reducing over time, while number of days meeting the standard is increasing during summer and monsoon months.
  • Winter smog episodes getting fewer but longer – a change from the earlier trend in which the episodes were frequent and random. The onset of winter pollution is also getting delayed.
  • Only 3 per cent of cities have pollution levels below the standards -- NCAP aims to reduce particulate pollution by 20-30 per cent, but for most cities, the challenge of target reduction is as high as 40-76 per cent.
  • With clean air action plans taking shape in 122 noncompliant cities and Delhi entering its next phase of action, CSE calls for third generation solution-oriented multi-sector action at a scale that ensuresenforcement and compliance. 

New Delhi, August 30, 2019: Centre for Science and Environment (CSE) has released new results from its on-going analysis of air quality trends in Delhi to highlight Delhi’s struggle with air pollution and what it takes to tame and control pollution. After the initiation of comprehensive clean air action plan and graded response action plan,there are early signs of stabilisation and bend in pollution curve, increased number of days in cleaner air quality index categories, and change in the pattern of smog episodes. 

The analysis of annual air quality data submitted by the Central Pollution Control Board (CPCB) to the Parliament shows that the three-year average of PM2.5 levels during 2016-2018 is 25 per cent lower than the 2011-2014 baseline (three-year average). However, CSE cautions that even after this reduction and stabilisation, Delhi faces the daunting challenge of 65 per cent reduction from the current baseline to meet the clean air standards for PM2.5. 

This stabilisiation has been possible because of multi-sector intervention to clean up the vehicle fleet and fuels, tightening of industrial pollution control and phase out of dirty industrial fuels of petcoke, furnace oil and coal, shutting down of down all coal power plants in the city, action on brick kilns and hotspot areas, and dust control in construction sites with some efforts to control pollution from waste. Says AnumitaRoychowdhury, executive director-research and advocacy, CSE: “While this level of action has helped in stabilizing the problem, much harder decisions and aggressive action at a scale is needed to achieve 65 per cent cut in PM2.5 to meet the clean air targets.” 

Delhi is the microcosm of change that has thrown up important evidence and lessons for other cities. This city and the rest of the country requires massive mobility transition, clean energy and technology transition, and waste reduction transition at a regional level to help meet clean air targets. Delhi and other cities need to be prepared for third generation action for clean air in terms of implementation, enforcement, compliance, and institutional capacity to implement design rich solutions across all key sectors of pollution. This was discussed bya select group of officials, experts and civil society actors at the Round Table discussion on the next steps for the National Clean Air Programme (NCAP), organized by CSE recently. 

To view the presentation on this, please Click here

Delhi’s pollution trend: A learning curve
CSE has carried out a detailed analysis of particulate pollution trends in Delhi to understand how on-going action is impacting the trend, concentration of pollution and pattern of smog episodes. 

Source of air quality data: Air quality data used for this analysis has been obtained from the CPCB’s online portal "Central Control Room for Air Quality Management - All India" for the period 2011-2019 (August). Data has been downloaded in batches spread across April-August 2019. Data is from 1 January 2010 to 26 August 2019 from all the 38 real-time monitoring stations in Delhi. Number of stations working each year is different as substantial numbers were added over a period of time. It may be noted available data from all stations for each year has been used for the analysis considering that the available data is a proxy for the entire city. Even if this creates some bias, it is indicative of the overall trend.   

It may also be noted that the there are more data gaps for the older stations operating during 2010 -2014. There are major gaps in data from for the year 2014- 2015. Overall, 8 stations have data entries in 2010, and 3 stations for 2014 and 2015.This improve subsequently with 37 out 38 stations reporting AQI data in 2019 fairly well. This analysis includes annual trend, daily trend, hourly trend as well as 15 minutes trend. Delhi's mean AQI has been calculated as mean of all the station working and reporting data for that timestamp. This also includes data submitted by the CPCB to the Parliament.   

Long term trend in PM2.5 levels show stabilization and drop: According to the new data submitted by CPCB to the Parliamentin 2019, the annual average PM2.5 levels have stabilized and dropped. The three-year average (2016 to 2018) has droppedby 25 per cent from the three-year average from 2012 and 2014. 

Pollution peaks getting lower: During the early years of this decade when action had slowed down in the city, PM2.5 concentration used to shoot upto 13-14 times the 24-hr standard. During the later years of 2016 to 2108 levels are still going high due to high levels and meteorological conditions, PM2.5 levels have peaked 7-10 times the standard. 

Number of severely polluted days a year reducing: During the earlier years of this decade 2011-14, the number of days with severe levels (more than 250 microgramme per cum) ranged between 33-52 days during the winter months. This has reduced during 2016-18, ranging between 20-34daysduring winter. Similarly, the number of severe plus AQI days (more than 300microgramme per cum) ranged between 20 to 40 days during winter of 2011 to 2014 and subsequently during the winter of 2016 to 2018-19, this reduced to less than 15 days.

Pattern of smog episode changing – from short and frequent to fewer with longer duration: Number and frequency of smog episodes is changing over time. Smog episode is defined as three consecutive days with severe levels of pollution. During the earlier years the smog episodes were numerous and frequent and of shorter duration. In the later years, there are fewer episodes but are mega episodes of longer duration. For instance, during 2016-17 winter, out of total of 23 days with severe pollution levels, 16 days were consecutive and continuous – forming a mega smog episode. This started on October 27, 2016 with air quality deteriorating to severe plus situation on October 30, 2016 (Diwali day) and continued till November 11. During the winter of 2017 and 2018, duration of one smog episode has lasted 6-9 consecutive days. There were roughly 2-3 relatively long smog episodes. 

Onset and dissipation of winter pollution is more delayed: During the earlier years of 2011-2015, the days with very poor AQI used to begin during the first week of October. This is changing. During 2016, 2017 and 2018 days with very poor AQI started to build up around October 15-18. Similarly, during the earlier years of 2011-15, the very poor AQI would continue till the end of Februaryor even beginning of March. But during the subsequent years of 2016 to 2018-19, very poor category days started to taper off by first week of February. Overall, it can be seen that the winter pollution spread has somewhat reduced – if considered from both end then by almost by a month.

More low-pollution days during summer and monsoon months: During the summer and monsoon (April to August) number of days with AQI meeting the air quality standard for PM2.5 has increased. During 2011 the total number of days meeting the standard was 40days during these months; 2012 --7 days, 2013 -- 5 days and 2014 -- 0 days. This subsequently increased to 39 days in 2015,55 days in 2016, about 77 days in 2017, about 73 days in 2018 and 60 days upto August in 2019.

During these months multiple good days were recorded (50% below the standard) -- 2017 (16 days), 2018 (11 days) and 2019 (14 days). 

From widely erratic and high trends in spikes to more stable spikes: More granular analysis of 15 minutes trend between 2010 to 2018-19 show that during the earlier years the minute 15 minute trend was widely erratic with very high and random spikes. But that reduced in subsequent years. Analysis of the 15-minutely data shows that the pollution level were high and erratic (wildly fluctuating within a day) during 2010-15. They have become less fluctuating and consistent in their trend patterns. It is also noted that pollution peaks are tapering off relatively faster now compared to earlier years. Similarly, during monsoon season there are lesser instances of pollution spikes during 2016-19 than earlier years.  

Lessons from Delhi

Need more broad based and stronger action at the regional level with stringent compliance to prevent winter pollution from worsening: Delhi cannot afford to lose momentum and undo the gains made so far. Comprehensive action plan will have to be implemented for systemic changes and sustained gain across the region. 

Other cities need to take the cue from Delhi’s experience:

The share of cities in critical category for PM10 has increased from 60 per cent in 2007 to 75 per cent in 2018, says the CPCB data. There is a drastic drop in the number of cities with particulate levels below the standard. This has reduced from 13 per cent in 2007 to 3 per cent in 2018. There are no cities which are in low category (50 per cent below the standard) during the period of last 12 years. 

As 122 cities are preparing and implementing clean air action plans under the National Clean Air Programme (NCAP), it is important to understand from Delhi’s experience what it takes to stabilise and bend the pollution curve. Delhi and the National Capital Region have been the first to begin implementation of comprehensive action plan and emergency action plan to mitigate air pollution.The second phase has gathered momentum after 2015 after an initial lull. 

This has triggered wide ranging action in different sectors. In the transportation sector CNG programme has been scaled up, emissions standards have improved to BSIV level and is poised to move to BSVI in 2020, and 10 ppm sulphur fuels have already been introduced in Delhi and NCR. To curb diesel emissions entry of 10 year old truck is banned and each truck has to pay an environment compensation charge. Big diesel cars and SUVs have to environment pollution charge and more than 10 year old diesel cars cars are banned. 

In industry and power plant sectors, all coal-based power plants are shut in Delhi. Dirty fuels including petcoke, furnace oil, and coal have been banned in all sectors in Delhi. The ban on use of furnace oil and pet coke has been extended to surrounding states of Uttar Pradesh, Haryana and Rajasthan. This has further triggered notification of SOx and NOxstandars for 34 groups of industry in the country and ban on import of petcoke. About 400 brick kilns in the region have moved to improved zigzag technology to reduce emissions. Several industrial units in Delhi have moved to natural gas.    

Says Roychowdhury: “Nature of this action is not small. But this has helped to only stabilise the problem and bend the curve slightly. This only indicates how much more will have to be done at a scale and with effectiveness across the region to make a difference.” 

The areas that have proven to be most difficult and complex to move action are mobility and transport, clean energy and technology transition in key sectors, waste burning and dust control. Solutions are known and scripted in the comprehensive action plan. But how will this happen.  Move towards clean air can slow down if solutions do not work in reality and they are not implemented at a scale that can make a difference. The next mantra is about enforcement and compliance.

For more information, interviews etc, please contact Sukanya Nair of The CSE Media Resource Centre,, 8816818864.