Why Kejriwal and Modi govt can’t agree on source of Delhi’s air pollution

As Kejriwal dismisses Modi govt’s data that stubble burning causes just 10% of Delhi’s pollution, ThePrint on why there is such confusion on the source of the capital's chronic winter problem.

Stubble burning is one of the major pollution in Delhi | Photo: Praveen Jain | ThePrint

New Delhi: Delhi Chief Minister Arvind Kejriwal has accused the Modi government of “creating confusion” over the source of Delhi’s air pollution crisis, after the Centre’s monitoring agencies claimed that stubble burning was responsible for just 10 per cent of the air pollution in the national capital.

He was responding to a recent report by the System of Air Quality and Weather Forecasting And Research (SAFAR) agency, which falls under the Ministry of Earth Sciences. The report said stubble burning accounted for less than 10 per cent of the PM 2.5 particles in Delhi’s air despite the Air Quality Index (AQI) plunging to the “very poor” category last Wednesday. 

SAFAR, which puts out daily reports, has also estimated that the highest contribution of stubble burning to Delhi’s pollution so far this season, has been 19 per cent on some days.

With Delhi set for elections, the issue of air pollution has assumed political overtones, with the ruling Aam Aadmi Party (AAP) and the opposition BJP blaming each other for the crisis.  

The AAP government has been maintaining that stubble burning in Haryana and Punjab was behind the perennial winter pollution. With the report out, Kejriwal has argued that without the technology available to determine the exact source of pollution, all the data to the effect is “misleading”.  He also sought to know what the remaining 90 per cent of pollutants were. 

ThePrint explains why there is so much confusion regarding the source of Delhi’s chronic winter pollution. 

What is the problem with SAFAR’s data?

SAFAR analyses the sources of pollution through satellite data and predicts the air quality up to three days in advance. 

Its system is run by the Indian Institute of Tropical Meteorology in Pune. It collects data on wind conditions, temperature, humidity through various sources and processes it at the institute’s supercomputer to analyse the causes of pollution, and also create prediction models of what could happen in the coming days.

However, SAFAR’s model of calculating the contribution of stubble burning on Delhi pollution does not make it possible for the system to ascertain the other sources of pollution within the city. 

SAFAR collects data on stubble burning from satellite images, including those from INSAT-3DR and MODIS. It then uses its GIS-based system to create gridded emissions inventory. Based on the real-time weather conditions, it estimates the movement of the PM 2.5 from outside the capital and then subtracts the emissions that appear to arise from within Delhi. 

This means that while SAFAR can calculate the percentage of emissions from stubble burning, it cannot pinpoint the exact sources of pollution from within the city. 

Can’t the CPCB then ascertain the source of pollution?

Put simply, no. The Central Pollution Control Body (CPCB),  a statutory organisation under the Ministry of Environment, Forest and Climate Change (MoEF), is a monitoring agency. 

It is responsible for monitoring real-time data on air pollution across the country through a web-based system that captures data from continuous monitoring stations and calculates the AQI based on the averaged measurement of pollutants. 

AQI is the measure of the amount of pollutants in the air but it does not reveal anything about the source of these pollutants. 

There are 37 real-time monitoring stations in Delhi from which CPCB acquires data. These stations are run by the CPCB, the IMD or the DPCC. They are meant to simply measure the level of different pollutants in the ambient air of the location. 

The AQI bulletin is published daily by the CPCB, and hourly data is openly available on their website.

SAFAR, meanwhile, collects data from various agencies and uses a computer model to predict air quality. It corresponds to the AQI data with its computer model to analyse how emission from various regions affects the Delhi’s pollution levels.

This system is meant to help people take precautions from being exposed to severe pollution wherever possible, and also inform the government about the possible causes of the deteriorating air quality.

Why there is a confusion on the source?

Since there is no central source or method to ascertain the sources of pollution, over the last few years multiple research institutions have attempted to throw light on the subject. However, almost all have arrived at different conclusions. 

In 2015, when the Kejriwal government unveiled the odd-even plan in Delhi, an IIT-Kanpur study reported that it was road dust that accounted for about 35 per cent of PM 2.5 in the air, followed by vehicles.

The following year, Ministry of Environment, Forest and Climate Change released data claiming that vehicular emissions and biomass burning contribute to 25.1 per cent and 25.8 per cent of the PM 2.5 in the winter air pollution in Delhi.

However, according to that report ‘Secondary particulates’ contribute to almost 30 per cent of the PM 2.5 and 25 per cent of PM10. Secondary particulates form due to reactions in the atmosphere from gaseous pollutants such as sulphur dioxide, nitrogen oxides, ammonia, and volatile organic compounds. This component of pollution has gone largely unaddressed.

A 2018 Harvard study put the blame on stubble burning, attributing almost 50 per cent of Delhi’s air pollution to the burning of crop residue in Haryana and Punjab. 

However, a TERI study reported that 36 per cent of the pollution has its source in Delhi itself, of which 28 per cent of the pollution was caused by vehicles. 

All of his has allowed political parties to keep quoting whichever report best supports their claims regarding the source of the pollution. 

There is, however, no confusion that the AQI has already deteriorated to ‘very poor’ and a multi-pronged approach is the need of the hour to combat the toxic smog set to engulf the capital.