Air pollution science, its sources, their impacts, the solutions to reduce pollution and associated limitations are adequately understood and are not a matter of debate any longer.
The real question that needs to be addressed now is the inaction or failure in implementing evidence-based solutions that can reduce the pollution that lingers in the skies all year round, and that is where the focus should now be.
These are the thoughts that ran through my head as I read in disbelief the headlines related to the Supreme Court hearing on 15 November: “This hue and cry (over stubble burning causing air pollution in Delhi) has no scientific basis”. ”Stubble burning is not the major cause”.
“In fact, now the cat is out of the bag. The farmers’ stubble burning contributes to 4 percent of pollution. So we are targeting something that is insignificant,” the court said.
That’s wrong! I said to myself and to my friends. The effect of stubble burning is scientifically proven, it is significant, and it is one of the major causes of pollution. Air pollution is my scientific domain of expertise. As a scientist, I object to this misrepresentation and feel compelled to provide a data update to rebut the public perception that the headlines managed to create.
It feels compulsory to collate what scientists have learnt and said in two long decades not only to reclaim the credit that they’ve brought to the air pollution issue but also to reclaim the public’s attention to validated science. As a mother, it feels imperative to advocate accelerated action towards environmental justice for a better future for our next generation, at the least.
What Do We Already Know?
The scientific community in India and abroad has done decades of pioneering work in monitoring, modelling, forecasting and studying the health and environmental impacts of air pollution.
Within the boundaries of scientific understanding, there is enough evidence to act on reducing air pollution and thereby protect the health of populations and our planet from its climate impacts.
Why Does Delhi’s Air Quality Receive Attention Only During Winter Every Year?
This is when the air pollution levels in and around the capital are the worst, leading to a public health emergency situation.
A quick look at Delhi’s hourly concentration of PM2.5 (from 2015-2021) measured by a high quality reference grade monitor, tells us two things: The pollution story repeats year after year and pollution levels are pretty high throughout the year (barring Monsoon).
The World Health Organization (WHO) recommends that air that is safe to breathe should have PM2.5 concentrations of less than 15 µg/m3 (24-hour average). National Air Quality Index (NAQI) considers PM2.5 concentrations below 30 µg/m3 safe. Now, in the chart below, notice how many days have concentrations of 150 µg/m3 and above.
There are persistent pollution sources in the region that are driving Delhi’s poor air quality conditions. Major sources of this year-round local pollution are the vehicles/transport sector, industries, biomass burning and dust.
Noteworthy is the fact that people living in the region have been breathing this unhealthy air continuously for more than a decade. PM2.5 values greater than 50 µg/m3 pose risks to health.
Crop Burning Does Not Have a Minuscule Impact!
During the winter months, pollution in Delhi soars to hazardous categories with multifold increase in PM2.5 levels each year.
When the Visible Infrared Imaging Radiometer Suite (VIIRS) on NASA’s Suomi-NPP satellite passed over India during October-November 2021, numerous fires (red dots) were burning in tvihe states of Punjab and Haryana.
Fire activity can also be seen in Uttar Pradesh, Madhya Pradesh, and a few other Indian states. Widespread smoke across the IGP region can be seen on several days.
In north-western India, crop residue/stubble left over after harvesting a crop is burnt in order to prepare the fields for the next seasonal crop. The winds carry pollutants caused due to this across the entire Indo-Gangetic plain (IGP) and even to central India and southern coast, deteriorating the air quality across all the cities downwind of the fires.
Unlike other sources of pollution, emissions from crop residue burning pumps large volumes of pollutants into the atmosphere in a short period of time, making stubble burning one of the major and significant contributors to regional air pollution in the winter months.
The cumulative fires detected by VIIRS over Punjab and Haryana (catalogued on the Carbon2Climate portal) during each month of 2017-2021 show two peaks in fire activity each year, corresponding to the two crop seasons : Kharif in summer and Rabi in the winter.
The fire activity in winter (see September to November) is higher and the number of fires in Punjab are higher than in Haryana by an order of magnitude. VIIRS data also shows that the fire count in Punjab this year is the highest since 2016 and has recently surpassed the fire count from last year.
Uttar Pradesh and Madhya Pradesh have active fire seasons during summer months and the summer fire activity has doubled and quadrupled, respectively, over the past five years. There is a smaller peak in these states’ fire activities during winter. It is no rocket science to guess what might be happening to the air quality due to all these emissions. But let's look at some data!
The Impact on Regions That Receive Transported Pollutants
Here is an example showing the PM2.5 levels in the Delhi-NCR region. The PM2.5 concentration (2019-2020) measurements by the central pollution control board (CPCB) show peaks in PM2.5 levels during every winter season; worst air quality days coinciding with the days of peak burning activity, as shown on the SAFAR portal.
The PM2.5 levels in Delhi-NCR increase by up to a factor of 8-11 times during the burning season. For example, on 7 November this year, the PM2.5 level monitored every 15 mins, ranged from 118 µg/m3 to 368 µg/m3 in Central Delhi. The contribution from transported smoke peaked to reach 48 percent on this day.
During Delhi’s first smog event this year, SAFAR estimates show that stubble burning contributed 25 percent to 48 percent percent of the PM2.5 pollution during 4 to 13 November 2021.
22 of the World’s 30 Most Polluted Cities Are in India
While Delhi receives all the attention in the pollution debate, recall that 22 of the World’s 30 most polluted cities are in India. On 9 November 2021, VIIRS instrument on NASA’s Suomi-NPP Satellite observed a blanket of smoke over North India that spread across an area of ~888,966 sq km!
Shown below is an example of PM2.5 levels in five cities in the Indo-Gangetic Plain (IGP).
During 3-15 November 2021, smoke from stubble burning nearly tripled the pollution, putting each of the five cities under “Unhealthy” air quality conditions. Unlike Delhi, however, year round pollution levels in these cities largely remain in the ‘good’ to ‘moderate’ air quality category.
What Do We Take Away From the Data?
High levels of PM2.5 over Delhi-NCR during non-burning seasons are telling of two things: Pollution is a year round problem and stubble burning is not the only cause of the city’s air quality problem.
Since the pollution poses a public health emergency situation in Delhi during winter months that attracts all the attention, the consistent local sources of air pollution, such as industries, vehicular emissions, open waste burning, dust, get systematically overlooked while seasonal stubble burning is put on centre stage.
However, stubble burning is also one of the major contributors to air pollution during the winter season and cannot and should not go unaddressed.
Is it possible to clean up this toxic air? Yes. The 2020 stringent COVID-19 lockdown in India has provided scientific evidence and confirmed that turning off all sources of pollution can indeed clean up our air! But is that a practical solution? No. Because reducing air pollution is not straightforward as it involves both socio-economical and political aspects that will need to be co-addressed effectively. This is the WHO’s massive new list of ways to create a healthier and safer environment.
When & Where Will the Buck Stop, Milord?
Every winter all this information is communicated by various experts on different forums.
Relevant organisations make recommendations to undertake immediate measures. And each year the Supreme Court returns to intervene and mobilise urgent action.
The big question then is: When we have a decade plus of well-rounded understanding of the problem and the solution, why hasn’t the pollution been reduced in Delhi or elsewhere in the country, and is in fact on the rise?
The answer is the lack of effective implementation of ACTION plans, allocation of resources, redressal of enforcement challenges and functional mechanisms to fix accountability of implementing air quality management plans.
While stubble burning does increase pollution levels, any action around mitigation takes a beating because farmers, as they have voiced, are not given viable, affordable, and accessible alternatives/resources.
Where Do We Go From Here?
Governments will need to engage with these and other stakeholders to address their needs and challenges and provide necessary support.
On the other hand, larger investments will need to be made in clean air technology to reduce pollution from other sectors (industries, automobiles, power plants etc).
Investments made on cleaning the air today will reap massive long-term health, environmental and economic dividends compared to the costs associated with controlling life-threatening toxic pollution.
Buried in the articles that made headlines last week, was a ray of hope that didn’t make headlines. It was the right observations and directives that the bench made: “There is a lot of stubble burning happening in Punjab and Haryana. We request state governments to pursue farmers to stop the burning for a week". “We don’t want to penalise the farmers”. “ What we're seeing is the plight of farmers...in what circumstances he is doing this...reasons why he's unable to follow these reports...what's being done?”. “Dust, industry and vehicles are main contributors. If you take steps relating to these three issues, pollution will come down”.
Thank goodness! I said to myself, with admiration for the bench.
Yes. Solutions exist, but who will take steps to accelerate transformative action to reduce year-round emissions from ALL the major sources of pollution? When and where will the buck stop, Milord?
(Dr Falguni Patadia is an Earth/Atmospheric scientist at STI USRA/NASA who uses remote sensing observations to study the impacts of atmospheric particles on air pollution and climate. This is an opinion piece and the views expressed above are the author’s own. They do not represent the views, opinion or position of any organisation/agency that the author works with. The Quint neither endorses nor is responsible for them.)