We know Delhi’s air is toxic. We even know the reasons why. But there are two great mysteries. One: How bad is it… really? Two: Why isn’t it getting better? Today we look at why we don’t have proper data on an ongoing catastrophe. Tomorrow: The do-nothing conundrum.
First, let’s state the obvious
Last week, Delhi was not just the most polluted city in the world—it was 5X as polluted as the city that came in at #2—Dhaka. Congress MP Shashi Tharoor summed up the state of affairs: “This city is essentially uninhabitable from November to January inclusive and barely livable the rest of the year. Should it even remain the nation’s capital?”
Good to know: PM stands for Particulate Matter, and the measurements—typically 2.5 or 10—refer to the size, i.e. less than 2.5 micrometres or less than 10 micrometres. Smaller the particles, and the more prolonged the exposure, the more hazardous they are to human health.
Next: the far too well-known reasons for this nightmare:
Vehicles: This is the number one contributor to Delhi smog—and plays the villain all year long. They are the largest emitters of PM 2.5—making up around 41% of the total (some reports claim 60%). The city adds 1,800 vehicles a day. There are 15 million (1.50 crore) vehicles on its roads—including commercial and private. Of these, 59 lakh are gas-guzzlers older between 10 and 15 years.
Industries: The 3,182 industries located across the NCR contribute around 18.6% of the smog: “Emission of the order of 200-1000 ton/yr is found over industrial zone next to major roads”.
Power plants: There are 12 thermal power plants around Delhi—which emit 281 kilotonnes of sulphur dioxide—or 46% of all SO2 in the air. Only two have taken measures to reduce sulphur dioxide emissions. The deadline to do as was way back in 2017. The new deadline is 2027.
Construction: The outskirts of the region are home to 360 brick kilns—whose peak business period is from December to June. Stone crushers contribute 19% of PM2.5 and 22% of PM10 pollution.
Stubble burning: Every year, farmers burn the dried stalks of rice crops to make room for the cultivation of wheat. The smoke spreads from Punjab and Haryana to Delhi where it mingles with the winter fog to create a toxic smog. But, but, but: This is a seasonal cause for pollution. And it contributes only 10% of PM2.5 and 7% of PM10 pollution.
Geography: The most critical factor that impacts air quality is the speed and direction of wind. Delhi is landlocked, and sits on a flat plain blocked off by the Himalayas. When northwesterly winds blow in—carrying dust, soot etc from Thar desert or even the Middle East—they are effectively ‘trapped’ in a bowl that extends from Punjab in the west to West Bengal in the east. Windblown dust contributes 21.5% of the pollution load.
Mystery #1: How bad is it?
Every year, reporting on Delhi pollution is near-apocalyptic. Yet, we can’t seem to get a handle on even basic facts.
Measuring the sources: We listed the most reliable data above on the causes of pollution above. But, in fact, there is no consensus on how to apportion blame among them:
During the past decade, there have been 15 source apportionment studies of which 10 have been based on direct sampling methods while five are based on secondary data. While sources of emissions remain the same in all the studies, the contribution from different sources to Delhi’s pollution varies greatly.
Pollution data is political. When AAP ruled only Delhi, all the city’s woes were blamed on Punjab farmers. Now that it’s in power in the state, the same party fiercely defends stubble farming.
Fudging the science: In the world of government-funded research, up can indeed be down. The government think-tank NITI Aayog, for example, declared that coal-fired power plants can suspend implementing technology to cut SO2 emissions—called FGD. Why? Because another sarkaari institute ‘found’ that their SO2 emissions “were not adversely impacting air quality.” Yet a recent independent report, the implementation of FGD technology could reduce emissions by up to 67%.
Show me the AQI: The most bizarre bit of data confusion is around the Air Quality Index. Last week, the Central Pollution Control Board showed an AQI reading of 494. But the numbers on international apps such as IQAir soared past 1600.
Turns out India doesn’t measure AQI past 500—and this is why:
"In our AQI scale, values from 451 to 500 fall in the ‘severe plus’ category, which is the highest level of air emergency and corresponds to the strictest anti-pollution measures envisaged so far,” said Dipankar Saha, former head of CPCB’s Air Laboratory Division. When the index was being devised it was felt that having values above 500 couldn’t be of practical use since health impacts plateau after a certain threshold.
In other words, you are so screwed once the index blows past 500—it doesn’t matter how bad it gets.
Also this: The wild gyrations in AQI numbers make them even more questionable. On Tuesday morning, the air quality stood at 485—down from 1,785 the day before.
Stubble fire-fighting fudging: We can’t even agree on stubble burning data. Over the past five years, the official number of stubble fires have dropped by 72% and 42% in Punjab and Haryana, respectively. But new data shows that farmers are avoiding detection by burning stubble in the late afternoons. That’s after NASA satellites have passed overhead—and cannot record the fires. But a Korean geostationary satellite—which stays in place—tells another story.
But the more telling bit is this:
A significant amount of work using ISRO satellites is going on in India for various applications. Unfortunately, not much attention is paid to air quality in this regard. This is one reason our official fire count data is dependent on NASA satellites. We have the capability of becoming independent in this area and may even launch a new high-resolution satellite. But this requires a push.
We don’t know because we don’t want to know… maybe.
The bottomline: In part two, we will tackle the second great mystery of Delhi pollution: Why haven’t we done a damn thing to clean our air?
Reading list
New York Times (login required) and The Hindu offer an overview of the latest crisis. Our previous Big Story and this Mint piece offer an overview of the core causes for Delhi pollution. Indian Express has all the data you need on the leading cause: vehicles—and comparative data on the different causes. Economic Times has more on thermal plants. Times of India and Indian Express explain why Indian AQI numbers are so different from the international scale. The Telegraph has more on Google’s new Air View tool—recently rolled out in India.
