I am a man of rituals. Just that they are not religious. As someone who has paralyzing procrastination tendencies, I follow a relatively fixed schedule. I’ve been living away from home in Delhi for the last 11 years, and one ritual has become a part of my identity. Wake up, show up at work, eat, and—the most important part—make a phone call. Back Home. To my dad. He has been living with asthma for as far back in time as I can recall, and now it’s advanced to Interstitial Lung Disease (ILD)—which is to say, as you read this, his lungs are dying. If I’m being brutally honest, the phone call in the night, just before I go to bed has one primary purpose: to confirm he is alive. As much as it hurts as I read the last statement, it’s been my life’s reality for the last seven years. And then, I read news reports of Delhi’s air quality like this:
Delhi’s air quality is something that is deeply personal for me. If you’ve not been living under a rock, you’ve probably seen some mind-boggling numbers pop up on your phone. 1919 AQI. When my phone rang and a friend inquired about the air purifier he wanted to buy and cited this number – I jumped off my chair and laughed. But it only lasted a few seconds, as this was a reality. Yeah, you read that right. Delhi had an AQI of nearly 1800. It’s almost like someone decided Delhi’s air needed to match its population density. As someone who had not seen numbers exceeding 200-300 for his life in Delhi, this is pure nightmare fuel. But hey, before you go ordering the air purifier off Amazon, let’s dig into what this madness actually means. Because, spoiler alert, not everything you see is what it seems.
Here’s the thing. Until a few weeks ago (at least in my recent memory), our point of reference for air quality in India was the National Air Quality Index (NAQI) issued by the Central Pollution Control Board (CPCB). They used a specific method to calculate AQI. Their method report states, “The sub-indices for individual pollutants at a monitoring location are calculated using its 24-hourly average concentration value (8-hourly in the case of CO and O₃) and health breakpoint concentration range.” So, essentially, it’s all based on 24-hour averages for most pollutants (8-hour averages for CO and O₃), which gives a kind of smooth, consistent reading of how hazardous the air has been over the last day. CPCB further forecasts AQI for the next week to give an overview of what to expect. Check it here. Indian Institute of Tropical Meteorology (IITM), Pune, also has an early warning system (EWS) in place where you can track current and future AQI. Think of it like your final grade in a class—it’s not based on one quiz (observation) but on everything you did throughout the term (the last 24 hours).
Now, enter IQAir. These folks have a different approach: they’re all about real-time data. It’s like the difference between your end-of-year report card and that one quiz you bombed last week. IQAir gives you a snapshot of the air quality at any given moment, which, let’s be honest, sounds like it should be better, right? Or, as one of my friends had put it, “If a person wants to use it to make a decision about whether to go outside, etc., using a 24-hour average is like saying, “the average temperature of this pot of water is 38 degrees over the last 8 hours, 24 hours, so I guess I can put my hand in it” when the water is currently boiling.” You want to know what you’re breathing right now, not what you were breathing yesterday. But here’s the kicker: real-time data comes with greater variability. It fluctuates—every hour—that’s why you see these enormous, scary spikes.
This is where it gets technical (and maybe a little boring, but hang in there). AQI is calculated using a standard formula:
where,
- Ip is the AQI of the pollutant (basically, the score for that specific pollutant).
- Cp is the concentration of that pollutant in the air.
- BPhi and BPlow are the breakpoints (upper and lower) that bracket the concentration of the pollutant.
- Ihi and Ilow are the AQI values corresponding to those breakpoints.
If we look at PM2.5—a pollutant everyone’s obsessed with right now—CPCB’s “satisfactory” range goes up to 60 µg/m³. On the other hand, IQAir gets strict. For them, that same concentration is already red-flag territory. While breakpoint progression is a linear function in CPCB’s yardstick, it’s exponential in US AQI followed by IQAir.
Let’s say the PM2.5 concentration is 38 µg/m³ right now, which is a dream for Delhi in November. For CPCB, that’s categorized in the “satisfactory” range, sitting pretty chill, with no worries of any sort. But for IQAir? It’s already a big deal. Their thresholds are much lower. And here begins my main grudge with Indian media outlets!
Imagine you’re someone who knows nothing about AQI calculations (no shame, even I don’t). You wake up, look at your AQI app, and see 1919. What’s the first thing you do? Panic. You cancel all your plans, duct-tape your windows shut, order an air purifier for every room, and consider wearing a gas mask indoors. Meanwhile, your mom, who’s been watching the news, is yelling about how things were never this bad when she was a kid. Even until last year! The media is running headlines like, “Delhi Approaching 2000 AQI, the Apocalypse Is Here,” and everyone is losing their minds.
But here’s the nuance. The air isn’t actually that much worse than it was last year or the year before, if that is any consolation. It’s just that we’re measuring it differently now. That’s not to say the air is good (it’s not). IT IS BAD. The worst we have ever seen. However, at the same time, the way we’re looking at it has changed, and no one’s really explaining that to the public.
Below are the PM2.5 concentrations over the last month for Mundka, the monitoring nearest station to my home, that read AQI of 1919. The left is from CPCB, that feeds into IQAir’s computation shown on the right. If we focus on Oct 20-Nov 18, these data overlap perfectly. You should be worried, if they don’t. Only difference is, on the left is CPCB’s hourly data, which is averaged over 24-hour period, and used to produce NAQI. The same data is also used for computation of hourly AQIs by IQAir.
Let’s break this down further. Imagine you’re tracking your bank balance. Would you rather look at how much money you had over the last month or see your balance in real time? Real-time data seems like the obvious choice, right? But here’s the catch: real-time numbers fluctuate. Maybe you got paid today, so your balance looks great, but tomorrow your rent clears, and suddenly you’re broke again. A 24-hour average smooths all of that out. It gives you a more stable view of what’s happening.
The same goes for air quality. CPCB’s 24-hour averages, following a different table, give you a big-picture view, while IQAir’s real-time data zooms in on the moment-to-moment changes. Neither approach is “better” or “worse”; they’re just different. I will argue IQAir is the future, but when we compare the two without understanding the context, it creates confusion.
Media ran with outrageous reports, without providing the context, and this missed the key element to news reporting, communication. Or, more accurately, the lack of it. The one job they had. No one’s really explaining to the public what these numbers mean, how they’re calculated, or why they’re different. Instead, we get sensationalist headlines and scary stats without any context. And for the average person who hasn’t spent hours Googling AQI formulas (seriously, who has the time?), it’s easy to assume the worst. Delhi’s AQI is suddenly 5 times worse than last year!
This lack of explanation is a massive problem. When people don’t understand what’s happening, they can’t make informed decisions. Should you avoid going outside today? Should you invest in an air purifier? Should you move to a new city? These are questions people are asking, and right now, they’re not getting clear answers. BUT how accurate is IQAir itself?
IQAir uses data from 21 individual stations—10 each from CPCB and DPCC, and one voluntary installation. Computations are made for each station every hour.
AQI by CPCB is calculated from 8 key pollutants. For IQAir, the AQI formula itself does not use all 6 of their monitored pollutants in one equation. Rather, each of the 6 pollutants has both a concentration and AQI value (see the table above, for PM2.5 as reference). The pollutant with the highest AQI level, or ‘risk to health,’ is deemed the “main pollutant,” and that pollutant’s AQI determines the overall AQI number across all the included pollutants. While overall AQI is the highest AQI of the 6 main pollutants, for a majority of locations, the main pollutant in the air is PM2.5 most of the time, which is why we put primary importance on measuring this pollutant.
But, for real-time AQI, the data is fed directly from the analyzers (maybe without scrutiny), thus it may look spurious. Even wildfires produce an AQI of 700-900, and so when you see 1900 and 2300+ in the left graphic captured on Monday, you see starkly different readings. For example, in Central Delhi, you can see AQI of 1844 and 725 next to each other. I’m certain IQAir takes due precautions for this data assimilation; however, regional variabilities can’t be neglected. This is why 24-hour averages are preferred for computations to get a general outlook of ambient air.
Below, you can see the daily AQI data from the last three years sourced from aqicn.org. Clearly, this week has been the worst on the record. But previous winters have not been great either. It’s only during the summer that Delhi can breathe easy, due to prevailing meteorological conditions, i.e., monsoons. Rain washes off a lot these pollutants and whatever left is blown away. However, even that breathing window is shrinking.
The problem is Delhi can’t solve this on its own. An IITM-IMD-CPCB joint study showed nearly 42% of Delhi’s air pollution is imported from North-Northwest. Further, 16% is sourced from South-Southwest and 17% from Southeast for more than half of the days during the winter/post-monsoon season. (Kishore et al. 2019). They used the particle tracking model HYSPLIT to find the source of key pollutants. Brick kilns, agricultural fires, power plants, industries, infrastructure construction, suspended dust, smoke from across the western borders, open fires for heating, high relative humidity due to low temperatures, little to no winds, and a constant high atmospheric pressure and low boundary layer on top of Delhi’s own traffic emission problems ensure the smog stays put around the entire Indo-Gangetic plains, and Delhi, for its population density and geographical location, becomes the epicenter for all the drama.
Can Delhi be saved then? I think about this a lot—can Delhi’s air be cleaned up, or is this just the way things are going to be? While it’s easy to feel pessimistic (that’s my superpower), there are reasons for hope. Other cities around the world, like London, Bergen, and Beijing, have managed to significantly improve their air quality through strict regulations, public awareness, and long-term planning. If they can do it, why can’t we?
The Delhi government devised the Graded Response Action Plan (GRAP) which can be seen here. We are currently on Grade 3. But we need to hold both the union and the state governments accountable. We need Rajasthan, Punjab, Haryana, and Uttar Pradesh on board to have any chance at solving this. India must look beyond the state border and the inter-party tussle if we are to survive. Delhi goes to polls in two months. Make your voice heard and demand the clean air and water as if your life depends on it. Because, spoiler alert, IT DOES!
(Feature image: Indian Express)
