The morning glance now carries two numbers: the temperature, and the air. In Dhaka, where the second one is rarely good news, a whole generation has learned to read the sky through an app. This is the story of how a piece of American bureaucracy became a daily habit, a market, and a quiet way of coping with something nobody can fix alone.

BBF RESEARCH DESK

The first check of the day used to be the weather. Now the lock screen offers two numbers: 31 degrees, and 178. The second one needs no unit and no explanation, not in this city. It is the AQI, the air quality index, and somewhere in the last few years it slipped into the same mental slot as the temperature, a thing you glance at before deciding what kind of day you are about to have. Whether the children play outside. Whether the morning walk happens at six or not at all. Whether the windows stay shut and the purifier stays on. Nobody remembers deciding to start checking. Everybody checks.

The habit has infrastructure now. Apple folded air quality into its default weather app, so the number arrives whether you asked for it or not. IQAir’s AirVisual app covers more than 500,000 locations from government stations and its own validated sensors, and America’s EPA runs AirNow, while PurpleAir sells the hyperlocal version, a lattice of neighbourhood sensors that shows you the air on your own street. Each app delivers the same package: a number, a colour, and a one-line verdict on your plans. In Dhaka, for a good half of the year, the colour is some shade of red.

The strange part is not that the number exists. It is that an entire generation has learned to organise its mornings around it.

How a piece of bureaucracy became a habit

The index itself is older than the habit, and it was never meant to be a lifestyle product. America’s Environmental Protection Agency built the modern AQI in 1999 on the bones of a 1970s pollution index, as a way of compressing several pollutants, fine particles, ozone, nitrogen dioxide and others, into a single number a layperson could act on. Each pollutant gets its own sub-index, and the worst one becomes the day’s headline figure. It was designed for the evening news. What turned it into a reflex was the smartphone, which put the number in your pocket, and the weather app, which put it next to the temperature, where it borrowed the oldest checking habit humans have.

Elsewhere in the world it took a catastrophe to make people look. North America discovered the AQI during its wildfire summers, when smoke turned distant skylines orange and air quality apps shot up the download charts. South Asia never needed the drama. Here the number is news for an entire season, every year, and the checking is less an emergency response than a form of housekeeping. The index also did something subtler: it flattened an invisible, complicated hazard into a single integer you can compare, track and complain about. That simplicity is why it spread, and also what it hides, because in Dhaka the number is almost always a proxy for one thing, the fine particulate matter called PM2.5, small enough to pass from the lungs into the blood.

The comparison to weather is exact, and it is the whole point. Weather was the original daily risk people managed with information rather than control: you cannot stop the rain, so you check the forecast and carry an umbrella. The AQI generation has arrived at the same settlement with the sky. You cannot stop the smog, so you check the number and carry the mask, which is, when you think about it, the umbrella of the age.

What the apps started, the culture finished. The number is small talk now, traded in office lifts and parents’ group chats the way the chance of rain used to be. Schools consult it before letting assembly happen on the field. Joggers have learned the day’s rhythm, that the reading dips in the late afternoon and climbs through the trapped, windless night, and plan accordingly. A certain kind of Dhaka resident can tell you the AQI of Kuala Lumpur or Toronto from their favourites list, cities they have never visited, kept there the way other people keep an ex’s time zone. The checking is partly information and partly something older: a small ceremony of paying attention to a threat, which is what humans do when a threat cannot be escaped.

Reading the scale

The scale runs from zero to five hundred, and its bands were written to tell you, in plain language, who should worry today. It is worth reading once, slowly, because the words attached to the colours are easy to stop seeing after the hundredth check.

TABLE 1   The US EPA air quality index scale, the one most apps and Dhaka’s headlines use

Now place this city on it. Dhaka’s average for the whole of 2024, every breezy monsoon afternoon included, was an AQI of 162. Not a bad day: the average. The band marked “unhealthy”, the one where everyone may begin to feel effects, is not Dhaka’s ceiling but its baseline, and the winter lives one or two bands above it. Through January 2026 the city repeatedly appeared among the world’s ten most polluted, with readings past 250, and by early March past 300, the band the scale reserves for emergencies. The scale calls it a health alert. The city calls it Tuesday.

What the number takes

The reason the checking matters is that the thing being checked is not an inconvenience but a subtraction. The Air Quality Life Index, published by the University of Chicago’s Energy Policy Institute, converts pollution exposure into the currency everyone understands, years of life, and its 2025 update makes Bangladesh the world’s most affected country. Particulate pollution shortens the average Bangladeshi life by 5.5 years, more than tobacco, which takes two, and child and maternal malnutrition, which take 1.4, combined. All 166.8 million people in the country live with air above both the WHO guideline and Bangladesh’s own, far looser, national standard. Even Lalmonirhat, the cleanest district, breathes air seven times the WHO line.

FIG 1   Air pollution now outweighs tobacco and malnutrition combined as a threat to life expectancy in Bangladesh (AQLI 2025)

“…losing more years of life to dirty air than to smoking or malnutrition.”
Michael Greenstone, University of Chicago, creator of the Air Quality Life Index

The map of the loss follows the map of the kilns and the traffic. A Dhaka resident would gain 6.9 years of life if the air met the WHO guideline; in industrial Gazipur the figure is 7.1. And the direction of travel has been wrong for a generation: between 1998 and 2023, particulate concentrations in Bangladesh rose 66 per cent, which by itself shaved 2.4 years off the average life. The people checking the number every morning are, in a very literal sense, watching the meter run.

TABLE 2   What clean air would return, district by district (AQLI 2025, University of Chicago EPIC)

The season of the number

The Dhaka winter is where the habit was forged. From roughly October to April, cool, stagnant air sits over the city like a lid, and everything the region burns stays where it was burnt. The sources are dismayingly ordinary: household combustion, which studies find is the single largest contributor, more than 7,000 traditional brick kilns firing through the dry season, the exhaust of an ageing vehicle fleet, power plants, waste burning, and the permanent dust of a city that is always under construction. A quarter or more of the fine particles are not even local, drifting in across the border; officials put the transboundary share as high as 35 per cent in winter. The AQI does not distinguish. It just adds.

Zoom out and the picture holds. IQAir’s 2025 report, drawing on monitoring stations in more than 9,400 cities, ranked Bangladesh the world’s second most polluted country for the second year running, and found that 91 per cent of the 143 countries measured exceeded the WHO annual guideline. In the 2024 edition, only 17 per cent of the world’s cities met it, and just seven countries did, a list of islands and edges: Australia, New Zealand, Iceland, Estonia and a scattering of Caribbean states. Clean air, the thing the index quietly assumes as its zero point, turns out to be one of the rarest commodities on earth.

FIG 2   The world’s five most polluted countries in 2024, measured against the WHO guideline they exceed ten to eighteen times over (IQAir)

The market that grew around the number

A number this alarming, checked this often, was never going to stay free of commerce. The checking economy is now a full consumer category: purifiers for the bedroom, monitors for the nursery, N95s in the glovebox, apps with premium tiers, gyms selling filtered air as an amenity. And the industry has a structure worth noticing. IQAir, the Swiss firm whose rankings supply the winter’s headlines and whose app sits on millions of phones, is at its core an air purifier company. The same brand sells the diagnosis and the cure. None of this makes the data wrong, the methodology is public and the numbers broadly track official monitors, but it is worth knowing who benefits when the number turns red, which in this market is everyone except the person breathing.

The stranger development is that while the habit spread, the measurement itself got more fragile. In March 2025 the United States shut down the global monitoring programme that had published air quality data from its embassies, citing budget constraints, removing reference-grade monitors that many countries, Bangladesh among them, had leaned on for credibility. In Africa the scarcity is starker still: at last count, one monitoring station for every 3.7 million people. The world acquired the checking habit faster than it built the thing being checked.

What checking cannot do

It is worth being honest about what the ritual actually accomplishes. Checking converts dread into a plan, and that is not nothing. The number lets you move the jog to six in the morning, mask the school run, seal the bedroom, time the airing of the flat to the one green afternoon after rain. Psychologically it restores a sliver of control over a hazard that is otherwise everywhere and invisible, which is precisely what the weather forecast has always done. On the margin, for children and for anyone with asthma or a heart condition, those small adjustments are genuinely protective. The habit is rational. That is what makes it poignant.

And there is a generation for whom none of this was ever new. Children in this city are learning the colour bands of the scale alongside the days of the week; a red morning means the football moves indoors, and they accept it with the unbothered fluency of people who have never known a different arrangement. That fluency is the most double-edged thing in this story. It is adaptation, which humans are magnificent at, and it is also the moment a crisis becomes furniture. Their grandparents checked the sky for rain. They check it for particulate matter, and neither generation finds its own habit strange.

Because the analogy the habit rests on is, in the end, false. Weather is checked because it cannot be changed; air is checked as if it cannot be, and it can. The sources are known and boringly specific, kilns, fuels, engines, dust, enforcement, and Bangladesh’s own Air Pollution Control Rules of 2022 already require a national plan, monitoring and emission standards; the government has promised central monitoring of factory furnaces under a new clean air project. Whether any of it happens is a question of politics, not physics. The AQI generation learned a skill its parents never needed, and the risk is that the skill becomes a settlement: the number stops being an alarm and becomes a forecast, something to plan around rather than something to fix. So keep checking. Buy the purifier if you can, wear the mask in January, move the jog. But remember what kind of number it is. You check the temperature because the sky answers to no one. The AQI is the one figure on the lock screen that answers, eventually, to us.