Indian cities do not suffer from a shortage of concern about air pollution. They suffer from an excess of watching. Screens refresh, apps ping, colours change. Masks go on and off depending on thresholds; schools shut when numbers cross a line and reopen when they fall. Rarely does anyone pause to ask what exactly changed, why it changed, or whether lungs noticed at all. Now many understand increased air pollution as they purchase Short-acting beta-agonists (SABA) and Inhaled corticosteroids (ICS). What a pity!
Ambient air quality in Indian cities is assessed through a defined set of criteria pollutants under the National Ambient Air Quality Standards notified by the Central Pollution Control Board. Urban monitoring stations routinely measure particulate matter (PM₂.₅ and PM₁₀), nitrogen dioxide, sulphur dioxide, carbon monoxide, ozone, ammonia, and lead, though the frequency and spatial coverage vary by pollutant and by city. Particulates are measured most widely. These measurements form the technical backbone of air quality regulation and reporting in India.
Despite this monitoring infrastructure, Indian cities consistently feature near the top of global air pollution rankings. In several recent years, Indian cities have constituted the majority of the global top ten or top twenty lists. Increasingly, air quality influences decisions about where people choose to live, work, travel, or invest, with many residents actively seeking to move away in the hope that cleaner air still exists somewhere else. While this happens, business of monitoring will continue, and makers of air purifiers will continue to flourish. These markets respond much more than the regulators. Citizen responses show that air pollution is something to be managed privately rather than prevented collectively.
Against this backdrop, the Air Quality Index emerged as a global solution to a communication problem. To make this information accessible, regulators across the world adopted AQI-type systems that translate concentrations into a single, comparable scale. In India, the AQI framework notified by the Central Pollution Control Board converts measured concentrations of individual pollutants into dimensionless sub-indices using predefined breakpoints linked to regulatory standards. The overall AQI for a location and day is defined by the highest, or worst, pollutant The logic is simple: highlight the dominant pollutant of concern and enable quick public advisories without exposing raw data.
Over time, however, this design has had unintended consequences in India. Because PM₂.₅ most frequently exceeds regulatory breakpoints, it almost always determines the AQI. Ambient air quality management has therefore narrowed, in practice, into management of particulates. Fluctuations in AQI are interpreted as fluctuations in particulates, even when other pollutants are elevated but do not numerically dominate.
But remember that particulate matter is far from a simple or innocent pollutant. Surfaces of PM₂.₅ carry chemically active mixture containing sulphates, nitrates, ammonium salts, elemental and organic carbon, trace metals, and complex organic compounds. These fine particles act as carriers allowing chemical transformations to continue both in the atmosphere and within the human respiratory system. Reducing this complexity to a single mass concentration hides substantial variation in composition, toxicity, and behaviour, even as regulatory reporting treats all micrograms as equivalent.
To unpack this complexity, regulators increasingly rely on source apportionment studies. Using chemical speciation and receptor modelling, these studies estimate the relative contributions of different emission sources—traffic, industry, biomass burning, road dust, and secondary formation—to observed particulate chemical composition. In India, such studies are typically commissioned by regulatory agencies to develop action plans and sector-specific measures. However, their findings do not feed into the AQI, which remains a concentration-based communication index rather than a diagnostic tool. Source apportionment is expensive, technically demanding, and time-consuming. An enduring irony is that by the time a detailed source profile is produced, emission patterns and particulate composition may already have shifted!
These constraints point to a more fundamental limitation of AQI itself. AQI is a short-term snapshot. It describes air quality at a particular place over a particular averaging period, but it does not capture how long people are exposed, how often high concentrations recur, or how exposure accumulates over months and years. It does not account for daily activity patterns, importantly indoor–outdoor movement, or time spent in high-exposure micro-environments. Used beyond its intended purpose, AQI risks becoming a proxy for safety or for a trigger for emergency rather than a signal of concern requiring proactive and sustained actions. Understanding air pollution in lived terms requires an exposure lens that integrates concentration, duration, frequency, and context.
This exposure perspective is not new. Before real-time sensors, air pollution was assessed using simple and inexpensive cumulative indicators: dust jars left on rooftops, sulphation candles exposed for weeks, and visible damage to plant leaves or loss of chlorophyll. These methods lacked precision, reproducibility and chemical resolution, but they captured accumulation. They did not reset at midnight. They made pollution visible and persistent, aligning more closely with how materials, ecosystems, and bodies experience polluted air. While such tools are insufficient for modern regulatory needs, they offer a conceptual reminder that air pollution is a process unfolding over time, not merely a sequence of instantaneous readings.
A truly robust response to air pollution would eventually require carefully designed epidemiological studies that link measured exposure to observed health outcomes over time, in collaboration with medical professionals. Such evidence narrows uncertainty, quantifies long-term burden, and exposes the limits of incremental responses. Yet this is precisely why it remains uncomfortable for governance. Long-term epidemiology does not refresh daily, cannot be averaged away, and once published, cannot be unseen. It forces accountability across political cycles and administrative boundaries. The hesitation to commission such studies is therefore less about science, and more about the consequences of knowing too much, too clearly.
Musing about nuances of AQI, I was reminded of another index: the Bombay Stock Exchanges (BSE) index who is facing competition of AQI today in terms of “visibility”. BSE index is a benchmark number that tracks the combined price movement of selected major listed companies, offering a snapshot of overall stock market performance and investor sentiment at a given point in time. The BSE index operates on regular trading days from 9:15 a.m. to 3:30 p.m. (Indian Standard Time), Monday to Friday, excluding weekends and officially notified trading holidays. AQI has no holiday, it operates 24×7 (at least it is supposed to be)
I imagined a conversation between BSE and AQI in the green room of television studio.
- BSE Index (immaculately dressed, numbers flashing confidently)
- AQI (slightly grey, colour-coded scarf, coughing politely)
BSE Index: “You look tense today.”
AQI: “I’m always tense. People stare at me every morning.”
BSE Index: “Ah, same here! When I rise, people celebrate. When I fall, governments panic.”
AQI: “Interesting. When I rise, people panic briefly. When I fall, governments relax.”
BSE Index (smirking): “And yet, they act on me.”
AQI: “They comment on me.”
BSE Index: “If I drop 800 points, there’s an emergency meeting by noon.”
AQI: “If I cross ‘Severe’, there’s a tweet, a mask advisory, and schools are shut down.”
BSE Index: “Capital leaving overnight scares them.”
AQI: “Lung damage… is apparently negotiable.”
AQI (curious): “Tell me, why do they trust you so much?”
BSE Index: “Because I represent money lost today.”
AQI: “Well, I represent life lost slowly.”
BSE Index: “Ah. Different discount rates.”
I asked my Professor friend what would happen if we combined these two indices? We will perhaps face the uncomfortable truth.
A combined index would do something radical:
- It would link wealth creation to environmental cost
- It would make it harder to celebrate growth without context
- It would force uncomfortable trade-offs into public view
Which is precisely why it will likely remain a thought experiment.
Professor heard my analysis. He laughed and said
“Dr Modak, we react to the BSE because it threatens portfolios.
We tolerate AQI because it threatens futures that we may not see
The day we combine the two, we may finally decide which one we value more.”
Are we ready to price air the way we price money—or will we keep pretending lungs are a non-traded asset?
You don’t have to answer!
Wow Modak ji
You’ve shown how we’ve learned to adjust to suffering instead of questioning it.
Markets shake us into action, but polluted air numbs us into acceptance.
This isn’t just about AQI—it’s about what we’ve normalised losing, quietly, every breath.
Thank you for reminding us that numbers may refresh daily, but nature and lungs do not. 🌱
Thank you !
Great piece. You nailed it precisely. Recently there was an statement from GoI that there is no conclusive evidence to link air pollution with impact on health.
The obvious question one would ask as to why doesn’t government commision such studies. Since outcome these studies will put government at a tight spot, no such studies are undertaken.
But why other stakeholders like NGOs and autonomous institutes fill this gap?
Very true. All evade
We in Bhutan worry much of the transboundary pollution than our domestic emissions. For time being, the air is much cleaner here. Visit Bhutan and feel it yourself, Prof.