From 30 to 551: How India Built Its Air Monitoring Network

30 stations. That is all India had in 2016 to measure the air quality of 1.4 billion people across 29 states.

By the end of 2024, that number hit 551. The question is whether that is enough, and the answer, once you look at the data, is a clear no.

We analysed 605,654 daily AQI readings from the Central Pollution Control Board (CPCB) database spanning 2016 to 2024 to trace how India's air quality monitoring network grew from a skeleton crew into something resembling a national system. The logic is straightforward: a monitoring station "exists" in a given year if it recorded at least one daily AQI reading. The first year it appears in the data marks when monitoring began at that location.

The Big Picture: 30 to 551 in Nine Years

The growth has been dramatic, but uneven.

Two things jump out. First, the growth accelerated after 2018, right when the National Clean Air Programme (NCAP) was being conceived (launched January 2019). NCAP required cities to have monitoring infrastructure before they could receive clean-air funding. That lit a fire under state pollution control boards.

Second, 2023 shows a dip to 291 active stations from 390 the year before. That is not stations being decommissioned. It is a reporting gap where many stations had data collection or upload issues for much of the year. The bounce back to 526 in 2024 confirms the infrastructure was always there. The problem was data pipeline reliability, not physical hardware.

Cities Covered: From 19 to 275

When India started real-time air quality monitoring in 2016, only 19 cities were covered. Most were the usual suspects: Delhi, Mumbai, Bengaluru, Hyderabad, and a handful of state capitals.

The expansion from 19 to 275 cities is a 14x increase. But India has over 500 cities with populations above 100,000. Nearly half of India's significant urban centres are still invisible to the national monitoring system.

Cities that got their first monitoring station only after 2020 include places like Mangalore, Puducherry, Bilaspur, Gorakhpur, and Darbhanga. These are not small towns. Mangalore has a population over 6 lakh. The fact that it had zero air quality data before 2021 is a blind spot in both research and public health.

The Delhi Effect: 39 Stations in One City

Delhi dominates the network. With 39 stations, it accounts for 7% of all CPCB stations nationwide, more than most entire states.

Kolkata stands out for the wrong reasons. A metro of 15 million people with just 7 stations. Compare that to Delhi's 39 for a similar-sized population. The WHO recommends one monitoring station per 200,000-300,000 urban residents for meaningful coverage. By that standard, Kolkata would need 50-75 stations. Chennai would need 37-55. Even Delhi, with all its stations, should have 63-95.

State-by-State: When the Rest of India Joined

The monitoring rollout was not uniform. The 11 pioneer states that had stations in 2016 were mostly the large, industrialized ones: Delhi, Maharashtra, Karnataka, Uttar Pradesh, Bihar, Haryana, Rajasthan, Telangana, Gujarat, West Bengal, and Andhra Pradesh.

Maharashtra had the most explosive growth, going from 3 stations in 2016 to 88 in 2024. That is a 29x increase. Most of that expansion happened in 2024 itself, when the state added monitoring to dozens of Tier 2 and Tier 3 cities.

Rajasthan is another striking example. One station in 2016 (Jaipur), then steady at 10 for years, before jumping to 29 in 2023 and 45 in 2024. The state clearly decided to invest late but hard.

The Northeast Gap

India's Northeastern states were the last to get air quality monitoring, and the coverage remains paper-thin.

Seven Northeastern states, combined population of ~50 million, share 18 monitoring stations covering 12 cities. Nagaland still has zero. Assam is the only Northeastern state with anything approaching real coverage, and even there, 6 cities with 9 stations leaves most of the state unmonitored.

The irony? Northeastern India has unique air quality challenges that go completely unmeasured: jhum (slash-and-burn) cultivation smoke, brick kiln emissions in Assam's Brahmaputra valley, and cross-border pollution from Myanmar and Bangladesh.

The Single-Station Problem

Here is perhaps the most telling statistic in the entire dataset.

77% of monitored cities rely on a single station. One sensor, one location, one reading representing an entire city. If that station sits near a park, the city looks clean. If it is next to a highway, the city looks polluted. Neither tells the full story.

A single station for a city like Gorakhpur (population 7 lakh) or Mangalore (population 6 lakh) is barely better than no monitoring at all. Air quality varies dramatically between a city's industrial area and its residential zones, between windward and leeward sides, between ground level and elevated locations.

How Much Data Are We Actually Getting?

More stations do not help if they are not recording data consistently. Here is how the reporting actually looks.

A station reporting 365 readings a year means perfect daily coverage. The average across all years hovers around 260-300, meaning roughly 70-80% uptime. That is not terrible by developing-country standards, but it means a month of missing data is entirely normal for any given station.

2017 stands out with an average of just 133 readings per station, suggesting many of the 55 new stations added that year were operational for only part of the year, still running into setup issues.

By 2024, the average improved to 303 readings per station. That signals maturing infrastructure and more reliable data pipelines.

What It All Means

India's air quality monitoring network has come a long way. Going from 30 stations tracking 19 cities to 551 stations across 275 cities in nine years is real progress that deserves acknowledgment.

The good news is that the trajectory is clear. 85 new stations came online in 2024 alone. Maharashtra nearly tripled its network in a single year. If this pace continues, India could have 700+ active stations by 2026.

The better question is whether traditional CPCB stations are even the right answer at this scale. At ₹1-2 crore per station, monitoring 500 cities with 3-5 stations each would cost ₹1,500-5,000 crore. Low-cost sensor networks, which can deploy 10-20 sensors per city at a fraction of the cost, are increasingly being discussed as a complement to the CPCB backbone. Read more about emerging air quality technology and the potential of sensor networks.

For now, the CPCB network remains the gold standard for official data. And the story it tells is one of slow but steady expansion from a handful of stations in a handful of cities to something that at least tries to cover the country. The next chapter needs to be about filling the gaps, because you cannot fix what you cannot measure.

Check the live AQI rankings for India's cities, or look up your city's current air quality to see the data these stations are generating right now.