Every November, the same thing happens. The sky over north India turns a dull grey, your throat feels scratchy by evening, and the family WhatsApp group fills up with AQI screenshots.
So which places actually have the dirtiest air on the planet? The Swiss air-quality company IQAir answered that in its World Air Quality Report 2025, released in March 2026. Here are the top 10 most polluted cities in the world from that report, with their yearly PM2.5 numbers, what is driving the smog in each one, and what it means for you.
Quick Answer: The Top 10 at a Glance
- Loni, India: 112.5 µg/m³, the world’s most polluted city in 2025.
- Hotan, China: 109.6 µg/m³, choked mainly by desert dust.
- Byrnihat, India: 101.1 µg/m³, an industrial town on the Assam-Meghalaya border.
- Delhi, India: 99.6 µg/m³, the capital region’s long-running smog problem.
- Faisalabad, Pakistan: 98.8 µg/m³, a big industrial city in Punjab.
- Rahim Yar Khan, Pakistan: 92.6 µg/m³, better than 2024 but still severe.
- Ghaziabad, India: 89.2 µg/m³, Loni’s NCR neighbour.
- Lahore, Pakistan: 88.9 µg/m³, famous for its winter smog.
- Sukkur, Pakistan: 88.6 µg/m³, a Sindh city that improved but stays in the top 10.
- Ula (Birnagar), India: 86.8 µg/m³, a small West Bengal town that surprised many.
For context, the World Health Organization’s guideline for yearly PM2.5 is just 5 µg/m³. Every city on this list is more than 17 times over it.
Most Polluted Cities in the World 2025: Comparison Table
| Rank | City | Country | 2025 PM2.5 (µg/m³) | 2024 PM2.5 (µg/m³) | Times WHO limit |
|---|---|---|---|---|---|
| 1 | Loni | India | 112.5 | 91.7 | ~22x |
| 2 | Hotan | China | 109.6 | 84.5 | ~22x |
| 3 | Byrnihat | India | 101.1 | 128.2 | ~20x |
| 4 | Delhi | India | 99.6 | 108.3 | ~20x |
| 5 | Faisalabad | Pakistan | 98.8 | 88.8 | ~20x |
| 6 | Rahim Yar Khan | Pakistan | 92.6 | 134.3 | ~19x |
| 7 | Ghaziabad | India | 89.2 | 74.5 | ~18x |
| 8 | Lahore | Pakistan | 88.9 | 102.1 | ~18x |
| 9 | Sukkur | Pakistan | 88.6 | 129.1 | ~18x |
| 10 | Ula | India | 86.8 | Not ranked | ~17x |
1. Loni, Uttar Pradesh: The World’s Most Polluted City
Loni, in Ghaziabad district on Delhi’s north-eastern edge, averaged 112.5 µg/m³ of PM2.5 across 2025. That is the highest of more than 9,000 cities in IQAir’s database, and roughly 23% worse than its 2024 reading of 91.7.
The report notes that Loni saw extreme pollution spikes in March, April and December. It sits in the same airshed as Delhi, so it gets the full NCR mix: heavy traffic, small industries, construction dust and winter weather that traps smoke close to the ground.
Good to know:
- Loni was not the top city in 2024. Its jump to number one shows how fast a fringe town can overtake a big metro.
- India’s own national standard for yearly PM2.5 is 40 µg/m³. Loni is nearly three times that.
- If you live or work in trans-Hindon areas, winter mornings and late evenings are usually the worst hours to be outdoors.
2. Hotan, China: Dust From the Desert Next Door
Hotan, an oasis city in Xinjiang, recorded 109.6 µg/m³ in 2025, up from 84.5 the year before. It is the only city outside South Asia in this top 10.
Hotan’s problem is mostly natural. It sits on the southern edge of the Taklamakan Desert, and dust storms can roll in quickly, sometimes cutting visibility to under 100 metres. Spring is the peak season. Older vehicles and local industry add to it, but desert dust is the main driver.
That makes Hotan a useful reminder: not all PM2.5 comes from chimneys and exhausts. It also means fixing it is harder, because you cannot switch off a desert.
- Main source: sand and dust storms.
- Worst months: spring, especially March and April.
- Big picture: China overall has improved a lot over the past decade, but dust-prone western cities remain outliers.
3. Byrnihat, Meghalaya: A Small Town With a Big Industrial Problem
Byrnihat topped the 2024 list at 128.2 µg/m³. In 2025 it improved to 101.1 but still came third worldwide. It sits right on the Assam-Meghalaya border, about 20 to 25 km from Guwahati.
Reports from Mongabay India and Climate Fact Checks point to a cluster of 80-odd industrial units on both sides of the border, including cement plants, coke units and sponge iron factories. Heavy trucks on NH-40, which runs through the town, unpaved roads and hills that trap pollutants make it worse. A Meghalaya pollution board draft found road dust was the biggest PM10 source and industry the biggest PM2.5 source.
The town has become a talking point between the two states, and the Meghalaya High Court has pulled up the state pollution board over delays.
- Why it matters: it proves severe pollution is not just a north Indian plains issue.
- Positive sign: a drop of about 27 µg/m³ in one year.
4. Delhi: Still the Most Polluted Capital Region
Delhi averaged 99.6 µg/m³ in 2025, slightly better than 108.3 in 2024. IQAir lists New Delhi separately at 82.2 µg/m³, a three-year low, but it is still the most polluted capital city in the world for the eighth year running.
The report flags a big April dust storm that pushed Delhi’s PM2.5 up by 15% that month. Then there is the familiar winter mix: vehicle exhaust, industry, construction dust, stubble burning in neighbouring states and cold, still air that keeps it all hanging over the city.
Delhi-NCR uses the Graded Response Action Plan (GRAP), which brings in bans on construction, curbs on trucks and older vehicles, and sometimes school closures when AQI crosses set levels. Critics call these steps reactive rather than long-term fixes.
- Worst season: late October to January.
- Small win: the yearly average dropped about 8% from 2024.
5. Faisalabad, Pakistan: Textile Hub Under a Grey Sky
Faisalabad, Pakistan’s third-largest city and a major textile centre, posted 98.8 µg/m³ in 2025, worse than its 2024 figure of 88.8. Pakistan as a whole was the most polluted country in the 2025 report, at 67.3 µg/m³.
Research cited by Pakistan’s PIDE think tank names fast industrial growth, unplanned urban spread, a growing number of vehicles running on low-quality fuel, and brick kilns as the main drivers in Punjab’s cities. A 2018 FAO study it quotes put transport at 43% of PM2.5 emissions, industry at 25% and crop burning at around 20%.
In October 2025, Faisalabad’s daily AQI hit 253, among the highest in Punjab that week, according to Pakistani media.
6. Rahim Yar Khan, Pakistan: A Big Drop, Still in the Top 10
Rahim Yar Khan, in southern Punjab, was among the very worst in 2024 at 134.3 µg/m³. In 2025 it fell sharply to 92.6, yet still ranked sixth in the world.
IQAir’s lead author Christi Chester Schroeder has said big year-to-year swings can often be put down to weather patterns such as wind or rain. So a drop like this is welcome, but it does not automatically mean the sources have been fixed.
Like the rest of Pakistani Punjab, the city deals with farm residue burning, brick kilns and vehicle smoke, especially during the winter smog season.
7. Ghaziabad, Uttar Pradesh: NCR’s Second Name on the List
Ghaziabad averaged 89.2 µg/m³ in 2025, a clear rise from 74.5 in 2024. Together with Loni, which is part of the same district, it gives Ghaziabad district two spots in the global top 10.
The city shares Delhi’s airshed and many of its problems: industrial areas, heavy freight traffic, ongoing construction and the winter inversion layer that acts like a lid over the plains. The report says vehicle emissions, industry, crop residue burning and construction dust remained the dominant sources across India.
- Who should care most: daily commuters on NH-9 and Delhi-Meerut Expressway routes, kids and older family members.
- Tip: check the CPCB Sameer app before outdoor plans in winter.
8. Lahore, Pakistan: The Smog Capital of Punjab
Lahore improved from 102.1 µg/m³ in 2024 to 88.9 in 2025, slipping to eighth. Its winter smog still makes international headlines almost every year, with schools shut and flights hit.
Pakistani officials and experts list traffic, brick kilns and small factories burning tyres and plastic as fuel as major local causes. Temperature inversion in winter traps the smoke near the ground. Crop burning on both sides of the border adds to it, though experts in Pakistan stress it is one cause among many, not the only one.
Lahore and Delhi are a good example of how air does not respect borders. Punjab on both sides of the Wagah line breathes much the same winter air.
9. Sukkur, Pakistan: Improved, But Not Enough
Sukkur, a city on the Indus in Sindh province, dropped from 129.1 µg/m³ in 2024 to 88.6 in 2025. That is one of the biggest single-year improvements in the top 10, yet it still lands at number nine.
IQAir’s report does not break down city-by-city sources for Sukkur. As with Rahim Yar Khan, weather can explain part of a swing this large, so one good year is not proof of a lasting fix.
Four Pakistani cities in the top 10 tells you how serious the problem is across the Indus plains, not just in Lahore.
10. Ula (Birnagar), West Bengal: The Surprise Entry
Ula, also known as Birnagar, in West Bengal, closes the list at 86.8 µg/m³. It did not feature in the 2024 rankings, so its arrival caught many people off guard.
Its entry is a sign that pollution is not just a Delhi-NCR or north Indian story. The Indo-Gangetic plain stretches all the way to Bengal, and the same winter conditions that trap smoke over Delhi also affect towns further east.
Newer monitors in smaller towns also mean we are now seeing places that were simply not measured before. Expect more such surprises in future reports.
How We Picked This List
We did not make our own ranking. This list follows the city table in IQAir’s World Air Quality Report 2025, which ranks cities by their yearly average PM2.5 concentration. The report covers 9,446 cities in 143 countries and territories, using data from more than 40,000 government monitoring stations and low-cost sensors.
We cross-checked the numbers and locations with coverage in The Wire, Business Today, Outlook, Drishti IAS and Vajiram & Ravi, and used Mongabay India, Climate Fact Checks, Dawn and PIDE for local causes. Where we could not confirm a cause for a city, we left it out instead of guessing.
5 Myths About Air Pollution in India
- “It is only bad during Diwali.” Loni and Delhi had serious spikes in March and April too. Pollution is a year-round problem that just peaks in winter.
- “Stubble burning is the main cause.” It matters for a few weeks, but the report says vehicles, industry and construction dust stay dominant all year.
- “Small towns have clean air.” Byrnihat and Ula prove otherwise.
- “An indoor plant will clean my room.” Plants look nice, but they cannot match a proper HEPA air purifier for PM2.5.
- “Any mask works.” Cloth and surgical masks do little against fine particles. A well-fitted N95 or N99 is what helps.
One more number worth knowing: India’s National Clean Air Programme aims to cut pollution by 40% by 2025-26. But the IQAir report says 64% of its funding has gone to road dust, and only 1% to industrial pollution.
Our Take
Five Indian cities in the top 10, nine in the top 20 and, according to the report coverage, 66 in the top 100. India ranks sixth among countries at 48.9 µg/m³. That is not a list any of us wants to be on.
Loni is the headline, but the real story is spread: from Ghaziabad to Byrnihat to a small town in Bengal. Some cities improved, mostly helped by weather. Until vehicles, industry and coal power get real attention, the winter AQI screenshots will keep coming.
FAQs
Which is the most polluted city in the world in 2025?
Loni in Ghaziabad district, Uttar Pradesh, with a yearly average PM2.5 of 112.5 µg/m³, according to IQAir’s World Air Quality Report 2025.
How many Indian cities are in the top 10 most polluted cities?
Five: Loni, Byrnihat, Delhi, Ghaziabad and Ula. Pakistan has four and China has one.
Which is the most polluted country in the world?
Pakistan, at 67.3 µg/m³, followed by Bangladesh, Tajikistan, Chad and DR Congo. India is sixth at 48.9 µg/m³.
What is a safe PM2.5 level?
The WHO guideline for yearly average PM2.5 is 5 µg/m³. India’s national standard is 40 µg/m³. Only 13 countries and territories met the WHO guideline in 2025.
Is Delhi still the most polluted capital?
Yes. New Delhi was the most polluted capital city for the eighth year in a row, though its 2025 average of 82.2 µg/m³ was a three-year low.
Sources: IQAir World’s Most Polluted Cities and the IQAir World Air Quality Report 2025, plus reporting by The Wire, Mongabay India and Dawn. Figures are yearly averages for 2025 as published in March 2026; live AQI changes daily. This is general information, not medical advice.
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