Asia hosts the highest number of polluted cities, with 83 located in a single nation.

Asia is home to all but one of the 100 cities with the world’s worst air pollution, and a staggering 83 of those cities are in India, according to a 2023 report by IQAir. That means the vast majority of the planet’s most polluted urban areas are concentrated in a single country, and every one of those Indian cities exceeded the World Health Organization’s air quality guidelines by more than ten times. To put that in perspective, the WHO recommends average annual levels of PM2.5 — the tiniest and most dangerous form of particulate matter — should not exceed 5 micrograms per cubic meter. Many of these cities recorded levels well above 100.

This isn’t just a statistic about one country. The data reveals a broader pattern across South Asia, where 29 of the 30 most polluted cities are located in India, Pakistan, or Bangladesh. The report also found that air pollution trends in Southeast Asia are mixed, with the Philippines being the only country in the region to see a drop in annual pollution levels compared to the previous year. Understanding why pollution is so concentrated in this part of the world, and what it means for the people living there, requires looking at the specific pollutant involved, the sources driving it, and the regional dynamics at play.

What PM2.5 is and why it dominates these rankings

The IQAir report focuses specifically on PM2.5 because it is the most dangerous common air pollutant. When inhaled, these particles travel deep into lung tissue where they can enter the bloodstream. The health consequences are well-documented: PM2.5 has been linked to asthma, heart and lung disease, cancer, and cognitive impairment in children. IQAir Global CEO Frank Hammes noted that in the most polluted countries, air pollution is “likely shaving off anywhere between three to six years of people’s lives.”

What makes the situation in South Asia particularly severe is the combination of high population density, heavy reliance on fossil fuels for energy and transportation, and seasonal agricultural practices. The report found that Central and South Asia were the worst-performing regions globally, home to all four of the most polluted countries: Bangladesh, Pakistan, India, and Tajikistan. The scale of exposure is enormous — across India, 1.3 billion people, or 96 percent of the population, live with air quality seven times higher than WHO guidelines.

How the climate crisis is making air pollution worse

The IQAir report identifies the human-caused climate crisis as playing a “pivotal” role in influencing air pollution levels. This is not a separate issue — the two are deeply connected. The burning of fossil fuels releases both greenhouse gases and PM2.5, meaning the same activities that drive climate change also directly poison the air. But the relationship goes further: climate change alters weather patterns, including wind and rainfall, which affects how pollutants disperse. When wind patterns stall or rainfall decreases, pollution accumulates in the air rather than being cleared away.

Extreme heat, which is becoming more severe and frequent due to climate change, also worsens pollution. Higher temperatures can accelerate the chemical reactions that form ground-level ozone and other secondary pollutants. Additionally, the climate crisis is leading to more severe wildfires in many regions, which release massive amounts of PM2.5. In 2023, Canadian wildfires caused monthly average air pollution in Alberta to spike to nine times greater than the same month in 2022. Those fires also affected US cities like Minneapolis and Detroit, where annual pollution averages rose by 30 to 50 percent compared to the previous year.

In South Asia, the climate crisis is also lengthening and intensifying pollen seasons, which compounds respiratory health issues for populations already breathing hazardous air. The overlap between the causes of climate change and air pollution means that solutions targeting one often help the other, but it also means that progress on either front requires confronting the same fundamental drivers.

What gets missed in the global rankings

While the headline figure of 83 Indian cities in the top 100 is striking, several important nuances are easy to overlook. First, China used to dominate these rankings. A decade ago, Chinese cities routinely topped lists of the world’s worst air quality. However, a sustained campaign of clean air policies over the past decade has transformed the situation dramatically. A study last year found that this campaign meant the average Chinese citizen’s lifespan is now 2.2 years longer. But the progress is fragile — thick smog returned to Beijing in 2023, where citizens experienced a 14 percent increase in the annual average PM2.5 concentration.

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Second, the report highlights that indoor air pollution is a parallel crisis that often gets overlooked. Hammes noted that “the things that are causing outdoor air pollution are also sometimes the things that are causing indoor air pollution. So cooking with dirty fuel will create indoor exposures that could be many times what you’re seeing outdoors.” In many parts of South Asia and sub-Saharan Africa, households rely on solid fuels like wood, coal, or dung for cooking and heating, creating dangerous indoor PM2.5 levels that affect women and children most directly.

Third, the regional picture within Asia is not uniform. While South Asia dominates the worst rankings, Southeast Asia tells a more varied story. Indonesia was the most polluted country in the region, with a 20 percent increase in PM2.5 compared to 2022. Indonesia, Vietnam, and Thailand all had cities that exceeded WHO guidelines by more than ten times. In Thailand, authorities ordered government employees to work from home due to unhealthy pollution levels in Bangkok, and the tourist destination of Chiang Mai was briefly the world’s most polluted city due to seasonal agricultural burning. Only the Philippines saw a drop in annual pollution levels compared to the previous year, though it still faces significant challenges from vehicle emissions like those from jeepneys.

What can be done about air pollution in South Asia

Addressing air pollution at the scale seen in India and its neighbours requires action on multiple fronts, and the IQAir report makes clear that no single intervention will be sufficient. Hammes stated that significant improvement is unlikely without “major changes in terms of the energy infrastructure and agricultural practices.” Here is what those changes look like in practice.

Transitioning the energy sector away from fossil fuels

Coal-fired power plants are a major source of PM2.5 in India, which is the world’s second-largest coal consumer after China. Shifting to renewable energy sources like solar and wind would reduce both PM2.5 emissions and greenhouse gases. India has set ambitious renewable energy targets, but implementation has been uneven. The process involves retiring old coal plants, investing in grid infrastructure to handle variable renewable supply, and providing incentives for rooftop solar adoption. For households, this also means transitioning away from kerosene lamps and diesel generators, which contribute to both indoor and outdoor pollution.

Reforming agricultural burning practices

Seasonal agricultural burning, particularly of rice stubble in northern India and Pakistan, creates massive pollution spikes that blanket entire regions. The practice is quick and cheap for farmers, but the health costs are enormous. Alternatives include using mechanical equipment to incorporate stubble into the soil, converting crop residue into biofuel, or providing financial incentives for farmers to adopt no-burn methods. The Indian government has subsidised machinery for stubble management, but adoption remains low due to cost and availability issues. Enforcement of burning bans has been inconsistent, and the problem requires coordination across state and national borders since smoke does not respect administrative boundaries.

Strengthening vehicle emission standards and public transport

Vehicle emissions are a major source of PM2.5 in urban areas across South Asia. India has moved to Bharat Stage VI emission standards, which are equivalent to Euro 6, but the vehicle fleet is large and old. Retrofitting older vehicles, scrapping those that cannot meet standards, and expanding public transit systems are all necessary. Cities like Delhi have experimented with odd-even driving restrictions and congestion pricing, but these measures have had limited impact without complementary investments in metro rail, bus rapid transit, and non-motorised transport infrastructure. The challenge is compounded by rapid urbanisation, which increases vehicle numbers faster than controls can be implemented.

Addressing indoor air pollution from cooking fuels

For the hundreds of millions of households in South Asia that still cook with solid fuels, the solution is a transition to clean cooking options like liquefied petroleum gas (LPG), biogas, or electric induction stoves. India’s Pradhan Mantri Ujjwala Yojana scheme has provided millions of households with free LPG connections, but sustained use remains a challenge due to the recurring cost of refills. Programs that combine fuel subsidies with behaviour change communication and improved stove designs have shown promise, but the scale of the problem means progress is measured in decades, not years.

Frequently asked questions about the world’s most polluted cities

What this means for the region’s future

The concentration of the world’s worst air pollution in South Asia is not an accident of geography. It is the result of policy choices, economic priorities, and infrastructure investments made over decades. The IQAir report makes clear that without major changes to energy infrastructure and agricultural practices, significant improvement is unlikely. The health toll is already staggering — millions of deaths each year from air pollution-related illnesses, with the WHO estimating 6.7 million annual deaths from combined ambient and household air pollution. For the 1.3 billion people in India alone who breathe air seven times above WHO guidelines, the question is not whether action is needed, but whether it will come fast enough to prevent the worst outcomes. If this was useful, you might also want to read how government policy shapes pollution trends in the Philippines.

Sources

Smog chokes cities as air pollution worsens in the Philippines — A closer look at how Philippine cities compare to the global trends discussed in this article.

Jeepney emissions worsen Filipino air pollution — Examines one specific source of PM2.5 in the Philippines and what is being done about it.

The world’s 100 worst polluted cities are in Asia and 83 of them are in just one country. AccuWeather / IQAir, 2024.

World’s 100 worst polluted cities – in Asia 83 of them in one country. Caliber, 2024.