Countries With the Most Polluted Air in the World
Air pollution is one of the biggest environmental and public-health challenges facing the world today. From dense urban smog and vehicle exhaust to industrial emissions, agricultural burning, wildfires, dust and household fuels, millions of people are exposed to unhealthy air every day.
One of the best ways to compare air pollution between countries is by looking at annual average PM2.5 concentrations. PM2.5 refers to extremely small particles that can penetrate deep into the lungs and even enter the bloodstream.
According to the latest 2025 World Air Quality Report from IQAir, Pakistan had the highest annual average PM2.5 concentration among countries and territories measured, followed closely by Bangladesh and Tajikistan.
What Is PM2.5?
PM2.5 stands for particulate matter measuring 2.5 micrometers or smaller. These particles can come from vehicle exhaust, coal and other fossil-fuel combustion, industrial activity, construction, agricultural burning, wildfires and dust.
Because PM2.5 particles are so small, they can travel deep into the respiratory system. The World Health Organization identifies particulate matter as one of the most important air pollutants affecting human health.
The WHO’s annual guideline for PM2.5 is 5 micrograms per cubic meter (µg/m³).
That means countries with annual averages many times higher than 5 µg/m³ are experiencing extremely elevated levels of fine-particle pollution.
Top 10 Countries With the Most Polluted Air
The following ranking is based on 2025 annual average PM2.5 concentrations reported by IQAir.
| Rank | Country | 2025 Average PM2.5 |
|---|---|---|
| 1 | Pakistan | 67.3 µg/m³ |
| 2 | Bangladesh | 66.1 µg/m³ |
| 3 | Tajikistan | 57.3 µg/m³ |
| 4 | Chad | 53.6 µg/m³ |
| 5 | Democratic Republic of the Congo | 50.2 µg/m³ |
| 6 | India | 48.9 µg/m³ |
| 7 | Afghanistan | 48.0 µg/m³ |
| 8 | Mongolia | 45.6 µg/m³ |
| 9 | Egypt | 40.6 µg/m³ |
| 10 | Uganda | 40.0 µg/m³ |
The ranking is based on annual average PM2.5 concentration, not a real-time AQI reading.
1. Pakistan
Pakistan ranked as the world’s most polluted country in 2025, recording an annual average PM2.5 concentration of 67.3 µg/m³.
That level is more than 13 times the WHO annual guideline of 5 µg/m³.
Major sources of air pollution in Pakistan include vehicle emissions, industrial activity, brick kilns, agricultural burning, household fuel use and dust. Large cities can experience particularly severe smog episodes during certain times of the year.
The country’s position at the top of the 2025 ranking highlights the serious challenge Pakistan faces in improving urban and regional air quality.
2. Bangladesh
Bangladesh ranked second, with an annual average PM2.5 concentration of 66.1 µg/m³.
The country has several factors that contribute to poor air quality, including traffic, construction, industrial emissions, brick manufacturing and seasonal burning.
Dhaka and other densely populated areas can experience particularly poor air quality because large populations, traffic and industrial activity are concentrated in relatively small areas.
3. Tajikistan
Tajikistan ranked third with an annual average PM2.5 concentration of 57.3 µg/m³.
The country’s mountainous geography, urban emissions, heating needs, dust and other pollution sources can contribute to elevated particulate concentrations.
Its 2025 average was more than 11 times the WHO guideline.
4. Chad
Chad recorded an annual average PM2.5 concentration of 53.6 µg/m³, placing it fourth worldwide.
Unlike some heavily industrialized countries, Chad’s air pollution problem is strongly influenced by dust and other particulate sources, along with combustion and household activities.
The country’s dry environment can make airborne dust an important contributor to particulate pollution.
5. Democratic Republic of the Congo
The Democratic Republic of the Congo ranked fifth, with an annual average PM2.5 concentration of 50.2 µg/m³.
Sources of pollution can include household fuel combustion, transportation, industrial activity, waste burning and other forms of biomass burning.
The country’s ranking also demonstrates that severe air pollution is not limited to highly industrialized nations.
6. India
India ranked sixth in the 2025 country ranking, with an annual average PM2.5 concentration of 48.9 µg/m³.
India has some of the world’s most polluted cities, and air quality can deteriorate dramatically during severe pollution episodes.
Traffic, industrial emissions, construction, power generation, agricultural burning, household fuels and dust all contribute to India’s air-quality challenges.
According to IQAir, Loni, India, was the world’s most polluted city in 2025, with an annual average PM2.5 concentration of 112.5 µg/m³.
7. Afghanistan
Afghanistan recorded an annual average PM2.5 concentration of approximately 48.0 µg/m³ in 2025, placing it among the countries with the highest measured pollution levels.
Dust, vehicle emissions, household fuel use and other combustion sources can contribute to poor air quality.
8. Mongolia
Mongolia ranked among the world’s most polluted countries, with an annual average PM2.5 concentration of approximately 45.6 µg/m³ in 2025.
Mongolia’s harsh winters are an important factor in its air-quality problems, particularly around Ulaanbaatar. Heating fuels and winter weather conditions can cause pollutants to become trapped close to the ground.
9. Egypt
Egypt recorded an annual average PM2.5 concentration of approximately 40.6 µg/m³ in 2025.
Dust is an important factor, while traffic, industrial activity, construction and other emissions can further contribute to poor air quality.
10. Uganda
Uganda rounded out the top 10, with an annual average PM2.5 concentration of approximately 40.0 µg/m³ in 2025.
Household cooking fuels, transportation, waste burning, dust and other combustion sources contribute to air pollution in parts of the country.
Why Is Air Pollution So Bad in Some Countries?
There isn’t one single cause of air pollution. Several factors often combine to create unhealthy conditions.
Vehicle Exhaust
Cars, buses, motorcycles and trucks can release particulate matter and gases such as nitrogen dioxide.
Countries with rapidly growing cities and large numbers of older or poorly maintained vehicles can experience significant traffic-related pollution.
Industrial Pollution
Factories, power plants, refineries, steel production and other industrial operations can release particulate matter and gases into the atmosphere.
Coal and Fossil Fuels
Burning coal, oil and other fossil fuels can produce particulate matter, sulfur dioxide, nitrogen oxides and other pollutants.
Agricultural Burning
Farmers sometimes burn crop residues after harvest. Smoke from these fires can spread over large areas and contribute significantly to seasonal air pollution.
Household Cooking and Heating
Indoor and household pollution can also affect outdoor air quality. Burning wood, charcoal, coal or other polluting fuels produces smoke and fine particles.
The WHO estimates that 2 billion people primarily relied on polluting fuels and technologies for cooking in 2024.
Wildfires
Wildfires can produce enormous amounts of smoke and PM2.5. Smoke can travel hundreds or even thousands of miles, affecting communities far from the original fire.
Dust
Dust storms and naturally occurring dust can significantly increase particulate pollution, particularly in dry and desert regions.
How Dangerous Is PM2.5?
PM2.5 is particularly concerning because the particles are small enough to travel deep into the lungs.
The WHO says exposure to air pollution is associated with serious health problems including heart disease, stroke, chronic obstructive pulmonary disease, lung cancer and respiratory infections.
Short-term exposure to high concentrations can also aggravate asthma, reduce lung function and increase respiratory problems.
Children, older adults and people with existing health problems can be particularly vulnerable.
How Many People Are Exposed to Unsafe Air?
Air pollution is not just a problem in the countries at the top of the ranking.
The WHO estimates that 99% of the world’s population lives in places where air pollution exceeds its recommended guideline levels for fine particulate matter.
IQAir’s 2025 report similarly found that 130 of 143 countries and territories, or about 91%, exceeded the WHO annual PM2.5 guideline. Only 13 countries or territories met the guideline in the report.
This shows that air pollution is a global problem, even though some countries experience much higher concentrations than others.
Which Country Has the Cleanest Air?
The opposite end of the ranking is also interesting.
According to IQAir’s 2025 report, only 13 countries and territories met the WHO annual PM2.5 guideline of 5 µg/m³. They included Australia, Estonia, Iceland, Grenada, Panama, Andorra, Barbados, French Polynesia, Puerto Rico, the U.S. Virgin Islands, New Caledonia, Bermuda and Réunion.
The report also identified Nieuwoudtville, South Africa, as the world’s cleanest city in 2025, with an annual average PM2.5 concentration of just 1.0 µg/m³.
Why Air Pollution Rankings Can Change
Country rankings can change significantly from one year to another.
Weather, wildfires, dust storms, agricultural burning, economic activity, industrial production and changes in monitoring coverage can all affect annual pollution measurements.
For example, Chad ranked first in the 2024 IQAir report with an annual average of 91.8 µg/m³, but Pakistan moved into first place in the 2025 report.
This is why a country’s position on a pollution ranking should not necessarily be interpreted as a permanent label.
What Can Countries Do to Reduce Air Pollution?
Governments can reduce air pollution through a combination of policies and investments, including:
- Expanding clean and renewable energy
- Reducing coal and other high-pollution fuels
- Improving public transportation
- Promoting electric vehicles
- Enforcing industrial emissions standards
- Reducing agricultural burning
- Improving waste management
- Providing cleaner cooking and heating technologies
- Expanding air-quality monitoring networks
- Protecting and expanding urban green spaces
- Implementing pollution-control measures during severe smog events
Individuals can also reduce their exposure by checking local air-quality forecasts, limiting strenuous outdoor activity during severe pollution events and using appropriate indoor air filtration when necessary.
The Bottom Line
The world’s most polluted countries demonstrate how complicated the global air-pollution problem has become.
Based on 2025 annual average PM2.5 concentrations, Pakistan ranked first, followed by Bangladesh, Tajikistan, Chad and the Democratic Republic of the Congo.
But air pollution is not limited to these countries. With 99% of the world’s population exposed to air pollution levels above WHO guideline limits, cleaner air remains a global challenge.
Improving air quality can save lives, reduce disease and make cities healthier places to live. The good news is that air pollution can be reduced when governments, businesses and communities invest in cleaner energy, transportation, industry and household technologies.
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