The 2025 World Air Quality Report reveals the persistent global challenge posed by high concentrations of air pollution.
Unhealthy air remains a daily reality for residents in some of the world’s most polluted urban centers. Tens of millions of people live in these cities and are exposed to elevated risks of respiratory and cardiovascular conditions over time (1).
Many residents in these cities also face economic and social challenges that can compound the effects of long-term exposure to air pollution, challenges that are further compounded by exposure to industrial emissions, vehicular pollution, agricultural burning, and inadequate regulatory enforcement. Air pollution is an unequal burden for these residents, and for particularly vulnerable populations such as children, the elderly, and individuals with pre-existing health conditions, like asthma.
5. Kinshasa, Democratic Republic of the Congo
Kinshasa, the capital of the Democratic Republic of the Congo (DRC), ranked fifth among the world’s most polluted major cities in 2025. With an average annual PM2.5 concentration of 50.2 µg/m3, the city’s air quality remains in the hazardous air quality range as it has in prior years, continuing to pose serious health risks to city residents.
Air quality in Kinshasa, DRC on April 20, 2026. Source: IQAir.
Air pollution in Kinshasa can come from both indoor and outdoor sources. Indoor cooking with wood and charcoal, a common practice in many households, contributes significantly to airborne particulate matter. Forest fires, often linked to agricultural clearing and land management, release clouds of smoke into the atmosphere. Industrial activities and regional agricultural burning also contribute to poor air quality, compounded by limited regulatory oversight and enforcement.
One of the biggest challenges to mitigating pollution is the lack of reliable air quality monitoring infrastructure in the DRC. While some monitoring stations exist, the DRC—like much of Africa—lacks the comprehensive networks needed to accurately track pollution levels and inform public health responses.
4. Kolkata, India
Kolkata, India, was one of the world’s most polluted urban centers in 2025. With an average annual PM2.5 concentration of 51 µg/m3, it’s the city’s worst average since 2021’s annual average of 59 µg/m3.
This change reflects regional trends, where rapid industrialization, vehicular emissions, and seasonal agricultural burning frequently create a haze that lingers over the city for much of the year.
Air quality in Kolkata, India on April 21, 2026. Source: IQAir.
Kolkata’s air pollution sources are deeply rooted in both local and regional activities. Vehicle emissions, industrial activity, construction dust, and unregulated waste burning add to the burden (2). During the winter months, crop residue burning in neighboring states and across the Indo-Gangetic Plain compounds the problem.
3. Dhaka, Bangladesh
Dhaka, the capital of Bangladesh, returned as the world’s third most polluted major city in 2025, with an average annual PM2.5 concentration of 68 µg/m3.
While Dhaka has experienced an improvement in average annual PM2.5 over 2024 and 2023 (measuring annual average concentrations of 78 and 80.2 µg/m3 respectively), its air quality remains far above safe levels.
Persistent air quality challenges continue to affect residents’ health. Exposure to PM2.5, particulate matter measuring 2.5 microns in diameter or smaller, has been linked to respiratory diseases, heart conditions, stroke, and cancer (3).
Air quality in Dhaka, Bangladesh on April 22, 2026. Source: IQAir.
Informal brick kilns, which number in the thousands across Bangladesh, contributes an estimated 11% of the nation’s PM2.5 emissions and an additional 17% of its carbon dioxide (4). An estimated 6,000 premature deaths can be attributed to brick kiln air pollutants despite government efforts to shut down illegal operations and promote cleaner technologies like zigzag kilns. Industrial activity and diesel generators further impact air quality, while seasonal crop burning in rural areas adds to the city’s winter smog (5). Vehicle emissions, driven by a growing number of cars and buses on Dhaka’s streets, are also a major source of airborne pollutants.
2. Lahore, Pakistan
Pakistan’s cultural and economic hub, Lahore, is again ranked the world’s second most polluted major city, with an average annual PM2.5 concentration of 88.9 µg/m3.
While the PM2.5 concentration is an improvement over 2024’s average annual PM2.5 concentration of 102.1 µg/m3, the city’s high average contributed to Pakistan ranking as the most polluted country in 2025. The health impact from exposure to high concentrations of PM2.5 is significant; 70% of Pakistanis report smog-related health issues (6).
Air quality in Lahore, Pakistan on April 20, 2026. Source: IQAir.
Seasonal crop burning in Punjab Province blankets Lahore in thick smog. Vehicular emissions, exacerbated by an aging fleet and weak enforcement of emission standards, contribute significantly to the problem. Industrial activity, dust from construction and brick kilns, many of which operate without pollution controls, further degrade air quality (7)(8).
1. Delhi, India
Delhi, India’s sprawling capital and one of the most populous cities in the world, has again topped the list of the most polluted major cities. With an average annual PM2.5 concentration of 99.6 µg/m3, its residents are exposed to to high levels of pollution on a near-daily basis.
The city’s 2025 average is a modest improvement over both 2024 and 2023 whose average annual PM2.5 concentrations were 108.3 and 102.16 µg/m3 respectively. However, it’s still an average that is well into the hazardous air quality range.
Air quality in Delhi, India on April 20, 2026. Source: IQAir.
Delhi’s air pollution is caused by a combination of factors. Regional crop burning, particularly in the neighboring states of Punjab and Haryana, sends plumes of smoke into Delhi’s atmosphere every winter, creating a thick haze (9). Vehicular emissions, driven by millions of cars, trucks, and motorcycles—many of which operate on outdated technology—continue to serve as a major contributor (10). Coal-fired power plants, industrial emissions, and landfill fires further degrade air quality, while construction dust and unmanaged waste burning add to the burden.
Same cities, too few changes
Despite Kolkata, India replacing Karachi, Pakistan among the top five most polluted major cities in 2024, the other four major cities were all listed in 2024. Though they demonstrated some small air quality improvements over the prior year, Delhi, Lahore, and Dhaka all mirrored their top three positions in the 2024 listing. Their return as the three most polluted cities reflects the struggle residents and activists face in improving air quality outcomes.
Because of the nearly year-round intensity of air pollution in all five cities, it is common to see them ranking among the most polluted major cities daily.
Air quality in Delhi, India on April 20, 2026. Source: IQAir.
Pathways to cleaner air
Air pollution poses elevated health risks, but there are practical ways to reduce exposure and improve air quality in major cities. Here’s how air quality can be improved:
What governments can do
- Strengthen air quality standards and enforce pollution control measures to create healthier urban environments.
- Invest in public transportation and promote renewable energy sources to reduce emissions.
- Implement stricter regulations on industrial and vehicular emissions.
- Expand air quality monitoring networks to inform policy decisions and public health strategies.
What communities can do
- Support programs, such as Schools4Earth, to create healthier environments for vulnerable populations.
- Participate in community-driven data collection efforts to raise awareness and address pollution sources.
What individuals can do
- Opt for sustainable transportation options like walking, biking, or public transit to lower emissions.
- Use energy-efficient appliances and indoor air purification systems to reduce personal exposure.
- Monitor air quality to help improve community air quality awareness.
- Access real-time air quality information to make informed decisions, especially on high-pollution days.
- Run an air purifier when air quality is poor.
- Wear a snug-fitting face mask outdoors on days when air pollution is severe.
Conclusion
Understanding and tackling urban air pollution starts with reliable, accessible data. Yet, in many parts of the world, comprehensive air quality monitoring remains limited or non-existent.
Communities with access to real-time air quality information are better equipped to make informed decisions to protect their health, advocate for stronger policies and enforcement, and address pollution at its source. By expanding monitoring networks globally, individuals are empowered to improve public health and create cleaner, safer cities for everyone.
