The 2022 World Air Quality report has shed light on the harmful effects of poor air quality in some of the world's largest cities, highlighting a need to address this issue to improve the health and wellbeing of their residents.
In contrast to smaller populations, the major cities most affected by high concentrations of unhealthy air quality suffer on two fronts; more potential sources of air pollutants and more people affected. For 29 million people in one of the top five listed cities, poor air quality was an almost everyday occurrence in 2022 – and has been for the past several years.
Here are some of the cities with the worst air quality, their air pollution sources, and a few of the most polluted cities in each region that may surprise you.
5. Peshawar, Pakistan
Crop burning blankets region in air pollutants
The fifth most polluted major city in 2022 was Peshawar, which is the sixth most populated city in Pakistan. Located near the border near Afghanistan in the northwest, Peshawar is home to about 2 million people affected by poor air quality.
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In 2022, the average annual PM2.5 concentration for Peshawar was 92 micrograms per cubic meter of air (µg/m3). PM2.5, particulate matter measuring 2.5 microns or less in diameter, causes respiratory and cardiac disease. It’s also the most common air pollutant.
Peshawar, Pakistan experienced unhealthy air quality on February 24, 2023. Source: IQAir.
In 2021, Peshawar had been the ninth most polluted city in the world.
Air quality in Pakistan and northern India is often hazardous during the crop burning seasons from April to May and from October to November. The region’s air quality can also be poor due to burning city waste, emissions from brick kilns, cremation, and solid fuel burning for cooking and heating.
4. Delhi, India
Sprawling city struggles to breathe
The fourth most polluted major city in the world in 2022 was also one of its largest. Delhi, India is home to about 29 million people. The city’s average annual PM2.5 concentration was 93 µg/m3, a small improvement over the 2021 annual average (96 µg/m3). Delhi was the fourth most polluted large city in the world in both 2021 and 2022.
The city has been working to improve the city’s air quality by reducing vehicle emissions and banning coal. Like Peshawar, Delhi air pollution can be hazardous due to similar sources, like drifting smoke during the crop burning seasons.
Air quality monitors in Delhi, India detected unhealthy to hazardous air quality on February 27. Source: IQAir.
3. Bhiwadi, India
Former most polluted city improves air quality
The third most polluted metropolis mentioned in the report is also located in India. Bhiwadi isn’t far from Delhi, about 78 kilometers to the southwest of the capital. With a population of 104,000, it’s much smaller than Delhi. But because it struggles with many of the same pollutants and their sources, it was also the most polluted city in the world in 2021.
In 2021, Bhiwadi’s average annual PM2.5 concentration was 106 µg/m3, making it the most polluted city in the world that year. Its 2022 average annual PM2.5 concentration of 93 µg/m3 is an improvement over both 2021 and 2020 (96 µg/m3).
2. Hotan, China
First time city below 100 µg/m3 in six years
Hotan, China has also improved its air quality. In 2021, the oasis city had an average annual PM2.5 concentration of 102 µg/m3 and has been over 100 µg/m3 since 2018. The city’s average annual PM2.5 concentration in 2022 was 94 µg/m3.
Though the air quality is improving, Hotan ranked as the second most polluted city in the world and the most polluted in East Asia.
Unhealthy air quality in Hotan, China on February 27. Source: IQAir.
Smoke and temperature inversions harm air quality
Pakistan’s capital city, Lahore, was the most polluted city in the world for 2022. By default, it was also the most polluted in Central and South Asia. There are about 11 million residents in Lahore.
The city topped the list of major cities experiencing air pollution in 2022, with an average annual PM2.5 concentration of 97 µg/m3. The uptick in air pollution in Lahore represents an increase over the previous three years (87, 79, and 90 µg/m3 respectively).
Very unhealthy air quality in Lahore, Pakistan on February 24. Source: IQAir.
In addition to hosting many of the same air quality sources noted in Peshawar, Delhi, and Bhiwadi, Lahore is subject to temperature inversions, a weather phenomenon that results in warm air being trapped below a layer of colder air. Pollutants are also trapped with the warm air layer and aren’t as easily dispersed and diluted by winds.
Most polluted regional cities
While some cities weren’t among the top five most polluted global major cities, poor air quality impacted people living in every region of the world.
PM2.5 concentrations were generally high in Africa and West Asia. In Africa, the most polluted city was Chad’s capital city N’Djamena with an average annual PM2.5 concentration of 90 µg/m3. And in West Asia, the most polluted city was Baghdad, Iraq, with an average annual PM2.5 concentration of 87 µg/m3. Both cities are near deserts and are subject to dust storms; Baghdad’s air pollution can be linked to vehicle emissions, generators use, and conflict (2).
Europe’s most polluted city was Herceg-Novi, Montenegro. The city experienced an average annual PM2.5 concentration of 53 µg/m3. Eastern Europe, particularly the Balkans, contends with year-round air quality issues from old vehicles and their emissions, temperature inversions in mountain valleys, and polluting regional industry.
The most polluted city in Latin America and Caribbean was Valparaiso, Chile with an average annual PM2.5 concentration of 39 µg/m3. In Southeast Asia, the most polluted city was Hanoi, Vietnam. It had an average annual PM2.5 concentration of 40 µg/m3.
The most polluted city in Northern America – the U.S. and Canada – was Coffeyville, Kansas with an average annual PM2.5 concentration of 19 µg/m3. The city is notable for its being home to heavy industry, including oil refineries, a smelting facility, and a nitrogen fertilizer plant (1).
What you can do
Even though air pollution is far too commonplace, there is hope as even the world’s most polluted cities strive to improve the air we breathe. You can be part of the solution:
- Let your local representatives know you care about your air quality – advocate for initiatives, propositions, and measures that can help target air pollution.
- On a personal level, you can lower your air pollution footprint. Reduce your own energy consumption and walk, bike or ride public transportation when possible.
- Stay safe: download an air quality app and limit your time outdoors or wear a high-quality face mask during poor air quality days.
- While indoors, you can close windows on poor air quality days and set A/C systems to recirculation mode.
- On better air quality days, set the A/C to fresh air intake or open windows to improve ventilation.
- Finally, you can help your own community by becoming an air quality data contributor. By becoming an air quality data contributor, you can increase our global understanding of air pollution and how it impacts human health.
Knowing a city and neighborhood’s air quality is the first step to empowering individuals to protect themselves on poor air quality days. Yet, there are many cities around the world that still lack air quality data – especially in Africa, West Asia, and Latin America and the Caribbean. Find your community on the Air Quality Map and become a Contributor.