Updated: Sep 8
According to the United Nations, almost two thirds (57%) of the world lives in cities. Urban areas see higher levels of pollution meaning billions of people are living in areas with unsafe air. Despite this, there are many cities in the world that are demonstrating how urban areas can live with cleaner air. Here you’ll find out what they are and what’s causing the most and least polluted cities.
Measuring the World’s Most Polluted Cities
To find out which are the most polluted cities in the world, we had to use a credible and validated source. For this reason, we decided to use IQAir’s 2021 air quality data, which measures the annual average of PM 2.5 concentration (µg/m³).
World’s Most Polluted Cities
The top ten list of the world's most polluted cities as of 2021 is:
Bhiwadi, India – 106.2 μg/m³
Ghaziabad, India – 102 µg/m³
Hotan, China – 101.5 µg/m³
Delhi, India– 96.4 µg/m³
Jaunpur, India – 95.3 µg/m³
Faisalabad, Pakistan – 94.2 µg/m³
Noida, India – 91.4 µg/m³
Bahawalpur, Pakistan – 91 µg/m³
Peshawar, Pakistan – 89.6 µg/m³
Bagpat, India – 89.1 µg/m³
Despite Bangladesh being the most polluted country in the world in 2021, 60% of the world’s top 10 most polluted cities are in India, with Bhiwadi taking the top spot. In fact, 70% of the top 50 most polluted cities in the world are in India, meaning that over 140 million people in India are breathing unsafe air. Cities in Pakistan, China, Bangladesh, Chad, Kazakhstan and Turkey fill the other 30%.
The combination of coal-fired power plants, factories, biomass burning and millions of vehicles are the main causes of smoke, smog and particulate pollution in India. This leads to over 2 millions premature deaths in the country each year.
This is the first time the city of Bhiwadi has risen to the top of the list as the PM2.5 concentration (μg/m³) went from 95.5 μg/m³ in 2020 to 106.2 μg/m³ in 2021. In 2020, the top spot belonged to the city of Hotan in China, which had an average PM2.5 concentration of 110.2 μg/m³, but has since improved its concentration levels to an average of 101.5 μg/m³.
The biggest increase in PM.25 concentration was from the city of Faisalabad in Pakistan, which went from 73.2 µg/m³ in 2020 to 94.2 µg/m³ in 2021, an increase of 21 µg/m³. However, many of the most polluted cities have seen improvements to their air pollution levels over the last few years, with the largest decrease going to Ghaziabad in India, which saw a 42.6 µg/m³ drop from 144.6 µg/m³ in 2017 to 102 µg/m³ in 2021.
Despite some improvements in the chart, all but one of the top 40 most polluted cities exceed the WHO air quality limit by over 10 times. This is a seriously worrying stat considering these cities house millions of people, all of which are affected by the air quality that they’re living in, and that we’re facing a climate crisis, which needs more drastic change if we’re to continue inhabiting a safe planet.
World’s Least Polluted Cities
The top ten list of the world's least polluted cities as of 2021 is:
Shu, Kazakhstan – 1.5 μg/m³
St. Helens, Australia – 1.9 µg/m³
Judbury, Australia – 2 µg/m³
Mornington, Australia – 2.4 µg/m³
Gretna, Australia – 2.6 µg/m³
Derby, Australia – 2.6 µg/m³
Alcoutim, Portugal – 2.7 µg/m³
Salao, Portugal – 2.7 µg/m³
Exeter, Australia – 2.7 µg/m³
Bredkalen, Sweden – 2.8 µg/m³
Although Australia was the 9th least polluted country, 70% of the top 10 least polluted cities are in Australia. This is mainly due to how remote the cities in this list are. But with increased urbanisation across the country and a growing population, which is resulting in increased energy consumption and transport, the country is far from hitting perfect scores when it comes to air quality.
Every place on the list above saw improvements to their PM 2.5 concentration levels since 2020 with perhaps the most notable being Salao in Portugal, which went from 5.7 µg/m³ to 2.7 µg/m³.
But while assessing this list might be thinking – can these really be classified as cities?
While most of these places have populations of under 5000, Gretna has a population of just 214 people. This hardly seems a fair comparison to Ghaziabad, which has a population of over 5 million.
While some government bodies state that a city must have a minimum population per square mile, ranging from 1,000 to 25,000, the true definition of a city is a place where many people live. So, this really depends on how you define ‘many’.
Although it's possible to compare pollution rates per square kilometre, the data obviously has serious flaws due to a far smaller population size, meaning far fewer vehicles on the roads, and far less industries and factories upon which the world relies. So in the short term, what would be an achievable rate of pollution for these most polluted cities?
How to Quickly Reduce Pollution Levels in the World’s Most Polluted Cities
When it comes to reducing pollution levels, there are no silver bullets or easy fixes, but with collective actions and government schemes, it’s possible to reduce the levels to improve the air quality.
Globally, governments are introducing schemes to reduce air pollution in cities. These include clean air zones, congestion charges, banning the most polluting vehicles, reclaiming road space for trees and green spaces and innovative technologies that scan the air for pollution.
If action isn't taken now, we'll likely see air pollution levels continue to rise each year. Now is the time to make a change.
Reduce Air Pollution in Your Community with Pure Air Zone
If you’re feeling a bit helpless after reading this, there are a few ways you can make a direct impact on air quality within your community and beyond.
Pure Air Zones is a concept developed by U-Earth that allows businesses to offer clean air to their customers, visitors, clients and employees. The more Pure Air Zones there are, the more impact on air pollution they’ll have.
If you’re a business, you can book a meeting with one of our air quality specialists to see how you and your company can make a difference today. If you’re an individual, you can prompt your favourite businesses (or any business at all!) to become a Pure Air Zone through the Pure Air Zone App or join our newsletter below to stay informed on how you can help.
Happy air purifying!