Mapped: New Survey Shows Air Pollution Changes In Cities Around The World

Air pollution is a serious matter. Who wants to visit a city only to end up walking its streets breathing acrid smells and harming your health? But air pollution doesn’t just mean the smog we can see – the really dangerous stuff is invisible to the naked eye. A 2022 report by the World Health Organization cites that 99% of the entire global population is breathing polluted, health-harming air. And with more than 6,000 cities across 117 countries now monitoring air quality, the data set is comprehensive and compelling.

Smoke and sunset cast a glow over Ulan Bator, Mongolia’s capital city.

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To try and clarify that into something usable, the air experts at HouseFresh have mapped 480 cities around the world, calculating the average air pollution level of the first nine months of 2019 against the first nine months of 2022 to see where air pollution has increased and where it has decreased. Using aqicn.org’s World Air Quality Index data for each city, they measured average levels of particulate matter 2.5 (PM2.5) – particles that are small enough to pass into our bloodstream (about three per cent the width of an average human hair) and cause a range of health problems – in the air. They then used a formula developed by AirNow to convert the PM2.5 figure into micrograms per cubic meter of air (µg/m3) values.

So, with the science taken care of we can look at the numbers and see where are the best places to take not only a metaphorical but also a real breath of fresh air. One thing to note – cities in Ukraine have been omitted from the report due to the inevitable impact on air pollution caused by the military conflict.

The Cities Where Air Pollution Has Increased And Decreased The Most

The ten best and worst performing cities for air pollution between 2019 and 2022.

HouseFresh

Of the 480 cities surveyed, the best performing is Ulan Bator (Ulaanbaatar), the magical capital city of Mongolia, which has seen air pollution decrease the most with PM2.5 levels dropping by -23.4µg/m3. That’s not to say, however, that this decrease makes it a bastion of fresh air. Noted previously as one of the most polluted capital cities on earth thanks to a mix of natural and manmade factors, it was subject to an air quality improvement plan in 2017 which appears to be showing positive results.

Dammam, Eastern Province, Saudi Arabia is an important location for the Saudi oil industry and the … [+] most polluted city in the survey.

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At the other end of the scale, Dammam in Saudi Arabia has seen air pollution worsen the most, with PM2.5 levels going up +111.1µg/m3. A significant center for the Saudi oil industry and home to both the largest port in the Persian Gulf and the largest airport in the world, it’s a clear hotspot for harmful PM2.5 air pollution and is currently the most polluted city surveyed. Of the world’s capital cities, Baghdad has experienced the worst increase in pollution, with PM2.5 levels going up +31.6µg/m3. A 2015 report notes that “81% of PM2.5 from Baghdad is dominated by dust, sulfate, gasoline and diesel.”

In Europe, Salamanca has seen PM2.5 levels increase the most by +5.1µg/m3 closely followed by Palma with +3.7µg/m3 – both Spanish cities soon subject to the introduction of low-emission zones for vehicles in an effort to help the nation reach climate neutrality by 2050. On the flip side it’s North Macedonian capital city Skopje that’s seen the biggest positive change in PM2.5 particles, with a decrease of -12.4µg/m3. Skopje was once Europe’s most polluted capital city and has far to go to achieve clean air, but implementing a Green City Action Plan has clearly been a good start.

Omaha is cleaning up its act and performed better than any other U.S. city in decreasing air … [+] pollution.

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In the U.S., Miami, Florida and Salt Lake City, Utah share the highest PM2.5 level increases, both seeing a +1.8µg/m3 rise since 2019. Salt Lake City suffers from a meteorological phenomenon known as ‘inversion’ thanks to its location in a valley where cooler, polluted air is trapped close to ground level under warmer air above it. Omaha, Nebraska has a more positive outcome with a decrease of -1.1µg/m3 in PM2.5 levels, although it still sits well down the overall U.S. ranking cities behind Honolulu, Providence, Salem, Tucson, Portland and Albuquerque.

The Cities With The Least And Most Air Pollution

You’ll find the cleanest air of any city in this report in Zürich, Switzerland with PM2.5 levels of just 0.5µg/m3. Placed first in both 2019 and 2022, it saw a consistent level of air quality during that period with a small decrease in PM2.5 levels of -0.1µg/m3. Second place is Perth with 1.7µg/m3 showing a drop of -6.2µg/m3 since 2019. Australia fares extremely well in the top ten cleanest cities with five entries including Hobart, Wollongong, Launceston and Sydney alongside Perth. Honolulu is the only U.S. city to make the top ten, taking tenth spot with levels of 4µg/m3, showing a tiny increase in pollution since 2019.

Breathe deep: Zurich in Switzerland has the cleanest air of any city surveyed.

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We already know the most polluted city to be Dammam in Saudi Arabia with a PM2.5 level of 155µg/m3. Almost all of the top ten most polluted cities are in the Middle East and Asia, with Lahore in Pakistan second worst with 98.1µg/m3 of PM2.5. Just behind it is Dubai, the miracle city born from the desert and home to the world’s tallest building, the Burj Khalifa. Elsewhere, India performs poorly with three cities in the bottom ten – Muzaffarnagar, Delhi, New Delhi.

Air pollution level changes in capital cities between 2019 and 2022.

HouseFresh