Cities are centers for commerce, industry, transportation, and city dwellers benefit from the education, employment, and social/recreational opportunities that an urban lifestyle offers. Cities, however, are also the most polluted places on Earth. And urban air pollution is a killer.
According to the World Health Organization, 4.2 million people die every year as a result of air pollution. While non-urban populations are exposed to some natural occurring air pollutants, such as surface dust and pollution from volcanic eruptions, and to the human-caused pollution from agriculture, power generation, and cars, urban populations, particularly in the world’s densest cities, suffer disproportionately from unhealthy air. (These are cities emitting the most carbon dioxide in the world.)
To identify the 22 cities with the worst air pollution in the world, 24/7 Wall St. reviewed air quality data for 95 of the most polluted cities from the IQAir 2021 World Air Quality Report. Data was pulled on April 8, 2022 at 10:30 a.m. Cities were ranked by PM2.5 concentrations in micrograms per cubic meter (μg/m3). PM2.5 is defined as particulate matter that is 2.5 microns or smaller in diameter — or about 36 times smaller than a grain of fine beach sand. Population figures for 2022 come from World Population Review.
Vehicles are responsible for a full 75% of all volatile organic compounds and 25% of particulate matter in urban air pollution, with the greatest impact in poorer countries where older cars emit dirtier exhaust. Domestic use of fossil fuels for cooking, heating, and light is another major source of pollution, with half the world’s population burning coal, wood, or charcoal in inefficient stoves, and 1.2 billion people burning kerosene for lighting.
Heavily industrialized cities suffer from the worst quality air, with smokestacks emitting not just conventional pollutants, like particulates, but also a plethora of chemicals, many of them highly toxic. And feeding these industries, as well as commerce and residences, are power generators, fueled by highly polluting coal, oil, and gas, where alternative clean energy has not made a significant showing. (These are 23 places where industrial air pollution is so bad it causes cancer.)
Not surprisingly, five of the 20 most populous cities in the world – Beijing, Delhi, Mexico City, Mumbai, and Karachi, which range in size from nearly 16 million to over 21 million people – are also among the 20 most polluted. More remarkable are the five cities of less than 3 million people in size that also make the most-polluted list – Krasnoyarsk, Russia; Dubai, United Arab Emirates; Tashkent, Uzbekistan; Kathmandu, Nepal; and Chiang Mai, Thailand.