The annual urban air quality survey by IQ Air (a Swiss air purification company) reports “PM 2.5” concentration per cubic meter of air in 7,812 cities in 134 countries and territories. (Punta Arenas to Nome; Dublin to Vladivostok; Cape Town to Oslo; Cairo, Dushanbe, Suva, Colombo, Chiang Rai, Sydney, etc.) PM 2.5 is “particulate matter” measuring 2.5 microns or less in diameter. Typically it’s smoke, soot, effluent, car exhaust, small acid drops produced by atmospheric chemical reactions, and the like. The survey’s 2024 edition, with figures for 2023, finds the world’s healthiest air in Kuusamo, a Finnish town of 15,000 about 500 miles due north of Helsinki. They breathe in just 0.3 micrograms of particulate matter per cubic meter of air. At the smoggy top, meanwhile, comes Begusarai, a Bihar industrial center with 3 million residents, at 118.9 micrograms per cubic meter.

Begusarai’s case is extreme but also representative: 84 Indian cities and towns show up in the survey’s 100 most air-polluted cities. National capital New Delhi comes in at 92.7 micrograms, Patna 88.2, Gwalior 68.9, and Meerut 78.9. Another six of the top ten are Bangladeshi and Pakistani towns — Lahore ranks fifth, just above New Delhi, and Dhaka is 24th — each with over 50 micrograms of dirt per cubic meter of air. In sum, the belt of fertile green land below the Himalaya and north of the Deccan Plateau, home to over a billion people, has the worst air in the world. This, in part, comes from geography (the Himalaya range is the world’s largest winter air-flow trapper) but also from poor policing of brick kilns, rubbish-burning, crop residue burnoff, vehicle emissions, and other sources policy can, in principle, address.

Three ways to put these numbers in context:

Compared to other big emerging-economy cities: City air is usually smokier in emerging economies than in top-end wealthy countries, but the Pakistan-northern India-Bangladesh belt is unique. For example, IQ Air puts Lagos’ PM 2.5 count at 21.8 micrograms per cubic meter of air, a fifth of the Delhi level. Mexico City’s is 22.3 micrograms, and Istanbul’s at 18.7. Others include Bangkok at 21.7, Cairo a dense 42.7, Shanghai 28.7, and Sao Paulo 14.3.

Compared to the U.S.: American cities and towns nationally averaged 9.1 micrograms, just between Germany’s 9.0 micrograms and Argentina’s 9.2, and in the mid-range of wealthy countries. (See below for a representative list.)  Big American cities range from Chicago’s relatively smoky 13.0 micrograms to Tucson’s desert-fresh 3.8; San Juan in Puerto Rico, with a sparkling 2.7 microgram reading, gets IQ Air’s title as the world’s cleanest-air capital. Coraopolis in Pennsylvania fared worst at 19.3 micrograms, but mainly by bad luck — Coraopolis was directly in the path of that June’s Canadian wildfire smoke river, and its 2022 rating was a better 7.2 micrograms.

Compared to other regions: In Europe, the highest continental air pollution rating goes to Plevlja in Montenegro at 40.7 micrograms per cubic meter. (It’s near a coal mine and a Yugoslav-era power plant.)  The western hemisphere’s top reading is in Chilean mountain town Coyhaique at 33.2 micrograms. though both are smoky by American and “developed-world-city” standards, neither would make a list of South Asia’s 150 most-polluted cities.

What does this mean?  High particulate matter counts aren’t merely unpleasant. The World Bank says they engender or inflame enough illnesses each year – heart diseases, strokes, lung cancer, a smaller number of lung infections — to cause 1.67 million Indian premature deaths to air pollution. That’s nearly a fifth of India’s 9.5 million total annual deaths; the comparable estimate for Bangladesh is about 160,000 of 859,000 deaths, and for Pakistan 128,000 of 1.6 million deaths. Overall, the World Health Organization attributes 6.7 million premature deaths to air pollution worldwide, or one in nine of the world’s annual 61.7 million deaths.

Two concluding thoughts: First, it’s rare to solve a problem before you recognize it, and the survey’s very broad coverage shows rapidly growing worldwide interest in understanding air quality levels. So the high-P.M. 2.5 countries participating in the survey deserve credit for transparency. (The regions least covered are the Middle East and sub-Saharan Africa.) Second, air pollution is not immune to policy. The U.S.’ national PM 2.5 average, for example, was 13.5 micrograms per cubic meter in 2000, so the 9.1 micrograms of 2023 represents a 30% cleanup so far this century. Likewise, Beijing’s 34.1 microgram count, though nothing to brag about, is vastly better than the New Delhi-like 101.6 micrograms in 2013. So policy can help. The cities and national governments at the top end of the list have the information they need to do better, and ought to use it. In this case, the “people are dying” cliché seems perfectly true, lots of them.