Clean air: what a country average shows and hides
Imagine two cities. In one, the yearly average of fine particles in the air is 7 units. In the other it is 18. Does that difference matter for how long people live?
The units are micrograms per cubic meter of PM2.5, which are particles smaller than 2.5 micrometers. They are small enough to reach deep into the lungs. The World Health Organization guideline for a yearly average is 5.
Few places meet it. The 2025 IQAir report covers 9,446 cities in 143 countries and territories. Only 14% of the cities met the guideline, and 13 countries and territories did.
The Air Quality Life Index at the University of Chicago estimates the cost in years. It puts the global average in 2023 at 24.1, nearly five times the guideline. Meeting the guideline everywhere would add about 1.9 years of life expectancy. For comparison, it gives smoking about 1.7 years.
Those figures work out to roughly one year of life expectancy for each 10 units above the guideline. We used that rule of thumb to estimate the lifelong cost for a few countries.
Fine particles by country, 2025, and a rough lifelong cost
| Country | Yearly average | Times the guideline | Rough lifelong cost |
|---|---|---|---|
| Mexico | 17.6 | 3.5 | 1.3 years |
| South Korea | 17.1 | 3.4 | 1.2 years |
| Japan | 9.8 | 2.0 | 0.5 years |
| Spain | 9.1 | 1.8 | 0.4 years |
| Portugal | 7.9 | 1.6 | 0.3 years |
| United States | 7.3 | 1.5 | 0.2 years |
| Panama | 4.8 | 1.0 | none |
The cost is our arithmetic, for a lifetime of breathing that air. A move at 65 changes only the years after it, so the effect would be smaller.
A country average can hide a lot. Inside the United States in 2025, the cleanest large city averaged 4.5 and the most polluted averaged 11.4. Wildfire smoke raised the national average to 7.3.
A yearly average also hides the worst months. A city can meet the guideline over twelve months and still have weeks of heavy smoke or dust.
Some countries are missing. Burundi, Turkmenistan and Togo were among the 30 most polluted countries in 2024. They are absent in 2025 because no usable data existed.
In Latin America, the Air Quality Life Index finds that the average resident could gain up to one year if the air met the guideline. In the most polluted regions the gain would be more than four years.
Public maps show a city's yearly average and its worst months. Both are easy to look up before choosing a place to live.
What did your city's number show? Tell us in the comments. Someone may be about to compare their own.
Sources we read
IQAir, 2025 World Air Quality Report, press release (9,446 cities; 14% meet the guideline; 13 countries). https://www.iqair.com/newsroom/waqr-2025-pr
Filterbuy, Global air quality rankings by country (IQAir 2025 figures for Mexico, South Korea, Japan, United States, city examples). https://filterbuy.com/resources/air-quality-aqi/global-air-quality-ranking-by-country/
Statbase, Air pollution data by country 2018 to 2025 (Spain, Portugal, Panama). https://statbase.org/datasets/environment/air-pollution/
University of Chicago Energy Policy Institute, Air Quality Life Index 2025 annual report. https://epic.uchicago.edu/wp-content/uploads/sites/5/2025/08/AR_2025_Global_English_Embargoed.pdf
Air Quality Life Index, Top charts 2025 (smoking comparison; Latin America). https://aqli.epic.uchicago.edu/post/aqli-top-charts-2025-en
Tell us in the comments