Nearly every country on Earth has dirtier air than doctors recommend breathing, a report has found.
Only seven countries met the World Health Organization’s guidelines for tiny toxic particles known as PM2.5 last year, according to analysis from the Swiss air quality technology company IQAir.
Australia, New Zealand and Estonia were among the handful of countries with a yearly average of no more than 5µg of PM2.5 per cubic metre, along with Iceland and some small island states.
The most polluted countries were Chad, Bangladesh, Pakistan, the Democratic Republic of the Congo and India. PM2.5 levels in all five countries were at least 10 times higher than guideline limits in 2024, the report found, stretching as much as 18 times higher than recommended levels in Chad.
Doctors say there are no safe levels of PM2.5, which is small enough to slip into the bloodstream and damage organs throughout the body, but have estimated millions of lives could be saved each year by following their guidelines. Dirty air is the second-biggest risk factor for dying after high blood pressure.
“Air pollution doesn’t kill us immediately – it takes maybe two to three decades before we see the impacts on health, unless it’s very extreme,” said Frank Hammes, CEO of IQAir. “[Avoiding it] is one of those preventative things people don’t think about till too late in their lives.”
The annual report, which is in its seventh year, highlighted some areas of progress. It found the share of cities meeting the PM2.5 standards rose from 9% in 2023 to 17% in 2024.
Air pollution in India, which is home to six of the 10 dirtiest cities in the world, fell by 7% between 2023 and 2024. China’s air quality also improved, part of a long-running trend that saw the country’s extreme PM2.5 pollution fall by almost half between 2013 and 2020.
The air quality in Beijing is now almost the same as in Sarajevo, the capital of Bosnia and Herzegovina. The latter was the most polluted city in Europe for the second year running, the report found.
Zorana Jovanovic Andersen, an environmental epidemiologist at the University of Copenhagen, who was not involved in the report, said the results highlighted some chilling facts about air pollution.
“Huge disparities are seen even within one of the cleanest continents,” she said. “Citizens of eastern European and non-EU Balkan countries breathe the most polluted air in Europe, and there is a 20-fold difference in PM2.5 levels between the most and least polluted cities.”
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Governments could clean their air with policies such as funding renewable energy projects and public transport; building infrastructure to encourage walking and cycling; and banning people from burning farm waste.
To create the ranking, the researchers averaged real-time data on air pollution, measured at ground level, over the course of the calendar year. About one-third of the units were run by governments and two-thirds by non-profits, schools and universities, and private citizens with sensors.
Air quality monitoring is worse in parts of Africa and west Asia, where several countries were excluded from the analysis. Poor countries tend to have dirtier air than rich ones but often lack measuring stations to inform their citizens or spur policy changes.
Roel Vermeulen, an environmental epidemiologist at Utrecht University, who was not involved in the report, said biases were most likely in data-poor areas with few regulated monitoring stations – particularly as satellite measurements were not used for the analysis – but that the values presented for Europe were in line with previous research.
“Virtually everyone globally is breathing bad air,” he said. “What brings it home is that there are such large disparities in the levels of exposure.”
