Almost everyone on Earth lives in areas with harmful levels of air pollution that breach new guidelines from the World Health Organization (WHO). The official figure is that 99 per cent of the world’s population is affected, up from 90 per cent four years ago under less stringent standards.

India has nine of the world’s 10 cities with the worst air pollution caused by a tiny pollutant known as PM2.5. Ahmedabad tops the list, with Delhi in third, a new database published today by the WHO shows. For a larger but still harmful pollutant, PM10, the top 10 list of the dirtiest places is more diverse, including settlements in Bahrain, India, Iran, Iraq, Pakistan, South Africa and Saudi Arabia.

Both pollutants are caused by a mix of fossil fuel burning in cars and power plants, but also by farming and natural sources such as desert sand. Chinese cities, which previously dominated lists of the world’s most polluted urban areas, have cleaned up their air considerably. Beijing, famous for its “airpocalypse” smog events in the past, still has high annual levels of PM2.5, but is now only the 76th most polluted city globally.

In a statement, WHO chief Tedros Adhanom Ghebreyesus said: “High fossil fuel prices, energy security, and the urgency of addressing the twin health challenges of air pollution and climate change, underscore the pressing need to move faster towards a world that is much less dependent on fossil fuels.”Low and middle-income countries are worst affected by harmful levels of particulate matter (PM) compared with the global average. For a third pollutant – nitrogen dioxide – the economic split is less clear and affluent countries are affected too.

The WHO updated its guidelines for recommended air pollution limits for the three pollutants last September, although they aren’t legally binding. Today’s new database update shows nowhere in South-East Asia and the Middle East and northern Africa is compliant with the new standards for PM. Only 13 per cent of European settlements are compliant, while the figure rises to 23 per cent in the Americas.

The database consists of 6743 settlements in 117 countries: over half are cities, and the average population of each settlement is almost half a million people.

Harmful air pollution now affects 99 per cent of everyone on Earth | New Scientist