Countries are finding that the urban economic development to which they aspire brings poisoned air, ill-health, massive costs, a low quality of life and, probably, an early death for a very great many people.

That is the stark conclusion from a reading of the new database of outdoor air quality from the World Health Organisation (WHO), for 3,000 of the world’s cities. While millions of people in rich countries suffer the cancers, heart and respiratory diseases that air pollution brings, the levels of air pollution in many Asian and African cities are said to be five or even 10 times worse.

Air pollution rising at an 'alarming rate' in world's cities Read more

The WHO data shows that there is now little or no escape from the plague of poisoned air; people in 98% of cities in low- and middle-income countries with more than 100,000 inhabitants are breathing air with pollution levels that exceed WHO minimum safety guidelines. That figure is almost halved in high-income countries, where the figure is 56%.

And the problem is rapidly worsening as most Asian and African cities burgeon without planning controls, as car numbers multiply and as industry and transport are allowed to pollute the air more or less unhindered. The WHO, which estimates more than 3 million people die prematurely from outdoor air pollution each year, suggests that it is 8% to 10% worse globally than five years ago.



But it admits it is impossible to know exactly. Pollution monitoring in most low-income cities is, at best, sparse and in most countries, unreliable or non-existent. Of the 3,000 cities in the WHO database, only 12 are from Africa.



But anyone who lives in Lagos, Tehran, Kabul or 1,000 other cities in poor countries knows well, the traffic is getting worse every year and the air is increasingly unbreathable. In the past, rich people in industrialised countries in Europe and the US would pay more to live upwind of industrial pollution, to escape the foul air. Today the rich and middle classes of Saudi Arabia, India and China leave town during the worst pollution episodes, or even relocate.



People in cities complain bitterly today but the full health tragedy will not be seen for many years. Because the effects of air pollution are chronic, or slow, they build up in the body and impact mostly on older people. Children exposed to heavy traffic fumes today will have smaller lungs and be more vulnerable to respiratory and heart diseases in their later years.



By not addressing air pollution now, governments, NGOs and individuals are storing up a health timebomb for the future, guaranteeing that hospital wards will be full of wheezing people with hearts and lungs permanently damaged just by living near busy roads or factories. The vast costs to the economy of caring for an increasingly infirm older population will have to be met later.



But the report brings hope. The air quality in more than 700 of the cities in the database can be compared over 10 years and here the WHO sees many cities are reducing air pollution. By checking traffic growth, reducing industrial smokestack emissions, increasing the use of renewable power sources, and prioritising walking and cycling networks, they are rapidly – and cheaply – improving air quality and cutting the number of deaths. According to the UN, more than half of the 3,000 monitored cities in high-income countries and around one in three of those in low- and middle-income countries have lowered their air pollution levels by more than 5% in the past five years.



Most governments and individuals still do not see air pollution as a major issue, but as one of the inevitable prices of economic development. They may easily understand that people die of malaria, obesity, alcohol or malnutrition, but may not appreciate the grave risks of air pollution.



Yet it’s the biggest killer in the world and likely to put the biggest brake on development in the future.