The Capital Cities With the Deadliest Air Pollution

In May 2018, the World Health Organisation (WHO) released a worrying report. They estimated that 9 out of 10 people worldwide are breathing polluted air, with those living in low-income cities hit hardest.

Although air pollution is often less visible than other kinds of pollution, that doesn't mean that it's less deadly. The WHO believes that 4.2 million people die every year as a result of breathing polluted outdoor air.

Poor urban air quality has been linked to strokes, heart disease, lung cancer and respiratory diseases including asthma. Damage to unborn children and a decline in sperm quality have also been linked to dirty air.

Polluted air contains tiny particles called particulate matter (PMs), some of which are small enough to slip through the lung's natural filter system and enter the bloodstream.

These tiny pollution particles in the air vary in size. The different sizes are generally gathered into two groups during pollution studies: the larger PM10 and the tiny PM2.5.

Both sizes of particles are harmful. PM10s can penetrate the deepest part of the lung, causing respiratory illnesses. PM2.5 particles can actually pass through the lungs and end up in other organs, including the brain.

It's a scary thought that the air you breathe may be slowly killing you, but that's the case in a lot of major cities. Given the current U.S. government's dismissal of the very real dangers of air pollution, it seems as though a global solution won't be coming from America any time soon, despite air pollution causing 200,000 early deaths a year in the U.S. alone.

But how worried you should be depends greatly on where you live. The WHO has released a list of the most polluted cities in the world, with the option to measure by either PM10 or PM2.5 levels.

When ranked by PM2.5 levels, the top 10 cities with the worst air quality are in India, with the exception of Bamenda in Cameroon at number seven. The most polluted cities in the U.S. are Bakersfield and Visalia-Porterville, both in California.

To ensure a fair spread of countries, we've made a list of the most polluted capital cities in the world, ranked by their PM2.5 levels—the particles that are small enough to enter the bloodstream.

Bear in mind that no level of PM2.5 in the air is truly safe, but the WHO says that a desirable limit is 10 micrograms/m3. In comparison, the worst capital on our list has a massive 143 micrograms/m3—over 14 times the WHO's target level.

Washington DC doesn't make the top 50, but levels there are at 9 micrograms/m3, within the target level—but only just.

The world's capital cities still have a long way to go to ensure citizens are not being endangered by dirty air. Here are the 50 worst offenders.

This article was updated to correct a typo.