The World Health Organization has stated that any areas with air quality above 10 particles per million (ppm) is considered to be unhealthy.
The ancient city of Peshawar, Pakistan, which in recent decades has been taken over by brick kiln factories and traffic, currently has an air quality of 23 ppm, making it one the most polluted cities on the planet.
Riyadh, Saudi Arabia
Riyadh is not only the capital city of Saudi Arabia and the country’s largest city, it’s also the dirtiest. In addition to high industrial waste and heavy traffic, air quality is greatly affected by frequent sand storms in this desert metropolis.
In recent years, Saudi government agencies such as the Ministry of Health, the National Water Co. and the Higher Commission of Development of Riyadh have come together to try and find solutions to this environmental crisis.
It’s difficult to determine which city is the smoggiest in the world because not all nations collect enough accurate data. One such city that is thought to be near the top is Zabol, an eastern Iranian city situated on the Afghani border.
The World Health Organization declares Zabol to be the worst offender when it comes to PM2.5 data, which measures particles that are 1/30th, the size of a human hair. These particles are small enough to enter the lungs and tissue and can cause extensive health problems.