Over 1 million people die every year due to outdoor air pollution and many more are affected, according to the World Health organisation.
The main causes of death are tiny particles which enter the lungs and bloodstream, leading to enhanced pulmonary and coronary problems. Anything over 20 micrograms per cubic meter is considered dangerous by the WHO.
New York City averages 21 micrograms per cubic meter, while Los Angeles averages 25 micrograms.
But around the world some cities are far more dangerous than notoriously smoggy LA. Cities from Iran, India and Pakistan dominate this new list from the WHO’s Global Health Observatory Data Repository.
200 micrograms per cubic meter
Lahore is the second largest city in Pakistan. It is known for the Lahore Stock Exchange which is key to the city's economy. It is almost famous for its public and private transportation system that runs 24 hours a day, 7 days a week.
209 micrograms per cubic meter
Kanpur is home to approximately 5 million Indians. They are one of the biggest producers and exporters of textiles and leather. It is also home to the largest tanneries in India, which are also the primary source of the pollution throughout the city.
215 micrograms per cubic meter
Yasouj is the first of multiple Iranian cities on this list. They are known for their sugar processing plant and coal power plant which generates electricity for the entire area. Even now, the city is in the process of constructing a new private oil refinery.
216 micrograms per cubic meter
Gaborone is the capital and largest city in Botswana. It is the only city outside of Asia and the Middle East to make it on the list. Gaborone is one of the most rapidly growing cities in Africa, however, veldt fires from the dry winters and dirty second-hand vehicles are the main source of pollution in the city.
219 micrograms per cubic meter
Peshawar is located in a valley and the administrative centre for the Federally Administered Tribal Areas of Pakistan. Its massive expansion and influx of migratory workers has caused a boom in urban pollution. It is also a key city where the US launches many of its strategic campaigns in Afghanistan from.
229 micrograms per cubic meter
Kermanshah is located in western Iran and is famous for its oil refineries and manufacturing. It was once an agricultural centre, but has since emerged as an industrial centre. It has become one of the main importing/exporting gates of Iran.
251 micrograms per cubic meter
Two cities from neighbouring countries tie for fourth. Ludhiana is the largest city in the state of Punjab, and one of the richest in all of India. They produce 50% of India's bikes and 60% of their tractor parts. Quetta is a high-altitude city known as the 'Fruit Garden of Pakistan' because of its diverse plant and animal life. But it is also a transportation hub known for its railways and airport.
254 micrograms per cubic meter
Sanandaj is another city of western Iran famous for its numerous manufacturing industries. They produce carpets, cotton, woodwork, and metalware. Outside the city is a landscape of beautiful hills and mountains, but the city itself has become a sea of smog and commerce.
279 micrograms per cubic meter
Ulaan Baatar only ranks as the second most polluted city even though the country of Mongolia itself ranks #1. Ulaan Baatar is not only the capital of Mongolia, it serves as the country's transport and industrial centre. It manufactures nearly everything, from textiles to cement to processed foods. Just around the corner are the coal mines powering these industries.
372 micrograms per cubic meter
The Iranian capital of Ahvaz was found to have the highest annual average for outdoor air pollutants. Its no wonder it is the leader when it is an oil centre, transportation hub, and industrial city. It is known for producing silk and sugar as well as linking roads, rails, and pipelines to ports in the Persian Gulf.
NOW WATCH: Briefing videos
Business Insider Emails & Alerts
Site highlights each day to your inbox.