Skip to main content
Part of complete coverage on

Top 20 most polluted cities in the world

updated 6:03 AM EDT, Thu May 8, 2014
STORY HIGHLIGHTS
  • Delhi is most polluted city in the world in PM2.5 concentrations
  • Half of the top 20 most polluted cities were in India, according to data
  • PM2.5 is considered most harmful to health

(CNN) -- Air quality in most cities that monitor their pollution levels exceed what the World Health Organization deems as safe.

Delhi has the highest level of the airborne particulate matter, PM2.5 considered most harmful to health, with 153 micrograms. Not far behind is another Indian city, Patna with 149 micrograms. These figures are six times what the WHO considers a "safe" limit -- which is 25 micrograms.

Half of the top 20 cities in the world with the highest levels of PM2.5 were in India, according to the pollution data released by the WHO, which included 1,600 cities. Other cities with high levels were located in Pakistan and Bangladesh.

How pollution affects weather patterns
Global air pollution on the rise
China tackles 'airpocalypse'
Chinese school builds clean air dome

PM2.5 refers to the diameter measured in microns of particulates such as ammonia, carbon, nitrates and sulfate -- which are small enough to pass into the bloodstream and cause diseases such as emphysema and cancer.

The WHO data echoes an earlier study this year which found that air pollution in New Delhi is now worse than Beijing.

No Chinese cities ranked in the top 20 most polluted cities, despite thick, gray smog filling its cities and millions of residents commuting behind surgical masks. Beijing reported 56 micrograms of PM2.5. This year, Chinese leaders have declared "war on pollution."

Beijing's emergency measures amid fog of pollution

Delhi has been described as having weak enforcement of pollution controls by India's Center for Science and Environment, a public interest group.

"Originally designed as compact entities to reduce the length of travel ... (Indian cities) are becoming victims of killer pollution, congestion ... and a crippling car-dependent infrastructure," according to the group.

And the world's most polluted city is...

Air pollution has spread by increasing reliance on fossil fuels, coal-fired power plants, cars and the use of biomass for cooking and heating.

Cities with the lowest level of pollution were located in Canada, the United States, Finland, Iceland and Sweden.

ADVERTISEMENT
Part of complete coverage on
updated 11:13 PM EDT, Wed October 22, 2014
Cpl. Nathan Cirillo, shot while standing guard at Ottawa's National War Memorial, was known for his easygoing manner and smile.
updated 4:06 PM EDT, Wed October 22, 2014
Non-stop chatter about actress' appearance is nasty, cruel, hurtful, invasive and sexist.
updated 4:58 PM EDT, Wed October 22, 2014
Air New Zealand's new 'Hobbit' safety video stars Peter Jackson, Elijah Wood, elves and orcs.
updated 9:02 PM EDT, Mon October 20, 2014
A 15-year-old pregnant girl is rescued from slavery, only to be charged with having sex outside of marriage, shocked rights activists say -- a charge potentially punishable by death.
updated 11:33 PM EDT, Tue October 21, 2014
After sushi and ramen, beef is on the list of must-eats for many visitors to Japan.
updated 12:07 PM EDT, Mon October 20, 2014
Airports judged on comfort, conveniences, cleanliness and customer service.
updated 1:48 PM EDT, Wed October 22, 2014
Scientists use CT scans to recreate a life-size image of the ancient king.
updated 5:59 AM EDT, Wed October 22, 2014
Despite billions spent on eradicating poppy production, Afghan farmers are growing bumper crops, a U.S. government report says.
updated 9:19 AM EDT, Mon October 20, 2014
With so many new attractions on the way, the next few years are going to be a roller coaster ride.
updated 12:29 AM EDT, Thu October 16, 2014
Thomas Malthus famously predicted that rising populations would create a food crunch: Could this be true?
updated 6:33 AM EDT, Sat October 18, 2014
From "Sick Man of Europe" to the world's fourth largest economy.
updated 5:15 AM EDT, Wed October 22, 2014
Each day, CNN brings you an image capturing a moment to remember, defining the present in our changing world.
Browse through images from CNN teams around the world that you don't always see on news reports.
ADVERTISEMENT