Which cities face most, least air pollution according to new WHO data

By Jen Christensen, CNN

Updated 2203 GMT (0603 HKT) May 1, 2018

The Nigerian city of Port Harcourt used to be known as "The Garden City." Black soot is now everywhere.
Photos: The Nigerian city covered in soot
Port Harcourt, Nigeria – The Nigerian city of Port Harcourt used to be known as "The Garden City." Black soot is now everywhere.
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The city is in the oil-producing Niger Delta region.
Photos: The Nigerian city covered in soot
Port Harcourt, Nigeria – The city is in the oil-producing Niger Delta region.
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A social media campaign has been launched by radio host Sandra Ezekwesili, #StopTheSoot.
Photos: The Nigerian city covered in soot
Port Harcourt, Nigeria – A social media campaign has been launched by radio host Sandra Ezekwesili, #StopTheSoot.
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The cause of the soot is has been a mysterious to residents, but many think it's related to the destruction of illegal oil refineries.
Photos: The Nigerian city covered in soot
Port Harcourt, Nigeria – The cause of the soot is has been a mysterious to residents, but many think it's related to the destruction of illegal oil refineries.
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People say the pollution is affecting their health.
Photos: The Nigerian city covered in soot
Port Harcourt, Nigeria – People say the pollution is affecting their health.
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Residents have also taken to <a href="https://twitter.com/search?src=typd&q=%23stopthesoot" target="_blank">Twitter</a> to express their frustration.
Photos: The Nigerian city covered in soot
Port Harcourt, Nigeria – Residents have also taken to Twitter to express their frustration.
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"You go to bed, you wake up, you're covered in it," Ezekwesili told CNN.
Photos: The Nigerian city covered in soot
Port Harcourt, Nigeria – "You go to bed, you wake up, you're covered in it," Ezekwesili told CNN.
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A soot-covered hand.
Photos: The Nigerian city covered in soot
Port Harcourt, Nigeria – A soot-covered hand.
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"The air is thick with the soot," Ezekwesili said.
Photos: The Nigerian city covered in soot
Port Harcourt, Nigeria – "The air is thick with the soot," Ezekwesili said.
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Story highlights

  • 9 out of 10 people in the world breathe air that is highly polluted, a new report says
  • Air pollution is found in the home and outdoors
  • About 7 million people die each year because of this pollution, the WHO says

(CNN)Nine out of every 10 people on the planet breathe air that contains high levels of pollutants and kills 7 million people each year, according to a new study from the World Health Organization.

The study is an analysis of what the WHO says is the world's most comprehensive database on ambient air pollution. The organization collected the data