San Francisco residents are breathing the world’s worst air into their lungs amid a spate of wildfires around California, according to a ranking of approximately 80 major cities around the globe.
The city registered the highest air quality index on Friday in a ranking by AirVisual, a company that has developed a popular app that tracks air pollution, and that pulls in data from sources such as government monitoring stations, satellites and community contributors.
San Francisco hit an air quality index score of 205 on Friday, topping cities such as New Delhi (201), Mumbai (161), Beijing (129) and Dubai (127).
The poor air quality came amid northern California fires that have burned as much as 146,000 acres, left 71 dead and over 1,000 people missing.
AirVisual wasn’t the only source to rank the San Francisco area so high when it came to concentrated air.
San Francisco itself ranked second with a PM2.5 concentration of 164.2 in the past day on a ranking by Berkeley Earth, a website that tracks air pollution around the world.
Topping the list was nearby Oakland, with a concentration of 160.3.
Both were followed on Berkeley Earth’s list by the northern California city of Stockton (157.6), state capital Sacramento (142.4) and San Jose (126.6).
PM2.5 refers to levels of fine particulate matter in the atmosphere that have diameters of less than 2.5 micrometres.
The conditions have forced schools to close and public transit to shut down, as the region deals with what looks to be the “worst air quality” it has ever seen, Dan Jaffe, environmental chemistry professor at the University of Washington, told KTLA5.
The wildfires raging around California are considered the worst that the U.S. has seen since the early 20th century, when a firestorm burned across the Northern Rockies in 1910, killing 87 people, while the Cloquet Fire of 1918 in Minnesota killed 450 in total.