Due to the wildfires raging in Northern California, San Francisco, Stockton and Sacramento were the world’s three “most polluted cities” on Friday morning, according to Berkeley Earth, a nonprofit that aggregates data from air-quality monitoring sites, CNN reported.
PurpleAir, which has a network of sensors around the world, also showed that California had worse air than traditional smog hotspots in India and China.
CNN meteorologist Brandon Miller confirmed that “no region on Earth had as many air quality stations in the highest ranges” of particulate matter, or PM, the toxic mixture of particles and droplets that worsens after wildfires.
Those values, he said, “stretched for hundreds of miles over Northern and Central California, from the mountains to the valleys and the coast.”
Schools, colleges and public transit have closed as smoke from the Camp Fire descends on the region.
“It appears to be the worst air quality ever experienced in San Francisco,” said Dan Jaffe, a professor of environmental chemistry at the University of Washington. He called the situation “an air quality emergency,” and experts said the smoke could undo decades of progress on pollution.
“We have made tremendous efforts and investment to clean up our air with considerable benefits for public health,” said Dr. Daniel Jacob, a professor of atmospheric chemistry and environmental engineering at Harvard University. “But now it’s like we’re getting stabbed in the back with those wildfires.”
