Worst cities

In its survey of 1,412 U.S. towns and cities in 2020, IQAir found that 24 of the 25 worst for particulate pollution were in California. But because the wildfires had the biggest impact in central and Northern California, just one of those was in Southern California — Del Rey in Los Angeles County.

In a major change, it was no longer urban areas with the dirtiest air. Ranked at the bottom nationwide was Yosemite Lakes and then Oakhurst, near Yosemite National Park, followed by Springville, outside of Sequoia National Park.

But it was a lot worse elsewhere on the globe.

Of the 4,744 towns and cities surveyed worldwide, Yosemite Lakes was 233rd worst. It was the only U.S. location that failed to at least reach a “moderate” annual rating on the U.S. Air Quality Index, registering a particulate matter concentration of 37.8 that qualified it as “unhealthy for sensitive groups.”

Worst in the world? Hotan, China, with a particulate concentration of 110.2, followed by Ghaziabad, India, at 106.6, both of which qualified for an “unhealthy” rating for the year. Hotan had one month of a “hazardous” rating and another of “very unhealthy,” while Ghaziabad had three days of “very unhealthy” air.

Yosemite Lakes reached “unhealthy” levels for two months during the fires, while Oakhurst reached “very unhealthy” for a single month, in September, and “unhealthy” the following month. But together they combined for seven months of the highest level of good air quality, dubbed the World Health Organization “target.”

MINDY SCHAUER — STAFF PHOTOGRAPHER Wildfire smoke helps create an eerie orange glow along Irvine Boulevard near Alton Parkway in Irvine in October. The West Coast fires hurt air quality worst in September, when the U.S. accounted for 77 of the world’s 100 most polluted cities and towns.