Update, December 15: Another serious warning is in effect in San Francisco on Friday morning, as the EPA’s AirNow site assesses air quality in SF as “unhealthy,” posing a special risk to the most vulnerable but also approaching dangerous conditions even for those in more robust health:
“People with heart or lung disease, older adults, and children should avoid prolonged or heavy exertion,” according to the EPA scale, and “everyone else should reduce prolonged or heavy exertion.”
The present Air Quality Index of 153 is comparable to atmospheric conditions in the Bay Area during the October fires.
Walter Wallace, spokesperson for the Bay Area Air Quality Management District, tells Curbed SF it’s unusual to see unhealthy air centered on the city like this but says there’s “no dramatic event” that’s to blame and “no real reason” for the smoggy outlook beyond simply being an inevitable bad day.
“It’ll get dramatically better around 6 or 7 p.m.,” Wallace says, encouraging Bay Area residents to keep indoors as much as possible in the meantime.
The air quality warnings currently in effect for Wednesday and Thursday in certain Bay Area counties call for conditions not nearly as bad as those from the fall, but they do warrant caution, particularly in the North Bay and Santa Rosa areas.
During October’s wildfire crisis across Northern California, if you recall, air quality in the Bay Area got so bad that it rivaled proverbially smoggy Beijing. But this week’s won’t be nearly as rough.
In San Francisco and Oakland, the Environmental Protection Agency’s AIRNow site warns that Thursday’s forecast calls for some uncommonly bad air, rising to a level designated Unsafe For Sensitive Groups [USG], meaning that the very young, the elderly, or those with medical conditions that affect their breathing should avoid prolonged exposure to the air outside.
It’s worse in the North Bay, with a USG warning already in effect for Wednesday across an area covering Marin, Sonoma, and Napa Counties and the same on Thursday.
The San Francisco-based Bay Area Air Quality Management District agrees, warning of a potentially hazardous atmospheric funk in Oakland, Berkeley, and especially the North Bay through Thursday. A Spare the Air warning is in effect for Wednesday and Thursday, making wood-burning fires illegal.
Berkeleyside notes this is the fifth such warning since Friday.
Note that the forecast is not nearly as bad now as during the fires. In October, the Air Quality Index rose as high as 158 in San Francisco; this week, regulators anticipate highs of only about 102.
A score of between zero and 50 is considered “good,” and is usual for San Francisco most of the year. “Unsafe” levels of pollutants are a cause for caution but not usually alarm.