Wildfires have been raging across Los Angeles County since Tuesday morning, but only in the past 24 hours or so has the city’s air quality begun to suffer.
That’s because of the classic path of the Santa Ana winds, Alistair Hayden, a public health professor at Cornell who studies how wildfire smoke affects human health, told me. “Yesterday, it looked like the plumes [from the Palisades fire] were all blowing out to sea, which I think makes sense with the Santa Ana wind patterns blowing to the southwest,” Hayden said.
But with the Eaton fire now raging near Pasadena, northeast of Los Angeles, the air quality across large swaths of the city is deteriorating, Hayden said. That’s because the winds are now carrying a smoke plume as they travel down to the coast. And the situation is still changing rapidly.
At 6:30 p.m. Pacific time on Wednesday, the historic core of L.A. registered an air quality index of 105, according to the AirNow fire and smoke map, part of the federal government’s national air quality index. Anything over 100 is considered unhealthy for sensitive groups such as asthmatics. In Pasadena and East Los Angeles, the AQI was in the high 180s, 190s, and even the low 200s, which ranks as “unhealthy” or “very unhealthy” for everyone.
The AirNow map is a joint effort of the Interagency Wildland Fire Air Quality Response Program and the Environmental Protection Agency, incorporating smoke plume data from the National Oceanic and Atmospheric Administration’s satellites, Hayden said.
It also shows readings from the EPA’s permanent air quality monitors set up across Los Angeles. And it includes data from cheaper, commercial sensors — from manufacturers such as PurpleAir — that people can set up in their homes and backyards. The AirNow site also calibrates the data from those commercial sensors so that they can be more accurately compared to the government’s more robust and scientific air quality sensors. (Many websites that display the PurpleAir data do not calibrate the data in this way, he said, which can lead to faulty readings.)
In recent years, wildfire smoke has become a major driver of America’s air pollution.
“We’ve been so successful that cleaning up our air through the Clean Air Act and other state-level activities that the air has been getting better for decades,” Hayden told me. “Now, with the growth of these huge wildfires emitting large amounts of pollution, that has undone some of the progress of all this awesome work over this past decade.
“It’s amazing what we can do when we choose to do so,” he said. “But it shows there’s more work needed to be done of how do we protect communities from this current and growing threat of not just wildfires, but the smoke from those wildfires as well.”
