This story originally appeared on Inside Climate News and is part of the Climate Desk collaboration. It is third in a series about health risks following the Los Angeles wildfires that destroyed Pacific Palisades and Altadena. This story was supported by the Pulitzer Center.
Nicholas Spada was used to fielding urgent requests when wildfire smoke blanketed cities. But these weren’t the usual calls.
For one thing, it wasn’t even fire season.
Winter was supposed to be the quiet period when wildfires die down and researchers like Spada perform instrument maintenance, write grant proposals and go home for dinner.
Instead, 2025’s so-called offseason ignited January 7, when the Santa Ana winds came howling through Los Angeles, bringing gusts upwards of 100 miles per hour, after more than eight months without meaningful rainfall.
By nightfall, thousands of homes in Los Angeles’ swanky Pacific Palisades neighborhood and the Altadena community north of the city were gone.
The next morning, Spada was fielding call after call at the University of California, Davis, from fellow air researchers at universities across the country who were packing instruments and other gear and heading for Los Angeles, many on their own dime.
They would be studying urban fires—not normal wildfires or even urban-wildland interface fires—but urban fires in which most of the fuel was manmade: lawn chemicals, asbestos insulation, lead paint, lithium batteries. Very toxic stuff, in other words.
They asked Spada which instruments to bring, what measurements to take, where to set up downwind and when he would be there. The calls quickly morphed into a WhatsApp group that’s still going strong, as results continue to roll in sporadically all these months later.
Spada, a trim, energetic man with a close-trimmed beard and reddish hair, is a project scientist at UC Davis’ Air Quality Research Center. He is one of only a handful of scientists in the world proficient at using a nuclear method for detecting toxic substances in air particles to understand their impact on human health and the environment.
Spada uses protons to peer at nanoparticles, 1/100th the width of a human hair. It might be hard to believe that something that small could hurt you, but in fact air pollution is four to five times more dangerous when it’s minuscule.
At that size, particles can easily make their way deep inside the human body, penetrating into the cells of vital organs, such as the heart, lungs and even the brain.
Since the fires in Los Angeles, Spada has made it his mission to determine just how much of an exposure hit Angelenos took in January. He’s concentrating both on aerosolized toxic substances—such as lead paint, weatherproofed items coated in PFAS “forever chemicals,” and lithium batteries—whose particles are toxic no matter their size, and from nanoparticles, innately dangerous due to their size and readily formed in the extreme temperatures of wildfires.
Internally, nanoparticles can wreak havoc, disrupting normal bodily function, drastically increasing rates of cancer, autoimmune disorders, and dementia. At this diminutive size, even normally safe elements can become toxic.