Nicholas Spada Spent Months Analyzing Smoke From the LA Fires. He Thinks People Have a Right to Know, and ‘Air Is Everything.’

After the Fires: 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 off season ignited Jan. 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, one one-hundredth the size 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. 

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. 

Titanium, a typically inert element used in things like medical implants and white pigments found in everything from plastics to children’s crayons, is an example of this. Nanoparticles created when the pigment, titanium dioxide, is exposed to extreme heat are especially dangerous. The titanium dioxide converts into titanium monoxide, a much less stable form and therefore more damaging to tissues in the body. 

Scientists are just beginning to understand the troubling health impacts of these increasingly common megafires and urban blazes, and Spada is determined that survivors not be left in the dark.

Candace Tsai, an expert in nanoparticle risk assessment and associate professor of industrial hygiene at the University of California, Los Angeles, echoed the concern. “There is no known safe level of exposure to these types of ultrafine particles,” she said. “They don’t stay outside—they get indoors, they get into cells. And we are only beginning to understand their toxicological effects.”

A Right to Know

Spada’s work is governed by the philosophy that “air is everything,” and that people have a right to know—and that science should empower, not confuse.

“You don’t get to choose what you breathe. So we have to measure it, make it visible, make it actionable,” he said. “If you don’t have a Ph.D., that shouldn’t disqualify you from understanding what’s in your air. So I make cheat sheets. I write it like I’d explain it to my kid.”

Spada is now trying to help others find the answer to many of the same questions he remembers asking as a child in Bangor, Maine, growing up in the shadow of a vermiculite processing plant that coated his neighborhood in fine white dust. 

“Everyone had a cough,” he said. “There was this blighted area where nothing grew for about a mile around the factory. Everything was smothered under this fine white vermiculite powder. It was like the factory had created its own barren lunar landscape.”

When the plant was finally shut down for pollution violations, it left devastation in its wake: economic, environmental and human. “A lot of people were suddenly out of work. Homelessness went up. It felt like we’d been given a false choice—pollution or poverty.”

Spada wanted to find a better option.

As his work proceeded in the aftermath of the Los Angeles fires, he made sure to follow the code he developed back in Bangor. He wants to understand the pollution impacting families desperate to protect themselves and detoxify their homes from elements in the air and the ash coating everything, which Spada found truly alarming. 

“There’s a responsibility when people hand you something that came off their kid’s pillow,” he said. “You take it seriously.”

Six days after the fires started, Spada loaded up four air samplers, an extra pump and a batch of labeled pre-filters. He had already reached out to his contacts in LA, including Jeni Knack, an environmental health advocate, and Melissa Bumstead, a longtime activist for families near the Santa Susana Field Laboratory, who took the lead on locating those willing to house Spada’s monitoring arrays for a month or more.

“It looked like snow,” Bumstead said. “The ash was on my daughter’s swing set—that’s when I knew we had to do something.”

Spada drove south, accompanied by a playlist his older son, James, had made especially for the trip, and all the coffee he needed to stay alert. 

By 4 p.m., he was installing the first unit in a backyard at a volunteer’s home in West Hills. Bumstead and Knack had helped scout and secure several of the initial monitoring locations downwind of the Jan. 7 blazes, the Palisades and Eaton fires. 

“It looked like snow. The ash was on my daughter’s swing set—that’s when I knew we had to do something.”

— Melissa Bumstead

Spada is one of only two researchers in the world with expertise in “time sorted cascading impactor air monitoring.” The “DRUM” sampler, an admittedly terrible acronym, in Spada’s opinion, stands for “Davis Rotating Unit for Monitoring.” 

About the size of a carry-on suitcase, each sampler is fabricated to the Davis team’s specifications and weighs between 20 and 50 pounds, requiring their own custom-built stands.

The sampler uses a pump to continuously force air through a series of eight filters, ranging in size from PM10 all the way down to PM0.09, each trapping smaller particulate matter than the last—from 10 micrometers, or microns, to 9 one-hundredths of a micron. To put those numbers in perspective, the Environmental Protection Agency, in regulating air pollution, uses PM2.5 as a metric, and 2.5 microns is about 30 times smaller than the width of a human hair. 

The DRUM filters rotate at user-specified intervals, usually switching to a new section of filter every three hours. But in LA, Spada chose to set it to a two-hour rotation to get more precise data. 

This unique sampling method allowed him to see the evolution of dynamic air quality situations at much finer detail than other methods.

The monitors had to stay in place for a month. It would be an additional month and a half before he could book time in the particle accelerator. Preliminary results were at least six months away. 

Ultrafine. Inhalable. Persistent.

To understand what was—and wasn’t—unusual, Spada began by comparing the LA fire ash sample results to an ordinary wildfire that happened at the same time: the Hurst Fire, a brush fire that burned well over 500 acres of vegetation near Sylmar in Los Angeles County and also began on the morning of Jan. 7. 

“The Hurst fire burned a small portion of roadside vegetation. No homes were burned down, no vehicles, nothing like that,” he said. “It’s sort of a surrogate, where it’s like vegetation, but also impacted by just the urban landscape of LA. But it’s not contaminated with structure fire or vehicle fire or anything like that.”

The Hurst Fire samples had elevated levels of both lead, left behind by leaded gasoline, and arsenic, one of the most common naturally occurring heavy metals in surface soils across California. But there was a striking difference between those results and the results from the Eaton and Palisades fires.

“We’re talking about invisible pollutants with long-term health consequences.”

— Mohammed Baalousha

Those urban fires produced air pollution with significantly more lead, a neurotoxin. Among the other worrisome substances: cadmium, antimony and asbestos, all known or likely carcinogens.

“These weren’t wildland fire signatures,” Spada said. What showed up were “things you expect in old insulation, old paint. This was building debris, not tree bark.”

Most troubling about the Eaton and Palisades pollutants were their sizes: toxic metals weren’t just present—they were showing up in the smallest particles, under 0.1 microns. Ultrafine. Inhalable. Persistent.

Mohammed Baalousha, an environmental nanoparticle researcher at the University of South Carolina and collaborator of Spada’s who also reviewed particle samples from the LA fires, confirmed the danger. 

“The smaller the particles, the deeper they go into the lungs and the harder they are to remove,” he said. “That’s why this kind of analysis matters. We’re talking about invisible pollutants with long-term health consequences.”

The Initial Sampling Sprint

As early as the start of February, Spada began receiving ash samples from Altadena and the Palisades from his LA contacts, Bumstead and Knack.

The two women didn’t just organize drop sites—in the weeks following the fire, they were out in the field collecting samples themselves. While doing so, Bumstead and Knack were struck by just how few people were wearing proper protective gear.

“We saw crews … doing cleanup—digging through ash without any masks at all,” Knack said. Bumstead added that many of the volunteers “weren’t even wearing gloves.” 

The pair, suited up in P100 respirators, Tyvek suits and double gloves, tried to inform people of the hazards, but were shaken by the disregard for volunteers’ health. “They were helping—with the best intentions,” Bumstead said. “But nobody had warned them that the ash might contain toxic metals or worse.”

The contrast between the protocols Spada had trained them on and what they were seeing in the field left a lasting impression. “Nick walked us through how to do it right,” Knack said. 

Spada was extra cautious, explained Bumstead, as his mentor had died from health complications from exposures linked to his air quality research. “Gloves over gloves, tape seals, don’t cross-contaminate. He took it seriously, and so did we,” said Knack. 

But at the same time, “it felt like we were watching people walk into danger with open eyes—and no one stopping them,” she said. 

For a little over a week after Spada’s first visit, the pair took every opportunity to be out collecting in the field, talking with distraught residents, working around commitments to work and family, in a push to collect as many ash samples as possible before the January rains. Spada sent these samples on to South Carolina for his collaborator, Baalousha, to analyze. 

Spada is used to people not understanding his work. In addition to tracking the concentration of particles only a few molecules wide, his monitoring work looks for a panoply of toxic substances, many of which are perfectly safe until they reach nanoscale. 

The EPA never created exposure limits for this class of materials, safe at the macro scale, extremely dangerous at the nano scale. Given the lack of clear limits from regulators, Spada and his collaborators have had to use their best judgment, and what little research is available, to compile a set of ad hoc guidelines of their own. They’ve had to rely on just a few pieces of literature to create recommendations for substances like magnesium and titanium monoxide. 

In other cases, the academic community has known for decades that the EPA exposure limits are far too high, leaving people vulnerable to toxic doses of hazardous compounds, such as lead, lithium and barium. But rulemaking is slow at the best of times, and the Trump administration is now working to undo regulations rather than add them. That means new standards reflecting the most recent research on safe exposure limits are still a long way off. In the meantime, the academic community has had to collaborate to set best-practice exposure limits of their own for screening samples from the LA fires.

“Some areas had surprisingly little impact. Others were enormously impacted.”

— Nicholas Spada

The results trickled in from Baalousha’s lab in South Carolina, often leaving the scientists with more questions than answers. In reports prepared for the families who had submitted samples, Spada and Baalousha included a disclaimer: These were not diagnostic tools, not exposure-level tests, but environmental screeners compared against conservative thresholds agreed upon by an academic consortium. Due to a lack of data, many of these thresholds were based on child ingestion, not inhalation.

Still, even with all those limitations, some values were concerning.

“The data is more mixed than I expected,” Spada said. “Some areas had surprisingly little impact. Others were enormously impacted.”

Families who had been told their homes were safe emailed with follow-up questions. Knack and Bumstead fielded dozens of messages from neighbors confused about what the test results meant—or didn’t.

“One woman kept asking if it was safe to wipe down her counters,” Knack said. “We had to keep explaining that even Nick can’t answer that without doing air and surface testing inside.”

Within a few weeks, schools had reopened. Children were back on playgrounds that had been pressure washed but not tested. Portable high efficiency particulate air (HEPA) filter units were running in some classrooms, but without baseline data or ultrafine monitors, there was no way to measure what—if anything—remained in the air.

“I’d like to say it’s better,” Spada said. “But without data, you can’t assume anything. You either monitor it, or you’re flying blind.”

An Assist From the Manhattan Project

In early March, back at UC Davis, Spada began the slow, meticulous process of cataloging everything. Ash samples, air filters, metadata logs—all of it had to be cross-referenced, cleaned and sent to the right researcher for testing.

“I’m obsessive about clean data,” he said. “I don’t want to ever get into a situation where we’re giving people data that isn’t right. So we triple check.”

If the university’s Crocker Nuclear Laboratory looks like an above-ground fallout shelter, that’s because it is. Only, this concrete bunker was made to keep the radioactive material inside. 

The particle accelerator dates back to the earliest days of nuclear testing, built for the Manhattan Project, but was moved to its current home on the Davis campus in the 1950s. Spada shares the proton beam with more than a dozen other researchers, all jockeying for time for their projects.

Spada’s is one of the hardest projects to tune the beam for. “The beam is way over-powered to run my samples, at baseline,” Spada said, comparing the amount of power he needs to a couple drops of water, “but the beam, it’s like Niagara Falls.” 

The technique Spada relies on, Particle-Induced X-ray Emission (PIXE), is a focused stream of protons to knock electrons out of atoms embedded in the sample. As those atoms stabilize, they emit X-rays—and each element gives off a signature energy. “It’s like a fingerprint,” Spada said. “Every metal shows up in a different color of X-ray.”

Because PIXE is non-destructive, Spada can scan the same filter multiple times, looking for metals like lead, arsenic, cadmium and antimony—elements he frequently finds in urban wildfire debris. The beamline at Crocker is one of only a handful in the country equipped for this kind of environmental work. 

“It’s not fast,” Spada said. “Sometimes it takes a couple of minutes just to scan a pinhead-sized area. But it’s precise, and it tells us what’s really in the air people are breathing.”

Spada is still in the process of running each of the filters from his monitoring areas through thermal-optical analysis for organic carbon, and spectroscopy that could detect molecular structures, in addition to the PIXE process. 

Just the thermal-optical carbon analysis alone takes an hour per sample and gives just two numbers—how much elemental carbon and how much organic carbon. 

Spada had droves of samples to get through. 

“We turn everything into methane. We use a Methanator, which sounds like something out of Phineas and Ferb, but it’s how we detect the organic carbon fractions,” said Spada. Each type of carbon burns off at a different temperature, revealing its origin—wildfire, diesel, gasoline, building materials. Because the signatures from the LA fires weren’t consistent with typical wildland burns, he noticed a strange pattern in one of the samples early on—high sulfur, high chlorine. 

“We think it was from PVC pipes,” he said. “That’s one of the only materials that would give you both those elements. And it was from the Altadena set, so in a residential area.”

He flagged the findings for Baalousha. They have been reviewing each other’s results as an expedited substitute for formal peer review, and drafting community updates together.

“It was really important to him that we not just publish something academic,” Knack said. “He wanted it readable—like, for families, not scientists.”

Spada has been releasing reports on the ash samples on a rolling basis since he and Baalousha got the first results back in March. Each report went out with links to cleanup guidance, recommendations on protective gear and a glossary. 

He hopes to be able to release a preliminary report on the air conditions during the fires shortly. In mid-August, over seven months after they tore through LA, Spada was finally able to review his preliminary PIXE data while on leave from work, recovering from a routine outpatient surgery.

So far he’s found that the majority of nanoparticles were created and circulated in the air during the active fire phase, and once the fire had been contained and transitioned to the smoldering phase, the number dropped off steeply. “For example, in Pasadena, silicon in the 0.09-0.26 micrometer size range was 8 times higher during the active fire period,” Spada said via email. 

High concentrations of inorganic material was detected in the smoke at all four of his LA fire monitoring sites—Pasadena, Santa Monica, Hollywood and West Hills—indicating the man-made origins of the fuel. Spada and his team measured a long list of elements in the air: sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, potassium, calcium, titanium, iron, copper, zinc and more. They compared how much of each element was present during the “active fire” phase versus the “smoldering” phase, across different monitoring sites and particle sizes.

Almost every element showed higher levels during the fire itself, though the amount varied a lot depending on the element, location and particle size—with no obvious overall pattern. To make sense of it, the team plans to run a cluster analysis (a statistical method to group similar results). 

The biggest red flag came from the West Hills site—even though it was the farthest from the flames. Air monitors there picked up unusually high amounts of titanium, iron and copper in very tiny particles, the kind that can lodge deep in the lungs. 

That’s surprising, since West Hills should have been less exposed, except that smoke from the Hughes fire—a vegetation fire that began a few miles north of Santa Clarita on Jan. 22 and burned just over 10,000 acres before being extinguished about a week later—drifted directly overhead. 

For scientists, this finding is troubling and raises more questions than answers about what people were breathing during the fire.

Thus far, Spada has only had the time and resources to run the samples through PIXE analysis. While PIXE provides a strong basis to work from, it is neither the most accurate nor detailed form of metal analysis and thus far has failed to get precise measurements of certain key metals, such as arsenic, cadmium and lead. 

These preliminary results have helped Spada determine his course for the next phase of analysis: He plans to analyze all the samples using synchrotron-induced X-ray fluorescence (SXRF), which is complementary to the ion beam analysis the samples already underwent at Crocker Nuclear Lab. 

SXRF is a technique scientists use to figure out what elements are in a sample, like wildfire ash or tiny airborne particles. It starts with a synchrotron—a giant machine that speeds up electrons until they’re moving nearly at the speed of light. As they circle the track, the electrons give off powerful beams of X-rays. These X-rays are much brighter and more focused than anything a normal lab can produce, which makes them ideal for studying very small or complex samples.

When the X-ray beam hits a sample, it knocks electrons out of atoms inside it. To “fix” themselves, the atoms shift other electrons down to fill the gaps, releasing energy as new X-rays in the process. Each element (iron, copper, titanium, etc.) gives off a unique signal, almost like a fingerprint. By measuring those signals, scientists can identify exactly which elements are present and how much of each there is. The method is sensitive enough to pick up even trace amounts, and it doesn’t destroy the sample—making it a powerful tool for environmental research.

Spada hopes this next analysis will shed more light on the metal question, as it is a particularly powerful technique for quantifying metals in miniscule samples. He won’t know how bad concentrations of heavy toxic metals were during the fires until that analysis is complete.

“I’ve seen a lot of anomalous results from the various data streams surrounding these fires,” Spada said. “Fortunately, the academic consortium brings together a lot of experts with diverse skills and specialties. I think this collaboration is going to be important to fully understand the horrendous events in January so that we can better prepare for the future.”

Knack and Bumstead are grateful for Spada’s commitment to the data and people impacted. “Nick doesn’t just dump data on us. He explained things like nanoparticles so we could actually talk about it with our community,” said Bumstead. 

“He was really good about walking us through everything,” Knack added. “He makes it accessible.“ 

Transparency and Collaboration

Spada kept fielding calls all summer long. Some were from residents asking how to interpret the results. Others were from scientists hoping to compare notes. A few were from city officials. “Most of them were like, ‘You’re doing what now?’ I had to explain the whole setup again,” he said.

Baalousha, who has collaborated with scientists analyzing these kinds of fires across the country, put it simply: “This work is about justice,” he said. “If you don’t measure it, you’re allowing invisible harm to continue. I do this because people deserve clean air, even if they can’t see what’s wrong with it.”

That, to Spada, is the point. “I’m building a record,” he said. “But I’m also building trust. If people know we’re not going to hide the data, they’ll come back next time. And maybe next time, we’ll be ready sooner.”

Spada’s work doesn’t end with the test results. He takes the long view on scientific inquiry, always keeping the why in mind. 

“I’ve never been fully funded,” he said. “And I don’t know that I’d want to be. Limitations keep you creative.”

In his view, the future of air monitoring needs more than just funding. It needs better priorities. In Spada’s world, science is rooted in collaboration and data transparency. He’s developed portable samplers that can be deployed rapidly, trained community volunteers to handle ash safely and created data reports with plain-language footnotes.

He dreams of a world where every school has a baseline air quality record, every disaster has a monitoring protocol and every kid can check an app to see a real-time breakdown of PM2.5, nanoparticles and volatile organic compounds in their air.

“This work is about justice. If you don’t measure it, you’re allowing invisible harm to continue.”

— Mohammed Baalousha

“I’m not just doing this for the science. I’m doing this for James and Ronan,” Spada said, referring to his kids. “If they grow up in a world where clean air is an expectation, not a luxury, then maybe I did something right.”

He doesn’t see himself as an environmental evangelist. “I’m not trying to scare people,” he said. “I’m trying to help them measure what’s there—and decide what to do with that information.”

In moments of doubt, Spada returns to the lab. Not because it always offers answers, but because it allows him to keep asking questions.

“The world is full of problem solvers,” he said. “That’s how I stay hopeful.”