The Brief

A potent carcinogen may have spread to communities as far as nine miles downwind of the Eaton and Palisades fire burn zones during debris clean-up, according to a new peer-reviewed study in the journal Nature.

A team of researchers has been studying the air pollution effects of clearing the remains of more than 16,000 homes and businesses destroyed in the 2025 fires.

Scientists with UCLA and UC Davis drove through Altadena and Pacific Palisades in an electric vehicle with mobile air monitors periodically over about seven months after the fires. They measured nanoparticles of hexavalent chromium, or chromium-6, within the cleanup areas. Paint, auto parts, electronics and fire retardant are possible sources, but more study is needed to understand where the chromium came from, the researchers said. They also detected other airborne metals, including lead and arsenic.

The researchers used computer modeling to understand how far those airborne particles may have spread beyond the immediate burn zones. About 3 million people live in the areas that could have been exposed, according to the scientists’ models.

The highest concentrations of nanoparticles — particles less than 1/1,000th the width of a human hair — were measured in March 2025, about two months into the debris removal effort in both burn zones. But the toxicity declined as time passed.

“ The good news is that some of those toxic metals, they were converted back to less toxic forms over time,” said Michael Kleeman, professor of civil and environmental engineering at UC Davis and lead author of the study. “So in the months after the wildfire, the threat from this sort of decayed away.”

In communities outside the burn zones, concentrations diluted further as the plume moved downwind, Kleeman said. By eight months after the fires, the researchers measured that heavy metal concentrations had fallen to background levels for the L.A. basin.

The research highlights how “even after the fire is over, the danger isn't gone,” Kleeman said.

An aerial view of properties cleared of fire debris in Altadena in July 2025.

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Mario Tama

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Getty Images

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Cleared lots in the Palisades Fire burn zone stretch into the distance.

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Qian Weizhong

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VCG / Associated Press

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How concerned should you be? 

The researchers and outside experts emphasized to LAist that the study’s findings do not prove widespread contamination of homes, businesses or the environment.

“ I hope we can get a message of caution out there, but not panic,” said Kleeman.

Andrew Whelton, a Purdue University post-disaster environmental risk researcher who was not involved in the study, said the research is far from proving what, if any, harm to human health could occur, especially because no indoor testing was carried out.

“Drawing a line from street-level detections to indoor exposure, without confirming that the [chromium-6] outdoors entered homes at levels posing health risks, is a significant leap,” he said.

Whelton, who carried out soil testing in the L.A. fire burn scars, said he worries the paper could needlessly sow fear because so many open questions remain. He has argued for funding and establishing more comprehensive contaminant testing at the individual household level in the wake of such destructive fires — the most definitive way to know your personal risk.

“The bottom line: detecting nanoparticles in outdoor air does not mean harm occurred to 3-plus million people living and working inside buildings,” Whelton told LAist.

The average levels of chromium-6 detected in the air during debris cleanup in March were well below limits set for workplaces by the Occupational Health and Safety Administration, but above the U.S. Environmental Protection Agency long-term screening levels for homes, according to the study.

Still, those comparisons are imperfect because the particles measured were far smaller than what’s used for current health standards — meaning they can more easily travel throughout the body, Kleeman said.

“We don't know for sure what the concerning level should be,” he said.

Workplace standards, for example, are set for healthy adults working eight-hour shifts, “rather than for sensitive populations such as young children, pregnant individuals, older adults, or people with chronic illness,” said Jun Wu, an environmental health scientist and professor at UC Irvine’s School of Public Health, who also was not involved with the study.

More comprehensive study is needed to get at what true exposures may, or may not, have occurred, Kleeman and outside researchers emphasized.

“This is a single, novel finding based on limited sampling, with the downwind reach estimated by modeling,” Wu said, “so broader monitoring is the natural next step.”

Where the nanoparticles may have spread

The broadest potential plume was from the Palisades Fire, spreading as far as the southern San Fernando Valley to the north and Beverly Hills and West Hollywood to the east. Kleeman said computer modeling of prevailing winds show the plume being pushed toward central L.A.

“Santa Monica, Venice and moving toward central L.A. took the brunt of the plume,” Kleeman said.

Prevailing winds didn’t spread the plume quite as far in communities near the Eaton Fire, with modeling showing northeast Pasadena being the primary community affected.

A map from the study showing the ZIP codes where a airborne chromium-6 may have spread during debris removal.

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Courtesy UCLA / UC Davis

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Many unknowns remain about the public health effects of catastrophic fires in urban areas — and how far those risks may drift beyond the burn zone.

“More work is needed to understand how widespread and persistent these particles were, how exposure varied by location and cleanup activity, and what the health risks were for nearby residents,” said Sina Hasheminassab, an air quality researcher at NASA’s Jet Propulsion Laboratory who was not involved in the study.

Additionally, the study raises questions about how to better protect people’s health not only during, but also after destructive urban fires, said Wu.

“Much of our attention goes to the smoke during the active fire, but this study points to the cleanup and recovery phase,” she said. “This time window deserves just as much attention as the fire period itself.”

For example, some survivors whose homes survived never left during debris removal — some cited concerns about not being able to afford another place to stay without upfront insurance payouts, as well as worries about looting.

The study notes that workers in the burn zones faced the highest risk.

“Based on our field observations, many workers in the debris cleanup zone did not wear masks despite California requirements to provide approved air purifying respirators to workers,” the researchers wrote.

Crews remove wildfire debris on hillside property in Pacific Palisades last year. Researchers note in a recent study that many workers they saw weren't using respiratory protection.

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Charles Delano

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U.S. Army Corps of Engineers

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Survivors push for policy to protect public health after wildfires

Nicole Maccalla’s home in Altadena was damaged but ultimately survived the Eaton Fire. She and her two teenagers moved back in nearly six months after the fire, while debris removal was ongoing. Her daughter’s school nearby was also reopened just a month after the fires.

“ I know I was exposed. I know my kids were exposed,” Maccalla told LAist. “I'm not really sure what to do with that, to be honest.”

“Our entire community is really now guinea pigs,” she added. “It’s deeply concerning.”

Nicole Maccalla, with her kids, Seb and AJ. Their Altadena home survived the Eaton Fire but suffered serious smoke damage.

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Courtesy Nicole Maccalla

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Maccalla, a data scientist and member of Eaton Fire Residents United, helped guide ongoing research by scientists like Kleeman to better understand the levels of contamination after the fires.

She said this study is a warning.

“ I think in the future, we need to move a little slower in fire recovery. The goal should not be speed. The goal should be health and safety,” Maccalla said. “We rushed it, and I hope that we learn from this mistake.”

She and fellow survivors see some hope in a new bill they helped inform. AB 1642, or the Wildfire Environmental Safety and Testing Act, is making its way through the California Legislature.

The bill, written by Assemblymember John Harabedian, would establish the first statewide health standards for testing and cleaning up debris in and outside standing homes, schools, businesses and other structures after a wildfire.

Maccalla urged fellow survivors worried about the results of this study to prioritize caring for their mental and physical wellbeing.

“The stress of all of this is just going to be an added component that will be another contributor to us getting sick long term,” she said. “So many of us are still in survival mode. It's time, I think, to start taking care of ourselves a little bit.”

On Tuesday, street safety advocates and families of victims of vehicle collisions demanded that Los Angeles Mayor Karen Bass declare a state of emergency on traffic violence in the city.

Sandra Sanchez Loulakis’s son died last year after she said he was hit by a negligent driver.

“I’ve been struggling just to survive daily,” she said at the news conference organized by traffic safety nonprofit Streets are for Everyone. “This is what happens to a parent when they lose a child.”

The city has seen 8% more fatal traffic collisions this year than during the same period last year, according to LAPD data from the end of August.

Advocates said an emergency declaration would better coordinate resources to respond to traffic fatalities, which have exceeded the rate of homicides for the last three years.

“ This is not a matter of we don't know what to do,” Damian Kevitt, who leads Streets are for Everyone, said Tuesday. “This is a matter of we know exactly what to do. We’re just not making this a priority as a city.”

Kevitt said more than 1,250 people signed an open letter delivered to the mayor and L.A. City Council. One of the demands listed in the letter is for the city to restore transportation department staff.

Earlier this year, the city gave up $100 million in state grants to make streets safer because it did not have the personnel to complete the projects in compliance with state-mandated deadlines.

Draft executive directive on Vision Zero

It appears there had been momentum from the mayor’s office earlier this year to issue an executive directive recommitting the city to its Vision Zero goals of reducing traffic fatalities to zero.

According to emails from May shared with LAist, the mayor’s senior director of transportation told an activist that a draft executive directive was “under review” and expected to be released “within the next three weeks.”

The email was sent to Jonathan Hale, who organizes community members to paint crosswalks where there have been pedestrian-involved collisions.

The executive directive has yet to be released.

LAist submitted a public records request for drafts of the executive directive, but on Sept. 14, the mayor’s office responded saying it could not disclose any records.

“[The records] include drafts and/or deliberative process for which the public interest served in nondisclosure clearly outweighs the public interest served by the disclosure,” the office said.

The mayor’s office has not responded to requests for comment about the draft executive directive.

A new report commissioned by Olympics organizers estimates that the 2028 Games will generate at least $20 billion in economic output across Greater Los Angeles.

The analysis, prepared for LA28 by the nonprofit Los Angeles County Economic Development Corporation’s Institute for Applied Economics, looked at the economic effects of L.A. hosting the Olympics and Paralympics. It includes organizing committee spending, capital investments, publicly funded transportation and security investments, and tourism. 

In total, the report projects that new economic activity across Los Angeles, Orange, Riverside, San Bernardino and Ventura counties could total somewhere between $20.5 billion and $25.4 billion and add around 126,000 and 152,000 jobs to the economy.

A second less conservative methodology employed by the researchers estimates the overall economic output could be even higher, between $35.4 and $40.6 billion and up to 224,000 new jobs.

“ Together, they provide a responsible range, not an exaggerated promise,” Stephen Cheung, CEO of the Los Angeles County Economic Development Corporation, said at a news conference announcing the report on Tuesday. “ If we work together with intention, the Games can leave Los Angeles with more than unforgettable memories. They can leave us with stronger businesses, greater opportunities, and a more connected regional economy.”

Despite the 2028 Games being advertised as a "no-build" Olympics, the biggest chunk of spending laid out in the report is on capital projects, including the $2.6 billion L.A. Convention Center renovation, billions in LAX improvements, major transit projects like Metro ExpressLanes on the 105 Freeway, and venue renovations, such as upgrades to Rose Bowl Stadium.

The report also estimates that around $5.7 billion of LA28’s spending will be in the five county region. LA28 has a $7.1 billion budget and has pledged to keep 75% of its spending in the Greater L.A. area, and put 25% toward small businesses.

“ That economic impact is going to be felt far and wide and across Los Angeles, as well as the Southern California region,” LA28 CEO Reynold Hoover said Tuesday.

The report is the second economic analysis forecasting the effects of the 2028 Games to come out this month. A separate report submitted to the L.A. County Board of Supervisors in early September estimated that the Games would produce more than $13 billion in direct spending and a total economic output of $19.2 billion in Los Angeles County alone.

The same report also laid out the potential uneven distribution of economic benefits to the region, including limited benefits for Olympic venue sites that are not tourist destinations and parts of Los Angeles being excluded from the Games altogether.

HR&A Advisors, the consultant group that put the report together, identified Carson, Pomona, the City of Industry and Exposition Park as locations that are hosting Olympic events, but that could end up being “passthrough areas.”

“Although these areas may be active during the day, they may struggle to capture spending from visitors who pass through but do not spend money outside the venue,” the report states.

The county report also questioned what economic benefits will flow to parts of L.A. County that will be disconnected from Olympic and Paralympic activities, like Antelope Valley and Southeast Los Angeles.

Meanwhile, the analysis found that L.A.’s typical tourist destinations — including downtown L.A., Old Town Pasadena, downtown Long Beach and the Venice Boardwalk — can expect to be active areas for economic activity during summer 2028.

The Palisades and Eaton Fires last year destroyed thousands of homes in Los Angeles County. Thousands more were left standing, but choked with toxic fire residue.

On Tuesday, Gov. Gavin Newsom signed a package of bills that will make California the first state in the nation to establish smoke damage testing and cleaning standards for insurance companies.

Assembly Bills 1642 and 1795 will require insurers to test for smoke damage, cover the cost of cleaning contaminants, and keep paying for a homeowner’s alternative living expenses until the home is found safe to reoccupy.

The California Department of Toxic Substances Control will have until the end of 2028 to develop testing and cleaning standards for lead and asbestos, and until the end of 2029 to set rules for heavy metals and other pollutants.

Reaction to the bill

According to the state Department of Insurance, property owners filed 13,000 smoke damage claims for standing homes after the January 2025 fires. While insurers have covered testing and cleaning in many cases, other homeowners are still unable to return home as they battle with insurance companies over addressing smoke damage.

In a news release Tuesday, the governor and an author of one of the bills praised the changes to state law.

“These new protections will make insurer obligations clearer and give homeowners more financial flexibility when they need it most,” Newsom said.

Assemblymember John Harabedian said: “Science, not an insurance company’s opinions, will determine whether a home is safe.”

Insurance industry groups had opposed shifting rules and regulation away from the state Department of Insurance and to the Department of Toxic Substances Control.

Altadena residents pushed for change

Testing efforts by a group known as Eaton Fire Residents United found that lead, asbestos and heavy metals were still present in homes even after they were cleaned by professional remediation companies. Jane Lawton Potelle is the group’s executive director.

“California is leading the nation in how to recover safely after an urban wildfire,” she said in a news release about the laws’ passage.

Public health officials said smoke from the L.A. County fires was particularly toxic because it emanated from urban areas. The structures that burned often had lead paint and asbestos insulation.

The fires also destroyed cars, appliances and other human-made materials. This created more pollutants than smoke from fires in rural areas, which mainly burn through vegetation.

LAist covered the push to change smoke damage policies in a recent episode of our podcast Imperfect Paradise, which breaks down what these changes could mean for insurers, homeowners and how California adapts to climate change.

For years, California lawmakers and transit leaders have requested billions of dollars from the federal government to temporarily double L.A.’s bus fleet and support public transportation for the 2028 Olympics and Paralympics.

Those calls have grown increasingly desperate in recent months, with Los Angeles Metro saying time is running out to execute its plans.

Now, the transportation agency says that if it doesn’t get a guarantee that the money is secured by the end of the year, it won’t provide the extra buses. Instead, it would leave private Olympics organizing committee LA28 to come up with a new plan.

Metro staff laid out the timeline in a report submitted to the agency’s board that will be reviewed at a special meeting Wednesday.

“Transportation capacity cannot be procured overnight,” Metro wrote in a statement to LAist.

A looming funding deadline

If federal funds don’t materialize in time, LA28 could be left with a major logistical and financial challenge.

Metro, the countywide transportation agency, has thus far led planning for the enhanced bus service, which was seen as the cornerstone of the region’s strategy to get people around Los Angeles during the summer of 2028.

The board report outlines that Metro has, as of May, secured commitments from 28 transit agencies to loan or donate over 1,000 buses and more than 300 personnel to support the enhanced bus service.

In total, Metro has said it needs $2 billion from the federal government for the Games. Approximately half that appropriations request would be used to obtain, operate and maintain 1,750 buses — on top of its existing fleet — for the Olympics network.

Metro said that any additional buses it provides will depend on the amount of money it locks down. The agency told LAist that it needs to make decisions based on concrete funding well before the Games in order to secure the buses, operators and facilities.

LA28 also does not appear to be ready to pay for a temporary bus system, should federal funding never arrive. Its $7.1 billion budget does not include a line item for transit.

This in turn puts the city of L.A. at risk because Los Angeles is the financial backstop for the Games. L.A. and the state of California will cover cost overruns from the Olympics and Paralympics, should they occur.

LA28 CEO Reynold Hoover told LAist on Tuesday that he was not alarmed about Metro's impending deadline.

"[Metro CEO] Stephanie Wiggins and I are working really close together to work with the administration to find the funding," Hoover said. "I'm pretty confident that the administration and the Congress will find funding that Metro needs."

When asked if the Olympics could be put on without a supplementary bus system, Hoover told LAist that a bus program for the Olympics would be a part of the Games "one way or another in some scale or form."

What did Metro and LA28 agree to?

Metro can exit its role orchestrating the Olympics bus system according to a memorandum of understanding with LA28 outlining the parties’ obligations for the 2028 Games.

According to the agreement, approved by Metro’s board in March, Metro is not required to provide additional services beyond its status quo if it doesn’t secure supplementary funding for its enhanced bus service.

The September board report that will be the subject of Wednesday’s meeting outlines that without “funding certainty,” its agreement with LA28 will expire.

“The organizing committee will need to seek another delivery partner for spectator and workforce transportation,” the agency wrote in the board report.

This summer, lawmakers included $875 million for Olympics-related transportation needs in a spending bill that still needs to move through the appropriations process. According to the Metro report, that funding would be covered by rescinding money for passenger rail projects in other parts of the country, meaning it has an uphill battle passing through the legislature.

Jacie Prieto Lopez, an LA28 spokesperson, said in an emailed statement that Olympics organizers were working with Metro to “jointly engage key partners on Capitol Hill and the White House as appropriations and budget decisions are made.”