This is the first of a two-part series examining lead contamination following the Los Angeles Fires of 2025. This article addresses the developing science. The second will examine what that science requires from insurance companies investigating and adjusting smoke, soot, and ash claims.

A recent Caltech Watson Lecture should be required viewing for anybody involved in the Los Angeles wildfire recovery. In “Lead Contamination: An Old Foe Rises from the Ashes of the Eaton Fire,” Caltech geochemist François Tissot explains why an urban firestorm is fundamentally different from a vegetation fire. The Eaton Fire did not burn only trees and brush. It burned older homes, vehicles, batteries, paint, wiring, plumbing, plastics, electronics, treated materials, and decades of accumulated household products.

Many of the homes destroyed in Altadena were built when lead-based paint and other lead-containing materials were common. When those structures burned, the lead did not disappear. It became part of the smoke, ash, and fine dust carried into surrounding communities.

The Caltech Research Followed the Smoke Plume

Following the fire, Tissot and his Caltech team collected more than 300 samples from 52 homes. The sampling area extended from properties deep within the burn zone to communities miles away. The researchers found that lead concentrations generally followed the Eaton Fire smoke plume. Lead was detected at elevated levels on surfaces more than seven miles from the burn zone, which was the farthest distance sampled. The Caltech team reported that lead on uncleaned surfaces inside homes was generally highest near windows and other exterior openings, but contamination was also found farther into the structures.

That finding should end the notion that wildfire contamination necessarily stops at the property line or remains outside a standing home. Smoke and fine dust follow air currents. They enter through windows, doors, attic vents, garages, gaps in the building envelope, and mechanical systems. They settle on horizontal surfaces and contents. Once inside, particles can be tracked through the home, disturbed during cleaning, or redistributed through an HVAC system.

The California Department of Insurance’s Smoke Claims and Remediation Task Force similarly recognized that the extent and location of contamination may depend on wind direction, weather, proximity to the fire, the integrity of windows and doors, attic ventilation, and the type and operation of the HVAC system. The report noted that urban wildfire residue may contain lead, other heavy metals, asbestos, volatile organic compounds, and other substances released from the built environment.

Obvious Sampling Locations May Not Tell the Entire Story

The Caltech findings show that locations near windows and doors are important because they are likely entry points. They do not establish that testing should stop there.  Contamination may settle in window tracks, attics, insulation, garages, crawlspaces, closets, ductwork, wall cavities, carpets, bedding, upholstered furniture, toys, books, electronics, and other contents. Some of those places are easy to overlook. Some are inconvenient or expensive to test. That does not make them scientifically irrelevant.

The Department of Insurance task force received recommendations calling for property-specific sampling that considers attics, crawlspaces, areas behind walls, ducts, porous surfaces, bedrooms, living areas, floors, windowsills, garages, and other locations indicated by the structure and suspected pathways of contamination. 1

Not every home will require testing in every possible location. A modern, tightly sealed home outside the primary smoke plume presents different questions than an older house downwind from hundreds of burned structures.  But the location of the samples should follow the facts of the property.

Cleaning Helped but Not Always

The Caltech research also contains encouraging news. Researchers reported that cleaning reduced lead concentrations by approximately 90 percent on the surfaces they compared, bringing most cleaned areas below the EPA dust-lead benchmark they referenced.

That finding is important because it shows that the presence of lead does not automatically mean a standing home must be demolished or that every item inside must be discarded. Competent remediation can work.

But “most” is not the same as “all.” The Caltech findings also demonstrate why the success of cleaning should not simply be assumed. The surface may look clean and still retain measurable contamination. One cleaning method may work on a hard countertop but fail on carpet, upholstery, flexible ducting, unfinished wood, insulation, or another porous material.

The Department of Insurance task force noted that post-remediation testing can quantify whether cleaning was effective and determine whether additional work is necessary. It also recognized that testing for lead and asbestos presents clearer questions than many emerging contaminants because established health and worker-protection standards exist for those substances.

Remediation is supposed to remove the contamination. It should not be considered successful merely because the contractor completed the work and sent an invoice.

Contents Cannot be Treated as an Afterthought

Wildfire residue can settle on mattresses, pillows, clothing, upholstered furniture, rugs, toys, books, artwork, appliances, computers, musical instruments, and other personal property. Whether those items can be successfully restored depends on the material, level of contamination, cleaning process, intended use, and whether the result can be verified.

The task force report discussed professional cleaning of porous contents while recognizing that items which cannot be effectively cleaned may require disposal. It also noted particular concerns involving bedding, infant items, toys, apparel, and other property associated with hand-to-mouth contact or prolonged personal exposure.

A generic conclusion that “all contents are cleanable” is not a scientific evaluation. Neither is the opposite assertion that everything must be thrown away. The proper answer requires an item-specific or category-specific assessment performed by people with the right expertise.

The Science is Important but Should Not Be Exaggerated

The Caltech team has described its results as preliminary and not yet peer reviewed. The researchers are continuing to study many of the same homes and are working to better understand how contaminants moved with the fire plume and persisted over time. Some lead found in older homes may have existed before the fire. Lead-based paint, old plumbing materials, urban soil, roadway deposits, and ordinary household dust can complicate causation.

The Department of Insurance task force also recorded substantial disagreement over universal testing mandates, fixed geographical zones, testing methods, background contamination, and clearance standards. California public health representatives cautioned that every wildfire and every property are different and did not endorse one automatic list of contaminants for every home.

Those limitations should be taken seriously. The science does not presently establish that every smoke-exposed home must be gutted. It does not prove that every detected particle was caused by the Eaton Fire. It does not establish that every item of personal property must be discarded.

What it does establish is that the risk is real, lead can travel with an urban fire plume, standing homes can be affected miles away, and testing location and methodology matter. 2

Lead Should Be Taken Seriously

The Caltech video and continuing research change the claims conversation. Insurance adjusters and those suffering from fire loss should not assume that the lack of visible soot means no contamination. Policyholders should not assume that any detected lead automatically requires total demolition. Both positions substitute a predetermined conclusion for an investigation.

The reasonable approach begins with investigating the property and the fire. The issues are where it is located, what burned nearby, how the smoke traveled, how the home was constructed, where particles could have entered, which materials and contents were exposed, and who lives there.

The science and facts of the loss should determine where to look. 3

The next article will address what good faith claims handling requires now that insurers know lead may be present in places that are difficult to see and easy to avoid.

Thought For The Day

“No safe blood lead level in children has been identified. Even low levels of lead in blood are associated with developmental delays, difficulty learning, and behavioral issues.”
—Centers for Disease Control and Prevention

1 California Department of Insurance, Report of the Smoke Claims and Remediation Task Force to Insurance Commissioner Ricardo Lara and Other Interested Stakeholders (Mar. 9, 2026), available online at https://www.insurance.ca.gov/01-consumers/140-catastrophes/Smoke-Damage-Claims-and-Remediation-Task.cfm

2 Lori Dajose, One Year Later, Fire Research Continues to Support the Community, California Institute of Technology (Jan. 7, 2026) (describing planned resampling of the same homes and modeling of lead transport through the fire plume), available online at https://www.caltech.edu/about/news/one-year-later-fire-research-continues-to-support-the-community. Los Angeles County Department of Public Health, Preliminary Soil Testing Results from Eaton & Palisades Fires (Apr. 16, 2025) (noting multiple possible sources of lead and uncertainty regarding how much detected lead came from the fires). U.S. Environmental Protection Agency, Where Is Lead Found? (identifying older paint, legacy gasoline deposits, soil, and household dust as common sources), available online at https://www.epa.gov/lead/where-lead-found (last updated Oct. 28, 2025).

3 Centers for Disease Control, Testing for Lead Poisoning in Children (Mar. 11, 2026), available online at https://www.cdc.gov/lead-prevention/testing/index.html?utm_source=chatgpt.com.