On Jan. 7, two residents on opposite sides of Altadena — Francois Tissot, a Caltech professor who studies the geology of ancient Earth and our solar system, living in the east side of town; and Jane Potelle, an environmental advocate living in the west side — fled the intensifying red glow of the devastating Eaton fire.

The inferno devoured home after home, unleashing what experts estimate to be tons of dangerous metals and compounds, from lead to asbestos to the carcinogen benzene. Carried through the vicious winds, the toxins embedded deep into the soil, seeped into the blood of first responders, and leaked into structures in the area that hadn’t burned down.

Within weeks, Altadena residents whose homes had withstood the fire began to return — yet few were testing for contaminants both Tissot and Potelle knew were almost certainly sitting in their still-standing houses.

Working independently, they both decided to create a comprehensive picture of the contamination lurking within surviving homes, both in the burn area and miles outside it.

They came to similar results: In the houses inside the burn zone, there was lead — a metal capable of dealing irreversible damage to the brain and nervous system — at levels far exceeding 100 times the Environmental Protection Agency’s allowable limits. Tissot’s group also found lead levels exceeding the limit over five miles from the fire’s perimeter.

“Children exposed to lead will have diminished cognitive development,” said Tissot, referencing studies that found exposure to leaded gasoline in though the 1990s was correlated with a drop in children’s IQ (an imperfect but useful metric for reasoning ability) by up to seven points.

“To me, what’s at stake is the future of a generation of zero- to 3-year-olds,” Tissot said. “If nothing is done, then these children will be exposed. But it’s totally avoidable.”

Potelle, frustrated with the lack of government response to contamination concerns, started a grassroots organization with other Altadena residents with standing homes to collect and publish tests conducted by certified specialists.

The organization, Eaton Fire Residents United, or EFRU, found lead in every single one of the 90 homes for which they’ve collected test results. Of those, 76% were above the EPA limits.

EFRU and Tissot’s team were distressed by these data, particularly seeing debris-removal and remediation contractors work without masks in the burn area and some residents even begin to return home.

In early April, Anita Ghazarian, co-lead of EFRU’s political advocacy team, went back to her standing home within the burn zone to pick up mail. She watched as a grandmother pushed a toddler in a stroller down the street.

“She has no idea … this area is toxic,” Ghazarian recalled thinking. The gravity of the situation sunk in. “To me, it’s just — unfortunately — a calamity waiting to unfold.”

Evidence mounted in the 1950s that even small amounts of lead exposure could harm children’s brains. But by the time the U.S. banned lead in paint in 1978, roughly 96% of the homes in Altadena that burned in the Eaton fire were already built. In the Palisades, that number was 78% — smaller, but still significant.

Jared Franz looks at the state of his kitchen, which survived the Eaton Fire, but is inhabitable due to smoke damage.

(William Liang/For The Times)

Dust from the fire inside the Franz family’s home.

(William Liang/For The Times)

After the Eaton fire, Tissot did a quick back-of-the-envelope calculation to understand what his Altadena community might be dealing with: roughly 7,000 homes burnt with 100 liters of paint per house and 0.5% of that paint likely made of lead.

“That’s something like several tons of lead that have been released by the fire, and it’s been deposited where the fire plume went,” he said.

As the Eaton fire roared in the foothills of the Angeles National Forest the night of Jan. 7, Tissot fled with his two kids, along with the rest of east Altadena.

Meanwhile, Potelle sat awake in her living room on the west side of town, listening to the howling winds as the rest of her family slept.

When Potelle got the evacuation order on her phone around 3:30 a.m. Jan. 8, her family joined the exodus. As they raced to gather their belongings, Potelle grabbed protective goggles she had bought for her son’s upcoming Nerf-battle birthday party.

Even with them, the soot, smoke and ash made it impossible to see.

The family made it to a friend’s house in Glendale, but as the toxic smoke plume swelled, Potelle had to evacuate yet again, this time to a friend’s garage. Tissot, then in Eagle Rock, left for Santa Barbara the next day as the smoke’s incursion progressed southwest.

As Altadena turned into a ghost town on Jan. 9, some residents — including Potelle’s husband — crept back in to assess the damage. Potelle waited for her husband’s report and watched on social media from the safety of the garage.

“People are just videotaping themselves driving through Altadena, and it’s block after block after block of burnt-down homes. The reality of it started to strike me,” Potelle said. “This is not just carbon. This is like, refrigerators and dishwashers and laundry machines and dryers and cars.”

Fires like these, with smoke made of car batteries, paints, insulation and appliances — and not trees and shrubs — are becoming increasingly common in California. These fuels can contain a litany of toxic substances like lead and arsenic that are not present in vegetation, waiting to be unlocked by flame.

Potelle’s home sustained visible smoke damage. So, she made two trips to a disaster support center set up temporarily at Pasadena City College, hoping to get support from her insurance company and the government for soil and in-home contamination testing.

Officials directed Potelle back and forth between her insurance company, FEMA, the L.A. County Department of Public Health, and the California Department of Insurance. Potelle — who, at this point, had already started to develop a cough and chest pain, which she suspects came from her visits to the burn area — left with without clear answers, feeling dejected.

“I’m driving, going back to my friend’s garage … and I’m just realizing there’s no one looking out for us,” she said.

Potelle set out to find the answers herself.

“Here’s the thing, if you don’t know what’s in your home when you remediate, you could just be pushing those contaminants deeper into your walls, deeper into your personal items,” Potelle said.

Tissot, meanwhile, visited his home a week after the fires to find the windows exploded, melted or warped; the walls cracked; and ash and soot everywhere. He too decided that he ought to do his own testing for contamination.

In his day job, Tissot runs a lab with sophisticated machinery able to discern what metals are present in samples of material, usually comprised of rock and dirt, based on their atomic mass: Only lead has an atomic mass of 0.34 trillion billionths of a gram. He normally uses the machine to study rare elements and isotopes from space and eons ago.

He gathered his lab team together on the Caltech campus to use the equipment to test samples from their own backyard.

The team took 100 samples from windowsills, desks and stairwells in the Caltech geology and planetary science buildings. Some surfaces were untouched since the fire; others had been cleaned by Caltech’s trained custodians.

The team found multiple uncleaned surfaces with lead levels above the EPA’s limits. And while the cleaned surfaces had about 90% less lead, some still exceeded the limits.

Tissot quickly set up a webinar to announce the findings. The chat exploded with requests from homeowners in Altadena asking Tissot to test their houses.

Around the same time, Potelle noticed some folks on Facebook sharing the results of in-home contamination testing — which in many cases, they had paid for out of pocket.

Inspired, she advertised a Zoom meeting to discuss a strategy for mapping the test results. Sixty residents showed up; Potelle coordinated the group so that residents could submit results to EFRU’s Data Unification team for analysis.

Meanwhile, Tissot connected with residents who messaged him to set up a testing campaign. The researchers donned full hazmat suits in early February and entered the burn area to test homes and meet with homeowners.

ERFU posted its first dataset of 53 homes on March 24. Tissot’s group announced their results, which included data from 52 homes, just a week later, confirming what many had feared: There was lead everywhere.

“What was surprising to me is how far it went,” said Tissot. “We got very high levels of lead even miles away from the fire, and what’s difficult is that we still can’t really answer a simple question: How far is far enough to be safe?”

The two groups hope their data can help homeowners make better-informed decisions about their remediation and health — and apply pressure on leaders to take more action.

Tissot wants to see the government update its guidebooks and policy on fire recovery to reflect the contamination risks for intense urban fires, and to require testing companies to report their results to a public database.

Nicole Maccalla, a core member of EFRU’s Data Unification team, hopes to see officials enforce a common standard for insurance claims for testing and remediation so every resident doesn’t have to go through the same exact fight.

“You’ve got people stepping up to fill the void,” she said. “There should be an organized, systematic approach to this stuff, but it’s not happening.”

Times data journalist Sandhya Kambhampati contributed to this report.