On a Sunday in February, a white Ford van zigzagged through the fire-ravaged neighborhood of Altadena, Calif. Ash piles lined front yards. Charred washing machines sat on bare concrete foundations.
“I can’t imagine coming back to this,” said Albert Kyi, a graduate student researcher at the University of Texas at Austin, briefly looking up from his laptop and out the van’s window.
He and his colleagues, however, were there to help people learn whether it was safe to do just that. A mast poking out from the van’s roof was sending readings on hundreds of compounds in the air to the laptop. This laboratory on wheels was so sensitive, Mr. Kyi said, that it could detect the chemicals produced by someone peeling an orange outside.
The data the team was gathering was part of a newly launched study tracking the health impacts of the Los Angeles wildfires over the next decade. By traversing the 38,000 acres that encompass the two burn zones in Altadena and the Pacific Palisades along with the surrounding region, the researchers hope to fill gaps in the data on air, soil and water quality. Already, they have found cause for concern.
More than 16,000 homes and buildings were destroyed, and another 2,000 were damaged during the recent fires. So far, there is only limited information for the tens of thousands of residents returning home to the affected areas about whether or when it might be safe to grow vegetables in their backyards, swim in their pools or go for a morning run, especially as rebuilding efforts stir up potentially toxic ash.
The researchers were detecting high concentrations of furfural, a compound associated with burned vegetation. “There are also spikes of styrene and benzene,” Mr. Kyi added, his voice muffled by a respirator mask.
These volatile organic compounds, or VOCs, were of particular concern because at high levels, they can cause cancer. They could have been produced by melted plastic or gasoline in the burned cars sitting in driveways. In the atmosphere, they can form small particles that can irritate the lungs and increase the risk of lung disease, stroke and heart attacks.
That’s why a second vehicle behind the van was recording real-time counts of particles of pollutants so fine they can reach deep into the lungs and pass into the bloodstream or even the brain when inhaled. In the burn zone, the levels of such ultrafine particles were at some points as much as five times higher than the levels typically seen in areas unaffected by wildfires or heavy traffic.
There’s still much scientists don’t know about the health risks of these and other emissions that may have been produced by wildfires, including at what level they might become dangerous, or how other factors, like a person’s genetics or preexisting health conditions, might affect those risks.
Even with only preliminary data, the researchers could say one thing with little doubt. No one should be in or near the burn zone without a mask — especially not doing any kind of exercise, whether that was an evening walk or working to clean up what remained.
On Returning Home, a ‘Toxic Soup’
In the past, researchers studying wildfires and human health have largely focused on the immediate effects of smoke inhalation and the dangers faced by frontline workers such as firefighters, who are at significantly greater risk of developing lung cancer and heart disease.
But as wildfires around the world have become more frequent and severe, they are posing a greater risk to far more people. That makes it more important than ever to know exactly what pollutants are in the smoke and where they end up.
During the nearly monthlong fires in the Pacific Palisades and Altadena, for example, plumes of smoke and ash traveled dozens of miles from the active burn zone, passing over the homes of millions of residents before blowing out to sea.
“People are going back into their homes and living in a toxic soup,” said Michael Jerrett, an environmental health scientist at the University of California, Los Angeles who is collaborating on the new effort. Dr. Jerrett’s previous research has suggested that more than 50,000 premature deaths in California between 2008 and 2018 can be attributed to particle pollution from wildfires.
The fires had been burning for about a week when the new research collaboration began to take shape. A representative from the Spiegel Family Fund, a philanthropic organization created by Snapchat co-founder Evan Spiegel, began reaching out to prominent wildfire researchers, said Dr. Kari Nadeau, a physician and environmental health expert at Harvard and one of the leaders of the new effort. Mr. Spiegel had seen his father’s home destroyed by the Palisades fire.
The research effort will monitor residents for heart disease, respiratory problems, cancers and other conditions over the next decade — an idea drawn from the registry established for those exposed to smoke and dust from the 9/11 attacks.
Inside the burn zone, the federal government is overseeing the removal of debris along with the top six inches of soil to reduce toxins. The E.P.A. has said it won’t retest the soil after the cleanup — even though soil remediation and rebuilding efforts can stir up potentially harmful particles that had already settled.
The fires were still burning in late January when Mr. Kyi and other students at the University of Texas were asked to load up the van in Austin and drive west to start collecting these samples. Because the van is an electric vehicle — to prevent the machinery from sucking in its own tailpipe emissions — the team had to stop for a charge every 100 miles along the way.
So far, the researchers say, readings suggest that the pollutants more than a mile outside the burn zone have become diluted enough by the surrounding air that they pose little danger. “I don’t think people need to worry about moving out of Los Angeles,” said Yifang Zhu, an air pollution researcher at the University of California, Los Angeles, collaborating on the research.
Inside the burn zone, however, the researchers are still trying to ascertain the contamination and the long-term risks. While some of the chemicals the team has identified have been linked to cancers and developmental disorders, most have never been studied for their health effects. Some early research has also found elevated levels of lead in ash and dust samples collected from the region, but it was not as severe or as widespread as initially feared.
Another concern that has emerged from previous studies: The intense heat of wildfires can transform a normally benign form of chromium, a metal found in certain California soils, into a carcinogen known as hexavalent chromium, which can end up in airborne dust and ash. The researchers are awaiting their results regarding chromium levels and are also looking for so-called “forever chemicals,” which are used in refrigerants and nonstick coatings and don’t break down in the environment. These and other results will be shared as they come in on the project’s website and in peer-reviewed publications.
Even houses that escaped the flames may hold hidden dangers, which is why the researchers are also testing indoor air. Smoke and ash that has worked its way into homes will continue to release volatile organic compounds for many months or more. Six months after the 2021 Marshall Fire in Boulder, Colo., some residents who returned to their homes inside or near the burn zone developed sore throats, frequent headaches and coughs.
Josh West, a professor of earth sciences at the University of Southern California, lost about one third of his home in the Pacific Palisades to the fires. “The house is caked in smoke, but the left side is not structurally damaged,” he said.
He is leading a separate research project to understand how the contamination on the ground and water is spreading out from the burn zone, but the biggest personal question he is facing is whether any of his house can safely be salvaged.
“What do you do about the stuff you don’t see?” he said. “It’s hard to get your head around the extent of the contamination.”
