In an unprecedented collective scientific effort to understand the short- and long-term health impacts of wildfires, researchers from four universities have launched a 10-year study of the Los Angeles fires. The wildfires that began in early January 2025 killed 29 people, destroyed more than 16,000 structures, and exposed millions to toxic smoke.

The research aims to evaluate which pollutants are present, at what levels, and where, and to assess the respiratory, neurological, cardiovascular, reproductive, and immune system impacts of the wildfires.

The Los Angeles Fire Human Exposure and Long-Term Health Study (L.A. Fire HEALTH Study) is being launched with the support of a visionary gift from the Spiegel Family Fund. The multi-institutional collaboration is a consortium led by researchers from Harvard T.H. Chan School of Public Health, the UCLA Fielding School of Public Health, University of California, Davis, and the University of Texas at Austin with expertise in environmental exposure assessment, health outcomes, wildfire risk assessment and management, and data science.

“This was an environmental and health disaster that will unfold over decades,” said Kari Nadeau, John Rock Professor of Climate and Population Studies and chair of the Department of Environmental Health at Harvard Chan School, professor of medicine, Harvard Medical School, and practicing physician at Beth Isreal Deaconess Hospital. “By bringing together experts from across multiple institutions and disciplines, we can rigorously examine the health effects from the wildfires’ toxic particles and gases that have spread hundreds of miles beyond the fire zones and provide the communities with this information in real time.”

Wildfire hazards

Wildfires in Los Angeles and other urban areas present unique hazards as buildings, cars, and products are incinerated, exposing people to particulate matter, gases, chemicals, heavy metals, asbestos, PFAS, microplastics, and other toxic pollutants. They settle out of the air into soil and dust and can become resuspended during recovery and rebuilding efforts. Water quality can also be affected.

The potential health impacts on millions of Los Angeles residents from exposure are many and include:

• Acute respiratory symptoms and worsening of lung conditions, including asthma and COPD
• Neurological impacts, including headaches and cognitive issues
• Cardiovascular effects, including increased risk of heart disease and stroke
• Immune system disruption
• Reproductive health concerns
• Increased cancer risk

“Air pollutants, such as those from wildfires, are linked to short-term health problems such as asthma and longer-term ones such as Alzheimer’s disease,” said Anthony Wexler, director of the Air Quality Research Center at UC Davis.

“Here in Los Angeles, we know that communities need accurate and timely information about what individuals and families can do to prevent and mitigate health effects from fires, both in the near- and long-term,” said Michael Jerrett, Jonathan Fielding Chair in Climate Change and Public Health, and professor in the Department of Environmental Health Sciences at the UCLA Fielding School of Public Health. “With this study we can supply sound science to help residents repopulate and rebuild their neighborhoods safely, and for the first time, we can learn about the long-term health effects of wildfires.”

Study aims

The L.A. Fire HEALTH Study has two primary objectives: First to examine which pollutants are present, at what levels, where, and how they change over time; and second to determine if the fires and aftermath are associated with chronic health effects in the nearby population.

In the study’s first phase, teams are mapping and understanding exposures during the fires, including emissions from the burning of vegetation and buildings and the composition of pollutants in the wildfire smoke. As part of the air sampling effort, a mobile van will be deployed, equipped with advanced measurement technologies that can measure the chemical composition of particulate matter and gases in real time.

A study of homes in the area will include monitoring indoor and outdoor air, drinking water, house dust, and soil samples, and assessing the role that building design and filtration plays in limiting infiltration of wildfire pollutants. A novel approach to estimate smoke infiltration into homes will also be used. “Building materials can absorb infiltrated smoke, creating the potential for exposure to harmful compounds for weeks and months after a wildfire. By taking measurements inside and outside of homes, we can quantify how building materials impact exposure and provide insights on when it is safe to return to homes in areas impacted by wildfires,” said Lea Hildebrandt Ruiz, associate professor in the McKetta Department of Chemical Engineering at the University of Texas at Austin. A novel model of 14 million homes in California built with advanced machine learning will allow researchers to understand how much smoke entered homes and where.

A key goal of all these efforts is to share evidence-based, rapid answers to the affected communities. In addition, the findings will be shared with civilians, firefighters, businesses, researchers, and government agencies.

The Spiegel Family Fund, which is funding the study, was founded by Evan Spiegel, the co-founder and chief executive officer of Snap, Inc. He grew up in Pacific Palisades, a town devastated by the recent fires, and still lives in Los Angeles with his family. In an emotional love letter to the city as the fires raged, he wrote: “We are not the first community to face a megafire. We will not be the last. But we will use our strength, our ingenuity, and our love to create again and anew.”

By funding the research study, Spiegel said he hoped to help spur that recovery and learn critical insights that could protect health and well-being both in Los Angeles and in other cities affected by wildfires in the future.

Other researchers on the team include Joe Allen, Francesca Dominici, Amruta Nori-Sarma, and Mary Rice from Harvard Chan School; Dave Allen, and Pawel Misztal from UT Austin; and David Eisenman, Katie McNamara, and Yifang Zhu from UCLA Fielding.

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