After the January 2025 Eaton and Palisades fires, researchers fanned out across the city to collect what data and samples they could. Doctors started thinking of ways to collect patient data to better understand the immediate and long-term health impact. Some questions were simple but frustratingly hard to find answers to, like: What was in the smoke? Other questions, like those exploring the long-term health impacts, will take years to untangle. But answers are beginning to emerge.
Lingering effects: During the fires, researchers measured high levels of benzene, a carcinogen, at their outdoor sites. The high benzene levels dissipated after the burning stopped, but other dangerous gases actually increased later on, especially indoors. A few health-harming gases, including toluene and carbon tetrachloride, became more concentrated inside people's homes a few weeks after the fire.Hexavalent chromium, which can cause cancer, can be produced when fires burn through certain types of soil or rock, as well as during industrial processes like welding.
Health impacts: Scientists have known that in the short term, wildfire smoke exposure leads to more respiratory issues, such as asthma and COPD; increases the risk of developing dementia; and affects people's immune responses. But the full array of impacts, and the long-term costs of exposure, are still muddy.
What's next: Ongoing research will explore the different health outcomes for people who experienced different levels of smoke and toxin exposure. A UCLA-led study has enrolled over 4,000 people from across the city to follow their health changes long-term. Another study will focus on the specific health outcomes for those who stayed behind at their homes to fight the fires, giving them extraordinarily high smoke doses. The LA Fire Health study consortium is also tracking the long-term health impacts on firefighters and first responders.
Last January, fires were raging across Los Angeles, smothering some 20 million people across the region in toxic smoke and ash.
L.A. residents worried that the air was toxic, the soil contaminated, and the water poisoned. Questions swirled about the health risks created by the burns — and there were few answers at hand from city, state or federal leaders.
Scientists from Los Angeles and around the country quickly scrambled into action as fires burned through the Pacific Palisades and Altadena. The priority, says UCLA physician and disaster researcher David Eisenman, was keeping people safe in the short term. But the fires also presented a moment to learn crucial missing information about the health effects of wildfires to help those affected and to better protect people's health from the inevitable next ones.
"This won't be the last wildfire that Los Angeles sees," says Eisenman. "Part of the community recovery process is to learn from what we experienced."
Researchers fanned out across the city to collect what data and samples they could. Doctors started thinking of ways to collect patient data to better understand the immediate and long-term health impact. They soon joined together to form a consortium that tied together 10 research institutions, developing a phalanx of research studies to explore some of the most pressing questions brought up by affected community members.
Some questions were simple but frustratingly hard to find answers to, like: What was in the smoke? Other questions, like those exploring the long-term health impacts, will take years to untangle. But answers are beginning to emerge.
Extra-dangerous smoke
Wildfire smoke is dangerous under any conditions. Exposure to high smoke levels is linked to respiratory problems such asasthma and COPD, cardiovascular issues and even dementia.
But from the first moment the Palisades and Eaton fires took hold last January, UCLA air pollution expert Yifang Zhu knew they were different. Because it wasn't just trees and plants burning: There was plastic from people's houses, and car batteries and asbestos tiles — a "toxic soup" of air pollutants, she says.
What was in that soup, and how dangerous it might be to human health — that wasn't clear. Official air quality monitors in downtown Los Angeles, miles away from the heart of the fires in Altadena and Pacific Palisades, recorded high levels of lead and arsenic in the air during the burns. Researchers from Caltech and the Georgia Institute of Technologylater measured lead concentrations in air samples both near and far from the fires. Lead levels, they found, were elevated, even miles away, signaling that smoke and ash from the burns spread the dangerous heavy metal widely.
But many scientists suspected the smoke and ash spread other toxic particles and gases widely, too — chemicals that standard EPA and state monitors didn't test.
"We need to test more than just what the EPA calls for. And the EPA has limited resources," says Kari Nadeau, an environmental health scientist at Harvard University and one of the leads for the new research consortium. "But as academics, we can test for hundreds of things all at once, which helps the community. Because what you don't know, you don't know, but it can still hurt you."
Before the fires, Zhu and her team had been getting ready to sample the air at Aliso Canyon, where a natural gas leak in 2015 had caused major health problems for nearby residents. When the fires broke out, the team pivoted, taking their sampling equipment as close to the fires as they could.
That opportunity was special. Researchers are rarely ready to deploy at a moment's notice to capture samples during disasters such as the LA fires. The special circumstances let Zhu's team "set the stage about what's going on during this active fire burning all week," Zhu says.
Dust and ash from the Palisades and Eaton fires spread across the Los Angeles region.
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Zhu's team set up air filters to capture the ash, and they captured air samples inside and outside homes in the Palisades and Eaton fire regions. In the air samples, they looked for more than 20 different volatile organic compounds — gases, many of which harm human health, and are likely to be produced by the fires. And while the fires were still burning, they measured high levels of benzene, a carcinogen, at their outdoor sites.
Lingering risks
The high benzene levels dissipated after the burning stopped, Zhu found. But other dangerous gases actually increased later on, especially indoors. A few health-harming gases, including toluene and carbon tetrachloride, became more concentrated inside people's homes a few weeks after the fire.
The message was clear. "The fire impact doesn't really disappear with the active flame," Zhu says. Homes themselves can absorb dangerous gases in the drywall, furniture and other soft materials, releasing them for days and weeks after the smoke has dissipated. People need to know that their homes might be contaminated long after the fire is out, she says.
That wasn't the only lingering risk. Another research team started to look for a contaminant called hexavalent chromium, which can cause cancer, sometimes known as the "Erin Brockovich" contaminant, made famous by the movie of the same name. It can be produced when fires burn through certain types of soil or rock, as well as during industrial processes like welding. It's not often searched for after wildfires, but the researchers found it lingering in the air around cleanup sites long after the fires were out.
"It's actually one of those things that … makes you pay attention differently," says Joe Allen, an exposure scientist at Harvard University, who has been conducting ongoing research on building safety after the fires. And the contaminant was found in tiny particles so small that they can penetrate deep into people's lungs, bodies, and even directly to their brains.
"We've seen hexavalent chromium in soils after fires. I don't think anybody expected to see it in air. I don't think anybody expected to see it exclusively in the nanoparticle size range," Allen says.
Ash also contaminated people's homes, as well as soil and water across the region. The water impacts seemed to clear quickly, though longer-term effects are still being tracked. But levels of lead and other heavy metals inside people's homes and in the soil around them often remained high, even after cleanup was supposedly done.
"That is an ongoing question," says Allen. "Do we have enough funds to remediate all these properties, or are we just putting some people back into properties that are not properly cleared?"
Zhu was impressed by how much she and others learned about the dangerous smoke and ash. But she also worries they probably only scratched the surface. "We are only detecting things that our method allows us to detect. So even though we learn a lot from that, you know, I wonder what we missed," she says.
What does this all mean for people's health?
Scientists have known that in the short term, wildfire smoke exposure leads to more respiratory issues, such as asthma and COPD; increases the risk of developing dementia; and affects people's immune responses. But the full array of impacts, and the long-term costs of exposure, are still muddy.
"We know a lot about the health effects of wildfire smoke," says Allen. But "we don't know all that much about urban wildfire smoke. We certainly don't know what happens when you expose a population of 20 million people in the greater Los Angeles area to smoke like this, enriched in these toxic metals and other pollutants. "
The research is beginning to uncover some of the health impacts.
Cheng and colleagues collected data from the emergency room at Cedars-Sinai, one of the busiest in the region, and particularly close to the Palisades fire. In the 90 days following the fires, they saw a 24% increase in respiratory issues — and a 47% jump in heart attacks.
It was "very striking," she says. "This actually surpassed heart attack rates during January of all prior years, even during the worst years of COVID."
Homes and businesses in parts of Los Angeles were reduced to rubble and ash.
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AFP via Getty Images
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Abnormal blood tests also spiked, increasing by more than 100% over previous levels. That included unexpected blood sugar readings, signs of a disrupted immune system, and changes to people's metabolic profiles — signals, Cheng says, of bodywide stresses that could be precursors to many different health problems down the line.
"For a very large number of people who lived through these January wildfires, the wildfire exposures led to some kind of a biochemical or metabolic stress in the body that likely affected not just one, but many organ systems," she says.
The team is now tracking some of those patients, trying to understand what health issues their unusual bloodwork might have signaled coming.
The ER data is likely just skimming the surface, says Eisenman. Longer-term health problems, from heart issues to mental health stresses, are likely to linger or develop in the coming years.
Ongoing research will explore the different health outcomes for people who experienced different levels of smoke and toxin exposure. A UCLA-led study has enrolled over 4,000 people from across the city to follow their health changes long-term. Another study will focus on the specific health outcomes for those who stayed behind at their homes to fight the fires, giving them extraordinarily high smoke doses. The LA Fire Health study consortium is also tracking the long-term health impacts on firefighters and first responders.
Much of the emerging research is being supported by private philanthropy, says Eisenman. The wildfires happened just before the Trump administration began its campaign to tighten budgets for many of the science agencies that have historically funded post-disaster research, like the National Science Foundation.
"That gap was really filled in by the research community, who did ongoing and extensive and really thoughtful testing of air, of water, of soil, of debris for toxins, and really rapidly communicated those results back to the community," he says. But how to financially support the long-term future of some key studies, he says, is still uncertain, because many major federal research funding resources — like NSF and the National Institute of Health — have shifted priorities under the Trump administration.
How to protect yourself and your family
The biggest questions for the ongoing research, many of the researchers say, are about how best to protect yourself from similar fires in the future.
Allen says there are some clear lessons. Overall, the less smoke one inhales, the better. So while outside, he says it's crucial to wear an N95 mask, or even a respirator that can protect you from the fire's gases.
Indoors, keeping clean air is crucial, says Zhu. Using air filters, ideally HEPA-rated, can lower indoor pollution significantly. Carbon filters are particularly effective at removing the gases, Allen says. People can also install HEPA filters in a car's air-handling system to keep the air clean while they drive.
"You want to control what you can control," says Allen. So inside your space, clean up dust and ash thoroughly. Filter the air. And consider a low-cost air monitor to keep track of the air quality inside.
For people most impacted by the fires, Allen stresses that adequate cleanup of soil and buildings is critical. "It was a bit of the Wild West out there" after the fires, he says. A lack of standardized testing protocols and a hodgepodge of policies from different insurers "really harmed the survivor community."
That lack of guidance left many unsure whether their homes were safe to live in again, and many others were forced to go back to homes that were demonstrably still unsafe.
"We need more coordinated recommendations and rules to help people know whether their homes are safe," Allen says.
It will take years to get a full picture of the health impacts of the LA fires, many of the researchers say. But it's critical to learn from the tragedy, says Nadeau, the Harvard environmental health scientist — to "be able to say, OK, in the future, here's what to do to protect your children or protect your elderly community against stroke," or lung cancer, or the myriad other risks from the wildfires that will, inevitably, come again.
Reporting for this story was supported by the Nova Institute for Health.
The Supreme Court hears arguments Monday in an important gun case that has united an array of strange bedfellows, from conservative gun rights groups to liberal civil liberties groups.
Why it matters: At issue is a federal law making it a crime for drug users to possess a firearm. It's the same law that was used to prosecute then-President Joe Biden's son for illegal gun possession — only this case involves marijuana use and gun ownership.
What's next: A decision in the case is expected by summer.
Read on... for more about the case.
The Supreme Court hears arguments Monday in an important gun case that has united an array of strange bedfellows, from conservative gun rights groups to liberal civil liberties groups. At issue is a federal law making it a crime for drug users to possess a firearm. It's the same law that was used to prosecute then-President Joe Biden's son for illegal gun possession — only this case involves marijuana use and gun ownership.
The briefs in the case present diametrically different versions of the facts. On one side, the Trump administration portrays Ali Danial Hemani as a drug dealer and someone with terrorist ties and a marijuana habit. Importantly, he is not being prosecuted for any of those offenses, however. Rather, the government has charged Hemani with violating a federal gun law that bars people with drug addiction from possession of firearms, a crime punishable by up to 15 years in prison.
The 5th U.S. Circuit Court of Appeals threw out the indictment, declaring that the federal law violates Hemani's Second Amendment right to own a gun.
The Justice Department appealed to the Supreme Court, arguing that because Hemani admitted to FBI agents that he used marijuana several times a week, he is a "persistent" drug user, thus rendering illegal the possession of the gun he bought legally and keeps securely in his home.
Hemani's lawyer, law professor Naz Ahmad of the City University of New York, paints a very different picture of her client. Hemani, she notes, was born and raised in Texas, "attended high school there, played on the high school football team, attended the University of Texas at Arlington, was an honor student there" and is "a really valued member of his local religious community."
"The Second Amendment doesn't support disarming and prosecuting somebody for mere possession of a firearm if they happen to have used marijuana occasionally," she says.
"That's a mismatch," she adds, especially at a time when 40 states, to one degree or another, have legalized marijuana use.
If the court rules against Hemani,she says, "the statute could apply to anybody. It could apply to somebody who uses like a marijuana sleep gummy."
The Trump administration's advocate, Solicitor General D. John Sauer, acknowledges that under the Supreme Court's landmark gun decision four years ago, the government has a heavy burden to show that modern-day gun laws are analogous to laws in place at the nation's founding. But he contends that the statute used to prosecute Hemani is both justified and analogous to founding-era laws and practices.
Specifically, in his Supreme Court brief, Sauer points to the harsh punishments imposed during the founding era on "habitual drunkards." And he contends that both Congress and the states have restricted firearm possession by illegal drug users "for as long as that social evil has plagued America."
That said, for the most part, the case seems to have united groups from left to right, from civil liberties groups to gun rights advocates.
"It's outrageous that they tried to get him on a marijuana gun charge," says Aidan Johnston, director of federal affairs for Gun Owners of America. He contends that the government is seeking to criminalize conduct that was widely tolerated at the founding.
"It was the universal custom of founding-era militias to imbibe," he notes, adding that Thomas Jefferson and other famous Americans "possessed firearms while being users of drugs ranging from opium to cocaine."
At the opposite end of the ideological spectrum are a variety of gun-safety groups that fear that if Hemani wins his case, it could gouge a hole in the existing system of national background checks.
Under the current system, dealers are required to first clear the sale by submitting the buyer's name to the FBI's National Instant Criminal Background Check System. The hitch is that there is a very small window in which to complete the check — just three days. And gun-safety groups say that anything that makes the rules more complicated and unclear could really screw up the system.
"We're saying" to the court, "whatever you do, it's essential that you keep the rules clear so that in that short window, federal agencies can give a quick answer to the dealers," says Douglas Letter of the Brady Center to Prevent Gun Violence.
An adverse ruling, he says, would mess up the criminal background check process. That, in turn, would result in "so many, particularly women and children, who will die if that kind of a system is not in place."
A decision in the case is expected by summer.
Copyright 2026 NPR
Mariana Dale
explores and explains the forces that shape how and what kids learn from kindergarten to high school.
Published March 2, 2026 12:26 PM
A March 2020 LAUSD Facebook post recognized Chait's tenure with the district which includes teaching elementary school, serving as an assistant principal and principal before moving into district administration.
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Courtesy Los Angeles Unified School District
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Topline:
Longtime administrator Andres Chait addressed the public as acting superintendent of Los Angeles Unified School District for the first time Monday. His comments came ahead of a closed board meeting to discuss his employment and ongoing labor negotiations with district unions.
What did he say: Chait said his priority as acting superintendent is to keep the district focused. “ We remain committed to academic excellence and student wellbeing,” he said Monday. “Our core values remain unchanged. I know transitions can create uncertainty, but our district is strong.”
Who is Chait? Chait has worked for the district for nearly three decades, most recently as chief of school operations. His responsibilities included overseeing school safety, athletics and the district’s office of emergency management.
Longtime administrator Andres Chait addressed the public as acting superintendent of Los Angeles Unified School District for the first time Monday.
“ We remain committed to academic excellence and student wellbeing,” he said ahead of a closed board meeting to discuss his employment and ongoing labor negotiations with district unions. “Our core values remain unchanged. I know transitions can create uncertainty, but our district is strong.”
Chait has worked for the district for nearly three decades, most recently as chief of school operations. His responsibilities included overseeing school safety, athletics and the district’s office of emergency management.
A justice department spokesperson said the agency had a court-authorized warrant but declined to provide additional details. The reason for the searches is unknown.
Listen to Chait's full comments
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Lab Assistant Abraham Jimenez loads blood samples for automated serology testing for measles immunity status at the Los Angeles County Department of Public Health laboratory in Downey on Feb. 26, 2026.
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Ariana Drehsler
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CalMatters
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Topline:
California is battling measles outbreaks across seven counties as federal funding cuts gut local health departments and vaccine skepticism fuels spread among unvaccinated children.
Outbreaks: California has a high enough vaccination rate — about 95% of kindergarteners — to provide herd immunity against measles, but throughout the state pockets of unvaccinated communities drive outbreaks, experts say.
Read on... for how local health departments are fighting the infection with less funds.
This story was originally published by CalMatters. Sign up for their newsletters.
When a possible measles case is identified in California, a phone rings at the local health department and the clock starts ticking.
Laboratory workers need to process samples as soon as possible to confirm the case. And a public health nurse must call the patient to find out where they’ve been and who they’ve been in contact with recently.
If test results are positive, the communicable disease team has 72 hours or less to identify anyone who has been exposed and may be at high risk of infection or serious illness. Those people must quarantine or take a dose of a post-exposure prophylaxis to prevent spread. For the next 21 days nurses will monitor the group for symptoms.
“That’s ridiculously infectious,” said Dr. Sharon Balter, director of acute communicable disease control with Los Angeles County public health. “It balloons very quickly, and because measles spreads very fast we have to get on it right away. We can’t say we’ll wait until tomorrow.”
California has a high enough vaccination rate — about 95% of kindergarteners — to provide herd immunity against measles, but throughout the state pockets of unvaccinated communities drive outbreaks, experts say.
Shasta and Riverside counties are working to contain localized outbreaks. These are the first measles outbreaks in the state since 2020 and are happening at a time when health departments have less money and fewer staff than in recent years. In total, seven counties have reported a total of 21 measles cases this year, according to the California Department of Public Health.
“The United States is experiencing the highest numbers of measles cases, outbreaks, hospitalizations and deaths in more than 30 years, driven by populations with low vaccination rates,” said California Public Health Officer Dr. Erica Pan in a statement earlier this month. “We all need to work together to share the medical evidence, benefits, and safety of vaccines to provide families the information they need to protect children and our communities."
Containment comes with high costs
Investigating any communicable disease is time-intensive and expensive. The first three measles cases reported in L.A. County this year cost an estimated $231,000, according to a health department analysis.
Why does it cost so much? Because a disease investigation often requires a legion of public health nurses, physicians, epidemiologists and laboratory scientists to follow-up with hundreds of contacts, Balter said.
A computer shows an analysis of measles sequencing results at the Los Angeles County Department of Public Health laboratory in Downey on Feb. 26, 2026.
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Ariana Drehsler
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That includes sometimes visiting homes or exposure sites. For example, a recent exposure at a daycare required nurses to wring urine out of used diapers to test babies for measles. County health workers monitored 246 people who had been exposed to those first three measles cases — and the work is ongoing.
On Feb. 19, the county reported its fourth measles case. All of them were related to international travel. Other cases in California also have primarily been related to travel either internationally or to states where there are outbreaks. An unvaccinated child in Napa County contracted measles in January after traveling to South Carolina.
Riverside County health officials reported one measles case where the child had not traveled recently, and Shasta County health officials suspect their first case could be related to travel in Southern California but are waiting for DNA testing for confirmation.
Orange County reported two travel-related cases this year.
Health departments have fewer resources, more cases
Local health departments rely heavily on federal funding to prevent the spread of infectious diseases, but last year, the Trump administration slashed nearly $1 billion of public health funding from California. This year it attempted to claw back another $600 million from California and three other Democratic states.
Pending lawsuits froze the cuts, but local health departments are treating the money as a lost cause because they cannot bear the financial risk if a judge eventually rules in favor of the Trump administration.
Health departments are also confronting decreased public confidence: The high-profile questioning of vaccine safety and effectiveness by U.S. Secretary of Health and Human Services Robert F. Kennedy Jr. has complicated public health’s struggle to contain the spread of preventable infections.
California Democratic leaders are aggressively fighting Kennedy’s direction. They sued to block the administration’s new vaccine guidelines, which stripped universal recommendation from seven childhood vaccines. They blame Kennedy and the Trump administration for “dismantling” the Centers for Disease Control and Prevention and stoking fears over debunked claims that vaccines cause autism.
The state also released its own vaccine guidelines and formed an alliance among four western states to share public health information and recommendations.
“Everything including the outbreaks, the financial cuts, the questions from the federal government that are arising are making our work very difficult,” said Dr. Regina Chinsio-Kwong, Orange County public health officer.
Lab Assistant Abraham Jimenez loads blood samples for automated serology testing for measles immunity status at the Los Angeles County Department of Public Health laboratory in Downey on Feb. 26, 2026.
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Ariana Drehsler
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CalMatters
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Lab Assistant Abraham Jimenez loads blood samples for automated serology testing for measles immunity status at the Los Angeles County Department of Public Health laboratory in Downey on Feb. 26, 2026.
The outbreak, which lasted four months, spurred state lawmakers to pass some of the strictest childhood vaccine requirements in the country.
But even a single measles case requires “vast amounts of infrastructure” to contain, Chinsio-Kwong said. On average, the department identifies and monitors 100 exposed people per case. Since the start of last year, Orange County has lost $22 million in federal cuts to public health. The department is trying to protect their communicable disease surveillance work, but it gets harder with every cut.
“We're trying to prioritize our communicable disease control division,” health officer Chinsio-Kwong said. “There are a lot of different federal cuts, but we're putting that as front and center: That has to be saved no matter what.”
Measles spread in unvaccinated groups
Six hundred miles north, Shasta County is grappling with its first measles cases since 2019 and the state’s largest outbreak of the year.
In late January, a sick child visited a health clinic in Redding with measles symptoms that laboratory testing later confirmed. Health officials interviewed 278 people and identified six locations where others were exposed: a restaurant, a church basketball game, a gym, a park, Costco and the clinic.
They also identified seven other cases among family members or neighbors who were in close contact with the child.
It can take 21 days from the time of exposure for measles symptoms to develop. On Feb. 19, just before the end of that period, health officials confirmed a ninth case.
That person didn’t recognize the symptoms and visited several places while contagious, including a school, a church service, a basketball game and a clinic, said Daniel Walker, a Shasta County supervising epidemiologist. Now, the contract tracing process has started over. The communicable disease team expects to interview even more people this time.
All cases have been among children who were unvaccinated or did not know their vaccination status.
“It’s a great time to get immunized, because you can’t know when you’re next going to be exposed…especially because we’re in an outbreak situation,” Walker said.
Supported by the California Health Care Foundation (CHCF), which works to ensure that people have access to the care they need, when they need it, at a price they can afford. Visit www.chcf.org to learn more.
The U.S. attacks on Iran over the weekend, in conjunction with the Israeli military, marked a stunning new phase in relations between the two countries. But it is hardly the first time Washington and Tehran have clashed politically and militarily.
U.S. helps orchestrate coup: A key moment in U.S.-Iran relations goes back to 1953. A CIA-led campaign topples the elected government of Iran. The coup allows Mohammad Reza Pahlavi, the last shah (or king) of Iran, to consolidate power around himself. Pahlavi goes on to lead Iran for the next two and a half decades, becoming a strong U.S. ally.
Iranian Revolution and the U.S hostage crisis: In early 1979, following months of protests, Pahlavi fled Iran. The revolution had been led by Ayatollah Ruhollah Khomeini, a Shia cleric who was living in exile. Khomeini returns to Iran and oversees the country's transition to an Islamic republic, becoming Iran's supreme leader. In November of that year, a group of Iranian students stormed the U.S. embassy in Tehran and captured 66 Americans.
The 2015 nuclear deal: The U.S. reached a deal with Iran and five other world powers to curb Iran's nuclear capabilities in exchange for the removal of some punishing United Nations sanctions. In 2018, President Trump during his first term pulls the U.S. out of the Iran nuclear deal and reimposes sanctions on Iran.
Read on ... for more key moments.
The U.S. attacks on Iran over the weekend, in conjunction with the Israeli military, marked a stunning new phase in relations between the two countries.
But it is hardly the first time Washington and Tehran have clashed politically and militarily.
Here are some key historical moments between the U.S. and Iran.
1953: U.S. helps orchestrate coup that overthrows Mohammad Mosaddegh
Great Britain had controlled Iran's oil industry for decades, but in 1953 Iran's elected prime minister, Mohammad Mosaddegh, nationalized the country's oil sector.
That move prompted Great Britain to appeal to the U.S. for help, and what resulted was a CIA-led campaign to topple Mosaddegh's government. The coup allowed Mohammad Reza Pahlavi, the last shah (or king) of Iran, to consolidate power around himself. (The CIA, long suspected of having a hand in the revolt, officially acknowledged its role in 2013.)
Iranian opposition leader in exile Ayatollah Ruhollah Khomeini gives a speech as journalists surround him at Roissy airport near Paris on Jan. 31, 1979, before boarding a plane bound for Tehran. Khomeini establishes an Islamic republic in Iran.
The revolution had been led by Ayatollah Ruhollah Khomeini, a Shia cleric who was living in exile near Paris after being expelled by Pahlavi in 1964. Khomeini returned to Iran and oversaw the country's transition to an Islamic republic, becoming Iran's supreme leader. Khomeini established a hard-line theocracy and labeled America the "Great Satan." In November of that year, a group of Iranian students stormed the U.S. embassy in Tehran and captured 66 Americans.
A U.S. rescue attempt in the spring of 1980 codenamed Operation Eagle Claw, which was approved by President Jimmy Carter, was hampered by mechanical problems, a severe dust storm and a crash that killed eight service members. It failed to secure the release of the hostages.
Reagan's tenure was also marked by a now-infamous transaction with Iran.
Officials in his administration were discovered to have sold weapons to the country in the hope that it would help secure the release of American hostages held in Lebanon by Hezbollah, a militant group allied with Iran.
The Reagan administration used the proceeds of the arms sales to fund the paramilitary Contra rebel group fighting against the socialist Sandinista government in Nicaragua.
Reagan confirmed the story in a 1986 White House press conference and took public responsibility for what's become known as the Iran-Contra affair.
Late 1980s: Tensions in the Persian Gulf
Thousands of people mourn in July 1988 in Tehran, during the funeral service for those who died when an Iranian passenger jet was shot down over the Gulf by the U.S. military.
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Iran and Iraq were engaged in a war since 1980, and toward the end of that decade, Iran began to attack oil tankers belonging to Kuwait and Saudi Arabia, Iraq's financial supporters.
In 1987 the U.S. begins a military campaign known as Operation Earnest Will to protect Kuwaiti tankers.
Still, that incident touched off another military operation called Operation Praying Mantis, in which U.S. forces retaliated for the explosion by attacking several Iranian oil platforms.
The U.S. reached a deal with Iran and five other world powers to curb Iran's nuclear capabilities in exchange for the removal of some punishing United Nations sanctions.
The deal allowed Iran to continue enriching uranium for civilian energy purposes, but President Barack Obama argued that it would curb the country's ability to create a nuclear bomb. Iran also agreed to increased inspections of its nuclear facilities.
The Biden administration held indirect talks with Iran, and when Trump returned to office in 2025 he signed an executive order with the goal of exerting "maximum" pressure on Iran to end its nuclear weapons ambitions.
2020: U.S. drone strike kills Maj. Gen. Qassem Soleimani
A major recent development in U.S.-Iran relations occurred not in Iran itself but in neighboring Iraq.
Just a few days into 2020, U.S. forces launched a drone strike near the Baghdad International Airport and killed Maj. Gen. Qassem Soleimani, among others.
Soleimani, who led an elite branch of Iran's Islamic Revolutionary Guard Corps known as the Quds Force, was seen as one of the country's most influential officials.
2025: U.S. and Israel strike Iranian nuclear sites
In June, the U.S. and Israeli militaries launched a dramatic assault on several Iranian nuclear sites. For the U.S., the military escalation followed what had largely been a diplomatic effort to deter Tehran from pursuing a nuclear weapon.
Trump said in a speech from the White House that the goal of the operation was to scuttle Iran's nuclear enrichment capabilities.
"Tonight, I can report to the world that the strikes were a spectacular military success. Iran's key nuclear enrichment facilities have been completely and totally obliterated," Trump said, though there are questions about exactly how much damage was dealt.
In March, Director of National Intelligence Tulsi Gabbard had said that U.S. intelligence believes Iran "is not building a nuclear weapon and Supreme Leader Khamenei has not authorized the nuclear weapons program that he suspended in 2003."
