This project is based on an analysis of federal satellite imagery by NPR’s California Newsroom and Stanford University’s Environmental Change and Human Outcomes Lab

Western wildfires pose a much broader threat to human health than to just those forced to evacuate the path of the blazes.

Smoke from these fires, which have burned millions of acres in California alone, is choking vast swaths of the country, an analysis of federal satellite imagery by NPR’s California Newsroom and Stanford University’s Environmental Change and Human Outcomes Lab found.

The months-long analysis, based on more than 10 years of data collected by the National Oceanic and Atmospheric Administration, and analyzed down to the ZIP code level, reveals a startling increase in the number of days residents are breathing smoke across California and the Pacific Northwest, to Denver and Salt Lake City in the Rocky Mountains and rural Kentucky and West Virginia in Appalachia.

When looking at major U.S. cities, the analysis found the starkest increase in San Jose, California, where smoke days were up more than 400 percent. San Jose residents breathed smoke 45 days a year on average between 2016 and 2020. In Los Angeles and San Diego, the number of days with wildfire smoke increased 230 percent to 32 days a year in Los Angeles and 23 days in San Diego. Even the East Coast was not immune, as prevailing winds carried smoke plumes from the Western United States and Canada thousands of miles away. In Philadelphia and Washington, D.C., our analysis found the number of days residents breathed wildfire smoke increased approximately 40 percent, to over 20 days of smoke on average in a year. 

“Literally no amount of exposure is safe,” said Marshall Burke, an associate professor of earth system science who led the project for Stanford University. Emerging research shows wildfire smoke exposure not only negatively affects the heart and lungs but also the brain. Smoke exposure also poses pregnancy risks. Children and older people are most vulnerable. “There’s no magic threshold under which we’re OK and beyond which we’re in trouble,” Burke said. “The lesson is that any amount is bad. And the more you get the worse it is.”

Experts say the scale of smoke inundation requires dramatic steps to curb the risk of wildfire and mitigate the impacts of climate change. But investigations from NPR’s California Newsroom have found the state and federal government have not done enough to manage forests, including using prescribed burns. Both have performed mitigation work on far fewer acres than promised to address the state’s wildfire crisis.   

The deluge of smoke was particularly acute in California, where people in some fire-prone areas are exposed to smoke an average of three months a year. An analysis of state hospitalization records by NPR’s California Newsroom found 30,000 additional admissions for respiratory and cardiac conditions in 2018, at the time a record fire year compared to two years before. 

Federally funded prescriptions for the asthma medication albuterol also spiked in the state, with 240,000 more claims for the drug in California in 2018 than in 2013, according to an analysis of data provided by the Centers for Medicare & Medicaid Services. The annual cost to taxpayers for the extra albuterol: $34 million.

Living With Smoke

Residents of the most smoke-stricken areas told us the relentless poor air quality had diminished their health and quality of life. 

“We’re exhausted from having to go through so many years of smoke,” said 61-year-old Tim Pedrozo, a third-generation dairy farmer in Orland, a small Northern California town of 7,800 that’s famous for breeding queen honey bees. 

Pedrozo is worried about his lungs. He suffers from dull headaches when smoke is in the air. “It’s just getting harder and harder to want to stay here,” he said.

Our analysis found Orland residents breathed smoke an average of 82 days a year between 2016 and 2020. Last year, when more acres burned than in any year in California’s modern history, smoke filled the air for nearly four months. 

Beyond his health, Pedrozo said his business has taken a hit. The farmer, with glasses and a gray beard, said he has tasted a smoky taint in the traditional aged cheese he produces. The persistent smoke keeps customers away from outdoor farmers markets, where he sells his cheese rounds.

Pedrozo’s cows, which graze on the 20-acre farm year-round, have also gotten sick. Last year, they suffered an outbreak of pink eye infections, he said, which Pedrozo attributes to a combination of smoke and dust. One cow lost an eye. Scientific research has linked wildfire smoke to both pink eye and permanent blindness in livestock.

“I don’t want to stick around and get worse,” Pedrozo said. So he is planning to sell his farm of 22 years and move with his wife to Missouri, where their son has already relocated. 

But the analysis by NPR’s California Newsroom and Stanford University found that even if worried Californians like Pedrozo flee the state, it will be hard to escape the smoke. 

“The impacts of wildfire smoke could be one of the largest climate-related impacts across the Western U.S. And as we're seeing increasingly, it's not just limited to the Western U.S.,” Burke said.

Burke’s lab used advanced computer modeling to examine the presence of smoke plumes overhead every day, in every community, from Hawaii to Florida. Reporters from the California Newsroom then compared the average annual number of days with smoke in the air from 2009 to 2013, when extremely destructive wildfires were less common, with the smoke days occurring from 2016 to 2020, when hotter, drier conditions, fueled by climate change, sparked record fire years. 

How far smoke can move through the air depends on the intensity of the fire and weather conditions. But the satellite images reviewed by NPR’s California Newsroom and Burke’s lab at Stanford show that, as winds carry wildfire smoke plumes from the West and central Canada across the continent, they spread farther and higher. According to NASA, these smoke plumes often go unnoticed, providing the illusion of cleaner air even as they inundate parts of the East Coast and the Midwest, including Missouri, where Pedrozo wants to move.

Our analysis found the Midwest experienced a slight drop in the number of days with smoke overhead since 2009. But Burke’s modeling of the satellite imagery shows the smoke there is now thicker, suggesting, he said, “wildfires are also worsening overall air quality in the Midwest, just as they are in the West." 

“This is no longer just a West Coast story. This is a U.S.-wide story,” Burke said.

The Kids Are Not All Right

Our analysis found the smokiest place in the West was Willows, California, a small town about 80 miles north of Sacramento. Last year, the August Complex Fire, then the largest in modern California history, burned more than 1 million acres, or more than 1,500 square miles, to the west in Mendocino National Forest. Two years earlier, the Camp Fire destroyed the Butte County town of Paradise, a 45-minute drive to the east, killing 85 people.

On the Friday in September we visited, a thick haze covered nearby mountains, but the sky had cleared up and the air quality was better than it had been earlier in the week. Cheerleaders for the local high school shook their gold and purple pom poms for a junior varsity football game, as hundreds of students and parents caught up with each other in between bites of steak sandwiches and cotton candy.

For Willows High School Athletic Director Greg Kitchen, the day's relatively clean air was a huge relief.

“I feel like I can breathe easy for a change. It's nice,” said Kitchen, as he watched the game from the sidelines. “It seems like the last five years or so air quality has just been something that we constantly have to monitor.”

Already this school year, Kitchen and other school administrators in the region have canceled outdoor sports practices and recess because of decidedly unhealthy air, to protect students’ health. 

Stacy Lanzi, a third grade teacher at Murdock Elementary School, said she sees her students and her own two teenaged sons struggle with runny noses, tiredness and itchy eyes during days with haze or thick smoke. 

“Kids will say, ‘I have a headache, I have a headache.’ You hear it all the time,” said Lanzi, who was born and raised in Willows. “And I’ll say, ‘Well, did you drink some water? Drink some more.’ There’s not too many alternatives, you know?”

Our analysis found Willows averaged 91 days of wildfire smoke a year on average between 2016 and 2020. Last year, smoke plumes inundated Willows for 122 days, or four out of 12 months.

“Without fail, there's always somebody who says something about, ‘Well, because of the smoke’ insert problem here,” said 27-year-old Brett Brown, a physician’s assistant who regularly treats patients at Glenn Medical Center, the small hospital in Willows. “Whether it’s ‘I haven't been exercising, so my diabetes is a little bit worse.’ Or ‘I haven't been able to breathe as well because my allergies are so bad.’” 

Brown, who suffers from asthma himself, said he has experienced firsthand how smoke can exacerbate his symptoms. Last year, he said, asthma flare-ups lengthened a case of bronchitis he developed.

The Smoky Reality of Climate Change

Climate change is at the root of this new reality, with rising temperatures and scant precipitation contributing to conditions that lead fires that burn hotter, faster and more frequently than ever before. Eight of the 10 largest fires in California history sparked since 2017.

Last year was the most active wildfire season in the state’s modern history. More than 4 million acres burned, nearly 10,500 structures were damaged or destroyed and 33 people died. This year could be even more destructive. Most of California is in “extreme drought” or “exceptional drought,” which means there is an abundance of dry vegetation ready to catch fire.

But experts say there are steps government officials and individuals can take to better respond to the growing risk. 

Decades of poor forest management have led to a dangerous buildup of undergrowth in California’s forests, providing the fuel for recent major blazes. Fire scientists say the state and federal government both need to significantly scale up their efforts to help reduce the potential of devastating wildfires. 

“What we’ve got at the state and federal level is a reactive policy—we’re going to respond to the fires,” said Char Miller, director of environmental analysis at Pomona College. “God that’s problematic, because it means you never get ahead of the curve.” 

Last August, California Gov. Gavin Newsom announced an agreement with the U.S. Forest Service that promised each would perform fire prevention work on 500,000 acres annually here by 2025. Today, however, the Forest Service remains far short of that goal. The agency told us they’d completed about 120,000 acres of treatment in California during the fiscal year ending Sept. 30. As for the state, Cal Fire was unable to detail its progress, even after multiple email requests. 

Prescribed burns are another potential path forward in California. In much of the Southeastern United States, where academic research shows prescribed burns are far more common, our investigation shows a substantial decline in wildfire smoke over the past decade.

Fire is a natural part of the ecosystem; without it, wildlands become overgrown with brush and small trees. That causes destructive conflagrations to replace the natural, low-intensity fires that serve as an ecological reset. Many state lawmakers support their broader use, and in recent weeks the California legislature has passed bills that would change liability laws and create a $20 million insurance liability fund. 

“We have to get people to understand that they may have to get exposed to a little smoke from prescribed burns to prevent catastrophic fires,” said John Balmes, a pulmonologist and professor at the University of California, San Francisco, who serves on the California Air Resources Board.  

Meanwhile, Pacific Gas and Electric—the state’s largest utility—continues to face scrutiny over its role in sparking wildfires. Earlier this year, the California Public Utilities Commission placed the company under “enhanced oversight” for failing to prioritize vegetation clearing around its most high-risk power lines. The company, which a federal judge called “a terror—T-E-R-R-O-R to the people of California,” last year pleaded guilty to 84 counts of involuntary manslaughter in connection with the 2018 Camp Fire. In July, the utility told the CPUC that a fallen branch may have started this year’s Dixie Fire, which has burned more than 960,000 acres, or 1,500 square miles, to date.

There are also changes individuals can make to reduce the health impacts of wildfire smoke, including installing indoor air filtration systems. “There are good data to show that these kinds of efforts can make a difference in protecting homes and saving lives,” said Balmes. But these devices can be costly. Balmes recommends the government do more to provide low-cost or free air filters. “But all this requires investment.” 

Erasing Progress on Air Pollution

The sharp rise in wildfire smoke is reversing decades of hard-won gains in air quality improvement made as a result of environmental legislation like the Clean Air Act, Burke said. “We had actually been having a lot of success in cleaning up our air,” he added, but the rapid rise in smoke is “threatening to undo decades of improvement and undoing them very quickly.”

One dangerous pollutant in wildfire smoke is PM2.5, tiny bits of airborne ash that are 30 times smaller than the width of a single strand of human hair. This particulate matter can be inhaled deep into the lungs, and even enter the bloodstream. The Environmental Protection Agency says they pose “the greatest health risk,” even causing premature death.  

These tiny particles in wildfire smoke are known to aggravate heart and lung diseases, like cardiac arrhythmias, heart attacks, bronchitis and asthma, with young children and older people especially vulnerable to its harmful effects. Researchers have also linked wildfire smoke to thousands of excess Covid-19 deaths, and are now exploring the links between exposure to wildfire smoke and strokes, pregnancy risks like preterm births and neurological disorders such as strokes and Alzheimer’s disease.

Smoke plumes may blanket an entire region, affecting every resident, irrespective of their income, but limited research suggests the health risks fall disproportionately on older people and especially poorer people, who are more often than not from Black, Brown and Indigenous communities. 

People of color who live in low-income communities often have “increased vulnerability to the effects of air pollution,” Balmes said. “They often have other stressors that contribute to ill health, like a lack of diet filled with fresh vegetables and fruits, which is actually protective in terms of the health effects of air pollution, and just their housing stock, which is often older, may be less protective as the bad outdoor air from wildfires penetrates more easily.”

Our analysis focused on the presence of smoke plumes in the air, rather than PM2.5 particles, because the network of EPA air quality sensors varies widely. Many urban communities lack monitors. So do rural areas, often those areas closest to the wildfires.  And the sensors that are in place don’t report on all days. But Environmental Protection Agency scientists say the presence of smoke plumes from wildfires tracks closely with the presence of fine particulates.

Between 2000 and 2010, the annual average PM2.5 concentration levels in California and Nevada declined 35 percent, according to an analysis of EPA data by NPR’s California Newsroom. By 2020, however, almost all those gains had been erased, with particulate levels nearly as high as they were two decades earlier. In the Pacific Northwest, PM2.5 levels last year surged higher than they were at the beginning of the century, thanks largely to an increase in wildfire smoke.

Indeed, with other sources of PM2.5, such as auto exhaust, in decline because of better emission standards, wildfire smoke represents an increasing share of particulates people are breathing. Burke’s team found that in the West, wildfire PM2.5 now accounts for up to half of all PM2.5 exposure, compared to less than 20 percent a decade ago.

These tiny particles aren’t the only pollutants to worry about. When the Camp Fire incinerated the town of Paradise in 2018, it destroyed nearly 19,000 buildings, including gas stations, two grocery stores, eight schools and a hotel. Everything inside those buildings went up in smoke—from paint thinner and Drano to plastics, oil and pesticides. A report on the Camp Fire, released this July by the California Air Resources Board, found toxic metals, including lead, traveled more than 150 miles and were picked up in air monitoring stations in Silicon Valley.

Stuck Inside, Alone

Brown, one of a handful of medical staffers at the family care clinic in Willows, says all the smoke days are affecting his patients’ mental health. The recommendation that people stay  indoors on bad air quality days intensifies feelings of isolation during the pandemic.  

“Say you are quarantined and then all of a sudden you can't even go in your own backyard without getting a major headache or having an asthma attack or worried that your kid is going to have long-term problems because of wildfire smoke,” he said.  

That isolation has been getting to Larry George, who lives alone, a block away from the hospital, in a gray, two-bedroom house. The 74-year-old Vietnam veteran and retired truck driver suffers from chronic obstructive pulmonary disease, or COPD. On hazy days, George almost never leaves his home.

When he has to go to the doctor’s office or grocery store, even walking a few steps to his white pickup truck is difficult. 

“It just feels like you’re not allowed to go out,” he said, wheezing in his living room, where he keeps an oxygen machine and a large TV screen tuned to Fox News. “You don’t have the freedom you had before.”

Like Pedrozo, he is thinking of moving to someplace with cleaner air.

Alison Saldanha is a data journalist who led this investigation for NPR’s California Newsroom, where Aaron Glantz is senior investigations editor. Farida Jhabvala Romero is a reporter for KQED in San Francisco. Caleigh Wells is a reporter and producer at KCRW in Los Angeles. 

George LeVines and Molly Peterson from the California Newsroom contributed reporting. Glantz edited this story together with the newsroom’s managing editor, Adriene Hill. The story was copy edited by Don Clyde.  Scott Rodd, state government reporter at CapRadio in Sacramento, also contributed reporting along with Lily Jamali from KQED. 

The California Newsroom is a collaboration of NPR and 17 public radio stations across the state, from San Diego to the Oregon border.