In the summer of 2018, vast swathes of California burned. The largest fire, known as the Mendocino Complex, scorched an area bigger than New York City. A few hundred miles to the east, Camp Fire raged so hot it created its own weather system, razing the small town of Paradise and killing 85. It was the deadliest in state history.

But the death toll wasn’t the only exceptional thing about these wildfires — where they struck also alarmed researchers. Urban wildfires were once rare, but a warming climate is increasing their frequency.

The impact of wildfires doesn’t stop at the buildings they destroy, the lives they claim, or the wreckage they make of the natural environment. The long-term health impacts of wildfires remain a mystery, but researchers suspect those impacts might last far longer than once thought.

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The effects of smoke exposure in the weeks, months and years following rural wildfires are understudied enough, but urban wildfires are practically uncharted territory. Now, a growing movement of researchers suggests that wildfires could be a new public health threat which policymakers are ill-equipped to tackle.

Entering the unknown

Wildfires are nothing new, but a lack of research has made the effects of exposure to their smoke something of an unknown for public health professionals.

“When these fires broke out, it was a shock to everybody,” said Irva Hertz-Picciotto, Director of the UC Davis Environmental Health Sciences Center, “but when I looked at the literature, I found there just wasn’t a body of evidence regarding long-term effects of wildfire exposure.”

The little research there is addresses the immediate effects following rural fires — largely regarding respiratory problems and cardiovascular conditions — but study of the longer-term health implications is thin on the ground. According to Hertz-Picciotto, it’s practically non-existent when it comes to wildfires that spread into and engulf urban areas.

"Smoke plumes can travel as much as 50 or 100 miles, exposing millions to heavy fumes"

“There are thousands of chemicals found in residential fires not found in rural wildfires,” Hertz-Picciotto continued. Plastics, asbestos, rubber and paint are just some of the more immediate materials concerning researchers. Precisely what those compounds mean for human health following a fire isn’t yet known.

And It's not just the communities at the heart of the wildfires that could experience the fallout, either. Smoke plumes from these fires can travel as much as 50 or 100 miles, said Hertz-Picciotto, exposing “millions” to “heavy particle smoke”.

California’s small towns might have borne the brunt of the wildfire season, but citizens across the country could also be suffering.

Plugging the gaps

Researchers are already starting to fill gaps in the evidence. Since 2010, the National Institute of Environmental Health Sciences has streamlined and shortened its funding process to allow time-sensitive research into the aftermath of natural disasters, and new measures to address post-wildfire health impacts are already beginning to emerge.

“Public awareness in the aftermath of these fires is vital,” said Christopher Migliaccio, assistant professor at the University of Montana and an NIEHS-funded researcher of rural wildfires. “People don’t want to change their behaviours, but for asthmatics, the elderly, and those with cardiovascular conditions, it’s vital that they understand the health risks of particulate matter in smoke.”

And with Smoke Sense, a mobile app, the US’s Environmental Protection Agency is already using technology to both better inform US citizens, and to gather data for a study on precisely how wildfire smoke is impacting their health.

The app bills itself as a “citizen science project”, asking ordinary people to help researchers understand how smoke exposure is affecting their health and what they do to avoid smoke inhalation. It also informs users of current and predicted air quality levels after a wildfire.

Another priority, according to Migliaccio, is the widespread distribution of specialised air filters, particularly in schools, hospitals and homes. “People don’t appreciate the particulate matter level is practically the same indoors as out; just going inside does not protect you,” he said.

But mitigating the after-effects of fires is only one part of a comprehensive policy response: preventing fires reaching urban areas is vital too.

“We cannot continue to build homes wherever we want”

“We’re encroaching more and more on the wildland-urban interface, and narrowing the distance between our wild land and our built communities,” said Hertz-Picciotto. “It opens up the possibility for more fires.”

According to one study, almost a third of California’s housing stock is built in this area — the zone where man-made structures give way to unoccupied land — and in many US states, that figure is even higher.

“We cannot continue to build wherever we want,” said Hertz-Picciotto, particularly when the evidence suggests that wildfires are only set to worsen as the climate continues to warm.

Structural reform

Both Migliaccio and Hertz-Picciotto emphasised that single measures or small tweaks are unlikely to either comprehensively mitigate the health impacts of wildfire smoke, or to prevent wildfires in future.

The blazes that wracked California last summer were national crises requiring complex governmental responses that cut across health, forestry, housing and emergency response agencies, with all the friction and miscommunication that cross-team responses entails.

“It was chaotic,” said Hertz-Picciotto, citing thousands displaced by the fires who still have no permanent home to go to, 6 months on from the most recent inferno.

But investing in mitigation and prevention, whether in changing the layouts of towns and cities, or ensuring new housing projects build on land not at risk of fire, could ease the burden of a spiralling federal spend on fire suppression, which has soared by 562% over the last 20 years.

According to a 2018 report by the National Institute of Building Sciences, every dollar spent on hazard mitigation saves $6 in future disaster costs.

“Today’s fires burn longer, they’re harder to fight, and they’re getting more common,” said Migliaccio. Investing in comprehensive wildfire research and response might no longer be a prudent move for the future, but an urgent response to the dangers of the present. — Edward Siddons