As the skies above the San Francisco Bay Area in California filled with smoke last week from wildfires ripping through nearby Sonoma County, Kari Nadeau and Mary Prunicki sprang into action.

The pair, scientists at Stanford University in the Bay Area, began calling in hundreds of people who had signed up to participate in their study of the long-term health effects of wildfire smoke. Previous research has linked air pollution from wildfires to surges in hospital visits for asthma and strokes. But it’s not clear whether exposure to wildfire pollution has lasting consequences — something that Nadeau, director of Stanford’s Sean N. Parker Centre for Allergy & Asthma Research, and Prunicki, a pollution biologist, hope to find out.

In early October, before the first large wildfires of the year sparked in northern California, their team assessed the circulatory, respiratory and immune systems of people enrolled in the study. The scientists began calling participants back to their lab on 28 October to undergo the same tests, which they’ll repeat in three months after the smoke has cleared. Nadeau and Prunicki have approval to continue assessments until 2037 and ultimately hope to enrol as many as 2,000 people — amassing a trove of data on how a person’s body responds over time to wildfire smoke.

Answers are sorely needed. Wildfires burned a record-breaking 760,000 hectares last year in California, destroying an area larger than the US state of Delaware. Almost 100 people died and hundreds of thousands of others breathed in sooty air for days. And climate models predict these blazes will grow larger and more frequent in the coming decades. The area burned in California each year will increase by 77% by the end of the century if greenhouse-gas emissions continue to rise, according to the state’s most recent climate-change assessment.

Lisa Miller, an immunologist at the University of California, Davis, says the Stanford study is one of the first to monitor wildfires’ health effects in a diverse group of people over several years. By understanding who is most affected by wildfire and why, Miller says researchers can create evidence-based guidelines for mitigating risk. She is particularly worried that smoke exposure could damage children’s lungs as they develop in ways that lead to chronic health problems.

“We have to be better prepared for these events,” she says. “Last year was everyone’s wake-up call that we need to be ready for the next big fire to happen — because it will happen again.”

Sooty skies

The idea for the health study arose last year, as the largest and deadliest blaze in California history — the Camp Fire — ravaged the northern part of the state. After the fire destroyed the city of Paradise in California’s central valley and turned skies brown above the Bay Area, Nadeau and Prunicki realized their skills were needed.

The pair has long studied how air pollution in the central California city of Fresno alters immune cells and causes allergies and asthma. In April, they reported that 7- and 8-year old children living about 100 kilometres away from wildfires in 2015 were exposed to more pollutants than were those living near prescribed burns — small forest fires that are purposely set to reduce overall fire risk ¹ .

The researchers suspect that the difference is due to toxic chemicals released when wildfires burn synthetic materials in houses and cars. “Wildfire is like a giant slug of air pollution all at once,” Prunicki says.

As the smoke from the Camp Fire hung over the Bay Area last year, she and Nadeau scrambled to launch a small study tracking the effects of wildfire pollution on health. They collected blood and saliva from about 100 people, and asked them to return for assessments a few months later. “We didn’t have time to collect tons of information, and it was sort of done in reverse,” says Nadeau.

In February, they submitted a proposal for a larger study to an ethical review board. To fund the work, they set aside about US$1 million from a grant they had received from the Parker Foundation in San Francisco, founded by Napster’s Sean Parker.

The team is conducting the wildfire research in the Bay Area because the air quality is typically better than that of Fresno, says Nadeau. This should help her team isolate the health effects of wildfire smoke from those caused by other environmental hazards.

Clearing the air

The scientists also began an 80-person study this week to test whether air purifiers can limit any health effects from exposure to wildfire smoke. Half of the students in a college dormitory in Fresno have air-filter machines installed in their rooms, and the other half have a sham machine. The goal is to work out how much air filters help, and who needs them most.

Michael Wara, an energy and climate policy analyst at Stanford, hopes to incorporate data from Nadeau and Prunicki’s health studies into models on the costs and benefits of various policies to curb wildfire damage to neighbourhoods and people. “Fire is a climate adaptation problem that California is confronting right now,” he says, “and not in 2050, and not in 2100.”

The researchers behind the northern California health study hope that its findings will help people around the world who are exposed to wildfire smoke. “This isn’t just a problem for the [US] west,” Nadeau says. “We need to know how to adapt better. Right now, people are left unaware.”