The indoor kitchen walls of rural houses in El Salvador were often black with soot, Rebecca Ciciretti noticed while working for the Peace Corps for almost two years. Mothers and children were often inside for many hours a day, cooking over an open flame.

"If that's what the walls look like, what do their lungs look like? Because they're over the fire multiple times a day," Ciciretti wondered at the time.

About three years after her work in El Salvador, Ciciretti was able to answer an adapted form of this question. With the support of a Fulbright research grant, she and a team of four other researchers looked at the effects of wildfire smoke on the respiratory health of children in Chile. Their findings, published in December 2022 in Atmosphere, suggest that more than 1 million children living in Santiago have an increased risk of developing respiratory illnesses such as bronchitis and pneumonia from exposure to this smoke. These findings are part of a small but growing research area revealing wildfires' extensive health impacts. These results suggest to many experts that public health policies may need to change to mitigate risk.

Significant health risks of bronchitis, pneumonia, and chronic lower respiratory diseases were found in Santiago for children. Children under one year were particularly susceptible to bronchitis, and children ages one to four were particularly susceptible to pneumonia when wildfires increased. 

Ciciretti wishes they could have covered more geography in the study, and accessed more data on PM 2.5, the smaller particles, to showcase the invisible threat that arises from the prevalence of these wildfires. Research in the study focused on PM 10, the larger particles, because a more robust dataset was available on these.

Wildfires are increasing worldwide due to climate change. According to research published in PNAS in 2016, the cumulative forest fire area in the western United States doubled between 1984 and 2015. According to a report released by the United Nations in February, wildfires are expected to increase 14% by 2030 and 30% by 2050. The U.N. report points to the health impacts: Hospital visits related to such respiratory issues are higher in children under five. An estimated 2,195 hospitalizations due to respiratory diseases were reported during an assessment of the 2019 Amazonian fires. In Indonesia, 500,000 acute respiratory infections were tied to smoke, and almost 3,000 deaths annually have been connected to wildfire smoke in the Brazilian Amazon. 

"We must learn to live with fire," said the authors of the U.N. report. 

Ciciretti agreed that systemic changes are important to respond to these events. In Chile, she said, that includes ensuring that buildings have good seals on windows and doors, making sure that kids with asthma aren't outdoors during wildfires, and putting alert systems in place, so people have more awareness about when a fire is coming. Masks are also a potential avenue, but to be effective against the types of air pollution from wildfires, these would need to be masks that can filter what is called PM 2.5, fine particulate matter that is so small it can enter deep into the lungs. According to the California Air Resources Board, long-term exposure to these particulates has been linked to premature death.

"One of the problems though is a lot of times you can see smoke, but those are the bigger particles. The issue is those PM 2.5, the ones you can't see as well, and so those you might be affected by, and you don't even know it," said Ciciretti.

Different cities have different risk levels, which can likely be tied in part to their geography, Ciciretti's research showed. She and her team studied two cities, Santiago and Valparaiso. Santiago is located in a tidal basin, which, in conjunction with the wind patterns, traps the air from fires, according to Ciciretti. Valparaiso is by the sea, which provides it with natural ventilation.

Los Angeles and Mexico City have similar geography to Santiago, suggesting that similar risk patterns could exist in those cities. 

The study starts a discussion, at least, she said. In her view, more people need to look at the effects of wildfire events. 

"That could lead to policy changes, more protection for children, more health protections in general," Ciciretti said. "Children are not the only vulnerable population, so I think just having that discussion of who is affected by these disasters."

Ciceretti says that the "most ideal" solution would be to figure out climate change, but because that isn't going anywhere right now, she says we have to figure out how to work with it.