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New Study Suggests Different Immune Outcomes Following Wildfires Compared to Controlled Burns

AAAAI News Release

AAAAI Annual Meeting

April Presnell

Research presented during 2019 AAAAI Annual Meeting investigates health impacts resulting from Fresno, California fires

San Francisco, CA – Controlled burns are often used to help reduce and contain wildfires, but it turns out which burn is occurring can actually have an effect on your health, according to research presented at the 2019 Annual Meeting of the American Academy of Allergy, Asthma & Immunology (AAAAI).

Data collected from seven year olds in Fresno, California was retrospectively analyzed to investigate what health impacts individuals might face post wildfire or controlled burn. Subjects resided 70 miles away from the site of the prescribed burn, and 90 miles away from the site of the wildfire. Data collection occurred three months after each type of burn to analyze blood, blood pressure and pulmonary function tests. Asthmatic subjects were taken note of prior to data analysis (38% for prescribed burn, 25% for wildfire). Linear regression models were then performed to investigate the effect of health outcomes between each group.

“The body’s immune system is in a state of constant flux, with various cell types increasing or decreasing depending on what the body is being exposed to,” said first author Mary Prunicki, MD, PhD. “In this study, we found that there were more Th1 cells in children who were exposed to the wildfire smoke, which was more pollution exposure overall. These cells are in a state of balance with other cells and dysregulation can lead to changes in the body’s response to allergic diseases, such as asthma, rhinitis, hay fever and food allergy.”

Similar immune changes can occur with air pollution exposure in general. The study found pollutant levels were higher during wildfires compared to prescribed burns, noting that a limitation of the study was that their measurement of pollutants was not able to distinguish wildfire smoke from other air pollutants. “Pollution is associated with an increase in methylation of the Foxp3 gene, which renders the gene less active and therefore, fewer immunoregulatory cells are produced,” Dr. Prunicki added. “The result is that the body is less able to keep immune homeostasis and may predispose the child to increased allergic disease.”  

Controlled burns are only performed during optimal weather conditions and as a result, people are exposed to less smoke. Even so, data on controlled burns and the health impacts of different types of fires is lacking. Rodd Kelsey, PhD, a co-author and lead scientist with The Nature Conservancy of California that provided support for the research, provided context as to why this study is so important. “Prescribed fire is a critical tool to increase the resilience and health of our fire-prone forests. Public concern about smoke impacts is one of the barriers to increasing the use of prescribed fire. Our hope is that, through better understanding of the comparative public health impacts of prescribed and unmanaged wildfire, we will be able to get more good fire on the ground in a way that benefits both nature and people."

Visit to learn more. Research presented at the AAAAI Annual Meeting, February 22-25 in San Francisco, California, is published in an online supplement to The Journal of Allergy and Clinical Immunology.

The American Academy of Allergy, Asthma & Immunology (AAAAI) represents allergists, asthma specialists, clinical immunologists, allied health professionals and others with a special interest in the research and treatment of allergic and immunologic diseases. Established in 1943, the AAAAI has nearly 7,000 members in the United States, Canada and 72 other countries. The AAAAI’s Find an Allergist/Immunologist service is a trusted resource to help you find a specialist close to home.