Type of Fire Affects Immune System Differently, Study Finds

There may be a difference between controlled burns and wildfires on one’s immune system, according to recent study.

The retrospective research involved collecting data from 7 year olds, some of whom had asthma and were exposed to 2 different types of fires around Fresno, California. Subjects resided 70 miles away from the site of the controlled burn, and 90 miles away from the site of the wildfire. Controlled burns are often used to help reduce and contain wildfires.

Data collection occurred 3 months after each type of burn to analyze blood, blood pressure, and pulmonary function tests. Linear regression models were then performed to investigate the effect of health outcomes between each group.

The controlled burn involved 32 subjects, 38% with asthma; the wildfire involved 36 subjects, 25% with asthma. Pollution exposures were assessed from central site monitors and distance-weighted to the subject’s home. Peripheral blood mononuclear cells were stained with metal-conjugated antibodies for surface markers and mass cytometry was performed. Methylation studies were also performed.

“In this study, we found that there were more [T helper 1] 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,” Mary Prunicki, MD, PhD, one of the authors, said in a statement.

Models controlled for age, sex, body mass index percentile, race, smoke exposure, and asthma status. T helper (Th) 2 cell percentages were increased (estimate [Est] = 1.88; standard error [SE] = .94; P = 0.050), but Th1 (Est = —2.13 SE= 0.52; P = .00018) and Th17 (Est = —1.10; SE = 0.48; P = .027) decreased post-wildfire versus prescribed burn.

There were also significant differences between groups for CD8+ cells, monocytes, and B cells. Foxp3 methylation in the promoter region was increased post wildfire (Est = 2.59; SE = 0.95; P = .0088). Pulse pressures were trending towards increased post wildfire (Est = 4.079; SE = 2.35; P = 0.088).

Similar immune changes can occur with air pollution exposure in general. The study found pollutant levels were higher during wildfires compared to prescribed burns. One limitation of the study was that the measurement of pollutants was not able to distinguish wildfire smoke from other air pollutants, the statement said.

“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,” Prunicki added. “The result is that the body is less able to keep immune homeostasis and may predispose the child to increased allergic disease.”

The researchers said additional study is needed to get a better understanding about the public health impacts of controlled burns and wildfires.

The research was presented at the 2019 Annual Meeting of the American Academy of Allergy, Asthma & Immunology (AAAAI).

Reference

Prunicki M, Zhou X, Nadeau K. The impact of a prescribed burn versus a wildfire on the immune and cardiovascular systems of children. Presented at the American Academy of Allergy, Asthma & Immunology 2019 Annual Meeting; February 22-25; San Francisco, CA. Abstract 248.