A new study led by researchers at Harvard T.H. Chan School of public Health indicates that exposure to fire smoke may alter the immune system on a cellular level. Fire smoke, which can contain particulate matter, gases, perfluoroalkyl and polyfluoroalkyl substances (PFAS), toxic metals, and carcinogenic compounds, has been shown to impact the body’s defense mechanisms.

The study, published on June 26 in nature Medicine, is the first to examine the specific cellular changes associated with fire smoke exposure, documenting how smoke can damage the body through the immune system. researchers found that healthy adults exposed to fire smoke exhibited alterations to their immune systems, including changes in the regulation of genes associated with asthma and allergies, and in immune cells that play a key role in fighting pathogens, compared to adults who had no exposure to fire smoke.

The researchers collected blood samples from two groups of adults matched by age, sex, and socioeconomic status: 31 smoke-exposed adults (firefighters and civilians) and 29 non-smoke-exposed adults. Participants had no acute or chronic conditions and were not taking immunomodulatory drugs. blood draws occurred within one month after smoke exposure.

Using single-cell -omic techniques, epigenetic assays, mass cytometry, and bioinformatic analytical tools, the researchers examined and analyzed individual cells within each blood sample.

The study revealed several cellular-level changes in the smoke-exposed individuals. These individuals showed an increase in memory CD8+ T cells and elevated activation and chemokine receptor biomarkers within multiple cell types. Additionally, they exhibited changes in 133 genes related to allergies and asthma, and more of their immune cells were bound with toxic metals, including mercury and cadmium.

“Our findings demonstrate that the immune system is extremely sensitive to environmental exposures like fire smoke, even in healthy individuals,” said lead author mary Johnson, principal research scientist in the Department of Environmental Health. “Knowing exactly how may help us detect immune dysfunction from smoke exposure earlier and could pave the way for new therapeutics to mitigate, or prevent altogether, the health effects of smoke exposure and environmental contaminants.”

The researchers suggest the study could inform environmental and public health policies. “Knowing more about exactly how smoke exposure is harming the body, we may increase public health campaigns about the dangers of smoke exposure and the importance of following evacuation procedures during wildfires,” said corresponding author Kari Nadeau, John Rock Professor of Climate and Population Studies and chair of the Department of Environmental Health. “We may also reconsider what levels of smoke exposure we consider toxic.”