The fact that smoke produced by structure fires and wildfires can harm the immune system is not new. But now, researchers have published a study that helps unravel the mechanisms by which smoke exposure can cause this harm.

What's happening?

As the Los Angeles area endured a series of historic, catastrophic wildfires in January, The Conversation examined a lesser-known impact of exposure to wildfire smoke: damage to immune systems.

The outlet cited higher rates of COVID-19 infection in New South Wales not long after the Black Summer bushfires of late 2019 and 2020. Reporting from The Conversation added that further research was required to quantify the scope of the risk and to understand exactly how smoke exposure can damage immune systems, with the potential to cause lasting harm.

Research on this topic is indeed ongoing, as a new late-June publication in the journal Nature Medicine establishes.

"We've known that smoke exposure causes poor respiratory, cardiac, neurological, and pregnancy outcomes, but we haven't understood how," co-author Kari Nadeau explained.

Nadeau is a professor of climate and population studies as well as chair of the Department of Environmental Health at the Harvard T.H. Chan School of Public Health.

"Our study fills in this knowledge gap, so that clinicians and public health leaders are better equipped to respond to the growing threat of difficult to contain, toxic wildfires," she added.

According to a release from Harvard, the authors identified 31 individuals, "firefighters and civilians," who had been exposed to smoke, along with 29 people who hadn't. Participants' blood samples were analyzed at a "cellular level," and researchers identified several key differences in the cohort of people who had been exposed to fire smoke.

That group demonstrated elevated levels and activity with respect to specific immune cells, and researchers found "changes in 133 genes related to allergies and asthma."

In addition to those differences, smoke-exposed participants' immune cells were "bound with toxic metals," including cadmium and mercury, ostensibly released into the air by materials as they burned.

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Why are these findings important?

As the researchers noted, immune system damage associated with fire smoke had previously been documented. But without more information about the nature of these risks, scientists knew they would be harder to address.

As global temperatures rise, wildfires and other forms of extreme weather are becoming more common and more deadly. Understanding the precise hazards posed by these mounting threats could enable policymakers to set standards that help safeguard the public and enable residents to take evidence-based steps to protect themselves.

What can we do about it?

Lead author Mary Johnson said that the team's findings show the "immune system is extremely sensitive to environmental exposures," even in the young and healthy. The Harvard principal research scientist hopes improved understanding of this issue will inform mitigation strategies.

"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," Johnson explained.

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