Wildfire Smoke and High Fuel Costs: Highlights from the Irving Institute's April Faculty Seminar

The air that sustains us can also bring us trouble.

So said two Dartmouth researchers during the Irving Institute's monthly faculty seminar for April. As they explained, the air can carry toxic wildfire smoke. The air can also bring extremes of heat and cold that lead to energy insecurity.

Toxic Wildfire Smoke

Toxic smoke from wildfires was the topic of the April faculty seminar's first presentation. Entitled "Wildfire Smoke Particles: Influence of an environmental factor in host-respiratory pathogen crosstalk," it was presented by Sadia Sultana, a postdoctoral fellow at the Geisel School of Medicine.

As Sultana explained, wildfire smoke is a complex mix of particulates and pollutants that's often more toxic than smoke from other sources. Indeed, wildfire smoke has been associated with human ailments that include heart attack and stroke, asthma, chronic obstructive pulmonary disease (COPD) and hypertension.

What's more, wildfire smoke is on the rise, Sultana said. For one, from 2003 to 2023 the frequency of wildfires worldwide doubled. Also, reduced precipitation and longer arid seasons are expected to increase the size of fire-prone areas by nearly 30% by the century's end. And in the United States alone, wildfire smoke is expected to cause 75% more premature deaths per year by 2050, compared with the years 2011 to 2020.

By composition, wildfire smoke is approximately 90% particulates, 10% volatile compounds and gases. These particulates are tiny, many smaller than 2.5 micrometers across. By way of comparison, the diameter of an average human hair is about 50 to 75 micrometers.

Sultana became fascinated by two related questions: Does human exposure to the tiny particulates in wildfire smoke impact the innate immune system? And if so, how?

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Sadia Sultana, Postdoctoral Fellow in the Geisel School of Medicine. (Photo by Andrila Hait Chakrabarti)

"When a pathogen enters our body, our innate immune cells—particularly macrophages–recognize the pathogens and secrete a cascade of chemical signals," she explained. (Macrophages are white blood cells that can engulf and destroy pathogens.)

To seek answers, Sultana conducted a series of experiments. First, she collected blood samples from healthy people, isolated the blood's macrophages, and treated them with wildfire particulate.

Next, after an 18-hour incubation period, Sultana measured the presence of an important enzyme in the macrophage culturing media. If wildfire particulates had damaged the macrophages, this enzyme would have leaked and impaired macrophage regular functions. Fortunately, the results were negative. At the concentrations tested, Sultana says, the particulate is not toxic to the macrophages. They were not damaged and did not leak.

Next, Sultana explored another question: Do the undamaged macrophages still perform the same way as a non-particle-exposed macrophage in terms of responding to an infection? To address this, she performed two more experiments. First, she investigated macrophage polarization state, which dictates how well macrophages destroy pathogens. Second, she analyzed macrophage pathogen-clearance efficiency using the respiratory pathogen Pseudomonas aeruginosa.

Sultana found that wildfire particulates can lead macrophages toward a pro-inflammatory state by triggering what's known as cytokine secretion. (Pro-inflammatory macrophages are most efficient at removing microbial pathogens.) However, even though macrophages polarize toward a pro-inflammatory state, they are not efficient at removing bacterial pathogens. This is why when those smoke particles enter our respiratory system, macrophages can sense the presence of those foreign matters and become activated. However, their function to remove bacterial pathogens is hampered.

Energy Insecurity

The second faculty seminar presentation for April came from Sarah Kelly, a Dartmouth lecturer in geography and head of the Irving Institute's Energy Justice Clinic.

In a presentation entitled "Energy Insecurity in Northern New England," Kelly made the case for expanding our understanding of energy issues. She called for traditional quantitative research to be augmented by qualitative research in mixed-method approaches that include interviews and workshops.

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Dr. Sarah Kelly, Lecturer in Geography, Research Scientist at the Irving Institute, and Head of the Energy Justice Clinic. (Photo by Andrila Hait Chakrabarti)

"We need a qualitative and community-based understanding of energy insecurity, which is interrelated with food and housing insecurity," Kelly said. "Not just quantitative decisions on how these programs work and who receives funding for them, but also on the community's limited understanding of these complex issues."

Kelly and her community partners have done just that. Since 2024, they've conducted interviews and surveys with residents of New Hampshire and Vermont's Upper Valley, exploring how they cope with rising heating-fuel costs. And working with nonprofit organizations, including LISTEN Community Services, they've also examined the effectiveness of the region's social safety functions. Survey design support and administration is being provided by Jennifer Jerit, Professor of Government.

The issue is especially important given President Trump's call for the elimination of LIHEAP, a U.S. federal program that provides states with funding to help some 6.7 million households pay their heating and cooling costs. "While these programs can be imperfect," Kelly said, "they're really critical."

That's especially true in the Upper Valley. Winters there are long, cold and snowy, and many houses are big, old and drafty.  With public transportation sparse, most residents get around with their own vehicles.

Interviews conducted by Kelly and her partners revealed that lower-income people are forced to make trade-offs. Should they pay for heating fuel, gas for their car, or food? "These are unreasonable choices," Kelly said. "People feel the safety net has been removed."

As for key elements of the energy transition, such as electric vehicles and heat pumps, low-income residents told the researchers those options are simply too expensive.

To help residents, Kelly and partners recently launched a weatherization workshop at a local senior center. Despite the famous rugged individualism of New Englanders, attendance has been encouraging. Maybe it's something in the air.

Learn more: Watch a video of the Irving Institute's April faculty seminar

Peter Krass is a contributing writer and editor to the Irving Institute.