The flames from wildfires aren’t always the most dangerous part
The spate of devastating fires hitting the Los Angeles area has dominated headlines and understandably so. At least 10 people have died and upwards of 180,000 people have been evacuated with more than 10,000 structures destroyed. One of these fires, the Palisades Fire, began burning on Tuesday and continues at the time of this writing, has destroyed at least 17,000 acres, the most in Los Angeles history. But there's also the Eaton Fire, the Hurst Fire, the Kenneth Fire and other fires in the area, many with little to no containment. While hundreds of thousands of Californians are fleeing from flames, there are other risks aside from the immediate damage: air pollution and the charred toxins that are left behind. To give one example, a recent study in the journal JAMA Neurology has looked at the effects of wildfire smoke on dementia. Previous research has established that tiny particles in the air (2.5 micrometers or less in diameter, known as PM2.5) are linked to dementia, but the researchers found that long-term exposure to wildfire smoke specifically “was associated with dementia diagnoses.” They added that as climate change worsens, “interventions focused on reducing wildfire PM2.5 exposure may reduce dementia diagnoses and related inequities.” To conduct their research, the scientists looked at health data from more than 1.2 million people from between 2008 and 2019 among members of Kaiser Permanente Southern California. Within this cohort, they discovered “people with higher exposure to wildfire fine particulate matter (PM2.5) had elevated risk of developing dementia,” explained Dr. Joan Casey, the study’s corresponding author and a professor of public health at the University of Washington. Because this study only examined existing patient data, Casey told Salon that scientists will need to do more research on the precise relationship between wildfire exposure and dementia. “We looked at the umbrella of all dementia diagnoses, but certain sub-types like Alzheimer’s or frontotemporal dementia might have stronger links with wildfire PM2.5,” Casey said. “We also want to understand the relevant time window of exposure. Here, we looked at exposure in the prior three years, but a longer window is likely important (up to 20 years.)” "As temperatures and humidity increase, conditions such as stroke, migraines, meningitis, epilepsy, multiple sclerosis, schizophrenia, Alzheimer's disease, and Parkinson's disease may worsen." The researchers’ work is unfortunately relevant to human beings because climate change is making wildfires more frequent and more intense. From California and Hawaii to Greece and Spain, more and more of Earth’s wooded areas are bursting into flame as humanity overheats the planet with heat-trapping fossil fuel emissions. While these conflagrations engulf millions of acres of lands, they belch fine particulate matter into the air, which humans inevitably inhale. But more and more research is making it clear how devastating to our health this toxic air can be. Although this study focuses specifically on wildfire PM2.5, other research firmly establishes that PM2.5 in general is bad for human health. A report from the National Bureau of Economic Research released last April found that wildfire smoke contributes to the deaths of around 16,000 Americans per year, with that number expected to rise to 30,000 by mid century. A systematic review published in the journal Neurotoxicology found a link between air pollution and increased depressive and anxiety symptoms and behaviors, as well as physical alterations in brain regions believed to be associated with those conditions. A 2024 study in the journal Ecotoxicology and Environmental Safety likewise found links between various types of common air pollution and diseases including PTSD and multiple sclerosis, while a 2021 study in the journal Neurology found a link between urban air pollution and central nervous system diseases. Want more health and science stories in your inbox? Subscribe to Salon's weekly newsletter Lab Notes. "The results of our studies on the effects of nanoparticles in the air show a link between exposure to air pollutants and neurological diseases and neuropsychiatric disorders," 2021 study lead author Mojtaba Ehsanifar, an assistant professor of environmental neurotoxicology at Kashan University of Medical Sciences' Anatomical Sciences Research Center, told Salon by email. Although Ehsanifar has not specifically worked on the effects of pollutants from fires, he noted that pollutants produced by both gases tend to be similar. He blames climate change for this problem. “A recent investigation establishes a connection between climate change and the exacerbation of certain neurological disorders,” Ehsanifar said. “As temperatures and humidity increase, conditions such as stroke, migraines, meningitis, epilepsy, multiple sclerosis, schizophrenia, Alzheimer's disease, and Parkinson's disease may worsen.” He added that as temperatures continue to rise, the heat will combine with the smoke to hurt our brains. "This is yet another example of the profound, yet grossly understated negative health consequences of human-caused climate change." “Currently, brains are already operating toward the upper thresholds of these ranges, and as climate change elevates temperature and humidity, our brains might struggle to maintain temperature regulation, even malfunctioning,” Ehsanifar said. “A high internal body temperature, especially above 104 degrees Fahrenheit, with cognitive impairment such as confusion, defines heat stroke.” This research underscores how global heating is intrinsically linked to our health. University of Pennsylvania climate scientist Dr. Michael E. Mann said it is fair to directly attribute diseases like dementia to climate change when they are demonstrably caused by wildfire exposure. “The connection is epidemiological, much like the negative health consequences of smoking are epidemiological, i.e. statistical in nature,” Mann said. “So in other words, while it’s always possible that a victim could have suffered neurological diseases for other reasons, we can say that exposure to wildfire smoke substantially increases the likelihood of e.g. developing dementia, enough so that there is effectively a causal connection there.” Mann added, “This is yet another example of the profound, yet grossly understated negative health consequences of human-caused climate change.” Dr. Kevin Trenberth, a distinguished scholar at the National Center for Atmospheric Research, told Salon that he is not surprised the study found adverse effects of wildfire pollution. The revelation that PM2.5 may indirectly increase dementia risk, however, was new to him. “But there is no question that air pollution is bad for health in many ways,” Trenberth said. “On bad pollution days, either one should not exercise or should do it indoors. So this affects exercise, which should help health. With wildfires around, one should not breathe the foul air. So this can be partially controlled from industry although mainly for larger particles. It is harder to see the smaller particles.” Nor are humans alone in suffering, Trenberth noted. “Think of all the poor animals exposed.” Scientists writing in 2022 for the journal Environmental Research described air pollution broadly as an underrecognized public health risk, arguing that “policy needs to be matched by scientific evidence and appropriate guidelines, including bespoke strategies to optimise impact and mitigate unintended consequences.” In addition to mitigating the impacts of climate change, experts urge ordinary citizens to take measures to protect their lungs during times of intense air pollution. Whether it is caused by wildfires, urban smog or any other source, the overwhelming evidence is that breathing it in is bad for a person’s respiratory health. What remains after a wildfire can also be dangerous. The charred ruins of houses and burnt out cars contain countless pollutants from melted plastics, paints, electronics and household waste. Until the environment is adequately cleaned up, the likelihood is that those who struggle with disease because of exposure to wildfires both during and after may continue to risk their health. “Seeing the magnitude of the relationship between wildfire PM2.5 and dementia was quite striking,” Casey said. “I was especially struck by how much stronger this relationship was for people living in communities with higher levels of poverty, suggesting that climate change is again increasing health disparities.” Read more about climate change
Climate change is making wildfires more common and more severe. The pollution is killing us
The spate of devastating fires hitting the Los Angeles area has dominated headlines and understandably so. At least 10 people have died and upwards of 180,000 people have been evacuated with more than 10,000 structures destroyed. One of these fires, the Palisades Fire, began burning on Tuesday and continues at the time of this writing, has destroyed at least 17,000 acres, the most in Los Angeles history. But there's also the Eaton Fire, the Hurst Fire, the Kenneth Fire and other fires in the area, many with little to no containment.
While hundreds of thousands of Californians are fleeing from flames, there are other risks aside from the immediate damage: air pollution and the charred toxins that are left behind.
To give one example, a recent study in the journal JAMA Neurology has looked at the effects of wildfire smoke on dementia. Previous research has established that tiny particles in the air (2.5 micrometers or less in diameter, known as PM2.5) are linked to dementia, but the researchers found that long-term exposure to wildfire smoke specifically “was associated with dementia diagnoses.” They added that as climate change worsens, “interventions focused on reducing wildfire PM2.5 exposure may reduce dementia diagnoses and related inequities.”
To conduct their research, the scientists looked at health data from more than 1.2 million people from between 2008 and 2019 among members of Kaiser Permanente Southern California. Within this cohort, they discovered “people with higher exposure to wildfire fine particulate matter (PM2.5) had elevated risk of developing dementia,” explained Dr. Joan Casey, the study’s corresponding author and a professor of public health at the University of Washington.
Because this study only examined existing patient data, Casey told Salon that scientists will need to do more research on the precise relationship between wildfire exposure and dementia. “We looked at the umbrella of all dementia diagnoses, but certain sub-types like Alzheimer’s or frontotemporal dementia might have stronger links with wildfire PM2.5,” Casey said. “We also want to understand the relevant time window of exposure. Here, we looked at exposure in the prior three years, but a longer window is likely important (up to 20 years.)”
"As temperatures and humidity increase, conditions such as stroke, migraines, meningitis, epilepsy, multiple sclerosis, schizophrenia, Alzheimer's disease, and Parkinson's disease may worsen."
The researchers’ work is unfortunately relevant to human beings because climate change is making wildfires more frequent and more intense. From California and Hawaii to Greece and Spain, more and more of Earth’s wooded areas are bursting into flame as humanity overheats the planet with heat-trapping fossil fuel emissions. While these conflagrations engulf millions of acres of lands, they belch fine particulate matter into the air, which humans inevitably inhale. But more and more research is making it clear how devastating to our health this toxic air can be.
Although this study focuses specifically on wildfire PM2.5, other research firmly establishes that PM2.5 in general is bad for human health. A report from the National Bureau of Economic Research released last April found that wildfire smoke contributes to the deaths of around 16,000 Americans per year, with that number expected to rise to 30,000 by mid century. A systematic review published in the journal Neurotoxicology found a link between air pollution and increased depressive and anxiety symptoms and behaviors, as well as physical alterations in brain regions believed to be associated with those conditions. A 2024 study in the journal Ecotoxicology and Environmental Safety likewise found links between various types of common air pollution and diseases including PTSD and multiple sclerosis, while a 2021 study in the journal Neurology found a link between urban air pollution and central nervous system diseases.
Want more health and science stories in your inbox? Subscribe to Salon's weekly newsletter Lab Notes.
"The results of our studies on the effects of nanoparticles in the air show a link between exposure to air pollutants and neurological diseases and neuropsychiatric disorders," 2021 study lead author Mojtaba Ehsanifar, an assistant professor of environmental neurotoxicology at Kashan University of Medical Sciences' Anatomical Sciences Research Center, told Salon by email. Although Ehsanifar has not specifically worked on the effects of pollutants from fires, he noted that pollutants produced by both gases tend to be similar. He blames climate change for this problem.
“A recent investigation establishes a connection between climate change and the exacerbation of certain neurological disorders,” Ehsanifar said. “As temperatures and humidity increase, conditions such as stroke, migraines, meningitis, epilepsy, multiple sclerosis, schizophrenia, Alzheimer's disease, and Parkinson's disease may worsen.”
He added that as temperatures continue to rise, the heat will combine with the smoke to hurt our brains.
"This is yet another example of the profound, yet grossly understated negative health consequences of human-caused climate change."
“Currently, brains are already operating toward the upper thresholds of these ranges, and as climate change elevates temperature and humidity, our brains might struggle to maintain temperature regulation, even malfunctioning,” Ehsanifar said. “A high internal body temperature, especially above 104 degrees Fahrenheit, with cognitive impairment such as confusion, defines heat stroke.”
This research underscores how global heating is intrinsically linked to our health.
University of Pennsylvania climate scientist Dr. Michael E. Mann said it is fair to directly attribute diseases like dementia to climate change when they are demonstrably caused by wildfire exposure.
“The connection is epidemiological, much like the negative health consequences of smoking are epidemiological, i.e. statistical in nature,” Mann said. “So in other words, while it’s always possible that a victim could have suffered neurological diseases for other reasons, we can say that exposure to wildfire smoke substantially increases the likelihood of e.g. developing dementia, enough so that there is effectively a causal connection there.”
Mann added, “This is yet another example of the profound, yet grossly understated negative health consequences of human-caused climate change.”
Dr. Kevin Trenberth, a distinguished scholar at the National Center for Atmospheric Research, told Salon that he is not surprised the study found adverse effects of wildfire pollution. The revelation that PM2.5 may indirectly increase dementia risk, however, was new to him.
“But there is no question that air pollution is bad for health in many ways,” Trenberth said. “On bad pollution days, either one should not exercise or should do it indoors. So this affects exercise, which should help health. With wildfires around, one should not breathe the foul air. So this can be partially controlled from industry although mainly for larger particles. It is harder to see the smaller particles.”
Nor are humans alone in suffering, Trenberth noted. “Think of all the poor animals exposed.”
Scientists writing in 2022 for the journal Environmental Research described air pollution broadly as an underrecognized public health risk, arguing that “policy needs to be matched by scientific evidence and appropriate guidelines, including bespoke strategies to optimise impact and mitigate unintended consequences.” In addition to mitigating the impacts of climate change, experts urge ordinary citizens to take measures to protect their lungs during times of intense air pollution. Whether it is caused by wildfires, urban smog or any other source, the overwhelming evidence is that breathing it in is bad for a person’s respiratory health.
What remains after a wildfire can also be dangerous. The charred ruins of houses and burnt out cars contain countless pollutants from melted plastics, paints, electronics and household waste.
Until the environment is adequately cleaned up, the likelihood is that those who struggle with disease because of exposure to wildfires both during and after may continue to risk their health.
“Seeing the magnitude of the relationship between wildfire PM2.5 and dementia was quite striking,” Casey said. “I was especially struck by how much stronger this relationship was for people living in communities with higher levels of poverty, suggesting that climate change is again increasing health disparities.”
Read more
about climate change