Growing evidence linking wildfire air pollution to dementia
It’s well established that any air pollution is likely to be bad for your health, with it claiming some 6.5 million lives around the world each year. But one type of emission is being increasingly linked to age-related dementia, and it’s also surging due to wildfires.
Particulate matter (PM) is a chemical composition the likes of sulfates, carbon, nitrates or mineral dusts. While it stems from vehicle and industrial emissions due to fossil fuel burning, eyes are now on a growing source of the hazardous compound: wildfires, and other types of burning of organic matter, such as through agriculture.
A subset of PM, fine particulate matter (PM2.5), is especially dangerous to human health because, being 30 times thinner than a human hair, it can not only lodge in lung tissue but cross into the brain after being inhaled through the nose. It can also cross the blood-brain barrier other ways.
Scientists from the University of Michigan have identified a link between agriculture and wildfire PM2.5 emissions and the onset of dementia among 27,857 adult Americans, with data drawn from the national Health and Retirement Study. Pollution estimates were based on the locations of the participants, who were older than 50 years and did not have dementia at the outset.
While around 15% of the participants developed dementia, the rate of cognitive decline was significantly greater in the areas of high PM2.5 concentration throughout the period of assessed data, between 1998 and 2016.
“These findings are quite timely given the increasing frequency of wildfire smoke in our communities,” said Sara Adar, an environmental epidemiology researcher at the University of Michigan’s School of Public Health. “Our data suggest that in addition to some of the more obvious health impacts of wildfire smoke like irritation to our throats and eyes along with breathing difficulties, high smoke days might also be taking a toll on our brains.”
Wildfires certainly aren’t a new phenomenon, but their frequency, severity and duration are increasing. And as the planet becomes hotter, wildfire seasons are starting earlier and ending later, with the prevalence of extreme weather such as heatwaves and drought providing a perfect platform for them to spark.
“While individual wildfires may be short-lived, these events are becoming more frequent in our communities due to warmer temperatures, drier conditions, and longer fire seasons,” Adar said. “As we’ve seen, wildfire smoke can also travel very far distances.”
And while PM2.5 unfortunately has many sources, the researchers identified how insidious wildfire emissions are for our health. Wildfires contribute up to 25% of fine particulate matter exposures in the US each year, but that rises to around 50% in some western parts of the country.
“We saw in our research that all airborne particles increased the risk of dementia but those generated by agricultural settings and wildfires seemed to be especially toxic for the brain,” said Adar. “Our findings indicate that lowering levels of particulate matter air pollution, even in a relatively clean country like the United States, may reduce the number of people developing dementia in late life.”
Previous studies have looked at the overall amount of PM2.5 in the atmosphere, but the researchers believe if one source is found to be more toxic than others, it can help us develop better long- and short-term responses.
“Given that the development of dementia could take a long time, this study mainly aimed to provide evidence for policymakers to reduce exposures to these sources of emissions,” said co-author of the study, Boya Zhang. “This work suggests that particulate matter air pollution from agriculture and wildfires might be more neurotoxic compared with other sources. However, more research is needed to confirm these effects, especially for these two sources which have received less attention in prior research.”
The research was published in the journal JAMA Internal Medicine.
Source: University of Michigan