Air pollution caused by wildfire smoke linked to elevated suicide risk in rural counties: U.S. research

Exposure to wildfire smoke could have a detrimental impact on not only physical health, but also mental health, according to new research from the U.S. which found that air pollution may elevate the risk of suicide among some demographics.

Researchers combined data on wildfire smoke exposure levels, air pollution concentrations and deaths by suicide in the U.S., and found that a 10 per cent increase in airborne particles in rural counties could cause monthly suicide rates to rise by 1.5 per cent.

The phenomenon was strongest among groups already at risk for suicide who also had a high exposure to outdoor air by living in rural regions. No association was observed between air pollution and suicide risk among urban populations.

“Air pollution has long been recognized as bad for physical health, but there’s now evidence that links it to mental health problems such as anxiety, depression and suicide,” David Molitor, a professor of finance at the University of Illinois’ Gies College of Business and co-author of the study, said in a press release.

“Given that wildfires are expected to become more frequent and severe in the coming decades because of warmer and drier climate conditions and ongoing human development in previously wild areas, it’s imperative that we fully understand the impact of wildfire smoke pollution. Most of the global population is regularly exposed to unhealthy levels of air pollution, and the emerging evidence suggests that this exposure is not only detrimental to physical health, but to mental health as well.”

In the research article, published Monday in the peer-reviewed journal Proceedings of the National Academy of Sciences, researchers described how they looked at data from 2007-2019 in the U.S. on suicide deaths by county and air pollution.

They used satellite measures of wildfire smoke and ambient fine particulate matter, specifically focusing on fine particulate matter that is 2.5 microns or less in diameter. Called PM 2.5, these tiny particles are considered one of the clearest measures of how dangerous air pollution is, as the particulate matter is inhalable and associated with a range of physical health issues, including asthma and an increased risk of cardiovascular and respiratory diseases.

Researchers laid out fluctuations in suicide rates each year next to monthly smoke exposure and PM 2.5 concentration levels, and analyzed across counties and demographics to see if there were any connections.

The pattern that emerged was that when the air quality was worse in rural areas, certain demographics saw an increase in suicide rates.

Just one additional day of wildfire smoke per month increases the monthly average concentration of PM 2.5 by 0.41 microgrammes per cubic metre, according to the research article, and a 13 per cent increase in the concentration of PM 2.5 per month could cause a two per cent increase in suicide rates in rural counties.

The demographics impacted the most were rural white males and working age adults in rural areas with no college education – groups which already had a higher than average risk for suicide.

Although the increase in risk is slight, researchers highlighted that it stands in contrast to urban areas, which saw no increase.

“We don’t detect any relationship between air quality and suicide in urban areas,” Molitor, who has been studying climate-related environmental hazards through the Center for Advanced Study in Illinois, said in the release. “Suicide rates were about 36 per cent higher in rural versus urban counties during our sample period. All of the effects seem to be concentrated in the rural populations.”

He noted that rural communities have long been impacted more by suicide, and that more research is needed into the varying factors that affect this.

“Suicide rates have increased by approximately 30 per cent over the past two decades, positioning it as the fourth leading cause of years of potential life lost before age 65 in 2020,” he said. “It’s far too prevalent, and highly unequal across demographic groups. It’s systematically higher in rural counties than in urban ones, and the urban-rural gap in suicide rates has been widening.”

With poor air quality and wildfires becoming more and more prevalent due to climate change, what now appears to be a small impact on mental health could become a larger issue down the road.

“Understanding the overall and disparate impacts of air pollution on mental health is crucial for developing effective strategies to protect vulnerable groups and increase population resilience to poor air quality,” Molitor said. 

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If you or someone you know is in crisis, here are some resources that are available.

Canada Suicide Prevention Helpline (1-833-456-4566)

Centre for Addiction and Mental Health (1 800 463-2338)

Crisis Services Canada (1-833-456-4566 or text 45645)

Kids Help Phone (1-800-668-6868)

If you need immediate assistance call 911 or go to the nearest hospital.