And climate change is making wildfires more frequent and more intense.
A comprehensive study, published this month in The Lancet, found wildfire exposure to be associated with an increased incidence of lung cancer and brain tumors. The grim news comes as climate change -- sped up by human activity -- continues to exacerbate wildfires across the globe.
Over a median 20 years, the researchers tracked more than 2 million Canadians, some of whom were exposed to wildfires, and analyzed related cancer outcomes.
In short, they concluded that people living within 50 kilometers (31 miles) of wildfires over the past 10 years had a 10% higher incidence of brain tumors and nearly a 5% higher incidence of lung cancer when compared with people living farther away.
"Wildfires tend to happen in the same locations each year, but we know very little about the long-term health effects of these events," Scott Weichenthal, an associate professor in the department of epidemiology, biostatistics and occupational health at Canada's McGill University, said in a statement. "Our study shows that living in close proximity to wildfires may increase the risk of certain cancers."
Even though we know some regions of the world are more prone to wildfires -- including places in the Southwest, California and Oregon -- deadly blazes in the vicinity of residential communities have been greatly ramping up in recent years. Both California and Oregon, for instance, have seen dramatic wildfire spikes in close proximity to people's homes, as evidenced by the tragedies of 2019 and 2020.
"Many of the pollutants emitted by wildfires are known human carcinogens, suggesting that exposure could increase cancer risk in humans," Jill Korsiak, a doctoral student in the department of epidemiology, biostatistics and occupational health at Canada's McGill University and lead author of the analysis, said in a statement.
Not only that, but wildfires can indirectly link to cancer risk, too.
A study from March found that lingering wildfire smoke ravaged Earth's ozone layer, which is basically our planet's shield that staves off harmful ultraviolet rays emanating from the sun. Without an intact ozone layer, our risk of skin cancer could well increase.
Simply put, wildfire upticks are a result of global warming. As humans contribute to greenhouse gas emissions with operations like burning coal for energy, they foster the perfect storm for wildfires. As an example, drought and dried organic matter are both direct outcomes of global warming and precursors to wildfire.
To make matters worse, scientists offer proof that wildfires in the US, for instance, will continue trending upward in severity as a result of such human-induced climate change. Already, the study found that US fires have grown four times larger and three times more frequent since 2000. "The worst fire disasters are still to come," one researcher said in a statement.
The team says further work is needed to "develop long-term estimates of wildfire exposures that capture the complex mixture of environmental pollutants released during these events."
In other words, could wildfires continue threatening human lives long after the final flame burns out?