Being exposed to the stifling air pollution caused by frequent wildfires can put people at a far higher risk of brain tumors and lung cancer, according to a new study published in the journal Lancet Planetary Health, As the climate crisis is rapidly intensifying, recurring wildfires could become more severe and even last longer.
Researchers have analyzed that wildfires emit pollutants in the air that end up in the water and soil as well and are also known as “human carcinogens”. This includes polycyclic aromatic hydrocarbons, benzene, formaldehyde, phenols, and heavy metals. The problem, researchers have noted, is that in North America wildfires tend to take place in the same areas every year. This makes nearby communities come in close contact with carcinogenic wildfire pollutants for long durations. Particularly pollutants like heavy metals and polycyclic aromatic hydrocarbons that leach into the soil and water.
In the Lancet study, researchers delved into the long term impacts of wildfire pollutants on residents who were exposed to them on a chronic basis. The team included participants from the Canadian Census Health and Environment Cohort that assessed the cancer outcomes and mortality of 3·6 million individuals from 1996 to 2015. The participants’ residential postcodes were available in the data, thanks to tax records. This enabled the researchers to assign wildfire exposures according to people’s postcodes.
They then excluded people younger than 25, those residing in urban areas with more than 1.5 million residents, and people who had recently immigrated to Canada. The analyzes finally included more than 2 million people who were followed for a median of 20 years. Out of that, there were around 43,000 lung cancer events and 3,700 brain tumor events.
Based on this, the researchers observed that people living within 50 kilometers of wildfires since the last decade reported a 10% and 4.9% higher incidence of brain tumor and lung cancer, respectively, as compared to those who do not live in proximity to wildfire prone areas.
“Environmental concentrations of pollutants emitted from wildfires depend on a range of different factors — including vegetation type and fire characteristics,” the researchers wrote. “Because other external factors such as wind patterns have an important role in determining where pollutants travel and deposit, a larger area burned might not directly translate into higher risk.”
The researchers noted that other than just higher levels of air pollution levels during wildfires, these extreme weather events can also contaminate water and soil. “Many heavy metals sequestered in soils and vegetation become more mobile and bioavailable following wildfires because of increased soil erosion and ash dispersal,” the researchers added.
This makes it possible for heavy metals to get deposited in nearby water bodies and also contaminate watersheds. Heavy metals are notorious for getting accumulated in fish and other marine animals that humans consume regularly.
“In addition, violations of exposure limits for nitrates, disinfection byproducts, and arsenic in surface and groundwater have been observed in wildfire-affected areas,” the researchers warned.
For instance, in California, drinking water was severely contaminated with benzene and volatile organic compounds following several wildfires. The researchers pointed out that this was partially from the melting of plastic water pipes.