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Study: Living in wildfire-prone regions may cause higher rates of cancer, brain tumours

The first-of-its-kind study found higher rates of lung cancer and brain tumours in people exposed to wildfires across Canada, including in B.C. 
wildfire smoke 2021
Smoke from wildfires blankets Kamloops on July 31, 2021.

Living in areas prone to wildfires may boost the risk of developing lung cancer and brain tumours, a new study from McGill University has found.

The first-of-its-kind study — which used health data on two-million people over 20 years — found higher rates of lung cancer and brain tumours in people exposed to wildfires across Canada, including in B.C.

The study, published in The Lancet Planetary Health, shows that people living within 50 kilometres of wildfires over the past 10 years had a 10 per cent higher incidence of brain tumours and 4.9 per cent higher incidence of lung cancer, compared to people living farther away.

Scott Weichenthal, associate professor in the department of epidemiology, biostatistics, and occupational health at McGill University, said wildfires tend to happen in the same locations each year, which means long-term exposure.

“We also know that forest fires release a lot of chemicals that are known human carcinogens … Our study shows that living near wildfires may increase the risk of certain cancers,” Weichenthal said.

The authors note that the research is important because projections indicate there will be greater fire activity fuelled by climate change in the future.

That has been borne out in B.C. with three of the most extreme fire seasons taking place within the past five years.

In the 2021 fire season, more than 520 building were burned, mostly people’s homes, and 32,000 people had to evacuate. Two people were killed in a wildfire that destroyed the Village of Lytton in the B.C. Interior. In 2017, another extreme wildfire season, 65,000 people had to evacuate their homes.

Wildfires are increasingly recognized as a global health problem, stressed researchers.

“Many of the pollutants emitted by wildfires are known human carcinogens, suggesting that exposure could increase cancer risk in humans,” said Jill Korsiak, a PhD student in Weichenthal’s lab who led the analysis.

In addition to impacts on air quality, wildfires also pollute aquatic, soil and indoor environments. While some pollutants return to normal concentrations shortly after the fire has stopped burning, other chemicals — including heavy metals and hydrocarbons — might persist in the environment for long periods of time.

“Exposure to harmful environmental pollutants might continue beyond the period of active burning through several routes of exposure,” Weichenthal said.

The study could have implications for governments’ efforts to lessen wildfire emissions and for individuals’ efforts to limit exposure, for example, by using indoor air filters, said Weichenthal.

Because of the first-of-its-kind study’s limitations, the researchers said further work is needed to refine the data used in estimating the chronic health effects of wildfires, replicating the study in different geographical locations and populations and further examining the effects of wildfire pollutants in soil, water and house dust.