Q: How does wildfire smoke affect lung cancer risk? And how does this compare to things like secondhand smoke?
As wildfire smoke turned the skies of the San Francisco Bay Area red in the summer of 2020, Dr. Kari Nadeau, a physician and scientist at Stanford University, was thinking about those most vulnerable. She worries about the workers at the local wineries, who race to protect their crops; and children who live near oil refineries and breathe in pollutants every day.
Throughout August, September and October, she regularly monitors air quality to reach unhealthy levels for anyone not wearing a mask. At that time, Dr. Nadeau speak in a public assembly that being outside and breathing that air is like smoking seven cigarettes a day.
But now, she said, she believes the health effects of breathing in a lot of wildfire smoke could be even worse. “Tobacco at least has a filter,” said Dr. Nadeau, who directs the Center for Allergy and Asthma Research at Stanford University.
While cigarette smoke, even second-hand smoke, proven to cause lung cancer, forest fire smoke does not. A limited number of recent studies published in the last few years have found a correlation between people exposed to wildfire smoke and and lung cancer. The scientists who carried out those studies say there is no proven cause yet and more research is needed.
“We don’t know much about the long-term health effects of wildfires,” said Scott Weichenthal, associate professor in the department of epidemiology, biostatistics and occupational health at McGill University in Montreal. “Until recently, fires were considered a one-time disaster, and we don’t understand how severe, sometimes recurring in a short period of time can affect the health of people on the road,” he said.
Experts know that, even in the short-term, particle pollution from wildfires – including tiny particles of ash, dust and soot – can worsen heart problems, reduce lung function and make exacerbation of asthma. In this way, wildfire smoke can affect health in the same ways as exhaust fumes from diesel or smoke from cigarettes.
Wildfire smoke can also include heavy metals like lead and arsenic, and dangerous chemicals like benzene and formaldehyde gas, all of which are found in cigarette smoke and can cause cancer.
“There is enough evidence that we should not look the other way,” says Dr. Nadeau.
To understand how the air you breathe can affect your risk of lung cancer, scientists say it’s essential to understand what’s harmful in the air, how much air is present and how long you’re exposed to it. touch it.
According to the Centers for Disease Control and Prevention, for example, exposure to secondhand smoke, at work or at home, may increase the risk of lung cancer in nonsmokers between 20 and 30 percent.
However, calculating the health risks from wildfires is much more difficult. What the smoke contains, and the potential health hazards it can bring, will depend in part on what the fire has consumed. For example, smoke from burning trees and vegetation poses different dangers than smoke from burning homes, cars, electronics or tool storage.
Fire smoke is also temperamental; literally it will be blown away by the wind. The toxic substances carried can be fleeting and difficult to identify, says Dr. Weichenthal. And it can be challenging to measure the extent to which people are exposed.
But as wildfires increase due to climate change, grow bigger and spread faster, researchers have recently begun to focus on people exposed to smoke and fire over long periods of time. For example, experts from the University of California, Davis, are monitoring survivors of the 2018 Camp Fire in Butte County, California. And at McGill University, Dr Weichenthal is part of a team that has analyzed the merits of two decades of Canadian public health records to better understand the health consequences of wildfires, driven in part by record fire years in Ontario and British Columbia.
“It wouldn’t be surprising to us that we would see some sort of increased cancer risk in these places,” he said. “We know that the chemicals that are being secreted are carcinogenic.”
Research by Dr. Weichenthal, obtained published in The Lancet in Mayfound that people who lived within 30 miles of wildfires in the last decade were about 5 percent more likely to develop lung cancer and 10 percent more likely to develop brain tumors than those who lived further away than.
Although the study had some limitations, Dr Weichenthal said, the findings “are important because so many people could be exposed”.
By far, the best evidence we have for a link between lung cancer and wildfire smoke comes from studies of firefighters. At the height of the fire season, tens of thousands of them work long shifts day after day, often without masks.
In a study published in 2019, Kathleen Navarro, who researches workplace safety environmental issues for firefighters at the National Institutes of Occupational Safety and Health, has estimated with her colleagues that firefighters have a short season. For example, people who work on the frontline for at least seven weeks a year for 5 to 25 years increase their risk of dying from lung cancer by 8 to 26% from exposure to secondhand smoke. They calculated that firefighters who worked twice that amount of time each year had a 13 to 43 percent increased risk of dying from lung cancer over the same time period.
“But there’s still a lot of unknowns about what happens every season,” said Dr. Navarro, who was a Hotshot firefighter in Oregon. factors are tighter among firefighters in the United States. One national registration for the health of the firefighters will open this fall.
However, even if there is no evidence that wildfires cause lung cancer in the community, Dr Nadeau said there is a lot of evidence to look for more protective policies and to take safety precautions.
“We should let this be a catalyst to help us better prepare to adapt to wildfires and climate change,” she said. And when there is smoke, “You should evacuate. You shouldn’t just hang around and wait. The smoke itself is a hazard to be avoided.”
Molly Peterson is a Los Angeles-based investigative journalist who focuses on the intersections of climate, disaster, and public health.