As wildfire season approaches, new studies show air pollution linked to severe health outcomes

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Experts are warning about the negative health impacts from air pollution as we head into wildfire season — and new research suggests it could exacerbate severe outcomes from COVID-19 and increase the risk of lung disease. 

While doctors have previously made the link between fine particulate matter (PM 2.5) — a pollutant emitted from anything burning — and how inhaling it can exacerbate asthma, lung and heart disease, they're still trying to better understand the long-term health impacts.

These studies show that chronic exposure to air pollution can increase health risks and with increased wildfires emitting more PM 2.5, experts say we must protect ourselves from polluted air as much as possible.  

According to a new study published in the Canadian Medical Association Journal, COVID-19 patients who live in areas exposed to common pollutants like fine particulate matter, nitrogen dioxide and ground level ozone are more at risk of severe outcomes like hospitalization, intensive care admission and death. 

"There's really no threshold to say, oh, this is a safe level of air pollution. It really should be as low as possible," said study author Dr. Jeff Kwong, a family physician, preventative medicine specialist and senior scientist at the Institute for Clinical Evaluative Sciences in Ontario.

"That's basically the bottom line message of what a lot of these studies are showing in air pollution and health, that there's no safe level," he said in an interview with CBC News.

Kwong says he hopes the research will persuade policy makers to reduce pollution levels. 

"We need to make sure we have good regulations to ensure that our air has a good quality, that it's not too polluted because there are harms."

Researchers examined a cohort of 150,000 people who have COVID-19 in Ontario and assigned a level of pollution exposure to each individual based on where they lived from 2015 to 2019.

They compared the health outcomes of patients who live in areas with the most pollution to those who live in areas with the least — and found the former were at higher risk of being admitted to intensive care.

People with chronic exposure to particulate matter and ground level ozone also had more risk of hospitalization and death, the study found. 

It didn't include people who live in long-term care homes because their vulnerability to severe COVID-19 outcomes and air pollution exposure differ from the general population. 

Low levels of pollution linked with lung disease

Scientists from the Research Institute of the McGill University Health Centre (RI-MUHC) found that even exposure to low levels of air pollution can be associated with poor lung function and chronic obstructive pulmonary disease (COPD). 

Their study was published in the American Journal of Respiratory and Critical Care Medicine last Thursday. Researchers estimated the amount of fine particulate matter and nitrogen dioxide 1,500 individuals were exposed to based on where they lived. Over the course of three years, they monitored their lung function through CT scans and spirometry tests — a simple test that measures how much air can be expressed in one forced breath. 

"We drew associations between how much air pollution each individual was exposed to and their individual lung function and saw that for small increments in air pollution, there was lower lung function," said Dr. Benjamin Smith, researcher at RI-MUHC and respirologist at the Montreal Chest Institute.  

Researchers also discovered that people who have smaller airways are more susceptible to lower lung function and COPD, compared to those with bigger airways. 

"One of the provocative outcomes of this study is the notion that there may be resilient and susceptible lungs," Smith said. 

"If we could look earlier in the lifespan to understand how those resilient and susceptible lungs form we might be able to really prevent the disease and the concerns about various exposures altogether," he said. 

Results not surprising: experts 

Dr. Courtney Howard, emergency physician in Yellowknife and former president of the Canadian Association of Physicians for the Environment, says she's not surprised by the studies' findings.

"Air pollution increases the levels of inflammation because the teensy tiny little particles of air pollution can actually go through our alveoli, the barrier between our lungs and our blood, into our bloodstream and lead to inflammatory cascades," said Howard. 

Howard says air pollution can weaken the immune system and long term exposure can make chronic diseases more likely. 

"This adds to the growing immense body of literature that tells us that air pollution is really horrible for our health and therefore we need to do everything we can to decrease the elements of air pollution that are within our control," she said.  

According to a report published by The Lancet, pollution was responsible for an estimated nine million deaths worldwide in 2019, six million of which were attributed to air pollution. 

Sarah Henderson, scientific director of environmental health services at the British Columbia Centre for Disease Control (BCCDC), says when it comes to health risks, heart disease is the primary condition associated with long term exposure to polluted air, followed by respiratory disease, cancer and diabetes.

"It doesn't typically put us at immediate risk, but over the course of days and months and years, air pollution is damaging to human health, all forms of it."

More wildfires, more pollution 

Henderson says PM 2.5 comes from many sources, including gasoline in a combustion engine or fuel from a factory. 

Nitrogen dioxide is created by combustion from vehicles and ground level ozone is created in the atmosphere when other pollutants interact with UV radiation, she says.

With climate change expected to prolong wildfire seasons, Henderson says she's expecting the amount of these pollutants to increase. 

"We've seen in Canada over the past decade that we're having more wildfires. That's going to mean more of that fine particulate matter in the atmosphere," she said. 

Fires exacerbate health risks 

In a study Howard conducted and published in the British Medical Journal in 2021, she found that visits to the emergency department for asthma at Yellowknife's only hospital doubled in the summer of 2014 — when the Northwest Territories saw its worst wildfire season that burned 34,000 square kilometres of forest. 

As residents dealt with two months of smoke, the average daily measurement of fine particulate matter that summer was five times higher compared to 2012 and 2013, the study found.

"Heading into summer, the things on my mind are extreme heat and wildfires," said Howard. "I want people to be aware that both can kill." 

Henderson says research shows that wildfire smoke can trigger not just chronic issues, but also acute events for people who have airway-related diseases, like asthma, chronic obstructive respiratory diseases or COPD.

It's also dangerous for people with heart disease as the smoke might trigger cardiac arrest, she says. 

Preparing for the worst amid climate change 

Last year, B.C. saw record levels of extreme heat, which killed hundreds of people, and one of the most severe wildfire seasons. 

"Disaster after disaster," Henderson said. "It's the cascading of these things together and the cascading of their impacts on health — that is what stands out to me most right now."

With climate change contributing to extreme weather events, she's preparing for the worst. 

"We have to always just go into these seasons expecting something worse than we've ever seen before. We can be very hopeful that that is not the outcome but if we are prepared or as we can be for that unexpected, unprecedented outcome, everybody's going to do better on the other side," she said.

Howard says everyone should have N-95 masks and air purifiers ready for wildfire season and people with asthma should get their inhalers refilled.

"So that people don't end up in that place where they're forced … to go outside through the smoky environment to get to a place where they can refill their inhalers or get their steroids. Let's anticipate that the same way we do with similar patients prior to cold and flu season," said Howard.

In addition, Howard says physicians should educate their patients about Canada's air quality index and when they should stay inside. She says she'd frequently see people running outside when the index was at eight or nine.

"It's time that we start to look at air pollution as a huge threat."