Forest fire smoke | Health impacts that can last for months

Quebec was invaded by smoke from the fires last weekend and is again these days. These orange clouds of fine particles can have an impact on our health… even months later.

Why is smoke from forest fires harmful?

In normal times, the levels of polluting particles in the air are below 10 µg/m^⁠3. But in the last few days, they have reached values ​​above 700 µg/m^⁠3 in parts of the province due to forest fires.

These extremely small particles measure barely 3% of the diameter of a hair. Their microscopic size therefore allows them to lodge deep in our lungs.

“Smoke pollutants are irritating and induce inflammation,” explains Audrey Smargiassi, professor at the School of Public Health at the University of Montreal. Smoke particles can also enter the bloodstream through the lungs and cause cardiovascular effects.

Can this smoke have long-term health impacts?

Long-term effects are still being researched, notes toxicologist and University of Montana professor Chris Migliaccio. But the first data tend to show that yes.

In 2017, the Seeley Lake area of ​​Montana faced an exceptional situation: a period of nearly two months when it was shrouded in smoke from wildfires. Daily levels of particulate pollutants averaged 220.9 μg/m^⁠3.

The team of researcher Chris Migliaccio followed a group of a hundred inhabitants of this region. “There was a significant decrease in lung function one year and even two years after exposure,” he says.

Smoke from fires can also make us more vulnerable to respiratory infections. A study from the University of Montana published in June 2020 showed that higher concentrations of fine particles in the air during the wildfire season are associated with an increase in influenza during the following winter influenza season, which is until 10 months later.

Poor air quality warnings for Montreal were in effect for about 48 hours. Is this a long enough period to affect the functioning of our lungs?

Yes, answers Professor Audrey Smargiassi. “Even a few hours of exposure can be enough to temporarily induce a reduction in lung function. »

The most vulnerable individuals, such as young children, the elderly and those with respiratory or cardiac problems, are particularly likely to be affected by smog, says toxicologist Chris Migliaccio.

The long-term effects of a 48-hour exposure have not yet been proven, however, he says.

Forest fires in Quebec are located several hundred kilometers from Montreal. Is the smoke less harmful when it arrives in the metropolis?

On the contrary. Particles released during wildfires can become more toxic over time, researchers have observed.

“We know that it is not good to breathe in smoke when you are near a fire, but we have found that over time the situation gets worse, until it becomes four times more toxic a day later,” Science Magazine told Horizon from the European Commission Professor Athanasios Nenes, atmospheric chemist at the Institute of Chemical Engineering Sciences in Patras, Greece, in July 2020.

In the air, small smoke particles interact with substances called radicals, which are chemically unstable molecules. This contact transforms smoke particles into highly reactive compounds that can cause damage to our cells and tissues, the specialist observed during his research.

“The greater the distance, the more likely these chemical changes are to occur,” adds toxicologist Chris Migliaccio.

The City of Montreal closed all of its sports facilities, including outdoor swimming pools, during the smog episode last Sunday and Monday. Wise decision or over-cautiousness?

“Unfortunately, with such poor air quality, it would have been foolish to stay outside,” says The Press University of California San Diego researcher Rosana Aguilera, who is interested in the impact of smoke from fires on health.

Professor Audrey Smargiassi also judges that it would be appropriate, during very high temperatures and forest fires, to promote access to indoor air-conditioned spaces rather than to outdoor places that can cool down.

If I have to go outside during the next smog episode, should I wear a mask?

N95 masks protect against particles from wildfires, provided they fit snugly to the face. However, medical masks and face coverings are not recommended by the Ministère de la Santé et des Services sociaux (MSSS).

Workers who work outdoors or people who may be exposed to smoke for a long time can obtain N95 masks free of charge in various health establishments. “Each CIUSSS has the information on its website,” said the deputy medical director of the Direction régionale de santé publique de Montréal, Dr.^r David Kaiser, at a press conference Thursday morning.