Wildfires in Canada: how long does wildfire smoke last and is it dangerous?

Smoke from hundreds of wildfires burning across Canada has triggered air quality alerts for millions of people in the northern US and Canada as smoke drifts south.

Tens of thousands of people have been evacuated across Canada because of the fires, which have burned more than 4 million acres so far this year. The resulting smoke has created a gray haze over many cities, including New York, and has obscured the sun in some places.

The fires also released a record amount of carbon into the atmosphere for May, which is still early in the North American fire season. Hotter and drier conditions are expected to make such fires larger and more intense due to climate change.

Where does the smoke come from?

As of June 6, there were more than 300 fires across Canada, more than 200 of which were out of control, according to the Canadian Interagency Forest Fire Center. The eastern province of Quebec has had the most fires. There were also numerous fires burning in the western provinces of Alberta and British Columbia. Much of the smoke that hit the northern US drifted south from the fires to the east.

Many of the fires started burning days ago and the fires in western Canada have been burning for weeks. But large amounts of smoke only reached the population centers the US after a storm system formed on the Atlantic coast and began blowing smoke south.

Smoke from the fires has also reached Europe, says Albert Ansmann at the Leibniz Institute for Tropospheric Research in Germany. “We’ve seen the smoke since the fire season started” in almost every layer of the atmosphere, including the lower stratosphere, he says. Wildfire smoke has been shown to deplete the ozone layer when it gets that high.

Some smoke has also reached parts of the Arctic Ocean, where it can cover sea ice and accelerate melting.

How long does wildfire smoke last and when does it go away?

It can take weeks or more to bring the wildfires themselves under control. But the weather system that carries the smoke into the northern US could change in the coming days. Large areas are likely to remain smoky until then.

Is air pollution from wildfire smoke dangerous?

Air pollution from wildfire smoke has largely the same health effects as other forms of air pollution, he says Patrick Kinney at Boston University. These are mainly due to the fine particles, or PM2.5, in the smoke, which can irritate the eyes, nose and throat and can be especially bad for people with asthma or heart disease, or for young children and the elderly.

Kinney says even a few days of such high levels of air pollution are enough to exacerbate existing respiratory problems and potentially trigger new ones. “I think there will be observable spikes in the number of people going to the emergency room,” he says. “The longer that takes, the more likely that is.”

State health advisories recommend staying indoors as much as possible, keeping windows closed and limiting the use of air conditioning. In smaller spaces, air purifiers can effectively reduce pollution. Wearing a high-quality mask when you go outside can also help filter out particles in the smoke. “I would probably wear a mask most of the time,” says Kinney.

Also the New York Department of Environmental Conservation advises people to avoid driving and if possible to reduce energy consumption to limit additional air pollution from car exhaust and power generation, although in general this could have only a small effect.

What causes high levels of air pollution elsewhere?

At one point on June 6, New York City was ranked by the Swiss as the city with the worst air quality in the world website IQAir. Detroit, Michigan, was also in the top 10. The smoke from these fires will eventually blow over these cities and the rest of the northern US, but most of the other cities high on the list are experiencing nearly similar levels of air pollution. always.

At the top of the list is Delhi, India, with high levels of air pollution mainly caused by exhaust fumes from inefficient vehicles and road dust from construction, as well as power plants that burn fossil fuels and farmers that burn plant waste. In Santiago, Chile, also in the top 10, burning wood to keep warm in winter is another source of air pollution.

Such chronic exposure to high levels of air pollution can have far-reaching health consequences, such as increased respiratory disease.