The smoke from wildfires is affecting millions of Canadians who are expected to linger for at least 2 days

Be patient, but don’t take a deep breath.

Smoke from Canadian wildfires today will make it hard for millions of people in the six largest provinces to breathe outside – and in some cases this bout of bad air is expected to last for days.

Environment Canada has released air quality statements for parts of the Northwest Territories and every province outside of Atlantic Canada, including large parts of Ontario and Quebec.

“Stop or reduce your activity level if breathing becomes uncomfortable or if you or someone in your care feels unwell,” says the weather bureau. “Contact your healthcare provider or local health authority if you develop severe symptoms or need advice.”

• Check the CBC News climate dashboard for air quality information and live updates on active fires across the country. You can also set your location to find out how today’s temperatures compare to historical trends.

People with lung conditions, including asthma or heart disease, older adults, children, pregnant people and those who work outside the home are at greater risk for smoke-induced health effects, the agency warns.

The statement covers a large contiguous area stretching from Windsor, Ont., all the way to northern Quebec, and includes a smog warning for an area of ​​Quebec that includes Rouyn-Noranda and Val-d’Or. That warning says “high concentrations of particulate matter” will return on Wednesday and could persist for days to come.

In Ontario, Environment Canada’s Air Quality Health Index warns of a “high risk” for the entire corridor of Southern Ontario, from Windsor to Ottawa.

The agency says pollution levels from wildfires can fluctuate over time and vary depending on location, but air quality is only expected to improve for some areas in Ontario and Quebec on Thursday night.

The Canadian Interagency Forest Fire Center website shows 487 active fires burning nationwide as of Wednesday morning, with 253 classified as uncontrollable.

Smoke also affects the US

The unhealthy haze also moved south of the border, settling across most of the Great Lakes region and spreading as far as Missouri and Kentucky.

The US Environmental Protection Agency’s AirNow.gov site showed Detroit in the “dangerous” range and warned that “everyone should stay indoors and reduce activity levels.”

Drifting smoke from the wildfires has drawn curtains of haze across broad swathes of the United States, penetrating southern Illinois, Indiana and Ohio, and moving into parts of West Virginia. The AirNow.gov site listed air quality in Cleveland, Chicago and Pittsburgh as “very unhealthy” on Wednesday. A larger circle of unhealthy air spread to St. Louis and Louisville, Ky.

The smoke has even reached Western Europe.

Earlier this week, the US National Aeronautics and Space Administration (NASA) said satellite images showed smoke stretching across the North Atlantic Ocean to France’s Iberian Peninsula and other parts of Western Europe.

Air quality in Europe has not deteriorated as much as in North America because of high levels of smoke in the atmosphere, NASA said.