Millions of Americans are facing dangerous air quality alerts as thick wildfire smoke drifting south from Canada pushes pollution levels to health risks comparable to smoking more than a dozen cigarettes in a day.
Conditions worsened sharply Friday, with major cities including Chicago, Detroit, Washington and New York listed among the most polluted metropolitan areas on the planet.
The National Weather Service has issued air quality alerts across 16 states, spanning the Upper Midwest — including Minnesota, Wisconsin, Michigan and Illinois — and extending east to New York, New Jersey, Maryland and Virginia.
The Environmental Protection Agency said air quality had reached “hazardous” levels from northern Minnesota to Columbus, Ohio, marking the agency’s most serious pollution category.
NWS officials warned residents in the hardest-hit areas to “avoid all physical activity outdoors” as the smoke continues to blanket communities.
The choking haze is coming from hundreds of wildfires burning across Canada, particularly in Ontario, and contains high concentrations of fine particulate matter known as PM2.5.
These tiny toxic particles, often produced by burning wood and industrial activity, are small enough to enter deep into the body, aggravating breathing problems and posing potentially deadly risks for people with heart or lung disease.
Health experts said the PM2.5 levels recorded Friday in Detroit — 292.6 µg/m³ — were roughly equivalent to inhaling the pollution from more than 13 cigarettes in one day.

Air quality monitors have deemed the air to be ‘hazardous’ in multiple US cities on Friday, July 17

Weather experts have said the intense smoke with create vivid sunrises and sunsets this week, like one seen in New York Friday morning

Pictured: Runners in Washington DC attempt to exercise despite heavy smoke from the Canadian wildfires reaching the Mid-Atlantic, including in Maryland and Virginia
According to live air quality-tracking website IQAir, Chicago’s air is currently filled with more than 240 µg/m³ (micrograms per cubic meter) of PM2.5 pollution – the equivalent of smoking more than 10 cigarettes in a day.
Berkeley Earth, a nonprofit research organization known for analyzing climate and air quality data, estimated that breathing air with 22 µg/m³ of PM2.5 pollution for one full day has roughly the same long-term impact as smoking one cigarette.
Dr Jonathan Tan from the Children’s Hospital of Philadelphia told AccuWeather: ‘When the AQI climbs into the 150+ range for a full day outside, that’s in the ballpark of [smoking] seven to nine cigarettes.’
Typically, the Air Quality Index (AQI) is measured on a scale from 0 to 500: ‘good’ (0–50) carries little risk, ‘moderate’ (51–100) may affect sensitive individuals, ‘unhealthy for sensitive groups’ (101–150) poses increased risk and ‘unhealthy’ (151–200) impacts everyone, limiting outdoor activity.
When outdoor air quality reaches the 300 to 500 ‘hazardous’ zone or surpasses that mark, the EPA warns that everyone should avoid all physical activity outside. As of 9am ET on Friday, both Detroit and Chicago had surpassed 380, according to IQAir.
Washington DC registered at 247, the third-worst polluted major city on the planet, and New York was fourth at 165 – all in the unhealthy to very unhealthy ranges.
The growing plume of pollution-filled smoke has been blamed on Canada’s lack of fire management services, which has now let roughly 800 wildfires burn through over two millions acres of land throughout the country this year.
Dan DePodwin, AccuWeather’s vice president of forecasting, told the Daily Mail: ‘Because a lot of Canada is very rural, in many parts of the country, they don’t actively fight fires, because there is very little to no population nearby.’
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On Thursday, Chicago (Pictured) was covered in wildfire smoke pouring south from Canada

The city of Detroit, Michigan (Pictured) has been ranked as the most polluted city on Earth due to the Canadian wildfire smoke

Residents in New York (Pictured) struggled to breathe outdoors on Thursday due to intense air pollution from the Canadian wildfires
‘So, the fires burn until they go out themselves, or they do minimal fire suppression. So that is part of it, that is occurring here,’ he continued.
The situation has drawn the ire of US lawmakers, who slammed the Canadian government’s alleged inability to contain the wildfires and the smoke reaching the northern US.
Congressman Nick Langworthy of New York said: ‘Americans should not be forced to breathe hazardous air year after year because Canada refuses to properly manage its forests.’
‘This is no longer a one-time emergency – it’s becoming an annual public health crisis. That is unacceptable,’ added Langworthy, who represents parts of Buffalo, which has been severely impacted by the toxic air crisis.
Congressman Bill Huizenga of Michigan also called on the Canadian government to work with the US on finding a solution to the annual wildfire problem north of the border.
‘Michiganders must stop paying the price for bad policy,’ Huizenga declared.

Air quality readings in Chicago on Friday, July 17 revealed ‘very unhealthy’ to ‘hazardous’ air throughout the entire city

Pictured: A woman in New York wears a face mask as the air quality remained in the unhealthy zone on July 17
NWS officials also urged anyone considered to be in a ‘sensitive group’ to poor air quality to remain indoors with the windows shut on Friday.
These groups include the elderly, young children, pregnant women and those with chronic health problems such as heart and lung disease.
‘If you don`t have an air conditioner, staying inside with the windows closed may be dangerous in extremely hot weather. If you are hot, go someplace with air conditioning or check with your local government to find out if cooling centers are available in your community,’ the agency recommended.
‘Make sure to keep pets indoors to limit their exposure to poor air quality,’ the AccuWeather team added in a statement.