These US cities have the world’s worst air quality as wildfire smoke settles in

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(NEXSTAR) – Parts of the U.S. have the worst air quality in the world on Thursday as wildfire smoke from Canada and Minnesota settles in.

The smoke started to move in across the upper Midwest and the Northeast on Wednesday, bringing hazy skies and a foul-smelling odor to millions. Conditions are expected to spread into Friday, reaching further south through the Midwest and into Appalachia and the East Coast.

Northern portions of Minnesota have far and away the worst air quality as of Thursday morning, the Environmental Protection Agency’s U.S. Air Quality Index shows.

The interactive map, seen here, shows Minnesota, Wisconsin, and Michigan, as well as parts of their neighboring states, swathed in shades of purple and maroon.

Purple signifies a “very unhealthy” air quality index, or AQI, of 201 to 300, which leads to an increased risk of health effects for everyone. Maroon, the highest level on the index, represents a “hazardous” level of concern, marked with an AQI of 301 or higher. Everyone is more likely to experience health impacts under these conditions.

As of 10 a.m. ET, north central Minnesota has the worst air quality in the U.S. with an AQI of 1,421. That’s nearly five times higher than the minimum level considered to be hazardous.

Camps throughout Northern Minnesota are closing and wilderness trips in the region are being cut short because of wildfires burning in the state, Minnesota Public Radio reports. The Boundary Waters Canoe Area Wilderness had to be slowly and methodically evacuated by wildlife officials earlier this week.

The nearby Minnesota Arrowhead area and Duluth rank as the No. 2 and No. 3 regions with the worst air quality in the U.S. They have AQIs of 1,086 and 923 as of Thursday morning.

Rounding out the top 10 are neighboring Midwest locales:

Toledo, Ohio: 649 AQI

Wisconsin’s eastern Northwoods: 627 AQI

Eastern portion of Michigan’s Upper Peninsula: 622 AQI

Southeast Michigan: 622 AQI

Grand Rapids, Michigan: 616 AQI

Central Minnesota: 607 AQI

Western portion of Michigan’s Upper Peninsula: 596 AQI

All of these regions have among the worst air quality in the world. IQ Air, which tracks air quality worldwide, ranks Detroit, Michigan, as having the most polluted air as of Thursday morning, with an AQI of 600 as of 10 a.m. ET.

Following Detroit are Toronto, Canada (390 AQI), Minneapolis (343 AQI), and Chicago (232 AQI).

Only Chicago’s rate falls outside the “hazardous” AQI level.

Parts of New York and Pennsylvania are shaded in red on the EPA’s AQI map. This means the air is “unhealthy,” potentially causing health effects to “some members of the general public” and, among those in “sensitive groups … more serious health effects.”

As of 9:30 a.m. ET, Philadelphia has an AQI of 182, putting it squarely in the unhealthy range.

Thursday’s forecast shows Minnesota and Wisconsin could experience the worst air quality, though conditions in Michigan, New Jersey, western and southern New York, and parts of Pennsylvania will still be unpleasant.

On Friday, the EPA’s forecasting suggests conditions will improve across these regions, but worsen in Maryland and Delaware.

Nexstar meteorologist Darrius Stringer said storms and rain could help clear out the smoke in the Northeast and upper Midwest on Saturday, with most states likely to experience much cleaner air by Sunday.

However, officials have warned that the fires could continue burning through the summer, posing another shot at smoke soiling the air in the coming weeks and months.

How dangerous is smoky air?

In some places, thick smoke was combining with extreme heat on Wednesday to make for dangerous breathing conditions outdoors.

The best advice is to stay indoors to avoid both the smoke and the heat, said Tyler Hasenstein, meteorologist with the National Weather Service in Chanhassen, Minnesota.

“Those two things coinciding with each other is not good from a health perspective,” he said.

High levels of fine particulate matter in the air from wildfire smoke may be unhealthy for sensitive groups, such as children and people with heart or lung conditions. The particulates can cause shortness of breath, coughing, dizziness or fatigue and aggravate heart and lung diseases and other chronic health issues.

Experts suggest wearing an N95 mask if you have to be outside and keeping your indoor air cleaner by closing windows and running an air purifier or air conditioner.

The Associated Press and Nexstar’s Alix Martichoux contributed to this report.

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