The hazy sun hangs behind Canadian wildfire smoke above an oak tree in southern Wisconsin, June 4, 2023. (Tom Purdy via Twitter)
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Wisconsin remains under a statewide Air Quality Advisory for fine particulate matter from wildfire smoke until noon Central Time on Thursday, according to the Wisconsin Department of Natural Resources. 

Canadian wildfire smoke is spreading north to south in what the DNR called a “highly dynamic” situation this week. The agency expects the worst impact noon Tuesday through noon Wednesday. 

“It is important to pay close attention to the air quality in your area and take action, especially if you don’t feel well,” the DNR said Tuesday in a news release.

The DNR and Wisconsin Department of Health Services recommend that people in all populations limit outdoor activities — and to take a break or move indoors if experiencing coughing and shortness of breath.

“Sensitive groups, which include people with heart or lung disease, older adults, children, those who are pregnant, and those who work outdoors – should consider moving all events inside,” the DNR said.

Tiny fine particulate matter, also known as PM2.5, a main pollutant released from wildfire smoke can “penetrate pretty deep into our lungs and get into our bloodstream,” Katelyn O’Dell, a researcher at George Washington University, previously told the Milwaukee Journal Sentinel and the Minneapolis Star Tribune

How can you check the air quality in your area and what do the numbers mean?

The Environmental Protection Agency monitors the air around the country and compiles an air quality index, or AQI.

Here’s what to know about the index and how to keep tabs on your area, especially in U.S. regions dealing with smoke from Canadian wildfires.

What does the air quality index measure? 

The index rates how clean or polluted the air is each day. The EPA uses this measure to keep tabs on five kinds of air pollutants. The main concern from the wildfire smoke is fine particle pollution. These particles are tiny enough to get deep into the lungs. They can cause short-term problems like coughing and itchy eyes, and in the long run, can affect the lungs and heart.

What do the numbers and colors mean? 

The index runs from zero to 500. The higher the number, the worse the air quality. That range is broken down into six color-coded categories. Green or yellow — in the zero to 100 range — the air is pretty clear. Once it gets up to orange, the air quality could be a concern for sensitive groups like kids, older adults or those with health conditions.

In the red and purple zones, the air quality is considered unhealthy for everyone.

At 10 a.m. on Tuesday, air at 16th Street in Milwaukee registered a purple 223, or “very unhealthy,” according to the EPA’s air quality index. 

(Courtesy of U.S. Environmental Protection Agency)

And if the index gets to maroon — at 301 or above — pollution levels are hazardous.

At these high levels, take precautions to avoid breathing in the dangerous air. That can mean reducing your outdoor activities, running air purifiers inside and wearing a well-fitting mask like an N95 when you’re outside.

“If you have to exert yourself, exert yourself less. Hydrate more,” said Dr. Leonardo Trasande, who studies environmental health at New York University.

What’s the air like in my area? 

Check, which updates every hour. The site shows a real-time map of the air quality across the country and also includes a forecast for the day ahead. The map pulls in measurements from a network of air monitoring stations across the country. States and cities may also offer more local guidance.

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