Wildfire Smoke Prompts Air Quality Alerts in Parts of 16 U.S. States

Smoke from wildfires in Canada and northeastern Minnesota has triggered air quality alerts for more than 100 million Americans across 16 states. Haze from the fires has reduced visibility across the Great Lakes, Northeast and Mid-Atlantic regions. The Canadian Interagency Forest Fire Centre reported 949 active fires as of Saturday afternoon.

Ontario and the Northwest Territories account for more than one-third of those fires. Prince Edward Island is the only province or territory without active fires. The fires have burned nearly 3 million hectares so far, with less than 20 percent under control or being held and more than 200 remaining fully out of control.

More than a dozen communities in Ontario are under mandatory evacuation orders. On Monday, just over two dozen members of the Namaygoosisagagun First Nation in northwestern Ontario were evacuated by boat. "I've never seen a fire that big.

It was angry. It was moving fast. The wind really did not help," said Miiyah Paavola, the 15-year-old daughter of Chief Helen Paavola. In northeastern Minnesota, more than a dozen fires have burned an estimated 77,000 acres in and around the Superior National Forest and Boundary Waters Canoe Area Wilderness.

Fine particulate matter known as PM2.5, produced by the smoke, triggers the alerts when concentrations reach levels that pose health risks. These particles are 30 times smaller than the thickness of a human hair and can penetrate deep into the lungs. An AQI value of 50 or below is considered good.

Levels reached hazardous ranges around Lake Superior earlier this week. "The impacts of the Canadian wildfires are causing great concern and harm across the United States," EPA Administrator Lee Zeldin said. " Short-term exposure can cause coughing, wheezing, shortness of breath, headaches, eye irritation and fatigue, according to the Centers for Disease Control and Prevention.

Physician-scientist Mary Johnson at the Harvard T.H. Chan School of Public Health noted that a 10-unit increase in PM2.5 correlates with rises in emergency visits for heart attacks, strokes and breathing problems. At AQI levels of 200, exposure equals smoking nine or 10 cigarettes a day for everyone, including infants and older adults.