Millions are under air quality alerts as wildfire smoke blankets large swaths of U.S.

 

Millions of people across the Upper Midwest and the Northeast are under air quality alerts Monday, as smoke from wildfires in Canada drift over the region.

Hazy skies are expected in Minnesota, Wisconsin, Michigan, northern Indiana, Pennsylvania, New York, New Jersey, Connecticut, Massachusetts, Vermont, Rhode Island, New Hampshire, Delaware and Maine, according to the National Weather Service.

Almost 200 wildfires are burning out of control in Canada, including 81 in Saskatchewan, 159 in Manitoba and 61 in Ontario. Figures from the Canadian Interagency Forest Fire Center indicate that more than 16.5 million acres have been scorched so far this year in what will likely be the country’s second-worst wildfire season on record.

A high-pressure system parked over the Midwest is trapping the smoke in place, causing air quality issues to linger for several days, according to the Michigan Department of Environment, Great Lakes, and Energy.

The air quality index Monday across 14 states in the Midwest and the Northeast ranged from “moderate” to “unhealthy” for the general public.

Wildfire smoke is of particular concern because it contains small particles that are less than 2.5 micrometers in diameter — around 4% of the diameter of an average strand of human hair. This type of air pollution is dangerous because the particles are small enough to reach deep inside the lungs, which can exacerbate or increase the risk of asthma, lung cancer and other chronic lung diseases.

Exposure to high levels of air pollution can also cause inflammation and weaken the immune system. Infants, children, seniors and pregnant women are especially vulnerable to unhealthy air quality conditions.

Studies have shown that climate change is fueling conditions for more frequent and intense wildfires. Warmer temperatures can dry out vegetation, which can increase the likelihood of wildfires igniting and spreading rapidly.

Cities affected by poor air quality Monday include Milwaukee; Detroit; Buffalo and Albany in New York; Boston and New York City. Many alerts will remain in effect through Tuesday, according to the weather service.

In the West, several wildfires are causing separate air quality issues in the region. More than 65,000 acres have been scorched in California's Los Padres National Forest, where hot and dry conditions have fanned the growth of the Gifford Fire.

In Colorado, the air quality index showed "moderate" readings Monday across large swaths.

“If smoke is thick or becomes thick in your neighborhood you may want to remain indoors,” the Colorado Department of Public Health and Environment said in its advisory. “This is especially true for those with heart disease, respiratory illnesses, the very young, and older adults. Consider limiting outdoor activity when moderate to heavy smoke is present.”

-Denise Chow, NBC News