For the second time this month, massive plumes of smoke from hundreds of out-of-control Canadian wildfires are polluting much of America's air.
Among the major U.S. cities now experiencing poor air quality are St. Louis, Milwaukee, Cincinnati and Chicago, while entire states have also issued air quality alerts, according to the National Weather Service.
These are Delaware, Illinois, Indiana, Iowa, Maryland, Michigan, New York and Wisconsin. Parts of Kansas, Minnesota, Missouri, North Carolina, Ohio, Pennsylvania and Virginia also have alerts. In the cities of Chicago, Cleveland, Detroit, Indianapolis, Milwaukee, Pittsburgh and Davenport, Iowa, air quality was in the "very unhealthy"range, according to airnow.gov.
The air quality is cause for concern because of tiny particulate matter, also called PM2.5, which is a dangerous pollutant.
It can travel deep into the lung tissue and enter the bloodstream, according to the U.S. Centers for Disease Control and Prevention. PM2.5 is associated with a variety of health issues, including asthma and heart disease.
Between 80 million and 120 million people are affected by this poor air quality, according to an analysis by the National Weather Service and CNN.
In some locations, residents have been asked to stay inside and run their air conditioning or to wear N95 masks if they need to go outside, CNN reported.
Smoke concentration may increase over New York City on Thursday, CNN reported. City police and firefighters planned to distribute masks, Mayor Eric Adams said. Levels were expected to be higher around the state than in the city.
More information
The U.S. Environmental Protection Agency has more on PM2.5.
SOURCE: CNN