A string of sports games and practices have been postponed as smoke from Canadian wildfires continues to choke the Midwest, Northeast and Southeast parts of the United States.

Around 75 million people are under air quality alerts as wildfire smoke shrouds major US cities, with Major League Baseball (MLB), the Women's National Basketball Association (WNBA) and the National Women's Soccer League (NWSL) forced to postpone games due to concerns over dangerous air quality.

The MLB postponed two games -- one between the Detroit Tigers and the host Philadelphia Phillies at Citizens Bank Park and the other between the Chicago White Sox and the New York Yankees at Yankee Stadium -- on Wednesday due to medical and weather expert warnings about "clearing hazardous air quality conditions in both cities," the league said in a statement.

Meanwhile, the WNBA was forced to postpone Wednesday's game between the New York Liberty and the Minnesota Lynx due to smoke impacting the Liberty's home arena, with the league noting that information regarding the rescheduling of the game would be provided at a later date.

The New York Racing Association (NYRA) canceled Thursday's training at Belmont Park due to "poor air quality conditions" affecting New York state, while in New Jersey, the NWSL postponed Wednesday night's Challenge Cup game in Harrison and rescheduled it for August 9.

"The safety of our players, officials and fans is our top priority. Following consultation with the NWSL Medical and Operations staff, it was determined that the match could not be safely conducted based on the projected air quality index," the NWSL said in a statement.

Smoke from Canada's fires has periodically affected the Northeast and Mid-Atlantic for more than a week, raising concerns over the harms of persistent poor air quality.

More than nine million acres have been charred by wildfires in Canada so far this year -- about 15 times the normal burned area for this point in the year -- and more than 10,500 people have been evacuated from communities across Alberta.

According to the MLB, the Phillies-Tigers game will take place at 6:05 p.m. (ET) on Thursday, while the Yankees and the White Sox will now play a doubleheader beginning at 4:05 p.m. (ET) on Thursday.

The Belmont Stakes is scheduled for Saturday at Belmont Park in Elmont, New York, and the NYRA said a decision on Thursday's live racing program will be made in the morning following a "review of the air quality conditions and forecast."