RIAU24.COM – Canada's most populous city, Toronto, has been deemed the world's most polluted major city after smoke from the country's worst-ever wildfires continued to impact air quality Wednesday.

Serious consequences of wildfires have been felt in at least 15 US states. Smoke from the wildfires affected cities across the United States and reached Europe thousands of miles away.

Air quality monitors cited by the AFP news agency show that more than 100 million people face potentially unsanitary conditions.

Toronto's Air Health Index is rated at 10 out of 10, which is called the “high risk” air quality classification.

Swiss company IQAir considers Toronto's air to be of the worst quality of any major city in the world.

Toronto Public Health said Toronto Emergency Management monitors the impact of poor air quality on municipal services and critical infrastructure.

The city has suspended outdoor activities at daycares. Depending on local conditions, school principals were given the autonomy to decide whether or not to let children go outside during recess.

PM2.5 pollutants (PM for Particulate Matter) are the most worrying by-products of polluting stimuli such as fires.

Due to its small size of 2.5 microns or less, it can easily circulate in the bloodstream, aggravating heart disease in susceptible people.

Warnings were issued from Ontario to the states of Minnesota and Michigan, in the northern United States, to New York and as far as the southeastern states of North Carolina and Georgia.

The air quality alert affects much of the southern United States and Midwest grappling with a severe heat wave affecting several million Americans.

The U.S. National Weather Service released a forecast heat index of up to 115 degrees Fahrenheit (46 Celsius) in north and central Texas.

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