Toronto recorded the worst air quality among major cities worldwide on Wednesday as smoke from wildfires in northwestern Ontario blanketed the city and drifted into the northeastern United States, prompting health warnings on both sides of the border.
Although the wildfires are burning in remote areas hundreds of miles from Toronto and pose no direct threat to major cities, thick smoke has spread across a wide region.
Environment Canada reported an Air Quality Health Index (AQHI) reading of 10+, categorised as “very high risk,” and warned that hazardous conditions could persist through Thursday night.
Residents were advised to limit outdoor activities, especially strenuous exercise, and those with respiratory conditions, older adults and children were urged to take extra precautions.
The smoke also reached New York City, where local authorities issued an air quality alert ahead of New Jersey’s hosting of the FIFA World Cup final on Sunday. Officials urged residents to reduce prolonged outdoor exertion and take frequent breaks if outside.
The US National Weather Service said smoky conditions could linger through the end of the week.