Toronto air quality ranks among worst globally as Ontario wildfire smoke spreads to US

Toronto was listed among the world’s cities with the poorest air quality on Wednesday after thick smoke from Ontario wildfires enveloped the skyline and crossed the border into the United States, triggering health warnings from local authorities. Air‑quality monitors recorded particulate‑matter concentrations that placed the city near the top of global rankings for hazardous conditions, prompting officials to advise residents to limit outdoor activities and keep windows closed.

The haze originated from several active wildfires in northern Ontario, where high winds carried fine ash and smoke southeastward, affecting both Canadian and American communities. Health agencies in both countries issued alerts recommending the use of masks, especially for vulnerable groups such as children, the elderly, and those with respiratory conditions. Monitoring stations will continue to track pollutant levels throughout the week, and officials indicated that improvements are expected as the fires are contained and wind patterns shift.