A thick, smokey haze continues to envelop the Greater Toronto Area as an orange-level air quality warning is still in place Thursday from Environment Canada.

The air quality health index across the GTA, including Mississauga, downtown Toronto and Oshawa, was at 10+ or at “very high risk” as of 6 a.m. Thursday.

Drifting smoke from forest fires in northwestern Ontario is causing poor air quality and reduced visibility for much of southern Ontario.

The national weather agency warned that everyone’s health, regardless of age or condition, was at risk due to heavy smoke conditions.

It urged people to limit time outdoors and to either reschedule or cancel outdoor events. For those going outside, the weather agency advised people to wear a “well-fitted and properly worn” mask, such as N95, to reduce exposure to fine particles in the smoke.

Toronto ranked third on Thursday morning in a list of the world’s most polluted cities, according to a global ranking by IQAir, a Swiss air quality technology company. For some time on Wednesday, the city was first before dropping down in the ranks.

WATCH | What to know about wildfire smoke in Toronto:

What you need to know about wildfire smoke blanketing Toronto

Toronto residents say they’re concerned about the air quality as a heavy layer of wildfire smoke blankets the city. CBC’s Clara Pasieka breaks down what you need to know about the poor air quality.

The air quality warning was first issued on Tuesday night and it’s expected to ease by Friday or the weekend, according to Environment Canada meteorologist Brian Owsiak.

He said the smoke will likely “flush” out with the shift in wind direction coming later in the week.

What symptoms to watch out for

Environment Canada warned residents may experience symptoms including headaches, eye and throat irritation, wheezing or chest pains.

Seniors, pregnant people, young children, people who work outdoors and those with existing health conditions are more likely to be impacted by the wildfire smoke. They’re advised to avoid going outdoors and to seek medical attention if experiencing symptoms.

“Check in on others who are in your care or live nearby who may be more likely to be impacted by wildfire smoke,” said Environment Canada’s warning.

For those camping out indoors, the weather agency advised on keep windows and doors closed as much as possible.

All city-run outdoor pools will remain closed Thursday closed mid-afternoon due to the air quality, Toronto said in a bulletin Wednesday afternoon. CampTO trips and outdoor programs have also been cancelled, the city said.

Toronto has also has opened six “cleaner air spaces” at City Hall, Metro Hall, North York Civic Centre, Scarborough Civic Centre, York Civic Centre and East York Civic Centre.