Environment Canada is warning of high levels of air pollution in Toronto today due to ongoing forest fires scorching wide swathes of Ontario and Quebec.

The government climate agency issued a Special Air Quality Statement for the City of Toronto just before 4:40 this morning, warning that smoke plumes from forest fires over northeastern Ontario and Quebec have arrived in the region, bringing air quality down to potentially dangerous levels.

Wildfire smoke's impacts on air quality can fluctuate wildly over short periods of time, but Toronto can expect the smoke plume's associated air pollution to stick around throughout the middle of the week. Conditions are only expected to improve for some areas of the city on Thursday night.

Wildfire smoke can pose health risks even at low concentrations, however, portions of the population, including people with lung disease like asthma, heart disease, older adults, children, pregnant people, and people who work outdoors, face the highest risk of experiencing smoke-related health effects.

If you must spend time outdoors, experts recommend wearing a well-fitted respirator-type mask that does not allow air to pass through small openings between the face and mask. Masks like N95s are great at keeping smoke particles out of your lungs, but they allow wildfire-related gases to pass through, so there will always be health risks associated with smoke inhalation.

It may seem like a mild day fit for outdoor activities, however, EnvironCan warns to "stop or reduce your activity level if breathing becomes uncomfortable or you or someone in your care feel unwell," and "contact your health care provider or local health authority if you develop severe symptoms or need advice."

Even those staying indoors during the smoke event are advised to take precautions. If the temperature indoors is comfortable, keep windows closed. HVAC systems should have the highest-rated MERV filter possible, while portable HEPA filter systems are also recommended.

Your activities at home can also affect indoor air pollution, and EnvironCan recommends not smoking or vaping indoors, burning candles or incense, vacuuming, or dusting surfaces, instead suggesting wiping or wet-mopping to avoid kicking up dust.

Health effects can creep up on you, so it's important to listen to your body and take a break from outdoor activities if you start to experience any symptoms.