Toronto Air quality today

What is in Toronto's air, and where does it come from?

Toronto's air pollution is a mix of hundreds of substances, including nitrogen oxides, ozone and particulate matter, which means tiny particles in the air ^[1]. Most of it comes from burning gasoline, diesel, natural gas and coal in cars, trucks, home furnaces, industry and power plants ^[1]. Traffic is the largest local source, followed by industrial and residential sources ^[1].

Some pollution also blows in from elsewhere ^[1]. A 2014 Toronto Public Health report found that over half of Toronto's air pollution is emitted inside the city's boundaries ^[4]. Ontario's environment ministry says pollution from the United States and beyond makes up a significant part of the province's ozone when ozone levels are high ^[5].

In Ontario's 2023 air quality report, the highest average levels of nitrogen dioxide were found in big urban areas with heavy vehicle traffic, such as the Greater Toronto Area ^[6].

How much harm does air pollution do in Toronto?

In April 2014, Toronto Public Health estimated that air pollution from all sources led to about 1,300 premature deaths and 3,550 hospitalizations in the city each year ^[4]. That was 23% fewer deaths and 41% fewer hospitalizations than its 2004 estimates ^[4].

Traffic had the greatest health impact of any source, with about 280 premature deaths and 1,090 hospitalizations a year ^[4]. That is about 1 in 5 of the premature deaths linked to air pollution in the city ^[4]. The city says air pollution can cause heart and breathing problems and is linked to cancer and other chronic diseases ^[1].

Does Toronto still get smog?

Smog is a mix of pollutants, mainly ground-level ozone and fine particles, and it can look like a brownish haze ^[1]. It can happen at any time of year, but it is most common in summer ^[1]. Smog advisories used to be common in Toronto, but the city has not had one since 2016 ^[1]. The city says smog remains possible ^[1].

Across Ontario, from 2014 to 2023, nitrogen dioxide fell by 28% and fine particles, called PM2.5, fell by 12% ^[5]. Ozone showed no clear trend up or down ^[5]. In 2023, 20 of the province's monitoring stations measured ozone above Ontario's one-hour limit at least once ^[6]. Ozone goes over that limit in the warmer months, while winter levels in 2023 were well below it ^[6].

Why does wildfire smoke reach Toronto?

Wildfire season in Ontario typically runs from early April to late October ^[6]. Hot smoke can be lifted several kilometres above the ground and carried hundreds or thousands of kilometres from the fires ^[6]. Fine particles are the main pollutant of concern in wildfire smoke ^[6].

The city says that because of climate change, Toronto, like many parts of North America, is having more poor air quality events due to wildfire smoke ^[3]. These events may undo some of the progress made in cutting pollution ^[3].

What happened in the smoke events of 2023 and 2025?

Ontario called 2023 an unprecedented wildfire season ^[5]. Fires burned about 15 million hectares across Canada, about six times a typical year ^[6]. Ontario issued 13 air quality alerts covering 55 days, and 7 of them, covering 49 days, were for wildfire smoke ^[5]. Winds carried smoke from Quebec into southern Ontario from May 29 to June 10, then from northern Ontario and Quebec from June 11 to July 1 ^[6].

The Air Quality Health Index, or AQHI, is Canada's 1 to 10+ scale of health risk from air pollution, based on ozone, nitrogen dioxide and particulate matter ^[2]. On June 28, 2023, Toronto's AQHI reached 10 ^[7]. That afternoon, a ranking by the air quality tracker IQAir listed Toronto as the worst of the world's major cities for air quality ^[7]. On Toronto Public Health's advice, city outdoor recreation programs moved indoors ^[7].

On July 14, 2025, smoke from fires in northern Ontario and the Prairies put parts of the Toronto area under a special air quality statement, during a heat warning ^[8]. IQAir ranked Toronto the second most polluted major city in the world at 8 a.m. that day ^[8].

What is Toronto doing about poor air?

Toronto Public Health has a Wildfire Smoke Response Strategy, which it reviews and updates every year ^[2]. Air quality alerts come jointly from Ontario's environment ministry and Environment and Climate Change Canada ^[2]. A yellow warning means the AQHI is forecast to reach 7 or more, a high risk, and an orange warning means 10 or more, a very high risk ^[2].

Since 2024, the Cleaner Air Spaces Network has offered places with air filtration systems rated MERV 13 for people who struggle to get clean air at home ^[2]. They include City Hall, Metro Hall and the civic centres in Scarborough, North York, East York and York ^[2].

To cut traffic pollution, a city by-law bans running a parked vehicle's engine for more than 60 seconds ^[1]. The TransformTO Net Zero Strategy aims to bring the city's greenhouse gas emissions to net zero by 2040 ^[1].

How to protect yourself in Toronto

Check the AQHI when planning time outdoors, and cut back on strenuous outdoor activity when it is high ^[2]. Children, older adults, pregnant people, people who spend a lot of time outdoors and people with heart or lung conditions may be more affected ^[2].

When the air is poor, keep windows and doors closed ^[1][2]. Use the best filter your heating and cooling system is approved for, and set it to recirculate if you can ^[1]. Without such a system, a portable air cleaner with a HEPA filter can clean the air in one area of your home ^[1]. Avoid candles, incense, frying and gas stoves indoors ^[1].

If you must be outside in smoke, a well-fitted N95 respirator can cut the fine particles you breathe, but not the gases in smoke ^[2]. Respirators should not be used by children under 2 ^[2]. If you cannot get clean air at home, a library, recreation centre, shopping mall or Cleaner Air Space can help ^[1][2].