Toronto's Air Pollution: Causes And Concerns

Toronto's air pollution comes from local sources and affects other communities. Traffic-related air pollution (TRAP) is the largest local source of air pollution in Toronto, followed by industrial and residential emissions. The pollutants at play are often referred to as TRAP, which includes benzene, nitrogen oxides, and particulate matter. Exhaust emissions from cars, trucks, and other vehicles are a major source of air pollution in Toronto. Beyond vehicular emissions, air pollution in Toronto is also caused by the wear of train wheels and rails in the Toronto Transit Commission (TTC) subway system.

Vehicle exhausts and tyre breakdown

The increasing weight of cars is also a factor. As cars get heavier, more particles are thrown off by tyres as they wear on the road. Car tyres produce a substantial amount of particle pollution, with tests showing that they generate more than 1 trillion ultrafine particles per kilometre driven. These particles, smaller than 23 nanometres, can enter organs via the bloodstream and have severe health implications. Tyre wear contributes to the release of toxic chemicals and carcinogens, with an estimated 300,000 tonnes of tyre rubber debris in the UK and US each year.

While electric vehicles (EVs) have been accused of producing more particulate matter pollution than petrol or diesel cars, this claim is controversial. EVs significantly reduce particulate matter from brake wear, and the assertion that tyre wear produces 1,000 times more particulate pollution than petrol or diesel exhausts is likely exaggerated. Nonetheless, tyre wear remains a concern for EVs, and cities with high EV adoption, like Dundee, have shown improved air quality due to reduced particulate matter from exhausts, tyres, and brakes.

To address vehicle exhaust and tyre breakdown pollution in Toronto, the city has implemented measures such as the TransformTO Net Zero Strategy, which aims for net-zero community-wide greenhouse gas emissions by 2040. The city has also prohibited idling for over 60 seconds under the City of Toronto By-Law 517. Additionally, the upcoming Euro 7 emission standards will address tyre and brake emissions by introducing officially measured limits.

Industrial emissions

Industrial processes release various pollutants into the atmosphere, including nitrogen oxides (NOx), sulphur oxides (SOx), ozone (O3), and particulate matter (PM). Nitrogen oxides are particularly harmful, as they can cause respiratory issues and worsen asthma. They are produced by vehicle engines, coal-burning power plants, and industrial activities such as mining operations. In addition, human-made volatile organic compounds (VOCs), which are also emitted by industrial processes, can react with nitrogen oxides in the presence of heat and sunlight to form ground-level ozone, a harmful pollutant that affects human health and the environment.

Particulate matter, which is another product of industrial emissions, refers to microscopic airborne solids or liquids that are smaller than 2.5 micrometres per cubic metre of air. These particles can be inhaled, damaging the lungs and leading to serious health issues, especially in children whose lungs are still developing. Acid aerosols, a type of particulate matter containing sulphuric or nitric acid, are produced by the combustion of fossil fuels and emissions from industrial sources such as coal-burning power plants, cement plants, and mining operations.

Indoor air quality is also affected by industrial emissions. A study by the University of Toronto found that the Toronto Transit Commission (TTC) subway system's Line 2 suffered from significant particulate pollution due to the wear of train wheels and rails during braking. The friction caused by braking emits fine particles that reduce indoor air quality. While Toronto's subway system uses limited forced ventilation, improving ventilation and implementing technological changes can help mitigate this issue and improve air quality for commuters.

To improve Toronto's air quality and reduce the health risks associated with industrial emissions, it is crucial to focus on reducing emissions from industrial sources. This can be achieved through regulatory measures, adopting cleaner technologies, and transitioning to more sustainable practices. By addressing industrial emissions, Toronto can make significant progress towards creating a healthier and more sustainable urban environment for its residents.

Residential emissions

In addition to the direct emissions from residential sources, indoor air quality is also a concern. For instance, children may be exposed to higher levels of pollutants as they play on floors where dust and pollutants can linger, and indoor air pollution can trigger asthma attacks and cause other respiratory issues.

Furthermore, a study by the University of Toronto found that the Toronto Transit Commission (TTC) subway system's indoor air quality is significantly influenced by the wear of train wheels and rails during braking. This issue, particularly along Line 2, which uses friction braking, contributes to particulate pollution and affects the air quality within the subway system.

To improve residential air quality in Toronto, several measures can be implemented. Firstly, reducing the use of natural gas and transitioning to cleaner energy sources can help decrease emissions of harmful nitrogen and sulphur oxides. Additionally, improving ventilation in residential spaces and investing in air filtration systems or portable air purifiers can effectively reduce indoor air pollution levels. Addressing the sources of indoor air pollution in the subway system, such as through technological changes or improved ventilation, will also positively impact the overall residential emissions in Toronto.

Subway systems

Toronto's subway system, the Toronto Transit Commission (TTC), has been identified as a source of indoor air pollution. A study by the University of Toronto found that the friction braking system used in Line 2 of the TTC significantly impacts indoor air quality. The wear of train wheels and rails caused by braking produces particulate pollution. This discovery is crucial for improving air quality along the TTC subway lines.

The study, led by Professor Greg Evans from the Faculty of Applied Science & Engineering, measured the chemical composition of particulate matter. It found that the degree of wear on the wheels and rails is influenced by the degree of braking applied, specifically the speed at which trains enter the station. The findings mark an important step towards improving indoor air quality and will hopefully influence the design of new subway lines in Toronto and other cities.

The TTC's limited forced ventilation system also contributes to the air pollution issue. Professor Evans notes that the TTC relies on trains pushing air like a piston as they move through the tunnels, which is not as effective as the continuous mechanical ventilation systems used in other cities like Montreal and Barcelona. Improving ventilation and reducing emissions are crucial steps to enhance air quality on subway trains and platforms.

While the subway system contributes to indoor air pollution, traffic-related air pollution (TRAP) remains the largest local source of air pollution in Toronto. Exhaust emissions from cars, trucks, and other vehicles are major sources of harmful pollutants, affecting the health of Toronto's residents. Toronto's air pollution problem is not limited to local sources, as the city's pollution can also impact other communities.

Wildfire smoke

Wildfires are a significant cause of air pollution in Toronto, with smoke affecting the city's air quality, public health, and ecosystems. In June 2023, Toronto's air quality was ranked among the worst in the world due to wildfire smoke, according to global air quality tracker IQAir. The smoke from forest fires in northeastern Ontario and Quebec blanketed the city, demonstrating the far-reaching impact of wildfires on air pollution.

The Air Quality Health Index (AQHI) is a crucial tool used in Toronto to monitor and communicate air quality to the public. It provides a scale from 1 to 10+, indicating the level of health risk associated with the current air quality. The AQHI is calculated based on concentrations of ozone (O3), nitrogen dioxide (NO2), and particulate matter (PM2.5). Toronto Public Health (TPH) has developed a Wildfire Smoke Response Strategy to address the impacts of wildfire smoke on the city's air quality and public health. This strategy includes processes for updates, response strategies, and preparedness activities to protect the health of Toronto's residents.

To protect themselves during periods of poor air quality due to wildfire smoke, Toronto residents are advised to stay informed by monitoring the AQHI and air quality alerts. Limiting outdoor activities, especially strenuous physical ones, is recommended when the AQHI indicates high levels of air pollution. Additionally, individuals should pay attention to their bodies and stop any activity if they experience difficulty breathing or other adverse health symptoms. Taking proactive measures, such as having a care plan in place, can help individuals manage their health during periods of high air pollution due to wildfire smoke.

While Toronto grapples with the immediate impacts of wildfire smoke, the underlying cause, climate change, is a significant concern. The increasing frequency and intensity of wildfires are linked to a changing climate, and Toronto, like many other cities, must adapt to these emerging challenges.

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