Media articles have reported on an air quality study performed by Health Canada in the TTC and other Canadian Metros.
Why was the study done?

Health Canada is performing studies that measure the impact of air pollution on public health because of the limited research on air pollution exposure in Canadian transportation.

How did TTC end up participating in the study?

Health Canada approached TTC to assess commuter exposures during use of the subway system. TTC voluntarily agreed to participate in the study to establish its own baselines for due diligence and to help shape the framework for future public health research.

What did the study look at?

Health Canada examined commuter exposure to air pollution during use of the metro in Vancouver, Montreal and Toronto. In Toronto this was exposure during use of the subway system during rush hour periods in 2010 and 2011.

The media articles mention high levels of PM2.5. What is PM2.5?

PM, or Particulate Matter refers to small particles and droplets in the air. PM has a wide range of sizes. PM2.5 refers to Particulate Matter with a diameter of 2.5 micrometers (┬Ám) and less.

What are the health effects of PM2.5?

Small particles are inhaled into the lungs. According to the World Health Organization, health effects of inhaling pollutants can aggravate of asthma and irritate eyes, nose and throat.

PM2.5 can be associated with an increased risk of heart and respiratory diseases, lung cancer and reduced lung function.

However, and this is important, there is no suggestion that the exposure seen in TTC subway stations are of a health concern. Nevertheless, the TTC will continue to mitigate any and all exposure, working with the JHSCs to ensure a healthy and safe environment for all.

Are there exposure limits for PM2.5?

There are no occupational exposure limits for PM2.5 in Ontario.

However, the majority of the components of the subway dust have individual occupational exposure limits that are applicable. In an air quality study, these components would be measured individually.

For public exposures, Environment and Climate Change Canada has established Canadian Ambient Air Quality Standards (CAAQS) for PM2.5 in outdoor air. However, outdoor air pollution standards do not apply to the subway.

What is the composition of TTC subway dust?

TTC subway air quality studies have analyzed subway dust on numerous occasions. The "black dust" is primarily iron oxide, with trace amounts of other metals. The dust also contains hair, skin, and clothing fibres. The black colour of the dust is due to the high iron content.

The study performed by Health Canada confirmed that the PM2.5 dust is mainly iron.

Why are PM2.5 levels higher in Toronto than Vancouver and Montreal?

The study identified that the concentrations are a result of the differing features of the systems:

  • Toronto is primarily enclosed;
  • Vancouver Skytrain is primarily outdoors; and
  • Montreal uses rubber wheels and wooden brakes.

TTC has subway dust levels that are considered typical in a global context. Similar dust levels have been found in other major metros like New York, London, and Seoul, which have similar features to Toronto.

Has TTC evaluated subway air quality?

Yes. The TTC has conducted major subway air quality studies in 1977, 1980, and 1995. The results indicated air quality improvements over the years. The 1995 study found that none of the 280 samples taken were above the occupational exposure limits for employees. It was determined that the subway air quality would not affect the health of employees or patrons who do not have pre-existing serious respiratory conditions.

What is the TTC doing to improve subway air quality?

The Health Canada study recommends considering improved ventilation, in-car filtration or conducting rail dust cleaning. These initiatives, among others, have already been underway at TTC, including:

  • Improved air filtration on subway cars;
  • A new track vacuum workcar equipped with HEPA filtration;
  • Corridor cleaning program;
  • Station and tunnel washing;
  • Track clean-up crews;
  • T1 air duct cleaning program; and
  • An updated subway air quality study.
Do I need a respirator when working in the subway system?

Respirators are not required for general use in the subway.