Editorial Archive

Safety Notice #7: Subway Air Quality Update

1/6/20 2:19 PM

From the Safety and Environment Department

The following information is provided as an update to the Safety Notice #6 – Subway Air Quality Update – issued on February 25, 2019.

Toronto Public Health – Subway Health Impacts Study – Background
In 2017, the Toronto Board of Health requested that Toronto Public Health staff oversee an independent study of the health risks of air quality for passenger in the subway system, particularly in relation to mitigation measures that could be implemented.

To understand the overall impact of the Toronto subway on the health of Torontonians, Toronto Public Health has carried out a Health Impact Assessment, including a human health risk assessment of air quality. Fine particulate matter (PM2.5) was one of the major areas of focus for the study. PM2.5 includes all solid and liquid droplets suspended in air with a diameter of 2.5 micrometres or less (about 30 times smaller than that of a human hair).

Toronto Public Health Study versus an Occupational Exposure Study
The health risk assessment approach used by Toronto Public health considered lifetime environmental health risks for passengers, including vulnerable groups.  This is very different from the process for occupational assessment like that used in the 2017-2018 TTC Subway Air Quality Study, which, in comparison, addressed set timeframes for healthy workers and relied on legislated occupational standards to prevent illness or certain effects in industrial situations. It should be noted that there is currently no occupational exposure limit for PM2.5.

Toronto Public Health Study – Summary of Findings
The Medical Officer of Health has indicated in the media that overall, the health benefits of taking the subway outweigh the potential health risks found in the Health Impact Study. Toronto Public Health recommends for residents to take public transit, including the TTC.

The Health Impact assessment found that taking the subway is associated with benefits to people’s health and well-being and is a health-supportive way to travel, especially as an alternative to personal vehicle use. Promoting the use of transit is important because it provides a safer alternative to driving, reduces outdoor air pollution and greenhouse gases, promotes physical activity and provides access to employment, education and social/community services.

The Health Impact Assessment also identified that improving air quality in the Toronto subway system is expected to be associated with health benefits for passengers. Air quality data collected shows that some levels of fine particulate matter (PM2.5) are elevated and contain high levels of some metals. The human health risk assessment concluded that levels of subway PM2.5 warrant mitigation.

The nine recommendations in this report are directed at various organizations from TTC to Metrolinx, and various other provincial and national organizations.

Toronto Subway Air Quality Health Impact Assessment

TTC’s Commitment to Improving Air Quality
The TTC remains committed to doing its part to improve air quality in the city of Toronto and in its underground subways.

The TTC has been actively pursuing ways to ensure that our fleet is moving to greener technology that will reduce greenhouse gas emissions and outdoor air pollution. In 2019, the TTC procured 255 second-generation hybrid buses that are 20 per cent cleaner than the previous generation. The TTC will procure 60 battery-electric buses that are 95 per cent cleaner than our current diesel fleet by end of Q1 2020.

Additional measures to reduce greenhouse gas emissions and air pollution in the subway include retrofitting existing work cars with the latest emission control technologies, such as catalytic converters and diesel exhaust filters. All new work cars are equipped with the latest emission control technologies. On the older T-1 revenue fleet, filters are being upgraded to Minimum Efficiency Reporting Value (MERV) 9. These air filters can remove pollutants as small as 1–3 microns, including PM2.5.

The TTC will be reviewing, monitoring and evaluating the effectiveness of these various mitigation measures in addition to the introduction of Automatic Train Control on Line 1 with respect to its impact on PM2.5 levels in the subway.

The existing research on subway PM2.5 and associated health effects to the public is limited. The TTC has partnered with Health Canada in two separate air quality monitoring campaigns in order to begin to bridge the research gap that exists.  Further collaborations with Health Canada are currently being considered.

The TTC has reached out to other transit organizations with similar subway systems, namely New York City Transit Authority and Transport for London as this issue is not unique to the TTC. We have begun to exchange information around PM identification, potential mitigation measures, emerging technologies, research opportunities and monitoring strategies as we all agree this issue warrants further exploration.

Link to TTC Subway Air Quality Study Reports:
Further information on the TTC’s Subway Air Quality Study and PM2.5 can be found at Safety and Environment’s intranet site (internal website).

If you have any questions, please contact Stephanie Fortin at 416-393-3262.

John O’Grady
Chief Safety Officer
Safety & Environment Department
January 6, 2020

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