A new study on the health impacts of air quality for passengers riding on Toronto's subway system has revealed riders are being exposed to "elevated" levels of air pollutants.

However, despite this, the city's medical officer is still encouraging the public to continue using the TTC.

"Taking the subway is associated with benefits to people's health and wellbeing and is a health-supportive way to travel, especially as an alternative to personal vehicle use," said Dr. Eileen de Villa in her report that was released Monday.

The study, conducted by Toronto Public Health, found levels of air pollutants on the subway contain "high levels of some metals," particularly on Line 2.

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"Air quality data collected in the Toronto subway system shows that, as is the case for other similar subway systems, levels of fine particulate matter air pollution (PM2.5) are elevated," said De Villa.

In the wake of the study, city councillor and Toronto board of health member, Joe Cressey, is also encouraging commuters to continue riding the subway.

"Toronto Public Health conducted a comprehensive health impact assessment of Toronto's subways. The conclusion — riding the TTC is a healthy choice. Like subway systems around the world, with more work we can still improve air quality."

De Villa says that while Toronto does demonstrate leadership in addressing subway air quality, she recommends the TTC should implement short-term "mitigation actions," including employee awareness and training programs.

The city's medical officer also recommends the TTC's board should identify medium and long-term mitigation measures that can be implemented to further improve air quality in the TTC's subway system.

This includes reviewing operational systems and procedures, such as automatic train control, train frequency, and ventilation systems.

Additionally, De Villa says city council should ask both the TTC board and Metrolinx to continue monitoring levels of the air pollutant in the subway system and to consider air quality in future city initiatives.

Toronto Mayor John Tory said making the subway safe for passengers and employees is his "number one priority."

"This includes making sure our subway system is absolutely safe for all those who use it — whether they are transit riders or TTC employees," said Tory in a statement.

Toronto Public Health launched this study in 2017 after the Board of Health requested an independent study of the health impacts of air quality for passengers in the subway system, particularly in relation to mitigation measures that could be implemented.

"Back in 2017, I said that it was not acceptable that the TTC hadn't conducted a new test on air quality since 1995 and welcomed this new study so we could confirm that we are on the right track and . have current information to help guide future work," said Tory.

"I am committed to making sure the TTC continues this work in the existing system and in all future subway projects."

You can find all past reports on the air quality on the TTC here.