The air in TTC tunnels may be more polluted than above ground in the streets of Toronto, but if you're a TTC operator you're not allowed to be concerned.

Three TTC employees were asked to leave work yesterday after showing up for the job with medical masks on, a day after a shocking report from the journal of Environment Science & Technology stated that the air quality in the TTC tunnels was equal to that of a smoggy day in Beijing.

Can you blame them? The study found that pollutants on trains and platforms were up to 10 times higher than outside air.

The three operators were sent home after refusing to remove the masks and according to the Union for TTC employees "refusing to work."

In an interview with CTV, one of the conductors said he showed up to work with the mask to help reduce exposure to pollution.

The TTC released a statement saying the "masks are unnecessary and, therefore, not permitted. If a worker refuses work, the Ministry of Labour is called and that has happened."

The TTC also claims updates have been made to improve air quality since the research was conducted and there's no major cause for concern.

Our Mayor, however, begs to differ. Tory thinks it's unacceptable that the TTC hasn't done more about air quality.

No word yet on if the three employees have returned to work, mask-free.