RT @jasmith_yorku
Switching out the particulate matter filter on my @Prescientx1 [breathe] respirator. I use this one primarily on the subway here in Toronto (and another one with the thinner bioaerosol filter while teaching).

Why #TTC employees work in the subway without masks boggles my mind.

@GuelphMarket @jasmith_yorku WOW. It would be interesting to do a physical and chemical analysis of that soot and see what it is. Street dust is one thing but subway brake dust is worse. Or maybe not.