We were a few hundred recruits who were exposed to it at that week and everyone seemed to be fine next day.
I'm fourty now and I've never experienced any problem that I would guess comes from my experience with tear gas.
(FWIW, I was exposed to it in a closed room but only briefly, not more than a minute or so I'd guess, possibly less.)
I'm not saying there isn't something worth protesting right now, but the timing is far from ideal.