eitland has been exposed to concentrated cs at least once, Anigbrowl multiple times including more than just once just this last week and it seems to be common in military training from what I read so I guess it is in fact well studied and reasonably harmless compared to many alternatives.
That said I agree with a number of people here that in most cases the best alternative might be to talk to people instead, and to not kill suspects in custody, obviously, and also to not handcuff and throw people on the ground when all that should be necessary was to ask simple questions.