Those paintballs are filled with oleoresin capsicum (OC) which is a far more persistent and "persuasive" substance. Getting hit with a CS paintball would be ineffectual due to the small amount and the fact that it wears off quickly.
What "long term side effects" does CS have? The US Army (at least) routinely puts all soldiers through a CS filled gas chamber as part of chemical warfare training and has done so for decades.
There are no longitudinal studies, because it is very difficult to find a sample of repeatedly tear-gassed subjects over relatively long timeframes. Hong Kong is a good example though, where estimates are that ~90% of the population have been exposed. In Hong Kong, long-term exposure has been connected with rashes, respiratory problems and chloracne.
I see from another reply from him that herewulf that you reply to has been repeatedly exposed to concentrates cs over multiple years.
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.
What "long term side effects" does CS have? The US Army (at least) routinely puts all soldiers through a CS filled gas chamber as part of chemical warfare training and has done so for decades.