I'm going to take a guess and say if it is used for pool water, it's not toxic. :P

Bactacil, something similiar sounding to that, is a non-chlorine alternative to chlorine that I've heard of. Does your mom do her own, or does she have a pool guy come over and take care of it? If the latter, ask them. If she does it herself, the cannister/box should have the manufacturer's telephone number on it- I'm sure they've been asked this question more than a few times.