Acid does not stay in your body forever, it does not build up in your spinal cord. Those are myths. Nor does acid contain bleach. It is LSD-25, or lysergic acid diethylamide, or sometimes acid sold today is ALD-52, a vey similar chemical. The dosage for acid is so small, that even if there was bleach, or strychnine, or many of the other chemicals claimed to be in it, the amount would be so small that it wouldn't poison you.

You can get flashbacks, but that probably won't happen from moderated use. However, you should look up HPPD(Hallucinogen PErception Persisting Disorder), and go to one of their message boards. Some of them claim to have gotten "flashbacks" from very few uses.

If you decide to do it, the risks are mainly psychological. You aren't going to poison yourself if the acid you get is legit. Research on erowid and find out, because there is a lot of false information all over the place.