I've seen other posts about this but it doesn't seem a definitive conclusion has ever been reached. Maybe we can do that here in this thread. Anyway... So I had this one red acrylic straight cylinder bong for years that I smoked out of on a daily basis. It's one of those thick acrylic ones that make a clinking sound almost like glass when you tap it with your fingernail. Anyway, I was never too good about cleaning it regularly but when I did, I used the 91% isopropyl alcohol and salt method and it seemed to work pretty well. Anyway, I just happened upon a post that said you should NEVER use high percentage rubbing alcohol to clean an acrylic bong because it will break down the plastic, cause it to crack and leech harmful chemicals into the bongwater. This has got me freaked out because I used this bong daily for YEARS. I still have the bong and peering down the tube, I don't see any visible cracks or disoloration (although it's kind of hard to see down there and I have to use a flashlight). I don't ever recall seeing the bongwater turn even the slightest shade of red either. The only degradation of the plastic I can see is on edge of the rim at the top where you put your mouth and I assume that is from traction/abrasion from my lips and is very slight anyway. I actually just did a little test on the outside of the bong and rubbed some 91% iso on it with a cotton ball for a few minutes and saw no destructive effect on the plastic and no red coloring on the cotton ball. Anyway, despite seeing no cracks or discoloration (except for a bit of residual dark staining from resin build-up), I'm still freaked out by the thought that there could have been some kind of reaction on a microscopic level that leeched harmful chemicals into the bongwater all those years. Am I just being a freak or what? I have to admit, I am somewhat on the hypochondriacal side. Please either help ease my mind or give me a reason why I should consult my doctor about this. Thanks! P.S. I would also keep the plastic stopper attached to the bottom of the tube when cleaning it. I discovered the plug is made from low-density polyethylene or LDPE. It says on this site that when exposed to isopropyl alcohol "LDPE and HDPE at 20C-50C show little or no damage after 30 days of constant exposure."