The plastic tanks cracked because of the liquids sitting in them for a prolonged period of time. As long as you don't hold the liquid in your mouth, you should be fine.
Disclaimer: I am not a scientist, nor am I a dentist. I am not a chemist. Take anything I say as coming from someone that has a tiny bit of common sense and applies what I know about liquids in tanks to liquids that are in a different state (vapor) that are bypassing the teeth (pretty much) and going to the lungs.