Everything I've read about rayon states that it is the best wicking material on earth... To be fair, most of my reading is on the rayon thread. If it's awful for me, I'm not sure I want to know (I do have plenty of unbleached cotton pads around) but the washing and cleaning is somewhat comforting, so I'm not sure I'll be reading further.
Given you can clean wounds with hydrogen peroxide and also ingest it as a vomiting agent, I'd have a bit of a hard time taking that terribly seriously, health wise. I mean, yeah yeah, I know about like, things in the lungs being different but I'd probably have an easier time with it than bleach.
Then there is the "used several years with no problems" but, and while I TRY to like, not place undue weight on my own lived experience, that is hard at times, so that would be another factor.
Although I will say it's not like unbleached cotton of various sorts is crazy expensive so unless you are going with familiarity and convenience mode, I'm going to guess it would also be fine for you to start using some dedicated for vaping cotton, it couldn't hurt.
Also I mean rayon's been around a fair amount of time for vaping, too? Haven't heard of any issues, and then there is my question: just how much issues can wick give you if it's not drenched in hemlock, etc. I'd say some of the impurities are going to be on a fairly low scale, period.
But again, I am speculating so everyone should just do what they are comfortable with, I guess. I don't want to return to the path of leaky wick that has to be rewicked every 10 minutes, so I freely admit I am biased in this area.
Also, yes, as a long term (reformed, now that my hair is platinum sliver!) dye-er, you'd be surprised at how easily hair can be killed off, etc. Bleach happens to be particularly bad, I might not use bleached ANYTHING, unless it went through some sort of purity process (I don't think boiling it would be enough, but again, Opinion, etc.)
Anna