Hydrofluoric acid is used in high school chemistry classes.
Glacial acids (highest concentration) are actually less dangerous than diluted acids. Diluting with water causes the hydrogen and the halogen to separate into ions (the hydrogen portion of it reacts with water to form a hydronium ion, or H3O+) which are what react with other things on contact. Since HF is relatively stable and likes to stay balanced towards less separation in water, hydrofluoric acid is actually one of the weakest acids. This is because the hydrogen and fluorine do not want to separate into their ions.
Ammonium bifluoride, when mixed with water, "can release hydrogen fluoride" (hydrofluoric acid).
http://www.solvaynorthamerica.com/Si...orideFinal.pdf
This does not mean that everything in the solution is HF. It means that there may be SOME in the solution. A 9% solution of ammonium bifluoride does not mean it's 9% hydrofluoric acid. David said above that the HF will be approximately 1/3 of the percentage solution of ammonium bifluoride. I have not verified this, but if it is true, you would be looking at 3% HF.
I'm not debating effects, as I don't know anything about them, but simply discussing how reactive hydrofluoric acid is, and what's actually in that etching solution. It's my understanding that the unseparated HF is what causes cellular issues. As with any chemicals, wearing gloves is key, and safety glasses are a very good idea. I can't remember if we used a fume hood in grade 11 chemistry - it's been a while.