Although I use it, I am always suspicious of them. When I touch them it smells so it cannot be good for fish either. If someone can confirm those regular yellow bands are safe without any special treatments, I would be able to sleep happier. 

I sent an email to the customer care address of the makers of the poly bands, asking them what the material is, and explaining that I want to use them in an aquarium.
I can only imagine the face of the person opening the email for the hair band place...lol
I am sure they have had some strange questions but I wonder if they have ever had a fish tank one. lol
Rubber bands are fine in the tank. The will "rot" over time and break loose, most often the plant that you are attaching with them will have attached by that time and you can remove it from the tank.