It is actually fiberglass. We have a habit of calling it vinyl here for some odd reason though.I don't find any reference to availability of vinyl window screen -- presumably fiberglass is what is meant. Aside from that, vinyl wouldn't be a very safe choice for animal contact, as it is a relatively toxic material.
Polypropylene, on the other hand, is generally considered the safest plastic in common use (far more safe than, for example, the styrene that ExoTerra frames are made of).
Being using that since my first viv in 2010 and never got a complaint. Those are widely used when growing vegetables so i imagine them to be food graded and not release any chemicals as those are litterally made for growing your tomatoes and zucchini in immediate proximity and water them too...so no worries.I just know it's not great to use typical weed barrier that has plastic in it. I'm trying to go buy materials today so a quick response would be much much appreciated.