Bathroom Tiles -- non-toxic adhesive

Don't use painted wallboard. It should be cement board. Otherwise water will get through the tile and mold will feast on the wallboard.

If you're tiling a wall in your bathroom that isn't exposed to water (i.e. outside the bath/shower, such as next to the toilet) then drywall is fine. There's no need to have an entire bathroom covered with cement board. I would knock down the existing paint with some sandpaper first though. It doesn't have to be sanded completely off, but should be roughed up enough so that it's no longer shiny.

As far as your original question, why not use thin set?

check http://www.greendepot.com/greendepot/

Too much is being made of this "outgassing" silliness. The gasses dissipate after a week or so. It's not like radioactive material, where it *radiates* toxins over the course of its life.

Agreed with NYCMatt. Gas will dissipate after a week MAX, most likely within first 3 days after applying the adhesive.

When you stay at Four Seasons, can you smell the adhesive gas in the bathroom? or develop any allergic reaction to the bathroom tiles in your room?

EVERYTHING is toxic to some degree. Some people even go to extraordinary lengths to find "low outgassing" furniture!

The irony here is that these same people use computers and laser printers that "outgas" toxins at many hundreds of thousands of times greater than their paint, carpets, sofa, or the glue behind their bathroom tiles.

What kind of "adhesive" is used for tiles? I thought it's just an old-fashioned thinset/mortar type of thing that's been around at least since Roman times.

There's a lot to sweat in life. So long as you aren't eating the adhesive, I wouldn't focus too much on this.

mastic is adhesive for tiles, but i think most people use thinset esp for wet areas

Use cement board and thinset mortar for wet areas around showers and tubs. I would continue this throughout the entire bathroom if you are installing floor to ceiling tiles. If no floor to ceiling tile use moisture resistant green board for the rest. You can use mastic on drywall for things like kitchen backsplash.

I'm with matt and the others and tend to worry more about what I'm breathing outside my apartment.

I thought mastic is for commercial vinyl tiles, not ceramic or stone. Go figure.

Mastic can be used for anything. They make a waterproof and mold resistant mastic for baths and showers too.. I've ripped apart a few bathrooms that used green board and mastic behind bath and shower tile and they were solid. I've also ripped apart some that you could push your finger through. As far as I'm concerned the right way is cement board, a schluter type membrane and thinset, but that's me and I'm not a pro so take it for what its worth.

These are all perceptive comments; thanks to all. I've learned a lot.