I think an acrylic surround will off-gas. How much and for how long I can't say.

We had an acrylic surround at our last house. I would never ever have another. They are not very easy to clean, and seem to always look water spotted. Tile, on the other hand will good for the life of the tile. Stick with the tile and leave the plastic and silicon for some industrial use. Who needs an industrial strength shower anyway, no matter how long we've been out working in the garden? :~)

Depending on how much you need to make the surround like most surrounds (with built-in soap holders and the like), you could consider a product like 3form's resin products. You would put up flat panels and then add things like soap holders and towel bars, but it would be attractive, would give you looks you could not possibly get with ceramic or glass tile, and would be easier to maintain than grout. Don't forget -- with tile you'll be buying a product that sometimes is produced under questionable working conditions and is very heavy despite being transported hundreds (or thousands) of miles. I'm considering 3form for my kitchen backsplash.

Here is a link that might be useful: 3form products

the "silicone backing" would offgas too much for me

Bill