How do you know if buttons are safe for scrapbooking?

I’d like to use buttons in my scrapbooking pages, but I don’t want to pay the price for what they sell in craft stores. What materials are generally safe (acid/lingin-free) to use on scrapbook pages?

Go to CropMom at http://www.cropmom.com and use your photos and CropMom’s graphics to create your scrapbook. They have thousands of graphics including buttons. It is fund, easy, and safe.