It's safe to drink water boiled in this glass IF no poisons have ever been put in the glassware. Borosilicate is the glass originally used to make Pyrex cookware--in Europe they still use it, but in...
Because the actual metallic salts added to the glass are unknown, the addition of some fluids (acids, or very hot liquids) could create a reaction. But most of the material is fused into the glass...