US Pharmacopea, products given this grade are suitable for use in pharmaceutical applications, and they usually have an FCC grade too, FCC is the Food Chemicals Codex, which means they are pure enough to be consumed or used cosmetically by humans.
Chemicals of USP grade are often more pure than lab/reagent grade I believe, because there are specific limits of contaminations like heavy metals, etc. that may have higher allowable limits in lab grade chems.
-blaaky