Well, yes. Borates may be non-toxic, but how cleanly do you think a boron fill in this kind of configuration could burn in air?
Think about it! ItÂ’s completely out of the question !
http://www.islandone.org/Launch/boron-sharp-article.htm
Boron combustion (including air) is a very rich research field, particularly in rocketry.
They don't seem to think it's a problem leaving boron combustion products in the atmosphere.
