I'm no expert, but I'm told it is safe as long as it is wet (in solution).
I believe your fire department may be a resource for gettting rid of it
(bomb squad).  They got very anxious about it at my last lab!

James Britt, DVM, DACVP
jbritt@mail.arlpc.org
Livestock and Poultry Commission Lab
#1 Natural Resources Dr.
Little Rock, AR 72205
501-907-2435
501-907-2410 (fax)