To be honest even the shipping of actual currency isn't especially secretive. (Probably so as to not draw attention.) Eighteen tons worth of twenty dollar bills...
There are things more hazardous than ADI's powders being shipped as a matter of course.
The most secretive product (apart from Naval Intelligence work in a former role) shipped around the Pacific was in fact - concrete. All involved were sworn to secrecy. It become plain to me that we were shipping thousands of tons of concrete each month to Mururoa Atoll on behalf of the French government. They must have concreted that whole island after they stopped nuclear bomb testing.
