First, in case you think I'm beating a dead horse, i'll make short shrift
of the so-called 380 tons of 'missing' HE in Iraq.
The jury is still out about what happened to it: sloppy bookkeeping and archived records?
slipshod military clerks? Or maybe it was theft?
[requiring at least a dozen tractor-trailers, or over three hundred Toyota
pickup trucks to move]...Yea! I'm being deliberately silly, but making a point....380 tons isn't a small load that can be easily concealed or moved without someone noticing.

If you live in North America, I wouldn't worry about it directly affecting you....

I'd me more concerned about 300Ibs of high-explosive stolen from
a California quarry several months ago, and the FBI and BATF have not
located it or the culprits yet...The longer it goes missing, the more likely it will be used....Al Qaeda cell, or wannabees, anyone?

And 'dirty' bombs? ...They maybe easier to make than one thinks.
The radioactive material may be as accessible as the Nevada desert.
Remember, that's where the US Department of Energy carried out alot of nuke
tests...A lot of radioactive material out there [Strontium, Cesium, Barium isotopes, etc.]. Not all of it on fenced-off military property.