Why would the military carry out this test/experiment/exercise over a moderate to heavily populated area? Don't they have designated ranges for popping stuff out of aircraft?
In an industrial situation you are obliged to dress up; suit, boots, gloves, eye protection; and have a breathing mask when you work with this stuff. If I was a citizen there, I would expect at least a pre-operation notice in the local print media, with instructions about what to do if you find clumps of it.
It is just thoughtless at best and arrogant at worst on the part of the military to operate like this in the civilian domain. Unforch this is not confined to the US - the military the world over works like this; live firing starts bush fires in
Canterbury, NZ and in Australia, and
noise issues from firing ranges.