Here's a huge thread on Reddit trying to figure out which mystery industry is the largest buyer of glitter: https://www.reddit.com/r/UnresolvedMysteries/comments/a8hrk0... No conclusive results yet, but I believe Reddit will deliver.
https://old.reddit.com/r/UnresolvedMysteries/comments/a8hrk0...
>defense department would be extremely secretive
>And they very much wouldn't care about the environmental impact
>A few hundred tons of glitter is significantly less bad than thousands of tons of agent orange and dioxin.
>And depleted uranium