BBC Report on Anthrax and a new way to spread it

I’ve just heard on Radio 1 that a BBC reporter has found documents explaining how to launch an anthrax attack by sending helium ballons up 10Km and then exploding them. Can this work? What amount of anthrax spores would you have to come into contact with to become infected?

From what I’ve heard in the past month or two, the general view is that you need a pretty good quantity of the stuff to be effective. That’s why you need a crop duster to strafe the Rose Bowl, rather than just firing a shell or exploding canister from the neighborhood down the street. Or an envelope that you’re opening in front of your face. Having said that, I imagine your balloon would still get some little old ladies (and men) as in Connecticut, and others who have weak immune systems.

From what I’ve read, you’d have to do this at night, because UV light would kill nearly all of the spores. Another problem would be that from that altitude, you couldn’t be sure that you would be hitting any particular target as upper air streams would send the spores every which way.

Still, I wouldn’t want to be underneath such a balloon.