Such miniscule doses have nothing to do with what is being discussed.
Look at the poor kids in the Chernobyl link.
We had pastures here in UK, thousands of miles away, that could not be used for years.
You would not want to be close or downwind of a dirty bomb, even though you may feel no ill effects atthe time.
Depleted uranium can be handled without any protection.You should certainly avoid breathing the dust, but the nuclides in a dirty bomb would be really nasty.