Zeus
That is scary stuff.
That's one of the reasons why I refuse to compost "found" yard waste!
Clopyralid does break down in compost but has a half life of up to a year or more, nasty stuff.
I'm a little peeved that it can be purchased on line when it has been "Deregistered" by the manufacturer to use on domestic lawns (wiki)
Don't want to derail this thread but
Here is a great site about persistent herbicides.