Worms were said to be Darwin’s favorite organism, and for good reason: it seems they can break down most anything. Studies have shown they can detoxify soil with cadmium, lead and other heavy metals.

Worms Produce Another Kind of Gold for Farmers
www.nytimes.com/2013/01/01/science/worms-produce-another-kind-of-gold-for-farmers.html
New research suggests that vermicompost, a worm-created soil additive, helps plants grow with more vigor, and makes them more resistant to disease and insects, than those grown with other types of composts and fertilizers. ...