From the ad:
“In fact, plants need some heavy metals, such as zinc and copper and molybdenum, for normal, healthy growth.”
I didn’t think that those metals were considered heavy metals, so I googled heavy metals up. They aren’t true heavy metals, they’re part of the transition metals which sometimes are classified as heavy.
I think the advertising is somewhat deceitful. On one hand, they’re admitting that it contains heavy metal, and then implies that it’s only the non-toxic kind. Good way to protect yourself from a lawsuit. *Gee, we told them it contained heavy metals and they bought it anyway.*
http://en.wikipedia.org/wiki/Heavy_metals