Will Falconer, DVM Moderator
Addendum: it appears I (and my guest) were misusing the word "bioconcentration." What we should have said instead is "biomagnification," which is the increasing concentration of toxins the higher up the food chain the eater lives. That's what I was referring to with the DDT and bald eagles example that I grew up with as a budding biologist.
Wikipedia does a decent job of explaining both, for those interested.