[jayventura]

> so any bio-accumulation of heavy metals or similar should be minimal

What is "minimal"? Bioaccumulation isn't a magic meter that says "everyting below this trophic level is safe to eat." It depends on the persistent toxin ( I choose the word toxin because bioaccumulation can occur for chemicals beyond heavy metals, like organochlorine pesticides ) that you're looking at, and what is the safe dose for humans.

E.g. let's say you have pesticide A and pesticide B. Cattle eat a certain amount of feed per day. At time of slaughter, pesticide A and B have a certain amount of concentration in fat tissue. It doesn't matter which has the highest concentration, it matters which is less safe to humans and at what concentration it harms us when it accumulates in our own tissues.