You can't find a definition of the term "heavy metals" that is meaningful, consistent, or agreed upon. It is a very loose term - almost meaningless. Some substances that are "heavy metals" by many definitions are essential nutrients, some have great medicinal purposes. Examples: copper, silver. Colloidal silver is a great antibiotic, and even "real doctors" are admitting that it is one of the few things that will kill MRSA without any possibility of resistance being developed. Cadmium is one of the harmful ones, but again, the levels have to be quantified.
When I worked in the d.c. motor brush industry, I was amazed to learn that brush materials used in automobiles - like in alternators and starters - have lead (also copper). And these are high wearing parts - dust guaranteed to be generated freely into the air. How is that allowed?
'98 LXi - Later Concorde gages (black w/ chrome rings)/'99 LX - LHS gages (white) - HIR bulbs