‘Heavy metals’ is a general collective term applying to
the group of metals and metalloids with an atomic density
greater than 6 g cm3. Although it is only a loosely defined
term it is widely recognised and usually applied to the elements
such as Cd (cadmium), Cr (chromium), Cu (copper),
Hg (mercury), Ni (nickel), Pb (lead) and Zn (zinc) which
are commonly associated with pollution and toxicity problems.