Chemistry International
Vol. 24, No. 5
September 2002
Highlights
from Pure and Applied Chemistry
"Heavy
Metals"A Meaningless Term? (IUPAC Technical Report)
by J.
H. Duffus
Pure and Applied
Chemistry, Vol. 74, No. 5, pp. 793-807 (2002)
Over the
past two decades, the term "heavy metals" has been widely
used. It is often used as a group name for metals and semimetals (metalloids)
that have been associated with contamination and potential toxicity
or ecotoxicity. At the same time, legal regulations often specify a
list of "heavy metals" to which they apply. Such lists differ
from one set of regulations to another and the term is sometimes used
without even specifying which "heavy metals" are covered.
However, there is no authoritative definition to be found in the relevant
literature. There is a tendency, unsupported by the facts, to assume
that all so-called "heavy metals" and their compounds have
highly toxic or ecotoxic properties. This has no basis in chemical or
toxicological data. Thus, the term "heavy metals" is both
meaningless and misleading. Even the term "metal" is commonly
misused in both toxicological literature and in legislation to mean
the pure metal and all the chemical species in which it may exist. This
usage implies that the pure metal and all its compounds have the same
physiochemical, biological, and toxicological properties, which is untrue.
In order to avoid the use of the term "heavy metal," a new
classification based on the periodic table is needed. Such a classification
should reflect our understanding of the chemical basis of toxicity and
allow toxic effects to be predicted.
www.iupac.org/publications/pac/2002/7405/7405x0793.html