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The answer to whether or not silver is, indeed, a
heavy metal, is not as easy to answer as would first appear. This document
looks at the legal, medical, and scientific qualifications of the term "heavy
metals", and questions both the common belief and relevancy of
the term "heavy metal".
Silver
in the News...March 2004
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 A Silver polymer which
releases silver ions ( Ag+ ) was found to be effective against the
SARS virus:
“ We tested the
compound against a four-hour, eight- hour, and 24-hour exposure period
and found no surviving SARS virus upon 24 hours of exposure to the
polymer...”
- Zhang
Panhe, professor at the Chinese Academy of Military Medical
Sciences
Read More: Silver Ions Effective Against SARS
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Why There is No Scientific of Medically Significant
Basis to Classify Silver as a Heavy Metal
Historically, There is no Consensus on a Scientifically Valid Definition
of Heavy Metal
"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."
- John H. Duffus, The Edinburgh Centre for Toxicology,
Scotland, "Pure and Applied Chemistry" 74, 793–807
Bjerrum’s Inorganic Chemistry contains the earliest
reference to the term "Heavy Metals" in chemistry, published
in 1936. Bjerrum defined heavy metals based on density. Any metal with
a density greater than 4 g/cm3 was thus considered
to be a heavy metal. However, Bjerrum's definition was never accepted,
nor used as a formal or official definition of a heavy metal. However, there is no relationship between density and
any reactive properties associated with metals, or any other element
in the periodic table. Heavy metals were redefined based on a gram
atomic weight, and also by the atomic number on the periodic table
( with many variations in "opinion" of the starting number
). By some of these "official" definitions of what a heavy
metal is, both Magnesium and Potassium are classified as heavy metals. The most widely used toxicology reference, Casarett and
Doull’s Toxicology, never uses the term “heavy metal”,
but only references toxic metals. This is most likely due to the fact
that the heavy metal classification, in any historical or modern form,
lacks scientific validity. A few thoughts by Stephen J. Hawkes of Oregon
State University, Department of Chemistry, demonstrate an
interesting perspective:
"The metals that I have seen referred to as heavy
metals comprise a block of all the metals in Groups 3 to
16 that are in periods 4 and greater. This seems to be a
definition that should be generally useful. It may also be
stated as the transition and post-transition metals. These
acquired the name heavy metals because they all have high densities,
but the usefulness of the term is related to their chemistry, not
their density. It is not necessary to decide whether semimetals should
be included as heavy metals, which is fortunate, since it is unlikely
that any decision would be generally agreeable."
From a chemical standpoint, the above definition is satisfactory.
However, it is clear that this definition of "heavy metal" may
not in any way be related with suspected toxicity, but has meaning
only pertaining to specific chemical properties. Hawkes also places the whole "controversy" in
rather comical perspective by sharing a chemistry teacher's answer
to the question: What is a Heavy Metal?
"I asked this question of my introductory chemistry
teacher over 50 years ago. He replied rather hesitantly, "A
metal that behaves in a heavy metal manner." A vague term requires
a vague definition, but just what is a 'heavy metal manner'?"
Medically and Legally: Classification of Heavy Metals
is Dependent on Regulatory Agency
Silver, medically, does not share the toxicology associated with what
are commonly described as heavy metals, and technically referred to
as "toxic metals", such as mercury, cadmium, arsenic and
lead.
Legally, the definition of what is or is not a heavy metal varies
depending on which regulatory agency one queries.
As an example, According to SIGNA's medicare qualification documents, silver
is not classified as a heavy metal. The most logical explanation
for this is simple: Silver does not pose the same health risks as
toxic metals, and there is no medical regularatory agency in the
world which claims that it does.
Summary
Is silver a heavy metal?
Silver, medically, does not share the toxicology associated with what
are commonly described as heavy metals. Legally, the definition of
what is or is not a heavy metal varies depending on which regulatory
agency one queries. According to SIGNA's medicare qualification documents,
silver is not a heavy metal.
The term heavy metal is not truly a scientific term, and there has
never been consensus on the meaning of this term in the scientific
community. Classification of "heavy metal" has never been
scientifically based on any actual quality associated with any element,
although many adaptations to the periodic table have been attempted.
There is no basis from a biological standpoint, a chemical standpoint,
or any other scientifically demonstrable standpoint including any medical
significance that would suggest any actual significant meaning for
the term heavy metal as applied to silver, or any other metal.
Please see the following references for further details:
http://www.iupac.org/publications/pac/2002/pdf/7405x0793.pdf
http://www.cignamedicare.com/partb/lmrp/nc/cms_fu/2001-006.htm
http://jchemed.chem.wisc.edu/Journal/Issues/1997/Nov/abs1374.html
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Content Copyright 2007 AVRA unless otherwise specified
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