Well Bruce, does that not tell you something interesting about the degree of
metal exposure in your subjects ? I think it's a bit sinister that a rather
low level chelation challenge can remove Hg and other (presumably toxic ?)
metals into the urine in measurable quantities.
Yes, everybody agrees that organic mercury is highly toxic and there is
another (separate) controversy about the level of organic mercury ingestion
by people who eat lots of certain kinds of fish (e.g. canned tuna - the tuna
fish being at the top of the pelagic food chain and hence concentrating in
its tissues mercury from other species).
However the scientific literature is stuffed full of data on the harmful
effects to human health of inorganic mercury, which if I was to summarise
here would make this a rather lengthy message (look for example at
http://www.amalgam.org). The difference with the literature on methylmercury
is that many of the unfortunate individuals who have been poisoned in this
way have high levels of mercury in their systems, suffer from acute exposure
symptoms, live in geographical clusters and can be examined in more or less
the same way as experimental animals. These factors usually do not apply
with inorganic Hg exposure, which often involves a degree of individual
hypsersensitivy to very low levels of the metal. The proof of the pudding is
whether the symptoms recede when the mercury is removed. Most people seem to
tolerate their fillings without harmful effect, but dental amalgam is so
widely used that there are nevertheless many people who react adversely. A
common clinical finding these days is gastro-intestinal Candida overgrowth,
which may not immediately be associated with immune suppression in the GIT
caused by leaching of inorganic Hg from fillings.
For those of you who are interested, this is by no means a new controversy -
dating back to the mid-19th century - and one which has not seen a
scientific resolution. I wouldn't claim to have figures, but I am told by
dentists who specialise in this area that it is an increasing problem,
possibly caused by changes in dental practice (teeth are "lined" before the
amalgam is inserted and this lining should remain intact).
Dental associations have repeatedly countered the controversy by claiming
that the Hg reacts with the other amalgam metals to form a biologically
inactive substance and by observing that dentists do not report any adverse
side effects in their patients. Long-term use of dental amalgam continues to
be offered as evidence of its safety (similar to the cigarette story that "I
've smoked them all my life and I ain't dead yet"). I do not find these
arguments particularly compelling, nor the argument than those who raise the
issue is are "quacks". Mercury is, of course, a cumulative poison and if you
get a renal or brain tumour 20 years later, you are unlikely to go back to
your dentist and complain. Don't expect any double-blinded trials, either.
Nick Miller,
London
-----Original Message-----
From: Clinical biochemistry discussion list
[mailto:[log in to unmask]]On Behalf Of Bruce Campbell
Sent: 26 May 2003 01:22
To: [log in to unmask]
Subject: Re: Mercury Level and dental amalgam
The fact that a challenge test with a chelating agent shows that a quantity
of a particular element can be removed from the body proves nothing in
itself. Since we installed an ICP-MS I have had the chance to have a look
at the results of challenge tests with several chelating agents and the
amounts of a variety of metals that appear in the urine are striking.
I am not aware of any evidence that the amounts of inorganic mercury
leached from dental amalgams cause toxic effects other than rare cases of
intra-oral mucosal hypersensitivity. Methylmercury is a lot more toxic but
even then it is hard to demonstrate effects from chronic low-level oral
exposure. The only data I know of is that on methylmercury from whalemeat
in the offspring of pregnant Faroe islanders.
Bruce Campbell
****************************************
Bruce Campbell FRCPA FAACB
Sullivan Nicolaides Pathology
Ph 61 (0)7 3377 8672
Fax 61 (0)7 3870 5989
Email [log in to unmask]
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