Re: Mercury Risk?

From: Ian Goddard (
Date: Sat Mar 17 2001 - 10:17:04 MST

Sorry to reply after such a duration... a busy week!

At 07:56 AM 03/07/2001 -0800, Spike Jones wrote:

> > >First, 300 mcg Hg/m3 is not equal to 0.3 mg/m3, but let
> > >us ignore that, since I didn't use it in my calcs.
> >
> > IAN: 300 mcg = 0.3 mg, or not? Or is that your point?
>Ian I was hoping you would let me slide on that one since
>Im not accustomed to the unit mcg. {8^D But if I had to
>guess and my lazy ass failed to look it up on the web, I
>would think it is a milli-centigram. 300 of these would be
>3 mg. Had they meant 0.3 mg, would they not have said
>300 microgram? {8-]

   IAN: I couldn't let you slide on that one, it
   (the conversion of micrograms to milligrams) was
   pretty much the only thing I added to the topic. :)

   Unfortunately I also disagree with your volumetric
   analysis of Hg0. I'm not going to take the time to
   root out a fallacy or do the math myself, instead
   I'll cut to the quick by noting that a friend with
   far more mathematics education than I (who we both
   know) was also skeptical of the mouth-air measure
   of 0.3 mg Hg/m3. He subjected it to examination
   and concluded: "My conclusion was that I could
   not disprove the 0.3 mg/m3 figure." His numbers
   were much lower than your numbers. If in fact
   the mercury vapor mouth-air reading was incorrect,
   the researchers and the peer-review process at the
   journal Neurotoxicology would be shoddy. One would
   tend to expect that these experts would get it right:

Neurotoxicology 1997;18(2):315-24

Mercury vapor inhalation inhibits binding of GTP to tubulin in rat
brain: similarity to a molecular lesion in Alzheimer diseased brain.

Pendergrass JC, Haley BE, Vimy MJ, Winfield SA, Lorscheider FL

College of Pharmacy, University of Kentucky, Lexington 40536, USA.

Hg2+ interacts with brain tubulin and disassembles microtubules that
maintain neurite structure. Since it is well known that Hg vapor (Hg0)
is continuously released from "silver" amalgam tooth fillings and is
absorbed into brain, rats were exposed to Hg0 4h/day for 0, 2, 7, 14
and 28 d at 250 or 300 micrograms Hg/m3 air, concentrations present
in mouth air of some humans with many amalgam fillings. Average rat
brain Hg concentrations increased significantly (11-47 fold) with
duration of Hg0 exposure. By 14 d Hg0 exposure, photoaffinity
labelling on the beta-subunit of the tubulin dimer with [alpha 32P]
8N3 GTP in brain homogenates was decreased 41-74%, upon analysis of
SDS-PAGE autoradiograms. The identical neurochemical lesion of similar
or greater magnitude is evident in Alzheimer brain homogenates from
approximately 80% of patients, when compared to human age-matched
neurological controls. Total tubulin protein levels remained relatively
unchanged between Hg0 exposed rat brains and controls, and between
Alzheimer brains and controls. Since the rate of tubulin polymerization
is dependent upon binding of GTP to tubulin dimers, we conclude that
chronic inhalation of low-level Hg0 can inhibit polymerization of
brain tubulin essential for formation of microtubules.

Visit Ian Williams Goddard --->

    "The more restrictions and prohibitions in the world,
      the poorer people get." Lao Tzu (Tao Te Ching)

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