OT: Mercury (Was: BBS software for the PDP 11)

[Cameron Kaiser]

> > https://en.wikipedia.org/wiki/Karen_Wetterhahn
> > http://i.imgur.com/0dXdc.jpg
> >
> >	Karen Wetterhahn spilled a drop of a Mercury compound on her latex
> > glove, and died of it 10 months later. 
>
> I have a hard time getting my head around Dr. Wetterhahn's poisoning.  How
> many molecules of the toxin could have possibly entered her body?
> How many molecules does it take to kill or fatally disable a cell?  After it
> does its damage, does the molecule become available again to do
> more damage?  How many cells in her body were actually killed?  Do the
> molecules somehow target the cells required to kill an individual?
> If you killed just the "right" cells, how many cells does it take to kill a
> person?

I can't answer the cell count, but I can give a general answer on the rest.

Mercury interferes with multiple enzymatic processes -- some of them
permanently -- and it can be slow to metabolize (half life of approximately
two months), meaning even a small dose can destroy a lot of cells. The central
nervous system is at greatest risk because these enzymes frequently repair
oxidative damage from metabolic processes, and nerve cells have high rates of
metabolism for processing.

As mentioned, mercury compounds are often far more toxic than the pure form.
Dimethylmercury is especially effective because the extra methyl groups enable
it to very easily enter the body and pass through cell membranes but
only very slowly be eliminated from it; some metabolites can actually bind
to tissues and remain. In this case, as little as 0.1mL is enough to cause
severe or fatal poisoning according to the OSHA bulletins I have here because
it will enter cells and accumulate there. Once it reaches the central
nervous system, that's it. The NEJM article on the Wetterhahn case (read:

	http://www.nejm.org/doi/full/10.1056/NEJM199806043382305

) estimates a lethal dose of the compound would be about 5mg/kg body weight.

(As an aside, though, mercury-containing antiseptics such as thiomersal
"Merthiolate" and merbromin can be safe and effective sterilizers in very
low concentrations. They work through the oligodynamic effect. I grew up
with my mother wielding the Mercurochrome whenever I'd get a cut, and I think
it was unfairly removed from the market -- not due to toxicity, but because
it was a generic product with no profit potential, so the pharmas wouldn't
do the studies and the FDA classified it as "non-GRAS" along with a number 
of other orphaned compounds in 1998. It is still very common outside the US.)

In the Wetterhahn case, latex and PVC gloves are also easily penetrated by
the compound (including those she was wearing), affording her no protection
at all when it spilled on her and was able to pass through her skin into the
bloodstream. It is also possible part of her toxic dose came from vapour,
although the fume hood should have reduced this. By the time her symptoms
indicated that she had indeed received a toxic dose, chelation therapy would
have been ineffective, as it indeed was. The estimated total dose per the
NEJM article was about 1.3g of mercury, over three times the lethal amount.

Don't mess with it.

(MD, MPH)

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