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{\bf Appendix~6}\\
{\bf Mercury Hazards in the Laboratory}
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\noindent OVERVIEW:  ``In the final analysis, there are no non-hazardous substances; 
there are only non-hazardous ways to use substances or levels of substances 
whose use poses no hazard.'' J.L.~Steinfield, at hearings on {\bf The Effect of 
Mercury on Man and the Environment}, U.S.~Printing Office, 1970

 The use of mercury in open manometers, barometers, plus
spilled mercury from broken 
Hg thermometers etc.~means that most laboratories have the potential for  
toxic effects from inhaling Hg vapor or from ingesting mercury. 
Since the vapor pressure (v.p.) of Hg is a sensitive function of 
temperature, the biggest hazard is from Hg contaminated hot surfaces.
Unless the room is tightly closed, the v.p.~of Hg 
generally is far below equilibrium: good ventilation is the simplest 
way to keep the Hg concentration negligible.  

 {\bf What are the toxic effects?} Ingestion of mercury compounds may give acute 
poisoning and result in death within a few days.  Other than suicidal 
intent, this is rare though organo-mercurial compounds can be concentrated 
by the food chains and many deaths in Japan finally resulted from eating 
fish badly contaminated with organo-mercurial compounds.  In the 
laboratory we are instead primarily concerned about possible chronic effects 
from extended exposure to the much less toxic metallic mercury vapors.

 Early signs of chronic Hg effects include slight digestive disturbances, 
(in particular anorexia), intermittent tremor, neurotic disorders.

\noindent ENVIRONMENTAL EXPOSURE:
Soil Hg ranges from 25-625~ng/g, highest in organic soils. 
Fossil fuels can contain 20 ppm 
(e.g.~some California crude oils); rain and snow $\sim $~0.2~$\mu $g/L;
unpolluted ocean samples 5-6~ng/L.
Ambient air contains $\sim $~0.05~$\mu $g/m$^3$, but in industrial areas and 
near agricultural fields treated with mercurial fungicides 
levels may run 10-15~$\mu $g/m$^3$;
well water generally has $\leq $~0.025~$\mu $g/L; 
however, human urine from those with no known exposure to Hg runs 
1-25~$\mu $g/L: food consumption alone provides $\sim $~25~$\mu $g of Hg per day. 
(The body rids itself of Hg primarily 
through the urine and fecal matter; the biological half-live of Hg in the 
body is $\sim $~60~days).
The Hg in human blood (of those eating few fish) runs $\leq $~10~$\mu $g/L 
whereas blood of heavy fish eaters may exceed 200~$\mu $g/L!  
Dental amalgam fillings gave breath levels
of mercury from 0.1-6.2~ng/L compared to $\sim $~0.06~ng/L for those with no 
amalgams.  Conclusion: organo-mercurial compounds 
concentrated in the the fish food chain seem to be the main route of exposure 
for the general population.  

 {\bf What concentrations of metallic Hg vapor
should one worry about?} OSHA's maximum allowable figure of 100~$\mu $g/m$^3$ 
in air is $\sim $~2000 times the normal air concentration, though only 
$\sim $10 times that in some industrial areas or near agricultural fields treated 
with Hg fungicides; however, there is some evidence that the OSHA limit has no 
margin of safety for some sensitive individuals.  Certainly 
continual breathing of 15,000~$\mu $g/m$^3$ (15~mg/m$^3$)
for several weeks makes most persons seriously ill. 

 {\bf What housekeeping procedures and precautions 
should one follow?} Take care to avoid Hg spills; if one occurs, the 
floor may be wetted (to reduce the v.p.~of Hg) and the Hg picked up 
immediately: a small steel pipe connected to a suction bottle by small bore 
rubber tubing facilitates the clean up.  Cracks in wooden floors may be 
cleaned with a wire brush and a solution of calcium polysulfide applied to 
react with missed metallic Hg.  (Or use a Hg spill powder of 85 grams of 
powdered sodium thiosulfate [``hypo''] with 15 grams of EDTA: ethylenediamine 
tetra acetic acid.  Sprinkle on the spill area, wet with a water mist and 
let sit overnight.)  Improved ventilation of course reduces the 
Hg concentration.

 If one has a large mercury spill (e.g.~from a manometer), call the UW 
Safety Department (262-8769) for help in the clean up: they have a special 
vacuum cleaner for mercury.

\noindent REFERENCES: D'Itri, {\bf Mercury Contamination} John Wiley \& Sons, 1977;
{\bf Toxicological Profile for Mercury}, U.S.~Public Health Service, 1989;
Clark Goodman, {\bf Mercury Poisoning}, Rev.~Sci~Inst.~9, 233, 1938.

\noindent AN INTERESTING ASIDE: {\bf Did Newton suffer mercurial poisoning}?  

J.R.M.~Seitz (Harvard) and 
J.Y.~Lettvin (MIT) argue that Newton's problems around age 50 were not 
psychic trauma following his mother's death but Hg poisoning:  Newton's 
``Optiks'' describes in detail how he worked in closed rooms exposed to 
kilograms of mercury.  They estimate that the vapor level exceed by a 
1000 fold factor that necessary for Hg poisoning.  This was also the time 
that Newton's handwriting became tremulous.  They also cite Newton's 
fondness for crimson rooms which at that time were likely painted with 
vermillion pigment (ground up cinnabar ore: HgS).  {\bf New Scientist}, 52, 
274, (1971).  

 Andrade (``Sir Isaac Newton, His Life and Works'', 1954) 
estimated that 
Newton devoted almost a quarter of his efforts to chemistry and alchemy.  
According to his secretary (Humphrey Newton, no relative!), Sir Isaac 
Newton while writing the ``Principia'' was also carrying out chemical 
experiments using a brick built furnace which he had constructed with his 
own hands and which he ran continuously six weeks at a time!



