Re: [Phys-l] Isotope chemistry and physics

["John Clement" <clement@hal-pc.org>]

Web definition:
-----------------------
Poison: Any substance that can cause severe distress or death if ingested,
breathed in, or absorbed through the skin. Many substances that normally
cause no problems, including water and most vitamins, can be poisonous if
taken in too large of a quantity. Poison treatment depends on the substance:
if there are treatment instructions on the substance's container and you are
sure it contained no other item, follow those directions immediately. Always
contact your nearest Poison Control Center if you are concerned about
possible poison ingestion.
------------------------

The common sense of the word poisonous is not very well defined as can be
seen from the above.  I would say it is most often used for substances which
are not needed for life, but which can kill us in sufficient dosages.  It is
doubtful that D2O is necessary, but over the millennia it may be that the
trace amount in water has been accommodated so its removal may be very
slightly harmful.  Has anyone looked at what happens to critters raised on
pure H2O with the D2O removed?  So using the word poisonous for D2O is
reasonable, but not very useful.

Among common things we ingest which are toxic or harmful in large doses are
nutmeg, and many vitamins.  Nutmeg is known to be hallucinogenic, but in
doses extremely close to a toxic dosage.  Fats and cholesterol are actually
necessary, but can be overdone.  Alcohol is beneficial in modest doses, but
toxic in large doses.  We would consider lead and mercury to be poisonous,
but like D2O have little effect in very low doses.  Tobacco smoke is a slow
poison.  Warfarin is used as a rat poison, but is the primary ingredient in
some anticoagulant drugs.  It is a moderately slow poison.

I would consider anything not necessary that can kill you in a few years,
weeks, or  minutes to be poisonous.  D2O would more properly be called a
cumulative poison because it is purged from your system very slowly.  This
would distinguish it from alcohol which is a fast acting poison or cobra
venom which is an instantaneous poison.  This definition distinguishes
between vitamins and venom, but leaves nutmeg and vinegar in limbo.

Common words are fun to argue over because there is often no one agreed on
definition.  But then some scientific words are not really firmly anchored.

John M. Clement
Houston, TX

> Whether D2O should be used as a solvent for medicines, etc is a separate
> issue altogether from the question I had. You classified D2O as poisonous,
> which, in the common use of the word, it isn't. In large amounts, it has
> toxic effects, but so do hundreds of other things we routinely ingest,
> such as animal fat. That stuff stays with you a LONG time and can make
> your heart fail after a few years. I'm simply asking you to not be
> sensational with your adjectives.