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Subject: Terminology


From: Simon Hogg <s.hogg>
Date: Thursday, August 8, 1996
>>Don't be fooled about the term "non-toxic."  It means that when a
>>product was tested, a complete kill did not occur. It does not mean
>>that it was without toxicity.  Kind of scary when you think about
>>children's toys.
>Please don't forget that, 'all things are poison, all things are
>essential, it just depends on the dose'. Water, common salt and
>carbon dioxide are all toxic if taken in excess but we would all
>accept that they are generally regarded as 'non-toxic'  Words like,
>'safe', 'non-flammable', 'clean', 'archival', etc., etc., can be
>defined to a level where they are meaningless, please let's accept
>common sense in this forum.
> Colin Williamson

This may be only a semantic point, but, then again ...  There is a
difference between toxic, poison, etc.  Each has its own particular
meanings, and although people use the terms interchangeably, this is
not always possible.

Here in the UK (EC, etc.) chemicals [that's another kettle of fish -
when is a chemical not a chemical,] when bought will quote on the
MSDS (Material Safety Data Sheet) the toxicity, mutagenicity,
carcinogenicity, LD50, and others (if known.)  A poison is a special
case, and something that is listed as a poison has its own special
handling procedures (and is not the same as *toxic*.)  I don't know
the legal definition of toxic, but I think it is more strict than as
stated above.  Non-toxic doesn't mean totally safe, but the
statement above implies that toxic only applies to those materials
where a 'complete kill' occurred.  This is vague, and the notion is
better expressed in terms of LD50, or similar.  Non-toxic is likely
to apply to those materials where the LD50 is below a certain level,
and related also to the exposure potential.  If something shows
toxic effects at a level of 50g per kg of body weight, but the
maximum exposure will be 1g total, then there can be little risk of
toxic effects.  (e.g. the 'apple juice' and plasticiser scares of a
few years ago.)

As a comment on the second point, I wouldn't count carbon dioxide or
water as toxic (not sure about common salt tho')  Carbon dioxide is
an asphyxiant, but carbon monoxide is toxic (but
non-cumulatively--another book!)  It's like saying being hit by a
car is toxic when it isn't--though it will probably kill you.
(conversely, not all things are essential.)

It's important to be aware of the risks of any chemicals that you or
your institution may be using, and also be aware of the preventative
measures. Ask you supplier for an MSDS for any chemicals that they
provide, and buy a good Health and Safety book.  Also be aware of
the *different* hazards--do not just say 'dangerous' or 'toxic,' but
above all, don't be scared of the chemicals--even the nasty ones.
Show respect when using them and take appropriate precautions, but
don't be scared to use them if they are necessary.

Simon Hogg
Imperial College, London, UK

                  Conservation DistList Instance 10:17
                 Distributed: Thursday, August 8, 1996
                       Message Id: cdl-10-17-004
Received on Thursday, 8 August, 1996

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