John Sankey on tue 15 jan 08
Many substances are highly toxic to some forms of life and not to
others. Two notable examples from pottery substances:
1. Copper is lethal to most invertebrates, microbes and fungi at
1 ppm single exposure, but we need half a milligram per day.
Our TOL is 20 mg/day (lifetime oral dose tolerable upper
limit).
2. Boron is lethal to chitin-shelled life - most insects -
because it makes chitin pervious to water vapour. This
mechanism doesn't affect humans. We need it only in trace
quantities; our TOL is 20 mg/day.
Lithium does not appear to be necessary for life. Oral doses of
300 mg/day are routinely used to treat human bipolar disorders
with no problems. Up to 2700 mg/day is used with intensive
medical monitoring. The toxicity mechanisms appear to be similar
to those of excess sodium and potassium i.e. cellular ionic
disruption.
In short, wear a proper mask while mixing glazes and ventilate
your kiln room properly so you won't inhale them. Once they are
melted into a glaze, none of these three pose any realistic
concerns to those using our pots.
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