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foodsafe leaching limits for oxides (fwd)

updated wed 3 may 00 on tue 2 may 00

> ---------- Forwarded message ----------
> Date: Sat, 29 Apr 2000 11:30:17 EDT
> From: John Hesselberth
> Reply-To: Ceramic Arts Discussion List
> ----------------------------Original message----------------------------
> sibylle wrote:
> >Concerning your info about mangan, what it the correctly way to use mangan
> >in aglaze? And can I colour my clay by kneading (or wedging, if you like)
> >mangawithout danger, working with a mask or can it poison me through the
> Hi Sibylle,
> The primary danger from use of manganese is in breathing the fumes that
> are released during firing. <

We used to think this was so, but now it really appears that whether you
inhale the dust or the fume, the problem is the same. There used to be a
separate air quality standard (TLV) for the fume. Now there is a single TLV
of 0.2 mg/m3 that applies to manganese no matter what its form or particle

Small fume particles can get into the alveoli and into the blood stream from
there. But small dust particles also get into the alveoli. And the large
particles inhaled in the lung are cleared and swallowed.

And of course, there are populations such as miners that were never exposed
to fume in any form that developed manganese Parkinson's disease.


> We actually consume quite a bit a manganese in our everyday diet so it is
> not among the most toxic of materials to ingest. <

In fact, a tiny amount is needed in the diet. It is an essential element in
involved in several basic enzymatic processes. But when the amount in the
diet exceeds this, the toxic problems begin. This is the same pattern with
many metals.

Absorption from the gut is low, but an important route. So be careful both
of kiln fumes and the dust around the pottery that may contain manganese.

> Nonetheless, we should
> be careful in handling it. Certainly a good dust mask (preferably HEPA
> type) should be worn when mixing glazes containing manganese dioxide. I
> am not aware of any problems being reported as a result of wedging clay
> containing granular manganese. Certainly of lot of potters use that type
> of clay. If anyone else has information of that type hopefully they will
> post it. <

I am personally convinced that the potters with manganese problems were being
exposed in several ways including to the dust.

There is no data on whether or not manganese can significantly skin absorb.
This probably is not a major route, but I never rule anything out without

Monona Rossol
181 Thompson St., # 23
NYC NY 10012-2586 212/777-0062