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no liner - wine glass question / mn leaching

updated tue 24 oct 00


John Baymore on sun 22 oct 00

I have seen little in the way of documentation. I have heard that it is
dangerous to breath the fumes or dust. On the other hand I have heard tha=
drinking water contaminated by manganese isn't necessarily harmful. I hav=
seen people assume that since apparently manganese is harmful or dangerou=
in the studio, (dust and fumes) that naturally it is harmful in/on the
finished product. (this is an assumption, not a fact) If in fact, the
fumes and the dust are what is harmful to us and in the finished glaze it=

is not a problem, then why are we worrying about leach testing for it?

I think I can generally point you toward some documentation resources.

There are two people who currently are, for whatever reasons, the
"generally accepted" experts in the area of toxicology in the arts. One =
Dr. Michael McCann and the other is Monona Rossol. Along with being an
Industrial Hygienist, and holding an MS, Monona also happens to have her
MFA in ceramics....which I imagine gives her a special affinity for "thin=
ceramic". Both of them have been deeply involved in this issue since at
least the 70's. As I understand it, both are used in court cases in the
field as "expert witnesses". So they seem to have some pretty reasonable=

professional credentials. Most of what they each have to say about
toxicological issues and prevention and the like generally is in agreemen=

Direct contact with either or both of them should provide you with plenty=

of information and documentation on possible concerns about manganese and=

the various routes that it might take to get into the body. First of all=
check out their various books....... they are available from The Potter's=

Shop and from NCECA. =

Maybe someone else will emerge soon as another generally recognized
"expert", and completely disagree with everything they both have to say. =
don't expect this to happen, since what they are saying tends to simply b=
based on generally accepted medical and industrial practices extrapolated=

into the arts field........... but who knows? They both often say that
available industrial studies can't be extrapolated exactly...... since th=
conditions under which artists use materials are different. What it seem=
to me they urge is "educated caution". As I have said many times
before..... when it comes to the health and safety stuff... I think there=

are two distinct "camps"...... the "glass is half full" people and the
"glass is half empty" people.

In the end, you'll have to look around, check out the available info, and=

make your own decisions about who/what you believe . That is until t=
local government in your country steps in and makes some "pottery laws"
. Like with the US FDA standards on lead and cadmium. =

As to the "drinking water ......... not necessarily harmful" thought.....=
it is not just the presence but specifically the LEVEL present. You CAN
commit suicide with iron supplement pills if you want to take that many
. A little iron your body needs..... a lot will make you sick or kil=

Without actual testing......... you have no idea of the LEVEL
present....... and hence no way to evaluate any potential risks to users.=

That is the key issue for suggesting testing. No data. No=

data..... no evaluation.

Lacking other more definitive standards or governmental regulations, I
think Monona Rossol's proposal that we as potters can use any available
published drinking water standards for reasonable INTERIM leach test
comparisons, is pretty good advice. My guess is that the drinking water
standards will be conservative. Which until we know more, seems prudent.=

Considering that there are some reasonably documented concerns about this=

particular compound as a potential toxin with some pretty grave potential=

consequences, a glaze / surface that MIGHT be leaching manganese compound=
into a liquid that is going to be ingested by people who have no knowledg=
that the compound might even be in there DESERVES to be tested and
evaluated just a little, I think. The fact that it costs so little to do=

the tests makes even a stronger case for doing it. Selling one piece pay=
for the tests. Why NOT test before selling?

If someone doesn't want to go to the bother or expense of testing....... =

maybe they shouldn't use the toxic material. Pretty simple really.

All of the research which I have seen so far is pointing to the fact that=
much as we are all looking for the "magic bullet" that will allow us to
reliably predict the leaching of some particular compound out of a glaze,=

we haven't come close to the answer to that just yet. Apparently there a=
just too many variables involved for this to come easily and obviously. =
the ONLY way right now is to lab test if something contains a potential
significant toxin. Then take the test results and make some educated
decisions about what to do with the information obtained. It may be that=

we will find that you will ALWAYS have to test because firing conditions
are such an important component. Who knows?

John Hesselberth and Ron Roy are doing a lot of research to advance this=

knowledge (way to go guys!) and probably know as much about predicting
potential leaching as anyone does right now.

What is kind of disturbing is that the vast resources of ACERS and the hu=
number of ceramic engineer types they represent are not apparently
aggressively directed toward answers to these questions. Nothing is real=
showing up on this in industrially oriented mags like "Ceramic Industry".=

Does this apparent lack of interest tell us that the leaching issue is =

1.) ........ a "tempest in a teapot "? (couldn't resist ) =

2.) ........ because industry doesn't want to open this can of worms out =
vested financial interests.

3.) ........ saying that we as craft potters are way ahead of the curve i=
being concerned about the issue? =

Food for thought.

I think the "manganese issue" in general is pretty least
relative to studio type exposures to the studio potter. I personally kno=
two people who supposedly have chronic manganese poisoning purportedly fr=
their ceramic activities. Ceramics was the only significant route in the=
lives for major exposure to this material. Can I personally verify this
diagnosis precisely as the cause....hell no. Have I seen their medical
charts? Nope. Have I personally run the tests? Of course not. So at
that level..... this is "heresay". But they have no reason to lie about =
to me that I can think of. Maybe for the "granduer" of having a "ceramic=
related occupational disease" ? Doubt it. =

Interestingly....both are VERY reluctant to talk about it publically to
anyone other than a friend or close professional associate.

One of them I happened to inadvertantly "diagnose" during a toxicology
presentation in my college level ceramics materials course many years ago=
.. =

This person came up to me after that particular class and said that he/sh=
had been seeing doctors for a couple of years with many of the symptoms I=

was just describing in class. No one had come up with anything definitiv=
and he/she was bouncing from doctor to doctor and test to test. He/she
went back to their physician...and sure enough, when he/she got an
occupational medicine specailist involved and they looked at the issue fr=
the occupational exposure point of view........ bingo. The GP's and
general medical types he/she had been seeing never THOUGHT of such exposu=
as a possible cause, and neither did the they weren't looki=
at it in a manner that would easily lead to such a diagnosis. This perso=
and I have casually kept in touch over the years. He/she is currently ve=
ill. As I understand it, much damage is pretty much irreversible and
somewhat progressive. It is very sad to watch him/her slowly deteriorate=

Via some background private email correspondence over the years I also so=
of "E-know" a third person who was/is on the CLAYART list who has told m=
they are also so afflicted. He/she has offered to send me copies of test=

reports and diagnosis...... but the sincerity of the emails we have
exchanged leads me to believe the story as "truth" ......... so I don't
feel that I need to see that stuff as "proof". Why would he/she lie to
me? So once again.... I have not seen any medical this cou=
be completely untrue. This is therefore "heresay" once again.

I have in the past gently encouraged this person to "come forth" publical=
on CLAYART....but he/she also does not want to.

People don't like to publically talk about their health situations, so
often we don't hear about this kind of stuff. Also, as with that student=

of mine ....often it is misdiagnosed for long periods or forever. =

Additionally, studio potters as a group are such a small population that =
my knowledge, no one is tracking occupational health data on us yet.

Now.... if a pottery CONSUMER happens to get sick because our product was=

pushing their total body burden of some toxin "over the edge"...... they
and we will probably never know. No one will ever think to look for such=

things as chronic light metal poisoning coming from the favorite morning
coffee mug.

So...... take the above accounts of potters getting sick from their craft=

as whatever you would like to take them as........ read up everywhere you=

can on the leaching subject............ and make your own decisions. =



John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA

603-654-2752 (s)
800-900-1110 (s)

"DATES SET: Earth, Water, and Fire Noborigama Woodfiring Workshop =

August 17-26, 2001"