Paul Lewing on tue 28 jun 05
on 6/28/05 7:40 AM, Bob Masta at pots@DAQARTA.COM wrote:
> I get the impression from Clayart discussions that
> manganese should be regarded as more toxic than listed
> here.
Bob, I think the reason it's regarded as more toxic here than in your
listing is that potters are exposed to it as it fumes out of a kiln during
firing, which is an unusual method of exposure. I'm sure your source was
only considering more normal routes of contact, such as skin contact, or
breathing dust.
Paul Lewing, Seattle
Earl Brunner on tue 28 jun 05
Back in the 70's at Utah State they were building the new art building (the
old ceramics studio at the time being in the "Art Barn"). They wanted to
make sure they set up the new studio with all of the proper safety stuff in
place, etc. so they sent some kind of environmental guy over to check out
our chemicals. I was one of the studio techs at the time, I was talking to
him about what I thought and understood the "BAD" stuff (lead, etc) to be.
He said, and I quote, "oh no, I see stuff here I'm MUCH more concerned
about..."
He then talked about a LOT of the colorants. Specifically nickel for
example, he said something about it being trivalent (whatever that means),
but I got it that trivalent was BAD. And hexavalent stuff, BAD.
Earl Brunner
Las Vegas, NV
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Bob Masta
Sent: Tuesday, June 28, 2005 7:40 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Relative oxide toxicity
In my case, I have been pretty conservative... or so I
thought. Sure, I use copper, but not those nasty things
like manganese that everyone talks about. However, in
going through my (outdated?) Condensed Chemical
Dictionary (1971) I find their ratings deviate from my
expectations in a couple of places. In fact, with their
simple rating system, copper oxides are listed as Highly
Toxic, right up there with lead, barium, and cadmium!
By comparison, manganese dioxide is listed as Moderately
Toxic and manganese oxide as Low Toxicity.
Highly Toxic:
antimony
barium
cadmium
copper (carbonate, oxide, sulfate)
lead
potassium chromate
selenium (fumes)
vanadium pentoxide
Moderately Toxic:
magnesium sulfate
manganese dioxide
Probably Toxic:
chrome oxide (by ingestion)
Slightly Toxic:
cobalt (metal)
Low Toxicity:
magnesium carbonate
manganese oxide
praseodymium oxide
selenium (metal)
strontium carbonate
tin oxide
No toxicity rating given:
iron oxides
nickel (Ni2O3 or NiO)
cobalt (carbonate, oxide)
I don't know whether the lack of rating on nickel and
cobalt here is supposed to reflect a lack of toxicity or
lack of data, but I think most sources regard iron as
non-toxic expect for people with certain conditions.
I get the impression from Clayart discussions that
manganese should be regarded as more toxic than listed
here. Anything else? I've always been pretty careful
with copper oxide, but I'm a little more concerned lately
since I've been doing Egyptian paste beadwork, which
involves prolonged skin exposure during forming.
And I'm wondering if maybe I've been too conservative in
avoiding manganese and nickel for regular c/6 glazes.
So far, I haven't seen any reason to avoid cobalt.
Best regards,
Bob Masta
potsATdaqartaDOTcom
____________________________________________________________________________
__
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
Bob Masta on tue 28 jun 05
I'd like to get a general feeling for relative toxicity
of colorant oxides. I realize that there are no simple
answers to this; even the same oxide may have different
toxicity depending upon whether it is ingested, breathed
as dust, or as fumes. But I suspect many of us have our
own relative rankings, such that we definitely avoid lead
in our glazes and don't worry in the least about iron,
for example.
In my case, I have been pretty conservative... or so I
thought. Sure, I use copper, but not those nasty things
like manganese that everyone talks about. However, in
going through my (outdated?) Condensed Chemical
Dictionary (1971) I find their ratings deviate from my
expectations in a couple of places. In fact, with their
simple rating system, copper oxides are listed as Highly
Toxic, right up there with lead, barium, and cadmium!
By comparison, manganese dioxide is listed as Moderately
Toxic and manganese oxide as Low Toxicity.
Highly Toxic:
antimony
barium
cadmium
copper (carbonate, oxide, sulfate)
lead
potassium chromate
selenium (fumes)
vanadium pentoxide
Moderately Toxic:
magnesium sulfate
manganese dioxide
Probably Toxic:
chrome oxide (by ingestion)
Slightly Toxic:
cobalt (metal)
Low Toxicity:
magnesium carbonate
manganese oxide
praseodymium oxide
selenium (metal)
strontium carbonate
tin oxide
No toxicity rating given:
iron oxides
nickel (Ni2O3 or NiO)
cobalt (carbonate, oxide)
I don't know whether the lack of rating on nickel and
cobalt here is supposed to reflect a lack of toxicity or
lack of data, but I think most sources regard iron as
non-toxic expect for people with certain conditions.
I get the impression from Clayart discussions that
manganese should be regarded as more toxic than listed
here. Anything else? I've always been pretty careful
with copper oxide, but I'm a little more concerned lately
since I've been doing Egyptian paste beadwork, which
involves prolonged skin exposure during forming.
And I'm wondering if maybe I've been too conservative in
avoiding manganese and nickel for regular c/6 glazes.
So far, I haven't seen any reason to avoid cobalt.
Best regards,
Bob Masta
potsATdaqartaDOTcom
William & Susan Schran User on wed 29 jun 05
On 6/28/05 10:40 AM, "Bob Masta" wrote:
> Sure, I use copper, but not those nasty things
> like manganese that everyone talks about. However, in
> going through my (outdated?) Condensed Chemical
> Dictionary (1971) I find their ratings deviate from my
> expectations in a couple of places. In fact, with their
> simple rating system, copper oxides are listed as Highly
> Toxic, right up there with lead, barium, and cadmium!
> By comparison, manganese dioxide is listed as Moderately
> Toxic and manganese oxide as Low Toxicity.
How is the toxicity rating derived?
Is it through ingestion? Inhalation of the raw material?
Skin contact?
The concern with manganese is the fumes when heated during firing and I
don't know if that is included in the toxicity ratings you quote.
--
William "Bill" Schran
Fredericksburg, Virginia
Snail Scott on wed 29 jun 05
At 10:40 AM 6/28/2005 -0400, you wrote:
>...However, in
>going through my (outdated?) Condensed Chemical
>Dictionary (1971) I find their ratings deviate from my
>expectations in a couple of places...
>Low Toxicity:
> magnesium carbonate
> manganese oxide...
The question that's not answered here is: Toxicity
by what means of exposure? Ingestion? Inhalation?
Skin absorption? What?
From your reference to making Egyptian paste, I assume
you are principally concerned with skin absorption.
Manganese seems to be a tolerably low risk for that
method of exposure. It's the (heated) fumes that are
such bad news.
Putting one 'hazard' classification on a material can
be terribly misleading, since toxicity can vary quite
a bit depending on the type of exposure.
Remember the old joke about water - fatal if inhaled?
-Snail
Ron Roy on fri 1 jul 05
Hi Bob,
I'm going by what Manona says in her book - The Artists Complete Health and
Safety Guide third edition. I also subscribe to her news letter - I find
her information up to date.
I see you do realize that how a chemical enters your body is important in
how it affects you - if you eat silica I would not expect any bad results
for instance - but breathing it is a danger - eating off glazes with silica
in them is not a damger either - at least not from the silica. So I'm
trying to explain the categories and she does that for each chemical we
use.
In your first list you have included copper - which is not nearly the
concern that lead and cadmium are for instance - in fact - unless you have
Wilsons disease - it looks like more of an irritant than a real poison - it
does affect the taste of food if it leaches out of a glaze though.
Some one pointed out that Manganese is a danger if the fumes are breathed
from a firing kiln - it is also absorbed from breathing dust. I would have
include it in your first list but not because there is a danger from eating
it.
In your last list - no toxicity - nickel is included and it is a carcinogen.
She also lists Cobalt as an animal carcinogen.
So to answer your question - I am saying - read her book - the part on
Ceramics and it will answer your questions.
When we talk about oxides getting into food we are really talking about
unstable glazes - the oxides are only a problem if the glazes you use as
liners allow the oxides in the glazes to leach into food - and how much
leaches.
An easy way to solve the glaze problem is to use only safe oxides in your
liner glazes - that way you don't need to worry about how unstable your
glazes are.
RR
>I'd like to get a general feeling for relative toxicity
>of colorant oxides. I realize that there are no simple
>answers to this; even the same oxide may have different
>toxicity depending upon whether it is ingested, breathed
>as dust, or as fumes. But I suspect many of us have our
>own relative rankings, such that we definitely avoid lead
>in our glazes and don't worry in the least about iron,
>for example.
>
>In my case, I have been pretty conservative... or so I
>thought. Sure, I use copper, but not those nasty things
>like manganese that everyone talks about. However, in
>going through my (outdated?) Condensed Chemical
>Dictionary (1971) I find their ratings deviate from my
>expectations in a couple of places. In fact, with their
>simple rating system, copper oxides are listed as Highly
>Toxic, right up there with lead, barium, and cadmium!
>By comparison, manganese dioxide is listed as Moderately
>Toxic and manganese oxide as Low Toxicity.
>
>Highly Toxic:
> antimony
> barium
> cadmium
> copper (carbonate, oxide, sulfate)
> lead
> potassium chromate
> selenium (fumes)
> vanadium pentoxide
>
>Moderately Toxic:
> magnesium sulfate
> manganese dioxide
>
>Probably Toxic:
> chrome oxide (by ingestion)
>
>Slightly Toxic:
> cobalt (metal)
>
>Low Toxicity:
> magnesium carbonate
> manganese oxide
> praseodymium oxide
> selenium (metal)
> strontium carbonate
> tin oxide
>
>No toxicity rating given:
> iron oxides
> nickel (Ni2O3 or NiO)
> cobalt (carbonate, oxide)
>
>I don't know whether the lack of rating on nickel and
>cobalt here is supposed to reflect a lack of toxicity or
>lack of data, but I think most sources regard iron as
>non-toxic expect for people with certain conditions.
>
>I get the impression from Clayart discussions that
>manganese should be regarded as more toxic than listed
>here. Anything else? I've always been pretty careful
>with copper oxide, but I'm a little more concerned lately
>since I've been doing Egyptian paste beadwork, which
>involves prolonged skin exposure during forming.
>
>And I'm wondering if maybe I've been too conservative in
>avoiding manganese and nickel for regular c/6 glazes.
>So far, I haven't seen any reason to avoid cobalt.
>
>Best regards,
>
>
>
>
>
>Bob Masta
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
David Hewitt on sat 2 jul 05
I don't disagree with Ron's general approach to this subject, but while
it is being discussed I would think that it is appropriate to add two
points.
Firstly, all the materials available to the potter can be handled
perfectly safely if the appropriate precautions are taken.
Secondly, it is wrong to think that glazes are only used on functional
domestic ware. With much of the ceramics produced this is not an issue
and it would be unnecessarily restrictive to limit such glaze recipes to
only using 'safe oxides'.
David
--
David Hewitt
Web:- http://www.dhpot.demon.co.uk
John Baymore on wed 6 jul 05
Firstly, all the materials available to the potter can be handled
perfectly safely if the appropriate precautions are taken.
In order to take the "proper precautions" for material handling..... one
has to know what the situation that one is taking the precautions about
actually IS. In the case of dust generation, kiln gas and fume generation
and the like, the first necessary step in order to take any precautions is
knowing the level of the potential contaminant in the air / environment.
The only way to do this for every given specific situation in the case of
airborne contaminants is through actual air sampling. Once you have this
concrete data...... you can take "appropriate precautions".
How many potters have air sampling done to establish hazard profiles?
SO..... lacking air sampling data......... how does one proceed? Some
will err on the side of caution....... some will err on the side of lack
of caution.
When it comes to the whole "health and safety" in the studio thing I think
tere are two basic "camps":
Those that see the glass as half full will say that until the material's
hazard is definitively proven... there is no hazard. Those that see the
glass as half empty will say that until the material is proven safe...
there is a possible hazard.
best,
................john
JBaymore@compuserve.com
http://www.JohnBaymore.com
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
"Please use compuserve address for direct communications."
URL Krueger on thu 7 jul 05
On Wednesday 06 July 2005 08:19 pm, John Baymore wrote:
> Those that see the glass as half full will say that until
> the material's hazard is definitively proven... there is
> no hazard. Those that see the glass as half empty will
> say that until the material is proven safe... there is a
> possible hazard.
I think we all would like this be a Black or White
situation, either it's safe or it isn't, but this can never
be. I believe it was Kelly that pointed out some time ago
we may be able to prove that something is _unsafe_ but we
can never really prove that something is _safe_.
What we all have to do is learn as much about the materials
and processes we use as we can and then use that knowledge
to make an intelligent risk assessment. If the risks are
too high, as lead, selenium and cadmium are for me, then we
will choose not to use those materials. If the risks are
below our tolerance threshold then we accept the risk and
will use the material.
The key to performing an accurate risk assessment is to
understand the data we have available. As an example, If a
data sheet for a material says it is dangerous at 0.1
microgram per cubic meter and another for a different
material says it is dangerous at 100 milligrams per cubic
meter we need to appreciate that there is a 1,000,000 fold
difference between the two.
--
--
Earl K...
Bothell WA, USA
Ron Roy on fri 8 jul 05
Hi John,
I see this as helpful in trying to see the problem - and how each of us
deals with it.
Wouldn't it be great if more of us understood the issues and the materials
so we could make better decisions about what effects our health and our
pots. If the authors and the teachers knew more it would be enough to
change the decision making among us for the better.
I'm not sure if the correct analogy would be full glass or empty though.
RR
>When it comes to the whole "health and safety" in the studio thing I think
>tere are two basic "camps":
>
>Those that see the glass as half full will say that until the material's
>hazard is definitively proven... there is no hazard. Those that see the
>glass as half empty will say that until the material is proven safe...
>there is a possible hazard.
>
>best,
>
>................john
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
| |
|
