Craig Dunn Clark on mon 12 jul 04
The statement that I have made is that I do not believe that low =
fired pottery is safe for food service. Stating this as an absolute is =
going overboard. Let me back away from such a catagorically dogmatic =
statement and say that I think that the use of low fire work for food =
service purposes is questionable when compared to what I consider to be =
the better alternative of high fired pottery with properly formulated =
glazes and a vitrified clay body.
The basis of this belief is that I do not know of any clay body that =
is vitrified at low fire temperatures. I may be wrong......just don't =
know of one. That does not mean that it doesn't exist. Because of this I =
do not think that the pottery has the inherent strength that is helpful =
for the rigors that pottery is subjected to from utilitarian work.
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
Ron & Nancy Hughes on mon 12 jul 04
Craig,
You are right about high fire, but the low temp is safe when the glaze
(glass) sits on and covers the clay. it is not as sturdy and chips easier.
But it has been used for thousand of years. It is sold in May Co. and
Macys's and any place else you care to look.
Raku glazes are crackle glazes (no matter how solid they look) and are
not food safe. American raku that is.
Respectfully Nance
mailtoandrew@FSMAIL.NET on mon 12 jul 04
Hello Craig,
If you may permit me to add my thoughts, as you state .... Certainly it
is true that in general lower fired bodies are not vitreous this is not an
absolute. And although the definition of low temperatures is open to
debate vitirification can be achieved down at 1100 centrigrade.
And is non- vitreous porous unsafe for food? Whilst commercial
establishments such as restaurants do prefer vitreous ware, not least due
to the enhanced strength, much earthenware is produced that passes the
necessary testing to prove compliance with all safety legislation.
Thats all,
Regards,
Andrew
Edouard Bastarache Inc. on mon 12 jul 04
Hum !!!
if it does not leach anything noxious in sufficient amounts, it is safe.
Smart.Conseil, an European expert in this field supervises the production
of 125,000 pieces per year at the Gien factory in France as a R&D
technologist. Gien's clay absorbs 18% and it is fired at C/1 in oxidation.
Its pieces covered by glazes containing lead and cadmium are monitored
according to the laws and by-laws of many countries because its production
is sold to many countries; 40% of of it is sold in the USA.
Later,
"Ils sont fous ces quebecois"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
http://sorel-tracy.qc.ca/~edouardb/
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
Malcolm Schosha on mon 12 jul 04
--- In clayart@yahoogroups.com, Ron & Nancy Hughes
wrote:
> Craig,
> You are right about high fire, but the low temp is safe when
the glaze
> (glass) sits on and covers the clay. it is not as sturdy and chips
easier.
> But it has been used for thousand of years. It is sold in May Co.
and
> Macys's and any place else you care to look.
> Raku glazes are crackle glazes (no matter how solid they look)
and are
> not food safe. American raku that is.
> Respectfully Nance
>
>
.............
Nancy,
Yes. In Italy many people prefer cooking in low fire cookware,
feeling that the food tastes better when cooked that way. When we
returned to the USA, many years ago, we brought some of the Italian
cookware with us (good for use on a stove); and my wife was very sad
when the last one broke.
In any case food was cooked for tens of thousands of years in low
fire ware, without any glazes at all. In the over all history of
pottery, grazes are a somewhat late development, particularly high
fire glazes.
This is not to criticize high fire cookware, it certainly has its
advantages.
Malcolm Schosha
Earl Brunner on mon 12 jul 04
I think one of the differences for someone who lives in more developed
countries (and I'm not trying to get into what is developed and isn't) is
that we live in such sterile environments that we aren't inoculated so to
speak to a lot of the flora and fauna out there. We might be more at risk
then someone who has survived in areas with poor drinking water and porous
cookware.
Another factor would be whether or not you have a properly functioning
dishwasher - they seem to do a pretty good job of more or less sterilizing
cooking and eating utensils. My parents always maintained there was a
significant drop in illnesses in our home growing up when the kids washing
dishes were replaced by the auto dishwasher.
Earl Brunner
Las Vegas, NV
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Malcolm Schosha
Sent: Monday, July 12, 2004 3:30 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: food safe pottery at low fire temperatues?
In any case food was cooked for tens of thousands of years in low
fire ware, without any glazes at all. In the over all history of
pottery, grazes are a somewhat late development, particularly high
fire glazes.
This is not to criticize high fire cookware, it certainly has its
advantages.
Malcolm Schosha
snakesmom2002 on mon 12 jul 04
--- In clayart@yahoogroups.com, Craig Dunn Clark wrote:
> The statement that I have made is that I do not believe that
low fired pottery is safe for food service.
Craig, I micaceous clay is vitrified at low temps (above ground and
pit firing)and, as I understand, is food safe. Many Native Americans
make, use, and sell this type of pottery. Coyote Clay sells micaceous
clay.
Carol
Ron Roy on mon 12 jul 04
Hi Edouard,
So are you saying it is OK for studio potters to do the same thing?
RR
>Hum !!!
>
>if it does not leach anything noxious in sufficient amounts, it is safe.
>Smart.Conseil, an European expert in this field supervises the production
>of 125,000 pieces per year at the Gien factory in France as a R&D
>technologist. Gien's clay absorbs 18% and it is fired at C/1 in oxidation.
>Its pieces covered by glazes containing lead and cadmium are monitored
>according to the laws and by-laws of many countries because its production
>is sold to many countries; 40% of of it is sold in the USA.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Edouard Bastarache Inc. on mon 12 jul 04
Why not,
if the industry can do it safely, we can do it.
Do not use noxious materials in the first place.
If you use noxious materials such as lead and
cadmium, use good work practices, proper
protection and ventilation, etc. Have your wares
tested in an accredited laboratory.
When it comes to encapsulated cadmium, I have
been thinking a lot about clayarters who were not
convinced by the allegations of the maker when it
came to its safety because of the separation between
the pigment and the capsule.
If the granules were cut very thinly by an apparatus
such as a "microtome" used in pathology labs to make
very thin slices of tissues to be studied under a
microscope and also shown on a screen, and sometimes
it happens that we see separations of different layers of
human tissues of the same sample, it is possible that the
same thing happened to the sliced granules.
Needless to say that cadmium-containing glazes must be
tested for leaching according to local laws and by-laws.
Later,
"Ils sont fous ces quebecois"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
http://sorel-tracy.qc.ca/~edouardb/
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
----- Original Message -----
From: "Ron Roy"
To:
Sent: Monday, July 12, 2004 9:38 PM
Subject: Re: food safe pottery at low fire temperatues?
> Hi Edouard,
>
> So are you saying it is OK for studio potters to do the same thing?
>
> RR
>
> >Hum !!!
> >
> >if it does not leach anything noxious in sufficient amounts, it is safe.
> >Smart.Conseil, an European expert in this field supervises the production
> >of 125,000 pieces per year at the Gien factory in France as a R&D
> >technologist. Gien's clay absorbs 18% and it is fired at C/1 in
oxidation.
> >Its pieces covered by glazes containing lead and cadmium are monitored
> >according to the laws and by-laws of many countries because its
production
> >is sold to many countries; 40% of of it is sold in the USA.
>
> Ron Roy
> RR#4
> 15084 Little Lake Road
> Brighton, Ontario
> Canada
> K0K 1H0
> Phone: 613-475-9544
> Fax: 613-475-3513
>
>
____________________________________________________________________________
__
> 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.
>
mailtoandrew@FSMAIL.NET on tue 13 jul 04
Hello all,
I think that both Edouard and Roy have made a couple of valid points that
highlight something interesting:
Certainly it is possible to produce food safe porous ware fired at low
temperature using glazes containing lead and cadmium. Although as a caveat
by food safe I mean demonstrable compliance with recognised regulations.
However is it feasible to expect craft potters to undertake the level of
testing practiced by industry? Whilst knowledge and understanding of the
risks must be considered essential the control and testing required to
ensure that a low fired glaze containing Pb and Cd are safe is extensive,
and expensive. A single test of a single mix of glaze is insufficient,
more likely is:
All firing in a narrow range, and to be monitored and recorded
Frequent analysis of raw materials
Frequent analysis of glaze batches
Frequent sampling and testing of ware.
Testing procedures to recognised standards
Production and testing to be open to audit
However as it is, hopefully, unarguable that ware used for food presents
minimal risk to the user what can a potter do? To start with:
Not be complacent
Know the risks, and how they can be minimised and monitored
Ask oneself .... Am I exposing myself and others to risks?
Minimise the risks
Ask oneself .... How can I prove that I have minimised these risks?
If one is producing ware for food use there is a moral, and increasingly
legal, responsibility to ensure it does not pose dangers to users. A
potter not wishing to meet these obligations can still continue, either
produce solely for their own use or ensure the ware can not be used for
food. A simple suggestion for the latter made sometime back on ClayArt was
to drill a hole when in the green state.
Life is full of judgements about risks; from the mundane such as when to
cross a busy road to a design engineer selecting the safety devices for a
nuclear power plant. A decision that effects just oneself differs to that
which could effect others.
With respect I think it is naive to suggest that the use of ware in past
millennia proves that current pots pose no hazard. Processes, materials
and understanding have changed. The performance of pottery produced, say,
three thousand years ago in Egypt gives very little indication to that of
ware made yesterday in North America. It is however unquestionable that
certain compounds can be leached from glazes, and that these can have
serious health implications.
Potters do have obligations above those of other artists; apart from
falling off a wall, which is most likely the responsibility of the gallery
or owner, how can a painting cause harm?
However those working with ceramics can consider themselves fortunate.
Their products have the potential to last longer than any other man made
artefact. Their very permanency can be appreciated from the finds of
archaeologist some of which have been dated to at least 15,000 BC.
Ceramics are amongst the strongest, hardest, most refractory and inert of
man made materials. They are resistant to any deteriorating effects of
water, salts, organic solvents and virtually all alkalis and acids.
Ceramics can be safe, functional and beautiful.
Regards,
Andrew
Edouard Bastarache Inc. on tue 13 jul 04
Hello Andrew,
one important thing about lead and cadmium is that both have
Biological Exposure Indexes, which means we can appreciate the exposure
of people in a rather precise manner using samples from biological fluids.
We can use those defined by Dr. Perrine Hoet in Belgium, Dr. Hoet with Prof.
Lauwerys has already co-authored a book published thrice since 1983 titled
"Industrial Chemical Exposure". We find these data on this web site in
french:
http://www.md.ucl.ac.be/toxi/mbi.htm
VBA :Valeurs Biologiques Admissibles, which is equivalent to BEI for
Biologic Exposure Index in the USA (ACGIH) .
1-Lead :
reference value
(general population) < 15 µg /100 ml (adult)
Université Catholique de Louvain- TOXI,
VBA:
- 40 µg/100 ml
F < 45 ans: 15 µg/100 ml, F stands for women in child bearing years.
2-Cadmium :
a-blood:
reference value:
(general population) <0,5 µg/100 ml
<0,1 µg/100 ml among non-smokers
Université Catholique de Louvain- TOXI,
VBA :
- 0,5 µg/100 ml (for preventing kidney lesions)
b-urine :
reference value
(general population ) <2 µg/g creatinine (smokers> non-smokers)
Université Catholique de Louvain - TOXI
VBA:
- 5 µg/g creatinine
(for preventing kidney lesions)
Therefore the health of potters and customers can be monitored adequately.
"Ils sont fous ces quebecois"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
http://sorel-tracy.qc.ca/~edouardb/
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
Jon Pacini on tue 13 jul 04
Greetings All, Hi Craig
Glad to see you back off that statement a bit Craig. It s good to
see someone say, just because I m not aware of it , doesn t mean it s
non-existent.
You can go through the back issues of CM and find an article at
least once every five years about adding frit to clay and making vitreous
low fire ware. So it shouldn t really be an unknown concept.
There are a multitude of vitrified low fire bodies in use industrially
along with their attendant glazes. I m going to have to beg ignorance myself
and say that I don t know of a single supplier who lists such materials in
their catalog. I know we don t list any, even though Laguna makes a number
of them as specials.
There seems to be a faction of Clayarters who don t think that potters in
general are capable of successfully making food safe low fire ware. I would
think that if you can teach potters to use glaze calculation to make food
safe ware at ^6 you can teach them to do it at any temperature.
Best regards
Jon Pacini
Clay Manager
Laguna Clay Co
Martin Butt on tue 13 jul 04
July 12 2004 Carol wrote;
pit firing)and, as I understand, is food safe. Many Native Americans
make, use, and sell this type of pottery. Coyote Clay sells micaceous
clay.>
We do indeed sell micaceous clay at Coyote Clay & Color, however our mica
clay is NOT vitrified at low temperatures. In fact it has fairly typical porosity
for an earthenware clay.
Thanks,
Martin Butt
Coyote Clay & Color
coyoteclay.com
Bob Masta on wed 14 jul 04
Another aspect to "food safe" is molds. My wife
had some inexpensive low-fired bowls with unglazed
footrings. They would soak up water and never really
dried out. When stored in a stack, the footring of an
upper bowl was against the glaze of a lower bowl, and
the perpetually moist, porous footring caused prodigious
mold growth. If you lifted the top bowl off the stack there
would sometimes be a visible ring of mold or mildew
on the bowl below.... ecchh!
Another reason for vitrification!
Bob Masta
potsATdaqartaDOTcom
Anne Webb on wed 14 jul 04
ed -
as we all know, in *theory* a lot of things sound great. utopias...
political systems,, even glaze analysis... but what may look good on paper
doesnt always work and what works in reality doesnt always look good on
paper. what works in an ideal situation may not work in another either.
i am sorry but i dont agree that studio potters exercise the same controls
as large industry to which you are referring. ..little capital, no time,
little to no enforced regulation....the quest for that luscious glaze.
"ahh so and so is using that glaze out of ceramics monthly and he knows what
he is doing so it must be good, so i wont have a problem." (of course not
thinking that "so-and-so" is in a different part of the continent and his
ingredients or the mine he gets them from vary somewhat from what you get
where you are.)
now dont get me wrong, there are some who succeed in doing things correctly,
but in actuality, how many studio potters that you know actually get their
claybodies and glazes tested by a lab on a regular basis, for example? i'd
wager not many. how many people look into peep holes without goggles? we
all (well some of us) know what we *should* do, but it doesnt always happen
that way...
and yes, i know, people have used lowfire pots to eat and cook from year
dot. prolly not ideal, but just what they had at the time.
cheers,,anne
>if the industry can do it safely, we can do it.
>Do not use noxious materials in the first place.
>
>If you use noxious materials such as lead and
>cadmium, use good work practices, proper
>protection and ventilation, etc. Have your wares
>tested in an accredited laboratory.
>
>When it comes to encapsulated cadmium, I have
>been thinking a lot about clayarters who were not
>convinced by the allegations of the maker when it
>came to its safety because of the separation between
>the pigment and the capsule.
>If the granules were cut very thinly by an apparatus
>such as a "microtome" used in pathology labs to make
>very thin slices of tissues to be studied under a
>microscope and also shown on a screen, and sometimes
>it happens that we see separations of different layers of
>human tissues of the same sample, it is possible that the
>same thing happened to the sliced granules.
>Needless to say that cadmium-containing glazes must be
>tested for leaching according to local laws and by-laws.
>
>
> > >if it does not leach anything noxious in sufficient amounts, it is
>safe.
> > >Smart.Conseil, an European expert in this field supervises the
>production
> > >of 125,000 pieces per year at the Gien factory in France as a R&D
> > >technologist. Gien's clay absorbs 18% and it is fired at C/1 in
>oxidation.
> > >Its pieces covered by glazes containing lead and cadmium are monitored
> > >according to the laws and by-laws of many countries because its
>production
> > >is sold to many countries; 40% of of it is sold in the USA.
_________________________________________________________________
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Edouard Bastarache Inc. on wed 14 jul 04
Well Anne,
we live in a free world, do whatever you like.
Later,
"Ils sont fous ces quebecois"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
http://sorel-tracy.qc.ca/~edouardb/
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
Edouard Bastarache Inc. on sun 18 jul 04
Hello Ron,
"Only if we are aware that there is a problem - if the ware is lead
glazed -
how are the customers supposed to know that?
RR"
The potter knows if he uses leaded materials and should warn users they
buy lead-glazed pots, and have them tested before putting them on the
market.
So says the law.(EB)
"I also see the permissable levels of the many toxins we use have changed
over the years - I wonder why?
RR"
Some day there won't be anymore room to lower them maybe if the
tendancy remains (hehehehe), will we live long enough to see that!!!
Just recently in Europe after studies conducted in China among
workers severily exposed to cadmium, with the help of
european experts from l'Université Catholique de Louvain,
the blood standards for the general population was raised significantly
They found that chinese workers, even if quite more severily exposed
than european workers, did not present much ill-effects.
So some may go down and some will go up.
It is now 0.5 µg/100 ml (smokers), the same level as for exposed
workers.
Understandable, the majority of the general population's exposure
comes from cigarette smoking.
valeur de référence
(population générale) <0,5 µg/100 ml
<0,1 µg/100 ml chez non-fumeurs
UCL - TOXI
(travailleurs) VBA:
- 0,5 µg/100 ml
mise ŕ jour le 26/05/04 par Dr. Perrine Hoet (updated at the end of May
2004)
Up until a few years ago aniline was considered a confirmed bladder
carcinogen.
It is not anymore because the older studies claiming it was so were severily
flawed.
(EB)
" Could it be there is still more to learn about the chemical soup we live
in?
RR"
Of course(EB)
"Ils sont fous ces quebecois"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
http://sorel-tracy.qc.ca/~edouardb/
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
Ron Roy on sun 18 jul 04
Only if we are aware that there is a problem - if the ware is lead glazed -
how are the customers supposed to know that?
I also see the permissable levels of the many toxins we use have changed
over the years - I wonder why?
Could it be there is still more to learn about the chemical soup we live in?
RR
>
>
>Therefore the health of potters and customers can be monitored adequately.
>
>Edouard Bastarache
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on sun 18 jul 04
Much harder to do at the lower temperatures Jon.
So much of glaze durability is dependant on the amount of silica and
alumina you have in a glaze. At lower temperatures you have to add more
flux so the amount od silica and alumina have to be less.
The other side of it is - high fire - is easier because it is easier to
melt with less flux and have more silica and alumina.
This is explained in detail in our book by the way.
The other problem with low fire is the difficulty in making vitrified ware
- with the kind of materials we use. Flux it enough to get it vitrified
this time but next time it's not - or over fired. Lots of flux needed for
low fire vitrification equals short firing range.
There are limitations inherent in low fired ware - it takes more
understanding to successfully do it in a way that limits the harm it can
cause.
It is not so much the teaching part that is the problem but rather the
equipment, controles and economics that make it difficult if not impossible
for most studio potters.
RR
>There seems to be a faction of Clayarters who don t think that potters in
>general are capable of successfully making food safe low fire ware. I would
>think that if you can teach potters to use glaze calculation to make food
>safe ware at ^6 you can teach them to do it at any temperature.
>
>Jon Pacini
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on sun 18 jul 04
Well some places are less free than others -
In Austria your table ware must pass leaching limits for Zn,Sb and Ba.
In Finland it's Cr,and Ni.
In Hungary - all other metals.
In Korea - As.
New Zeland - As and Sb.
Slovenia - Cr, Ba, Se and Sb.
Plus Lead and Cadmium of course.
RR
>Well Anne,
>
>we live in a free world, do whatever you like.
>
>
>
>Later,
>Edouard Bastarache
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Edouard Bastarache Inc. on sun 18 jul 04
" Well some places are less free than others -
In Austria your table ware must pass leaching limits for Zn,Sb and Ba.
In Finland it's Cr,and Ni.
In Hungary - all other metals.
In Korea - As.
New Zeland - As and Sb.
Slovenia - Cr, Ba, Se and Sb.
Plus Lead and Cadmium of course.
RR"
Well Ron,
like I have already told you "While in Rome, do like the Romans."
Later,
"Ils sont fous ces quebecois"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
http://sorel-tracy.qc.ca/~edouardb/
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
Edouard Bastarache Inc. on mon 19 jul 04
Hello Ron,
"Only if we are aware that there is a problem - if the ware is lead
glazed -how are the customers supposed to know that?
RR"
The potter knows if he uses leaded materials and should warn users they
buy lead-glazed pots, and have them tested before putting them on the
market.
So says the law.(EB)
"I also see the permissable levels of the many toxins we use have =
changed
over the years - I wonder why?
RR"
Some day there won't be anymore room to lower them maybe if the
tendancy remains (hehehehe), will we live long enough to see that !!!
That is another story
Just recently in Europe after studies conducted in China among
workers severily exposed to cadmium, with the help of
european experts from l'Universit=E9 Catholique de Louvain,
the blood standards for the general population was raised significantly
They found that chinese workers, even if quite more severily exposed
than european workers, did not present much ill-effects.
So some may go down and some will go up.
It is now 0.5 =B5g/100 ml (smokers), the same level as for exposed
workers.
Understandable, the majority of the general population's exposure
comes from cigarette smoking.
valeur de r=E9f=E9rence
(population g=E9n=E9rale) <0,5 =B5g/100 ml
<0,1 =B5g/100 ml chez =
non-fumeurs
UCL - TOXI
(travailleurs) VBA:
- 0,5 =B5g/100 ml
mise =E0 jour le 26/05/04 par Dr. Perrine Hoet (updated at the end of =
May
2004)
Up until a few years ago aniline was considered a confirmed bladder
carcinogen.
It is not anymore because the older studies claiming it was so were =
severily
flawed.
(EB)
" Could it be there is still more to learn about the chemical soup we =
live
in?
RR"
Of course(EB)
"Ils sont fous ces quebecois"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
http://sorel-tracy.qc.ca/~edouardb/
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
Anne Webb on mon 19 jul 04
i'm sorry.. i got sucked in again.
what are permissible levels of toxins?
i agree.. there is not enough known about them. what's permissible today
might not be a few years down the road when, say, they discover that
chemical X is really a carcinogen.
aunt betty who has been diagnosed with cancer, still eats off that dinner
set she got years ago when its glaze passed supposed legal standards. there
were no warnings of any health risk back when she bought her dinnerset, and
the potter or manufacturer sure isnt there telling her now that she really
shouldnt be eating off her prized dishes anymore. now it becomes customer
responsibility...?
in the meantime, how many people along the way have died of cancer because
of exposure to it. ..human guinea pigs? thats a high price to pay.
i'm curious...really...why do standards vary so much from country to country
re permissible limits (re ron's earlier post). does one country know
something that another doesnt? who is right? and why isnt the info the same
across the board?
is the deviation perhaps influenced by of a given country's economy (less
stringent standards in order to produce a lesser priced item and bolster
economy)?
anne
> "Only if we are aware that there is a problem - if the ware is lead
>glazed - how are the customers supposed to know that?
>RR"
>
>The potter knows if he uses leaded materials and should warn users they
>buy lead-glazed pots, and have them tested before putting them on the
>market.
>So says the law.(EB)
>"I also see the permissable levels of the many toxins we use have changed
> over the years - I wonder why?
>RR"
>
>Some day there won't be anymore room to lower them maybe if the
>tendancy remains (hehehehe), will we live long enough to see that!!!
>" Could it be there is still more to learn about the chemical soup we live
>in?
>RR"
>
>Of course(EB)
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John Hesselberth on mon 19 jul 04
On Monday, July 19, 2004, at 11:32 AM, Anne Webb wrote:
> i'm curious...really...why do standards vary so much from country to
> country
> re permissible limits (re ron's earlier post). does one country know
> something that another doesnt? who is right? and why isnt the info
> the same
> across the board?
> is the deviation perhaps influenced by of a given country's economy
> (less
> stringent standards in order to produce a lesser priced item and
> bolster
> economy)?
Hi Anne,
There are no hard answers to your questions but part of the reason
standards vary from country to country depends of who the influence
groups are in each country. These standards are not strictly based on
hard science. First, the science is rarely hard--it is usually based on
studies that leave room for interpretation even by honest, well
meaning, competent people. Second there are manufacturers who whine
about how many jobs will be lost if the standards are raised--what they
usually mean is how much their profits will go down, but that does
ultimately relate to jobs. Third, there are "the sky is falling" people
who say that any amount of anything is too much. And there is always
the question of whether a lower level is even technically possible to
achieve. I could go on, but I think I have made the point. These
standards are negotiated by people like I have described above and
others. Money often changes hands in the form of campaign contributions
or, sometimes I suppose, worse. Standards are ALWAYS a compromise of
viewpoints, and different countries/cultures have different sets of
values.
Regards,
John
John Hesselberth
http://www.frogpondpottery.com
http://www.masteringglazes.com
Anne Webb on tue 20 jul 04
Lee...
yes, the deviation of global standards undoubtedly has to do with
perspective.
i guess what my question was, though, was what kind of factors influence
"perspective" on this issue. ideally, one would think that the
determination of chemical safety standards should be based on empirical
evidence and should be fairly quantifiable. what kind of extraneous factors
are influencing this research, good or bad? is it faulty method, poor
resources, economic pressure, pressure from special interest groups, etc.
john i read your post last night but hadnt been able to respond til now.
your post kinda put things into perspective. food for thought eh?
Thanks..anne
>Anne Webb wrote:
>
>>is the deviation perhaps influenced by of a given country's economy (less
>>stringent standards in order to produce a lesser priced item and bolster
>>economy)?
>
>
> I think it is simply different perspectives.
>
> For example, they are much more particular about smooth bottoms
>on pots here in Japan. I have mentioned before, how all the pots in
>the show of the work of potters from Minnesota and Wisconsin about 5 years
>go, they had to bring in some Mashiko potters to smooth the feet on all the
>pots before the show opened.
>
> On the otherhand, the roads are narrow, even where there is
>room in the country for wider roads and there is rarely guard rails along
>the sheer drop off into the rice paddies and their ditches. Often,
>the runoff sewers on the sides of the road are not covered so it is easy to
>step right into them.
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Edouard Bastarache Inc. on wed 21 jul 04
Hello Linda,
the exposure limit for cadmium was set very low a
few years back not to prevent kidney effects but to prevent
lung cancer.
Prof. Bernard was not much impressed by the lung effects
in our discussions concerning the employees of Saft-France
who were overexposed to cadmium in the making of batteries
containing cadmium. Their type of exposure appeared quite more
severe than that of a studio potter.
Old heavy smokers may have blood cadmium levels close to
those who are occupationaly exposed and that is close to the
Biological Exposure Index : 0.5µg/100ml or 5 µg/L(1000 ml).
Tobacco smoke is a lot more noxious to the lungs (cancer) than
cadmium alone.
Later,
"Ils sont fous ces quebecois"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
http://sorel-tracy.qc.ca/~edouardb/
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
----- Original Message -----
From: "Linda Ferzoco"
To:
Sent: Wednesday, July 21, 2004 7:02 PM
Subject: Re: food safe pottery at low fire temperatues?
> Folks,
>
> What about cadmium's known interference with DNA? Is that not the
> basis of its being labeled a carcinogen?
>
> See (watch for wrapping)
>
> http://www.sciencenews.org/articles/20030719/fob7ref.asp
>
>
http://www.nature.com/cgi-taf/DynaPage.taf?file=/ng/journal/v34/n3/full/ng0703-239.html
> (the above article was published in Nature, one of the world's most
> prestigious scientific journals)
>
>
http://www.edie.net/gf.cfm?L=left_frame.html&R=http://www.edie.net/news/Archive/7115.cfm
>
>
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?holding=npg&cmd=Retrieve&db=PubMed&list_uids=12749863&dopt=Abstract
>
> and other articles which can be found by googling "cadmium dna"
>
> Short term effects on the kidneys are the least of the problems it
> seems to me.
>
> Linda
> --- "Edouard Bastarache Inc." wrote:
> > Hi Ron,
> >
> > "I'm not sure I understand what you are saying here - do you think
> > the
> > Cadmium limits are too low?
> > RR"
>
>
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>
Ron Roy on wed 21 jul 04
Hi Edouard,
I'm not sure I understand what you are saying here - do you think the
Cadmium limits are too low?
How long does it take for Cadmium to do it's damage - like how long ago was
the testing in China done?
I have seen that some suspects have been taken off the list - but I have
also seen many more added in my life time. Some of them approved drugs.
RR
>Just recently in Europe after studies conducted in China among
>workers severily exposed to cadmium, with the help of
>european experts from l'Universit=E9 Catholique de Louvain,
>the blood standards for the general population was raised significantly
>They found that chinese workers, even if quite more severily exposed
>than european workers, did not present much ill-effects.
>So some may go down and some will go up.
>It is now 0.5 =B5g/100 ml (smokers), the same level as for exposed
>workers.
>Understandable, the majority of the general population's exposure
>comes from cigarette smoking.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
=46ax: 613-475-3513=20
Edouard Bastarache Inc. on wed 21 jul 04
Hi Ron,
"I'm not sure I understand what you are saying here - do you think the
Cadmium limits are too low?
RR"
They were too low for the general population until Prof. Bernard and his
team studied
chinese workers exposed to severe levels without ill-effects, and for many
years.
They upped the value for the general population from 0.05 µg/100ml to 0.5
µg/100.
I have also changes my text accordingly but, Smart has not changed my text
on his site yet,
he will do so soon he told me last evening.
"How long does it take for Cadmium to do it's damage - like how long ago was
the testing in China done?
RR"
I have not found anything so far on the time of onset but the very long
biological
half-life of cadmium allows to assess excessive impregnation several years
after cessation of exposure.
Last summer I spent many hours helping union workers of Saft-France,
a maker of batteries containing cadmium, and I suggested to them to get in
touch
with Prof. Bernard at l'Université Catholique de Louvain in Belgium, whom I
believe
is one of the best experts in this field. It is from them I learned about
the studies in China.
Here is what he suggested for the medical surveillance of Saft workers.
Note that the difference in lab units in the case of blood cadmium,
he used is xx µg/100 ml and I use yy µg/L(1000 ml).
Cadmium
Prevention/screening strategy
1-The 2 µg threshold :
The Cd concentrations in urine (CdU) and blood (CdB), for a
non-professionally
exposed population, are normally lower than 2 µg/g creatinin and 2 µg/L,
respectively.
2-The 2-5 µg threshold :
Values ranging from 2 to 5 µg/g creatinine for CdU and 2 to 5 µg/L for CdB
are the sign of overexposure, especially CdB; or of body overload,
especially CdU,
due to a professional or an environmental exposure (very heavy smokers can
have
concentrations in this range if they are old).
This level of overexposure is without danger to the renal function nor to
the other
target organs (lungs, bone).
3.The 5-10 µg threshold :
Values ranging from 5 to 10 µg/g creatinin for CdU and from 5 to 10 µg/L for
CdB
are the sign of a more significant over-exposure which, whatever its origin,
corresponds to a signal for primary as well as secondary prevention
intervention.
A-Primary prevention :
It must be made sure that the exposure limit in the occupational setting
(cadmium in air) and the usual measures of personal hygiene are strickly
respected ( no smoking nor eating in the workshops...).
The respect of the air exposure limits and of personal hygiene measures
is essential to prevent the impregnation from continuing and coming close to
the critical thresholds of impregnation for the development of kidney
lesions
(10 µg/g creatinin for CdU and 10 µg/L for CdB).
Thus, it is a matter of preserving the safety margin offered by the 5µg/g
creatinin for CdU and 5 µg/L for CdB standard for professionally exposed
persons,
and this with respect to the critical thresholds of renal toxicity.
B-Secondary prevention :
It is recommended to do at least once a year a urine test to measure tubular
microproteinuria in order to make sure that the worker does not have a
particular sensitivity to Cd of physiopathologic origin or otherwise, which
sensitivity would expose him to a renal risk before the critical
thresholds
of impregnation are reached.
Standards are defined to protect the whole of workers but no standard
protects 100 % of the individuals except if there are very significant
safety
margins, which is not the case for cadmium (margin of a factor of two).
At this stage of impregnation, withdrawal from exposure is not justified
except
of course if the worker already suffers from renal disorders (due to another
cause
or to an old exposure to cadmium since effectively in tubular lesions, CdU
tends to
decrease and be lower than 10 µg/g creatinin).
4-The 10µg threshold :
Above 10 µg/g creatinin for CdU and 10 µg/L for CdB, withdrawal
from exposure is essential. At this level there is a risk of beginning renal
lesions.
This threshold corresponds to a risk of 1/10 for values which exceed a
little the threshold of 10 µg/g creatinin, that is to say 1 case of
tubular microproteinuria among 10 exposed individuals.
When the microproteinuria ranges between 300 and 1000 µg/g creatinin
(beta 2 microglobulin (b2m) or retinol binding protein (RBP),
the tubular effects will be sub-clinical, still reversible in certain cases,
and anyway little or not evolutionary. If there is microproteinuria, it
is recommended to conduct a complete renal functional investigation.
If impregnation continues, these two markers can climb and even exceed
10,000 µg/g creatinin. It is only at such levels of microproteinuria
that the renal effects become irreversible and are really likely to
gradually
compromise the renal function. Usually, such levels are reached only after
many years of exposure to Cd at levels way above the actual exposure limits.
5-Other risks, at the osseous or respiratory level, require levels of
exposure much more important than those leading to beginning tubular
effects.
Reference :
Communication personnelle du Professeur Alfred Bernard, Professeur
Université Catholique de Louvain, Directeur de recherches FNRS,
to Saft's workers (France), octobre 2003.
"I have seen that some suspects have been taken off the list - but I have
also seen many more added in my life time. Some of them approved drugs.
RR"
The limits are bound to change over time and only sound scientific studies
will tell.
Later,
"Ils sont fous ces quebecois"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
http://sorel-tracy.qc.ca/~edouardb/
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
Linda Ferzoco on wed 21 jul 04
Folks,
What about cadmium's known interference with DNA? Is that not the
basis of its being labeled a carcinogen?
See (watch for wrapping)
http://www.sciencenews.org/articles/20030719/fob7ref.asp
http://www.nature.com/cgi-taf/DynaPage.taf?file=/ng/journal/v34/n3/full/ng0703-239.html
(the above article was published in Nature, one of the world's most
prestigious scientific journals)
http://www.edie.net/gf.cfm?L=left_frame.html&R=http://www.edie.net/news/Archive/7115.cfm
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?holding=npg&cmd=Retrieve&db=PubMed&list_uids=12749863&dopt=Abstract
and other articles which can be found by googling "cadmium dna"
Short term effects on the kidneys are the least of the problems it
seems to me.
Linda
--- "Edouard Bastarache Inc." wrote:
> Hi Ron,
>
> "I'm not sure I understand what you are saying here - do you think
> the
> Cadmium limits are too low?
> RR"
Lee Love on wed 21 jul 04
Anne Webb wrote:
> i guess what my question was, though, was what kind of factors
> influence "perspective" on this issue. ideally, one would think that
> the determination of chemical safety standards should be based on
> empirical evidence and should be fairly quantifiable. what kind of
> extraneous factors are influencing this research, good or bad? is it
> faulty method, poor resources, economic pressure, pressure from
> special interest groups, etc.
It is just human nature. And different views and priorities.
When we sent our pots to the show five years ago, we had to include
the recipes for our glazes. We were told that barium was not allowed
in glazes in Japan. In America, it is not allowed in some States, but
is not nationally banned. In Japan, lawmaking is more centralized, so
it is easier to pass laws that effect the whole nation. Of course,
barium is not a traditional material used in glazes here. It was
introduced with western industrial methods. So maybe it was easier to
disallow.
We could use my previous example. We could ask something we
might be able to answer: "Why don't American potters generally use
smoothing stones on the bottom of their pots?"
--
in Mashiko, Japan http://mashiko.org
http://www.livejournal.com/users/togeika/ WEB LOG
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