Edouard Bastarache on mon 9 oct 00
Hello all,
Dioxins in clays:
Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) are
tricyclic aromatic compounds with similar chemical and physical properti=
es.
They are ubiquitous in the environment and usually do not occur
naturally.There are 75 positional isomers of PCDDs and 135 isomers of PCD=
Fs.
2,3,7,8-TCDD (TCDD) is the most toxic isomer, and the estimated toxic ris=
k
in humans is calculated in terms of =ABTCDD equivalents=BB. For exemple, =
the
toxic effect of different isomers is calculated in terms of the amount th=
at
would cause the same degree of toxicity as TCDD.
Octachloro-dibenzo-p-dioxine, produced during the synthesis of
pentachlorophenol (Norback et al. 1975), is quite less toxic than TCDD
produced during the synthesis of the herbicide 2,4,5-T.
The most important sources include contaminated products such as
chlorinated phenols and their derivatives. Polychlorinated biphenyls (PCB=
s);
incineration of municipal, hazardous, and hospital wastes; sewage sludge;
automobile operations; fossil fuel combustion; and emissions from fire
involving PCBs are other sources. Production of chlorophenols and their
derivatives; chlorophenol wood treatment; chlorine bleaching in the pulp
industry; and production and handling of iron, steel, and other metals, s=
uch
as aluminium, also yields dioxins.
Exposure has also occurred from herbicide use and from industrial and
transportation incidents. In occupational settings, exposure has occurre=
d
in chemical manufacturing processes and from handling the wastes from the=
se
processes.
Ingestion, inhalation, and dermal absorption are all thought to be routes=
of
exposure to PCDDs and PCDFs. However, exposure for most individuals will =
be
small and will come through a variety of sources.
It is generally accepted that about 98% of human exposure comes from food.
Dioxins are insoluble in water but lipophilic (soluble in fats) and other
hydrophobic materials, and bind to solid material such as soil and fly as=
h.
They have a low rate of metabolic breakdown, they preferentially accumula=
te
in adipose tissue, skin, liver, and breast milk in mammals. The amount o=
f
dioxins expressed as TCDD equivalents in breast milk of lactating women
often exceeds the tolerated Swedish daily intake of 5 pg/kg body weight b=
y a
factor of 20 to 30.
In soil TCDD has an extremely long half-life time, greater than 10 years.
The biologic half-life in humans has been measured to be in the range of =
5
to 8 years.
TCDD represents the most toxic synthetic compound known. It acts as a
complete carcinogen in several species.
By now, an increased risk for all cancer sites combined has been shown in
cohort studies on TCDD-exposed subjects, with an especially high risk for
soft-tissue sarcoma (STS).
In Seveso, Italy, area with TCDD soil contamination, excess numbers of
tumors have been found, including lymphomas and STS.
Among Vietnam veterans, increased mortality in STS was reported.
As has been concluded, TCDD is among the most potent identified chemical
carcinogens.It is transspecies, transstrain, transsex, multisite, and
complete carcinogen.
For humans, the immunotoxic effects by dioxins are probably at least as
serious as the carcinogenic properties.
It also causes chloracne in humans, which is the most precocious clinical
sign of
excessive exposure to TCDD. It may also cause allergic dermatitis and is =
an
eye
irritant.
When heated to decomposition it emits toxic fumes of CL-.
NIOSH REL (Dioxin) : Reduce to lowest feasible level.
Little is still understood about the potential effects on fertility and t=
he
developing nervous system in children by dioxins and related chlorinated
compounds.
Also of concern is the high content of dioxins in mother=92s milk and in =
the
food chain (e.g. some fatty fish)
Conclusion :
Not knowing the isomers( different levels of toxicity) identified in kaol=
ins
and ball clays and their concentrations, it is very difficult to discuss
this problem properly.
For obvious reasons, we should be more worried about employees working in=
mi
ning and processing these dioxin-containing clays, and by pottery factory
employees than by studio potters, hobbyists, teachers and their students.
The use of clays made without these could be recommended for those more
worried while awaiting more information on this subject from the mining
companies, even from those located on other continents
It gives a good exemple why good housekeeping of your studio, avoidance o=
f
unnecessary dusty operations and the use of a decent dust mask are import=
ant
factors.
Also stay away from some fatty fish!!!
Later,
Edouard Bastarache M .D. (Occupational & Environmental Medicine)
Author of =ABSubstitutions for Raw Ceramic Materials=BB
edouardb@sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/~edouardb/
References :
1-Occupational Medicine, Carl Zenz, last edition.
2-Sax=92s Dangerous Properties of Industrial Materials, last edition
3-Hazardous Materials Toxicology, Sullivan & Krieger, last edition.
4-Toxicologie Industrielle et Intoxications Professionnelles, Lawerys, la=
st
edition.
amy parker on tue 10 oct 00
So, not to ask a really stupid question, Edouard, but how exactly do the
dioxins get into the clay deposits which are thousands of years old? Is it
a matter of surface runoff, seepage into the water table, or what? Were we
preceeded by an ancient race who poisoned their environment and themselves?
Amy
>Dioxins in clays:
>Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) are
>tricyclic aromatic compounds with similar chemical and physical properties.
>They are ubiquitous in the environment and usually do not occur
>naturally.
>Edouard Bastarache M .D. (Occupational & Environmental Medicine)
Amy Parker
Lithonia, GA
Edouard Bastarache on tue 10 oct 00
Hello Amy,
here is an excerpt by a fellow clayarter posted recently.
It seems that dioxins may be "nature-made".
"In a regulation of 17 november 1999 the European Commission "on the
conditions for the authorisation of additions belonging to the group
'binder, anti-caking and coagulants' in feedingstuffs" states that
"...kaolinitic clays originating from certain mines situated in the Feder=
al
Republic of Germany have been found to contain extremely high levels of
dioxine. According to available information, this could be a contaminatio=
n
of geological origin... The use of feedingstuffs contaminated with dioxin=
es
may contaminate foodstuffs of animal origin... The acceptable level of
dioxins in kaolinitic clays should be restricted to the analytical limit =
of
determination... The contamination could in fact also concern other
authorised additives, as indicated by the fact that ball clay, sedimentar=
y
clays containing other minerals besides kaolin, originating from a mine i=
n
the United States has also been shown to be heavily naturally contaminate=
d
by dioxin of geological origin..."
Here was my answer to the origin of these dioxins:
"My hypothesis, for what it may be worth, is that dioxins produced by a h=
uge
pre-historic forest fire were trapped somehow in the weathering process o=
f
making kaolins and ball clays. Hypotheses exist to be proved."
I came up with this explanation because we know that the combustion of
fossil fuel produces these chemicals.
There are a few geologists on this list and none "pick up the glove " as =
we
say in french. Maybe they refrained just to be nice to me.
Later,
Edouard Bastarache
Dans / In "La Belle Province"
edouardb@sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/~edouardb/
-----Message d'origine-----
De : amy parker
=C0 : CLAYART@LSV.CERAMICS.ORG
Date : 10 octobre, 2000 14:00
Objet : Re: Dioxins in clays
>So, not to ask a really stupid question, Edouard, but how exactly do the
>dioxins get into the clay deposits which are thousands of years old? Is =
it
>a matter of surface runoff, seepage into the water table, or what? Were =
we
>preceeded by an ancient race who poisoned their environment and themselv=
es?
Michael Banks on wed 11 oct 00
I didn't refrain just to be nice Edouard... :) I was surprised and a
little unsettled to hear that dioxins could occur naturally in kaolinitic
clays. And a little sceptical to be honest. But then geologists once
thought plutonium didn't occur in nature, but now it appears to be there,
quite naturally..
Apart from your forest fire theory, another feasible source of
polychlorinated organic compounds (including dioxins and PCB's) could be
nearby coal beds. These are known to be rich in reactive aromatic compounds
such as phenols which could combine with the chlorine in naturally trapped
brine to produce the super carcinogens. Many fireclays and china clays are
closely associated with coal seams. The close association of coal with
white clay beds is genetic. Kaolinitic clays are often produced in
feldspathic rocks in contact with the coal by the strong acids which are a
by-product of the coalification process. Carcinogenic organic compounds
like the phenols, must migrate away from the coal into clays.
Michael Banks,
Nelson,
New Zealand
----- Original Message ----
Edouard Bastarache wrote: (Snip): .... kaolin, originating from a mine in
the United States has also been shown to be heavily naturally contaminated
by dioxin of geological origin..."
"My hypothesis, for what it may be worth, is that dioxins produced by a huge
pre-historic forest fire were trapped somehow in the weathering process of
making kaolins and ball clays. Hypotheses exist to be proved."
I came up with this explanation because we know that the combustion of
fossil fuel produces these chemicals.
There are a few geologists on this list and none "pick up the glove " as we
say in french. Maybe they refrained just to be nice to me.
Martin Howard on wed 11 oct 00
Could this be a gift from the dinosaurs, or such like large animals being
burnt alive in an one of the many violent changes in our plant's history?
In which case, can such deposits contain information about those creatures?
Pile on the hypotheses :-)
Martin Howard
Webb's Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
England
martin@webbscottage.co.uk
Martin Howard on fri 13 oct 00
Correction of SPELLING MISTAKES
Could this be a gift from the dinosaurs, or such like large animals, being
burnt alive in one of the many violent changes in our planet's history?
In which case, can such deposits contain information about those creatures?
Pile on the hypotheses :-)
Sorry all.
Martin Howard, the bad speller, bald-headed dinosaur at
Webb's Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
England
martin@webbscottage.co.uk
Ron Roy on mon 16 oct 00
Yet another reason for making sure kilns are well vented - RR
>For obvious reasons, we should be more worried about employees working in m=
i
>ning and processing these dioxin-containing clays, and by pottery factory
>employees than by studio potters, hobbyists, teachers and their students.
>The use of clays made without these could be recommended for those more
>worried while awaiting more information on this subject from the mining
>companies, even from those located on other continents
>
>It gives a good exemple why good housekeeping of your studio, avoidance of
>unnecessary dusty operations and the use of a decent dust mask are importan=
t
>factors.
>Also stay away from some fatty fish!!!
>
>
>References :
>1-Occupational Medicine, Carl Zenz, last edition.
>2-Sax=92s Dangerous Properties of Industrial Materials, last edition
>3-Hazardous Materials Toxicology, Sullivan & Krieger, last edition.
>4-Toxicologie Industrielle et Intoxications Professionnelles, Lawerys, last
>edition.
Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
=46ax 416-438-7849
Edouard Bastarache on fri 20 oct 00
Some disagree!!!
Later,
Edouard Bastarache
Dans / In "La Belle Province"
edouardb@sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/~edouardb/
-----Message d'origine-----
De : William Kaukler
Groupes de discussion : sci.materials.ceramics
Date : 20 octobre, 2000 00:08
Objet : Re: Dioxins in clays
Pure speculation.
None of the information provided can permit the conclusion that clays can
become hazardous materials in the way intimated. No evidence was provided
showing the degree of contamination any clay sample might have (based on
chemical analysis). The information may be available, but the conclusions
are unfounded unless the numerical data is provided to substantiate them. I
cannot see how the topic title was even discussed. It was rather a summary
of how bad dioxins are and general chemical affinities which did not include
clays (although soil and fly ash can be silicate but are not clay).
Firing of clay (or soil or fly ash if added) to crockery will decompose any
hydrocarbons and render them inert. As far as I know, clay used for pottery
and bricks is generaly obtained from deep (meaning old) sediment strata that
certainly predate the dioxins. Yes, clay strata can be infiltrated by
contaminated ground water, but those clay strata are not selected for fired
clay product production as they are generaly nearer the surface and provide
less desirable properties when processed.
Dr. William Kaukler
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