Dioxins Dioxines in Clays

Hello Mr. Schaum (USA-EPA),

here are my comments on the Battelle's report on dioxins :

Comment #1 :

It is a very interesting study/report. It was high time something got done concerning this potential problem among industrial and artist/artisan ceramists in North America.

Comment #2 :

But I would not use the results of this study to give advice to fellow ceramicists

which I do concerning other chemicals thoughout the world, mainly to the members of

an international newsgroup named « Clayart ».

I would prefer not to be sued legally.

I do not think the sampling was adequate, not large enough to represent the different situations confronted by my fellow ceramists.

I would much more prefer the sampling used in a Canadian study conducted in 1998

in British Columbia :

AUTHOR: Bob Hirtle; Kay Teschke; Chris van Netten; Michael Brauer

TITLE: Kiln Emissions and Potters’ Exposures

SOURCE: American Industrial Hygiene Association Journal v59 no10 p706-14 O’98 =

« Pottery kiln emissions were measured at 50 sites, 10 from each of 5 categories : professional studios, recreation centers, elementary schools, secondary schools, and colleges. »

To this method of sampling, industrial sites could be added, and settings where mining and processing takes place in order to have a good picture of what is going on.

Comment #3 :

The Monte Carlo simulations appear very neat but since the original sampling appears deficient, the authors of the report state the following :

« The simulation, using a variety of assumed input distributions, suggests that doses could extend to levels higher or lower than those estimated for the hypothetical scenario. »

(...)

« Therefore, the simulation results are best interpreted as preliminary indications of how to extrapolate the observations of this study to a broader population, and further study is recommended to confirm these predictions. »

Since we do not use these simulations in evaluating exposures of workers in Quebec, I will refrain from commenting.

Comment #4 :

Were gazeous dioxins emitted by kilns measured? No...

Maybe it was omitted because of the excellent ventilation used at Ohio State, at least it is what I saw on Battelle’s site a few months ago.

Excellent ventilation is often not the case in many studios, I know I have been making pots for 40 years, and visited many of them.

Recently a paper was presented by Dr. Alfred Franzblau of the University of Michigan, titled : « Human Exposure to Dioxins from Clay : A Case Report »

In this report it was observed that 3 ladies operating a pottery studio at home were overexposed to dioxins. The most exposed was operating 3 kilns in her basement without ventilation and the other 2 were quite less exposed for their kiln was located in their garage. Blood tests for dioxins and furans were done. The total TEQ (ptt) was 211 for the most exposed and 61 to 82 for the other 2.

Comment #5 :

Why is it that dioxins were not measured in the blood of the students at Ohio State?

I do not know, but they should be in a future study, it would complement the other means to assess exposure.

Comment #6 :

Gazeous dioxins in ceramics may come from 3 sources :

1-The clay,

2-The glaze,

3-From firing.

Firing drives off and destroys dioxins but in the bisque firing, new dioxins may be formed :

« Bisque Firing :

Glazing bisque ware is mainly a European invention used to overcome the difficulties of raw or once-fired tin glazes for majolica ware.

Chemical changes in the body during bisque firing are slight at first.When temperature reaches 350 to 400 F (178-204 C), all atmospheric moisture should have left the ware, causing little or no shrinkage.

Most of the chemically combined water will leave the ware at temperatures between 950 and 1300 F (510-705 C).

During this "water smoking" period considerable shrinkage occurs as both the chemically combined water and gases from the burning of organic materials leave the body.

If there are Cl- donors as impurities in the clay, dioxins could be formed since carbon monoxide is present as it has been already demonstrated recently in electric kilns, even if presumebly they fire in oxidation, and even if we allow the penetration of fresh air into the kiln by leaving at least one peep-hole unplugged in order to try to reach complete combustion in oxidation.

Bisque firing in a gas kiln is also done and the the most oxidized state obtained in this situation is "neutral fire", in between oxidation and reduction, with the production of more CO than in oxidation.

The dioxins already present in the ball clays of the wares could be emitted into the kiln room and also the stack (if bisque firing takes place in a fossil fuel kiln) around 421-510 C (Mckay et al, 1992). »

Glaze Firing :

Dioxins may volatize during this type of firing and be present in the room.

Once Firing :

Glazes for once-firing may contain larger amounts of clays, larger than in those used for glazing bisque-fired wares. In this very slow process, the wares are fired only once as if bisque firing and glaze firing were put end to end; the same comments as above apply.»

Comment #7 :

The special case of salt-firing :

Assuming that the pots were bisque-fired before being glazed and set into the kiln :

I-In the case of high fire salt firing, the salt is introduced into the kiln at the end, often times close to 2300 F; the formation of dioxins could occur in the stack because at this temperature at 8 feet above the bottom of the kiln the temperature of the gasses in the stack is between 800 -1000 F.

So the farther up in the stack, the cooler are the off-gases and there is certainly a point at which dioxins formation could occur due to the presence of carbon, carbon monoxide when the kiln is reducing, and the presence of a Cl- donor (salt).

II-Some high fire potters put salt in containers at different places in the kiln before starting to fire and it is volatized by heat during the process, it would be important to know at what temperature salt volatizes to see if dioxins formation is possible.

III-Some potters do salt low-firing, a technique I am not familiar with, actually it is said it is a salt-raku firing invented by an american potter, a modification of a japanese method.»

Comment #8 :

I believe we should pay attention to pregnant and breast-feeding women for dioxins can be noxious to them :

Effects on development :

I. In animals :

TCDD is teratogenic and toxic to the foetus. Studies in laboratory animals suggest that dioxins alter development (low birth weight, miscarriages, congenital malformations, etc.)

TCDD crosses the placental barrier.

II. In humans :

There are reports which indicate an increase in miscarriages or congenital malformations, more especially of the spine. We do not know much of the potential effects of dioxins and other chlorinated compounds on the development of the nervous system of children.

B. Effects on reproduction :

I. In animals :

The effects on reproduction seem to be very sensitive indicators of the toxicity of dioxin. Sudies in laboratory animals suggest unfavourable changes in reproduction (fertility, development of sexual organs, disturbances in the behaviour related to reproduction).

II. In humans :

We know few things of the potential effects of dioxins and other chlorinated compounds on human fertility. But occupational exposure to TCDD alters serum concentrations of male reproduction hormones.

C. Effects on breast milk :

TCDD is found in mother's milk; high levels of TCDD can be detected among adult children of mothers who were exposed to dioxins as production workers.

Comment #9 :

TCDD or TEQ represents one of the most toxic compounds known. Therefore an increase of only 10% above background level certainly represents a matter of concern to be taken into account by risk assessment specialists.

Comment #10 :

Foreign Ball Clays :

1-Australian Ball Clays :

« I regret I have no information about this but I have never heard anyone speak of it over here.
As far as I know most of the clays are mined in the Western Planes of NSW, in the Gulgong Area and to my knowledge there are no Coal measures in those locations.
The main pottery centres in Victoria are west of Melbourne but the coal measures are to the east. » (Ivor Lewis, potter in Australia)

2-English Ball Clays :

« To tell the truth I have heard nothing to suggest that there is any possibility of that. Because part of my job is to monitor the health and safety aspect of our materials, I try to keep an ear to the ground on any developments in that area over here. I'm not saying that I hear everything, but my Daughter is Technical Services Manager (Fine Art) at Bath Spa University College, so gets to hear stuff before most people, and keeps me pretty well up to date! » (Steve Mills, potter in the U.K.)

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Other Sites by the Author

DigitalFire, Canada

http://digitalfire.com/4sight/hazards/ceramic_hazard_dioxins_in_clays_323.html?logout=yes

Smart.Conseil, France

http://smart2000.pagesperso-orange.fr/dioxines.htm

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Ĝis la revido,

(A la revoyure)

Edouard Bastarache
Spertesperantisto
Sorel-Tracy

Quebec

edouardb@colba.net