Ron Roy on wed 20 oct 04
Yes trivalent chrome is a very stable compound - as opposed to some of the
other forms - like the water soluble kinds.
Monona mentions the fumes and the association between chrome and cancer,
severe allergies and asthma.
Keep in mind - chrome fumes - which means it condenses out on surfaces as
it cools - it is not trivalent any more.
The chrome used in cement in Europe has been banned now because so many
workers were having skin problems.
Even if a glaze is stable - there will be chrome on the surface from the
fuming. There is a limit for chrome leaching in Finland for ceramics and
glass by the way - Cr 2 mg/dm2 - same for nickel.
Yes we need a minute amount but it is a toxin when oversupplied - like so
many other things in life.
RR
>Hello Louis,
>a few statements before I answer your questions:
>1-Chromium is an essential trace element and is present in tissues in its
>trivalent state.
>
>2-In the industry, workers may be exposed to trivalent and hexavalent
>chromium compounds
>
> whose metabolic handling and toxicity are strikingly different.
>
>3-Trivalent chromium is absorbed poorly by inhalation and throught intact
>skin,
>
>resulting in a low order of systemic toxicity. However, should trivalent
>chromium gain
>
>access to the systemic circulation, toxic effects may develop.
>
>4-Trivalent chromium salts are absorbed after ingestion, but only 1% to
>25% of the
>
>dose ingested is absorbed.
>
>5-Trivalent salts are poorly absorbed through intact skin but, once the
>dermal barrier
>
>is broken, however, absorption may occur.
>
> 6-Trivalent chromium only penetrates with much difficulty into the skin
>and the risk
>
>of sensitizing is thus weak. Chromium metal is not in theory an allergen
>
>7-The risk of lung cancer appears non-existent among tanners using mainly
>trivalent
>
>chromium compounds.
>
> 8-Trivalent chromium per se is not genotoxic as demonstrated in epidemiologic
>
> studies among which one conducted among exposed tannery workers.
>
>
>
>Your questions now :
>
>
> "I want to make sure i am clear about something. Do you think that
> leached chromium from glazes is a cause for concern?I looked for your
> article and found:
> http://www.digitalfire.ab.ca/cermat/education/182.html
> Thank you.
>Louis"
>
>My answer is no considering the low order of toxicity of green chromium oxide
>generally used to color glazes.
>Secondly the amounts used are very low if you compare them to the amounts of
>lead compounds used in leaded glazes (EB)
>
>---------------------------------------------------------------------------
>---------------------------
>
>"I assume that the chromium leached from a glaze would be trivalent or
> become so in the gastro intestinal tract prior to absoption. Is this a
> reasonably good assumption? I read the toxic does and noticed that it
> was relatively high but wonder how much chrome might be considered a
> problem when leached from a glaze.
>Louis"
>
>Indeed, green chromium oxide is trivalent, I can not tell you how much
>may leach from a glaze, too many different glaze recipes are available.
>Chromium in glaze leaching is not regulated in North America for the
>above reasons, I do not know of any standard; but I would not worry
>about its presence in my "french pea soup"(EB)
>
>---------------------------------------------------------------------------
>--------------------------
>
>" Thank you for your time I have printed out your materials on the
> digital fire sight and keep them near the MSDS sheets. They are much
> more useful and provide a valuable service.
> Louis"
>
> Welcome(EB)
>
>---------------------------------------------------------------------------
>--------------------------
>There are other componds than green chromium oxide that can be used in
>ceramics:
>-iron chromite (trivalent, confirmed carcinogen during ore processing only,
>exposure limit=0.05 mg/m"),
>-potassium dichromate (soluble hexavalent, exposure limit=0.05 mg/m",
>confirmed human carcinogen)
>-stains (?).
>Later,
>Edouard Bastarache
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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