Alumina Toxicology
By Edouard Bastarache
Introduction
:
Occurs in nature as the minerals
bauxite, bayerite, corundum, diaspore, gibbsite.
Types :
I- Alumina or Aluminium Oxide, Al2O3. This oxide exists in several forms
:
*Alpha-Al2O3, the pure form obtained by
calcination at high temperature.
*Beta-Al2O3, is the compound
Na2O.Al2O3
*Gamma-Al2O3, stable to about 1000 C and
contains traces of water or hydroxyl ions.
II-Alumina Hydroxide
(Aluminium Hydrate, Aluminium Trihydrate, Hydrated Alumina),
Al(OH)3 or AlH3O3.
Uses :
In the production of aluminium,
refractory materials, synthetic abrasives etc, such as :
I-Alumina (Fused) :
In spite of its high m.p. (2050 C),
alumina can be fused in an oxy-hydrogen flame or in an electric
arc.By the former method, large single crystals (boules) can be
produced; they are used as bearings, and as dies for wire-drawing,
and for other purposes demanding high abrasion resistance. Fused
alumina made in the electric arc furnaces is usually crushed,
bonded with fine alumina powder, shaped and then sintered.
II-Alumina (Sintered) :
Alumina, sometimes containing a small
amount of clay or of a mineralizer, and fired at a high
temperature to form a dense ceramic. Sintered alumina has great
strenght and abrasion resistance, high dielectric strenght, and
low power factor.
III-Corundum (Emery) :
The only form of alumina that remains
stable when heated above about 1000 C,
also known as alpha-alumina.
It occurs naturally, but impure, in S.
Africa and elsewhere but generally it is produced by extraction
from bauxite followed by a firing process at high
temperature.
Toxicology
:
In general, aluminas are efficiently
eliminated from the lung and are considered to be nuisance dusts;
their role in fibrogenic lung disease remains unclear.
High aluminium levels (between 400 and
1080 mg/kg of wet pulmonary tissue) have been found in the lungs
of subjects exposed during 10 to 37 years to alumina dust.
Animal experiments indicate that
prolonged inhalation of alumina involves a rise in the
concentration of aluminium in the brain.
A review of the literature (1957), on
the pulmonary toxicity of aluminium carried out in the USA
concluded that aluminium, aluminium oxide and aluminium hydroxyde
Al(OH)3 do not cause pulmonary effects; the lesions reported by
some authors would result from the presence of other
substances.
I-Pneumoconiosis :
A number of epidemiologic studies of
aluminium smelter workers have confirmed either minimal or absent
fibronodular disease and no excess mortality associated with
pneumoconiosis.
The risk associated with chronic
exposure to alumina dust (Al2O3) is not entirely elucidated. Some
authors think that alumina can generate a pneumoconiosis
(aluminosis) while others have recommended the use of powdered
alumina by inhalation as a therapeutic and preventive method in
the case of silicosis.
Italian studies suggest that chronic
exposure to high
concentrations of alumina can
causea light pulmonary fibrogenic reaction and the presence of
small opacities on the chest X-ray.
A few cases of fibrosis due to a
prolonged exposure to alumina during the production of abrasives
were reported. It does not seem that these workers were exposed to
silica or asbestos.
II-Interstitial Fibrosis :
Studies seem to indicate that,
independently from exposures to other pneumotoxicants, massive
inhalation of aluminium or alumina can favor the development of
interstitial fibrosis.
III-Industrial Bronchitis
:
Excessive protracted nuisance dust
exposure (100 mg/year for more than 20 years) has been accompanied
by findings consistent with a minor degree of nonspecific chronic
industrial bronchitis.
IV-Asthma :
An asthmatiform syndrome has been
described among potroom workers attributed by some authors to the
exposure to volatile fluorides.
A respiratory obstructive syndrome has
also been described among workers involved in the manufacture of
aluminium fluoride.
Quebec's Exposure Limits
:
|
-
|
VEMP
|
Note
|
- Aluminium, oxide
- expressed as Al
|
10mg/m3
|
Pt,
|
Pt : Poussière Totale (Total
Dust), without asbestos fibers, and <1% crystalline
silica.
References :
1-Occupational Medicine,Carl Zenz,
last edition.
2-Clinical Environmental Health and
Toxic Exposures, Sullivan & Krieger; last edition.
3-Sax's Dangerous Properties of
Industrial Materials, Lewis C., last edition.
4-Toxicologie Industrielle et
Intoxications Professionnelles, Lauwerys R.R. last
edition.
5-Chemical Hazards of the Workplace,
Proctor & Hughes, 4th edition
Edouard Bastarache M.D.
Occupational & Environmental Medicine
Author of "Substitutions for Raw Ceramic Materials"
Tracy, Québec, CANADA
edouardb@sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/~edouardb/
Out Bound Links
In Bound Links
- (Materials - General)
Alumina Hydrate - Al2O3.3H2O
Alum Hydrate, Alumina Trihydrate, Hydrated Alumina, Alpha Aluminum Trihydroxide, Gibbsite
- (Materials - General)
Alumina - Al2O3
Aluminum Oxide
- (Materials - General)
Calcined Alumina - Al2O3 - Aluminum oxide
Alumina Calcined, Calcnd Alum, Ground Alumina, Corundum
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