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Iron oxide and Hematite

Iron (Fe) is an abundant metal,
constituting about 5% of the earth's crust.


Common iron ores are :

1-Hematite (Fe COLOR="#004080">2 COLOR="#004080">O COLOR="#004080">3),

2-Magnetite (Fe COLOR="#004080">3 COLOR="#004080">O COLOR="#004080">4),

3-Limonite (Fe COLOR="#004080">2 COLOR="#004080">O COLOR="#004080">3 COLOR="#004080">.H COLOR="#004080">2O),

4-Siderite (FeCO COLOR="#004080">3).

 

Of importance is that most ores mined
may contain between 10% and 12% free silica. Iron compounds have
many applications , and iron oxide pigments are used in coatings
and as colorants in ceramics, glass, plastics, rubber and the
like.


 

Environmental Levels and
Exposure :


 

A-Soil :

In comparison to most other metals, the
average concentration of iron in soil is very high, 5000
mg/kg.


B-Air :

In remote and non-industrialized areas
of the world, the atmospheric concentration is less than 1
ng/m³.Higher values are found in urban areas and close to
iron- and steel-producing plants.


C-Diet :

The daily intake of iron varies greatly
with the proportions of iron-rich and iron-poor items that
comprise the diet, but in most industrial countries, it typically
ranges from 9 to 35 mg/day.


 

Uptake and Distribution
:


 

Iron is an essential metal and takes
part in oxygen transport and utilization. Absorption of iron from
the gastrointestinal tract is adjusted to a fine homeostasis.
Under normal conditions, about 5% to 15% of iron in food is
absorbed, but the uptake increases considerably in the case of
iron deficiency or depleted iron stores. Normally, the human body
contains about 3 to 5 g of iron. Two thirds of this amount is
bound to hemoglobin in the blood.


About 20% to 30% iron in the body is
stored in storage proteins (ferritin and hemosiderin) Elimination
is slow and takes place mainly via bleeding and by desquamation of
mucosal cells


Increased gastrointestinal uptake and
deposition of iron in various organs may lead to secondary lesions
in these organs. In other diseases, iron deposition is a sequella
of pathologic processes.


 

A-Hemochromatosis :

A hereditary metabolism anomaly
characterized by increased absorption of iron which ends up after
the age of fifty in cutaneous pigmentation, liver cirrhosis and
sometimes diabetes. Other organs may be affected:


-pituitary,

-gonads,

-heart,

-articulations.

 

B-Secondary hemosiderosis
:


One usually distinguishes hemosiderosis,
which is an iron overload of tissues, from hemochromatosis which
comprises tissue lesions due to martial (iron)
accumulation.


 

1-Generalized :

It may be secondary to chronic
hemolysis, sideroblastic anemias, excessive iron intake by
parenteral route or, in the case of sideroblastic anemia, by oral
route.


It is also found in Kashin-Beck's
disease, a disease encountered in regions where drinking water is
very rich in iron salts.


 

2-Localized :

· within the lungs, due to
repetitive hemorrhages as in mitral stenosis, in idiopathic
pulmonary hemosiderosis;


· within the kidneys, as in
intravascular hemolysis, paroxysmal nocturnal hemoglobinuria;


· within the liver, in porphyria
cutanea tarda.


 

Occupational exposures to iron occur
during mining, both underground or open-pit, in iron and steel
foundries, during arc-welding, in connection with various metal
processing activities; and in silver polishing (using fine iron
oxide as a polishing rouge).


 

Toxic
Effects


 

A-Ingestion :

Ingestion of soluble iron salts, such as
those found in common iron tablets taken in the treatment or
prophylaxis of iron-deficiency anemia, are potentially very toxic.
In doses exceeding 0.5 mg of iron, toxic effects with vomiting,
ulceration of the gastro-intestinal mucosa, and intestinal
bleeding may occur. In severe cases, liver and kidney damage may
also develop.


 

B-Inhalation :

 

1-Siderosis:

Inhalation of iron, mainly in the form
of iron oxide fumes, can give rise to roentgenologic changes in
the lung due to deposition of inhaled iron particles. The retained
dust produces x-ray shadows that may be indistinguishable from
fibrotic pneumoconiosis.
It has
been named siderosis, iron pneumoconiosis, hematite
pneumoconiosis, iron pigmentation of the lung, and "arc welder's
lung"
, reflecting the fact that
it has been seen in many occupational groups exposed to iron oxide
fumes, including silver polishers.


Most specialists regard these
roentgenologic lung changes to be benign without having any
influence on the lung function or progressing to fibrosis.


 

2-Sidero-silicosis:

Siderosis is sometimes associated with
silicosis among iron ore miners if the exposure to free silica is
severe enough to cause fibrotic changes and subsequent
deterioration of the pulmonary function.


 

Carcinogenesis
:


 

Altough an increased incidence of lung
cancer has been observed among hematite miners exposed to iron
oxide, presumably as a result of concomitant radon gas exposure,
there is no evidence that iron oxide alone is carcinogenic to man
or animals. In a large (10,403) cohort study of Minnesota iron ore
(hematite) miners, they did not show any increased mortality in
lung cancer. This study is of particular interest, for the radon
levels in Minnesota iron ores, in contrast to most of the other
iron ore mines examined, was low. In addition, smoking was
prohibited underground, and diesel fuel vehicles were not used. No
evidence was found in a study for an increased lung cancer risk in
a plant producing sulfuric acid from pyrite (FeS2) where workers
had been exposed to iron oxide dust at very high concentrations
(50 to 100 mg/m³).


 

Thus it seems reasonable
to conclude that iron oxides are not carcinogenic.


 

 

Quebec's exposure limit
:


 

VEMP (Valeur d'Exposition Moyenne
Pondérée) = 5mg/m³


 

 

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.

Related Information

Links

Materials Natural Red Iron Oxide
Materials Iron Oxide Yellow
Materials Iron Oxide Black
Materials Iron Oxide Red
Materials Iron Chromate
Typecodes Article by Edouard Bastarache
Edouard Bastarache is a well known doctor that has written many articles on the subject of toxicity of ceramic materials and books on technical aspects of ceramics. He writes in both English and French.
People Edouard Bastarache

By Edouard Bastarache


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