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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 (Fe2O3),
2-Magnetite (Fe3O4),
3-Limonite (Fe2O3.H2O),
4-Siderite (FeCO3).
 
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.




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) Natural Red Iron Oxide

    Indian Red

  • (Materials - General) Iron Oxide Black - Fe3O4 - Ferrous ferric oxide, Synthetic Magnetite

    Fe3O4, Black Iron Oxide, BIO, Magnetite Powder, Iron(II,III) Oxide

  • (Materials - General) Iron Chromate - FeO.Cr2O3

    Ferric Chromate, Chromite, Chromate of Iron

  • (Materials - General) Iron Oxide Yellow - FeO.OH or Fe2O3.H2O - Fe2O3.H2O, FeO(OH), Goethite

    Iron(III) oxide, hydrated iron oxide, iron(III) hydroxide, yellow iron oxide

  • (Materials - General) Iron Oxide Red - Fe2O3 - Synthetic Hematite

    Ferric Oxide, Red Iron Oxide, RIO, Iron(III) oxide, Fe2O3, Hematite




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