Bentonite
Classification:
Bentonite is a rock created from sedimentated and encrusted volcanic ash; for details, see under the heading volcanic ash.
Synonyms/Trade Names:
Montmorillonite.
Chemistry/Composition:
It is composited of quartz, feldspars, micas (montmorillonite) and contaminations of chalk .
Medical Importance:
Key Hazards:
Chronic inflammation.
Involved Organs:
Lung.
Exposure/Epidemiology:
Bentonite has waterretaining properties, and is used in ceramics, foundry mould bonding, and also in insecticides and pesticides.
Thresholds:
In Germany, MAK 6 mg/m3.
Etiology/Pathophysiology:
Associated risks are not known.
Lung Diseases:
Associated diseases are not known, however, some cases of silicosis (induced by bentonite ores contaminated with quartz) have been described. In one study, chronic pneumonitis with severe dust deposits in bentonite exposed workers has been reported.
Clinical Presentation:
No associated symptoms are known.
Radiology:
Chest radiographs are usually normal.
Lung Function:
Usually normal.
Bronchoalveolar Lavage:
The mineral fibers can be detected in the lavage fluid.
Pathology:
Gross:
The lungs display no abnormal findings.
Histology:
The mineral particles can be deposited in the distant airways, and be ingested by macrophages, and transferred to the proximal lymph nodes. An increased number of intra-alveolar macrophages and mild mononuclear inflammatory infiltrates may be noted.
Prognosis:
Usually good and without serious sequelae.
Additional Diseases:
None.
Remarks:
In animal experiments, the storage of intra-tracheally instilled bentonite induced only a focal tissue reaction. The pulmonary lipids or phospholipids did not increase. Therefore, it is assumed, that bentonite has an oriented protein or polysaccharide surface, which protects the macrophages against the necrotizing potency of bentonite.
References:
search Pubmed for Bentonite
Adamis Z, Timar M, Kofler L, Tatrai E, Ungvary G: Biological effects of the respirable dusts from ore mines. Environ Res 41 (1986) 319-326
Bignon J: Lung Diseases and nonasbestos fibres. Eur J Respir Dis Suppl 126 (1983) 397-402
Elmes PC: Other isometric mineral dusts pneumoconiosis: bentonite. In: JK Howard, FH Tyrer (Eds): Textbook of occupational medicine. Churchill Livingstone, Edinburgh (1987)
Fraser RG, Paré, JAP: Diagnosis of diseases of the chest. WB Saunders, Philadelphia, London (1979)
Ivan M, Dayrell M, Hidiroglou M: Effects of bentonite and monensin on selected elements in the stomach and liver of fauna-free and faunated sheep. J Dairy Sci 75 (1992) 201-208
Reichel G: Auf anorganische Stäube mit geringen oder fehlendem Quarzgehalt zurückgehende Lungenveränderungen. In: WT Ulmer (Ed): Handbuch der inneren Medizin, Bd IV: Pneumokoniosen. Springer, Heidelberg (1978) 468-508
Schwarz T, Werner E: The effect of long-term bentonite administration on the metabolism of selected trace elements (Fe, Cu, Zn, Mn) in the dwarf goat. Arch Exp Veterinarmed 44 (1990) 591-597
Short SR, Petsonk EL: Respiratory health risks among nonmetal miners. Occup Med 8 (1993) 57-70
Tatrai E, Adamis Z, Timar M, Ungvary G: Comparative histopathological and biochemical analysis of early stages of exposure to non-silicogenic aluminum silicate and strongly silicogenic quarz dusts in rats. Exp Pathol 23 (1983) 163-171
Tatrai E, Ungvary G, Adamis Z, Timar M: Short term in vivo method for prediction of the fibrogenic effect of different mineral dusts. Exp Pathol 28 (1985) 111-118