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Role of surface free radicals in the pathogenicity of silica.

Authors
Castranova-V; Dalal-NS; Vallyathan-V
Source
Silica and Silica-Induced Lung Diseases. Castranova V, Vallyathan V, Wallace WE, eds., Boca Raton, FL: CRC Press, 1995 Dec; :91-105
Link
NIOSHTIC No.
00238731
Abstract
This chapter presented evidence supporting the theory that free radicals are generated on cleavage planes of silica (14808607) which result in greater cytotoxicity and pathogenicity of silica dust. The generation of radicals on the surface of silica and the generation of hydroxyl radicals by freshly ground silica were discussed. Results of studies on the in-vitro cytotoxicity, the inflammatory potential, and the in-vivo pulmonary response to freshly ground versus aged silica were presented. The data as presented indicated that grinding or fracturing crystalline silica breaks the silica to oxygen bonds and generates silicon based radicals on the cleavage planes. These surface radicals were able to react with water to generate hydroxyl radicals. The process appeared to involve a Fenton type reaction. The surface and/or hydroxyl radicals were toxic to pulmonary cells both in-vitro and in- vivo causing increased lipid peroxidation and membrane leakiness. Fresh silica was a more potent stimulator of reactive product generation by alveolar macrophages than was aged silica. Cytokine production may also be elevated after inhalation of freshly fractured silica, since bronchoalveolar lavage yields high numbers of inflammatory cells after the inhalation of freshly milled dust. Sandblasters, rock drillers, and silica flour millers are exposed to freshly fractured silica. Therefore, the authors suggest that these workers may be at unique risk of suffering pulmonary damage and developing disease.
Keywords
Lung-irritants; Lung-cells; Cytotoxic-effects; Silica-dusts; Pulmonary-function; Sand-blasting; Respiratory-system-disorders; Sand-blasters; Mineral-dusts; Dust-exposure; Dust-inhalation
CAS No.
14808-60-7
Publication Date
19951220
Document Type
Book or book chapter
Editors
Castranova-V; Vallyathan-V; Wallace-WE
Fiscal Year
1996
NTIS Accession No.
NTIS Price
ISBN No.
0849347092
NIOSH Division
DRDS
Source Name
Silica and Silica-Induced Lung Diseases
State
WV
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