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Characterization of Surface Properties Affecting the Activity of the 'Free Silica' Fraction of Respirable Dusts.

PB89187967

Publication Date	1988
Personal Author	Wallace, W. E.; Keane, M. J.
Page Count	24
Abstract	A two-part study was conducted to investigate the surface properties of the quartz (14808607) or 'free silica' fraction of respirable mine dusts. The degree of surface contamination of respirable quartz particles was studied using scanning electron microscopy with energy dispersive x-ray analysis (SEM-EDX) to distinguish alumino/silicate and magnesium silicate surface occlusions from the silicate particles. By varying the electron beam accelerating voltage, the depth of penetration could be reduced, so that the surface layer could be distinguished from the substrate material. Experiments were conducted on the relationship of measured SEM-EDX signal coming from the substrate to coating thickness and electron beam accelerating voltage. In the second part, modifications were made of respirable quartz particle cytotoxicity by surface treatment. As measured by erythrocyte hemolysis and pulmonary macrophage release of lactate dehydrogenase in-vitro, respirable quartz cytotoxicity was neutralized by boiling in water in glass test tubes for 10 to 40 minutes. The membranolytic potential was reduced to near zero by boiling up to 10 milligrams of quartz per milliliter of water. Replacing the medium with fresh water midway through the boiling resulted in full detoxification. Preboiling the medium with silica reduced the effect. Detoxification persisted after mild drying at 110 C for 8 hours and persisted after 3 days of resuspension in water at room temperature.
Keywords	Surface properties Quartz Mines(Excavations) Detoxification Surface finishing Silica minerals Dust In vitro analysis Bioassays X-ray analysis Respiratory systems Industrial hygiene Occupational safety and health Indoor air pollution CAS 1480-86-07 Scanning electron microscopy
Source Agency	National Institute for Occupational Safety and Health
NTIS Subject Category	57U - Public Health & Industrial Medicine 68A - Air Pollution & Control 68G - Environmental Health & Safety 99F - Physical & Theoretical Chemistry 48A - Mineral Industries
Corporate Authors	National Inst. for Occupational Safety and Health, Cincinnati, OH.
Document Type	Technical Report
Title Note	Final rept.,
NTIS Issue Number	198917

Characterization of Surface Properties Affecting the Activity of the 'Free Silica' Fraction of Respirable Dusts.

Characterization of Surface Properties Affecting the Activity of the 'Free Silica' Fraction of Respirable Dusts.
PB89187967

Publication Date	1988
Personal Author	Wallace, W. E.; Keane, M. J.
Page Count	24
Abstract	A two-part study was conducted to investigate the surface properties of the quartz (14808607) or 'free silica' fraction of respirable mine dusts. The degree of surface contamination of respirable quartz particles was studied using scanning electron microscopy with energy dispersive x-ray analysis (SEM-EDX) to distinguish alumino/silicate and magnesium silicate surface occlusions from the silicate particles. By varying the electron beam accelerating voltage, the depth of penetration could be reduced, so that the surface layer could be distinguished from the substrate material. Experiments were conducted on the relationship of measured SEM-EDX signal coming from the substrate to coating thickness and electron beam accelerating voltage. In the second part, modifications were made of respirable quartz particle cytotoxicity by surface treatment. As measured by erythrocyte hemolysis and pulmonary macrophage release of lactate dehydrogenase in-vitro, respirable quartz cytotoxicity was neutralized by boiling in water in glass test tubes for 10 to 40 minutes. The membranolytic potential was reduced to near zero by boiling up to 10 milligrams of quartz per milliliter of water. Replacing the medium with fresh water midway through the boiling resulted in full detoxification. Preboiling the medium with silica reduced the effect. Detoxification persisted after mild drying at 110 C for 8 hours and persisted after 3 days of resuspension in water at room temperature.
Keywords	Surface properties Quartz Mines(Excavations) Detoxification Surface finishing Silica minerals Dust In vitro analysis Bioassays X-ray analysis Respiratory systems Industrial hygiene Occupational safety and health Indoor air pollution CAS 1480-86-07 Scanning electron microscopy
Source Agency	National Institute for Occupational Safety and Health
NTIS Subject Category	57U - Public Health & Industrial Medicine 68A - Air Pollution & Control 68G - Environmental Health & Safety 99F - Physical & Theoretical Chemistry 48A - Mineral Industries
Corporate Authors	National Inst. for Occupational Safety and Health, Cincinnati, OH.
Document Type	Technical Report
Title Note	Final rept.,
NTIS Issue Number	198917