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Characteristics of dusts encountered during the production of cemented tungsten carbides.

Authors
Stefaniak-AB; Day-GA; Harvey-CJ; Leonard-SS; Schwegler-Berry-DE; Chipera-SJ; Sahakian-NM; Chisholm-WP
Source
Ind Health 2007 Dec; 45(6):793-803
NIOSHTIC No.
20033194
Abstract
Inhalation of cobalt (Co) and tungsten carbide (WC) particles, but not Co or WC alone, may cause hard metal disease, risk of which does not appear to be uniform across cemented tungsten carbide (CTC) production processes. Inhalation of Co alone or in the presence of WC may cause asthma. Hypothesizing that aerosol size, chemical content, heterogeneity, and constituent compaction may be important exposure factors, we characterized aerosols from representative CTC manufacturing processes. Six work areas were sampled to characterize aerosol size distributions (dust, Co) and 12 work areas were sampled to characterize physicochemical properties (using scanning electron microscopy with energy dispersive x-ray spectrometry [SEMEDX]). Bulk feedstock and process-generated powders were characterized with SEM-EDX and x-ray diffraction. The dust mass median diameter was respirable and the cobalt respirable mass fraction was highest (37%) in grinding. Morphology of particles changed with processing: individual, agglomerate, or aggregates (pre-sintered materials), then mostly compacted particles (subsequent to sintering). Elemental composition of particles became increasingly heterogeneous: mostly discrete Co or W particles (prior to spray drying), then heterogeneous W/Co particles (subsequent work areas). Variability in aerosol respirability and chemical heterogeneity could translate into differences in toxicity and support detailed characterization of physicochemical properties during exposure assessments.
Keywords
Air-contamination; Air-quality-measurement; Air-samples; Airborne-dusts; Airborne-particles; Particle-aerodynamics; Particulate-dust; Particulate-sampling-methods; Particulates; Dust-analysis; Dust-exposure; Toxic-effects; Breathing; Breathing-atmospheres; Breathing-zone; Chemical-properties; Aerosol-particles; Dust-analysis; Respiratory-hypersensitivity; Respiratory-irritants; Respiratory-system-disorders; Particle-aerodynamics; Particulate-dust; Particulate-sampling-methods; Particulates; Exposure-levels; Exposure-assessment; Toxic-effects
Contact
Aleksandr B. Stefaniak, Division of Respiratory Disease Studies, National Institute for Occupational Safety and Health, Morgantown, West Virginia 26505
CODEN
INHEAO
CAS No.
7440-48-4; 7440-33-7
Publication Date
20071201
Document Type
Journal Article
Fiscal Year
2008
NTIS Accession No.
NTIS Price
Issue of Publication
6
ISSN
0019-8366
NIOSH Division
DRDS; HELD
Source Name
Industrial Health
State
WV
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