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Risk of silicosis in cohorts of Chinese tin and tungsten miners and pottery workers (II): workplace-specific silica particle surface composition.

Authors
Harrison-J; Chen-JQ; Miller-W; Chen-W; Hnizdo-E; Lu-J; Chisholm-W; Keane-M; Gao-P; Wallace-W
Source
Am J Ind Med 2005 Jul; 48(1):10-15
NIOSHTIC No.
20027449
Abstract
It is hypothesized that surface occlusion by alumino-silicate affects the toxic activity of silica particles in respirable dust. In conjunction with an epidemiological investigation of silicosis disease risk in Chinese tin and tungsten mine and pottery workplaces, we analyzed respirable silica dusts using a multiple-voltage scanning electron microscopy-energy dispersive X-ray spectroscopy (MVSEM-EDS). Forty-seven samples of respirable sized dust were collected on filters from 13 worksites and were analyzed by MVSEM-EDS using high (20 keV) and low (5 keV) electron beam accelerating voltages. Changes in the silicon-to-aluminum X-ray line intensity ratio between the two voltages are compared particle-by-particle with the 90th percentile value of the same measurements for a ground glass homogeneous control sample. This provides an index that distinguishes a silica particle that is homogeneously aluminum-contaminated from a clay-coated silica particle. The average sample percentages of respirable-sized silica particles alumino-silicate occlusion were: 45% for potteries, 18% for tin mines, and 13% for tungsten mines. The difference between the pottery and the metal mine worksites accounted for one third of an overall chi-square statistic for differences in change in measured silicon fraction between the samples. The companion epidemiological study found lower silicosis risk per unit cumulative respirable silica dust exposure for pottery workers compared to metal miners. Using these surface analysis results resolves differences in risk when exposure is normalized to cumulative respirable surface-available silica dust.
Keywords
Silicates; Silicosis; Silica-dusts; Risk-factors; Risk-analysis; Tin-compounds; Tungsten-compounds; Miners; Surface-properties; Respirable-dust; Epidemiology; X-ray-analysis
Contact
W. Wallace, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown, WV 26505
CODEN
AJIMD8
Publication Date
20050701
Document Type
Journal Article
Email Address
wwallace@cdc.gov
Fiscal Year
2005
NTIS Accession No.
NTIS Price
Issue of Publication
1
ISSN
0271-3586
NIOSH Division
DRDS; HELD
Priority Area
Research Tools and Approaches: Exposure Assessment Methods
Source Name
American Journal of Industrial Medicine
State
WV; PA
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