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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
Author(s) -
Harrison J.,
Chen J.Q.,
Miller W.,
Chen W.,
Hnizdo E.,
Lu J.,
Chisholm W.,
Keane M.,
Gao P.,
Wallace W.
Publication year - 2005
Publication title -
american journal of industrial medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.7
H-Index - 104
eISSN - 1097-0274
pISSN - 0271-3586
DOI - 10.1002/ajim.20175
Subject(s) - silicosis , medicine , tungsten , tin , pottery , metallurgy , composition (language) , environmental health , archaeology , pathology , materials science , linguistics , philosophy , history
Background 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). Methods 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. Results 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. Conclusion 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. Am. J. Ind. Med. 48:10–15, 2005. Published 2005 Wiley‐Liss, Inc.