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Field Studies |
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Author |
Qiao NIU, et al Cross sectional epidemiological studies were carried out in three coal mines (Mines A, B
and C), that produce different types of coal in order to examine the relationship between
the prevalence of coal workers' pneumoconiosis (CWP) and factors contributing to the
development and seriousness of CWP, seven factors were taken into consideration and
two of them were calculated as "risk indices". They concerned composition (including
carbon, ash, volatile content of coat, free silica in coal dust and rock dust) and exposure
factors (including dust concentration, duration of exposure and type of operation).
Composition factors were: carbon 90%, ash 23.1 3%, volatile content 13.85%, free silica
in coal dusts 2.58% and free silica in rock dusts 32.88% in Mine A. Carbon 82%, ash 8%,
volatile content 28.5%, free silica in coal dusts 5.90% and free silica in rock dusts 33.0%
in Mine B. Carbon 94%, ash 20.46%, volatile content 10.76% free silica in coal dusts
2.04% and free silica in rock dusts 24.04% in Mine C. Differences in the coal dust
concentration over a period of 20 to 30 years were not significant in the three mines. The
rock dust concentration in Mine B was much higher than those in the other two mines. The
CWP prevalence was 2.22% in Mine A, 13.20% in Mine a and 1.86% in Mine C.
Analysis has shown that both composition and exposure factors were related to CWP
prevalence, but the strength of the relationship between the factors was different in the
three mines, especially in Mine B, where there was a high CWP prevalence, and the
association of CWP with free silica and high volatile content was strong. It was interesting
that, though the rank of coal in Mine a was much lower than those in Mine A and Mine C,
the prevalence of CWP in Mine B was much higher than those in Mine A and Mine C. This
result was in contrast with those reported before. The calculation of risk indices indicated
that there was a positive correlation between the risk indices and exposure duration.
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Abstract |
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