Living in the shadow of a dust cloud: occupational respiratory diseases in the South African mining industry, 1975 to 2009
Date
2012
Authors
Nelson, Gillian
Journal Title
Journal ISSN
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Abstract
Background
Silicosis rates in gold miners in South Africa are very high but there have been no
analyses of long term trends. While much research has been conducted on
occupational respiratory disease in gold, asbestos and coal miners, little is known
about the respiratory health of miners of other commodities, such as diamonds
and platinum, two of the most important minerals in South Africa. The ore bodies
from which minerals are mined often contain other „incidental‟ minerals and
compounds that may cause disease.
Aims
The aims of this thesis were to conduct the first ever analysis of silicosis trends in
black and white gold miners over a 33-year period; to discuss the role of oscillating
migration in the high rates of silicosis; and to explore the potential for workers in
the diamond and platinum mining sectors to develop occupational respiratory
diseases.
Methods
Gold, diamond and platinum mine workers were identified from the PATHAUT
autopsy database at the National Institute for Occupational Health. Trends in
silicosis from 1975 to 2007 were calculated separately for black and white gold
miners because of differences in exposure, patterns of employment and autopsy
referral patterns. The role of oscillating migration in the silicosis epidemic was
explored. Diamond mine workers with asbestos-related diseases at autopsy and
platinum mine workers with silicosis and/or fibrotic nodules in the lymph nodes
were identified. Supplementary data from other sources were reviewed to
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exclude all those who might have been exposed to asbestos or silica, respectively,
outside of the mining sector in which they worked. Asbestos lung burdens were
calculated for the case series of diamond miners and mine tailings and soil
samples were examined for asbestos fibres, using scanning electron microscopy.
Findings
The proportion of white miners with silicosis increased by 17% (from 18% to 22%)
over the 33-year study period. That of black miners increased 10-fold (from 3% to
32%), primarily due to the aging workforce and increasing periods of employment.
Adjusted odds ratios for silicosis increased with year of autopsy for black miners.
Oscillating migration has also played a major role in the silicosis epidemic.
Evidence indicates that diamond mine workers are at risk for developing asbestosrelated
diseases and that platinum mine workers are at risk for developing silicosis.
Conclusion
The gold mines have failed to control silica dust levels adequately and prevent
disease in mine workers. The sparsity of available dust measurements and poorly
documented work histories are major obstacles to conducting occupational
health research in South Africa; attention and legislation needs to be focused
urgently on these areas. The PATHAUT database is the only occupational
respiratory disease database in South Africa that can be used for disease
surveillance, trend analyses and research in all mining sectors.
Description
A thesis submitted to the Faculty of Health Sciences,
University of the Witwatersrand,
in fulfilment of the requirements for the degree of
Doctor of Philosophy