ETD Collection

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Author: search.filters.author.Nelson, Gillian

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    Chromosome damage in asbestos-exposed workers, measured by sister chromatid exchange
    (1994) Nelson, Gillian
    Objective: To determine the relationship between asbestos exposure and chromosome damage, as depicted by sister chromatid exchange frequency. Design: Descriptive, cross-sectional study. Setting: Asbestos-products factory Subjects: 31 asbestos-exposed subjects and 21 unexposed subjects Main outcome measure: Mean sister chromatid exchange (SCE) frequency per metaphase cell. Results: The control group had a slightly higher mean SCE frequency per cell than the exposed group (3.4%) but this difference was not statistically significant (p = 0.5935). Smoking contributed significantly to SCE frequencies in both the exposed and unexposed groups. The mean SCE frequencies per cell in the exposed group were 10.49 for smokers and 8.59 for non-smokers (p = 0.0078). The frequencies for smokers and non-smokers in the unexposed group were 10.83 and 8.58, respectively (p = 0.0257). Conclusions: The failure to observe an increase in SCE frequency does not rule out asbestos exposure as a genotoxic agent. Rather, it may help to resolve the limitations of this method for detecting genetic damage. Alternatively, the fibre levels to which this group was exposed may have been too low to cause chromosome damage.
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    Living in the shadow of a dust cloud: occupational respiratory diseases in the South African mining industry, 1975 to 2009
    (2012) Nelson, Gillian
    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 viii 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.