3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Alternative funding options for occupational diseases in South African mines(2018) Mushai, AlbertProvision of compensation to victims of occupational disease in the mining industry has been a key policy area in South Africa for decades. Yet in all those years, the common law never featured as a practical option for providing compensation. Workers’ compensation has always been preferred and for good reason. Workers’ compensation internalizes the cost of compensation and converts into a cost of production. In the process, compensation is expeditiously paid and at low cost. In return, there is a general exclusion of common law actions against employers. Accordingly, there is no record of successful litigation against an employer for an occupational disease in South Africa. The unexpected lacuna came in 2011 when the Constitutional Court ruled that mineworkers could sue their employers at common law for occupational disease. Various sections of South African society hailed the decision as a victory for mineworkers. Since then, courts have certified class actions against mining companies paving the way for mass-litigation in local and foreign courts by thousands of former miners. Anyone familiar with occupational diseases in South Africa and compensation thereof would find these developments perplexing. This study assesses the common law as a compensation mechanism and concludes that it is virtually impossible to apply its key elements of causation, fault, harm and wrongfulness to long latency diseases. Application of the common law to long latency disease requires the development of a new branch of jurisprudence as some cases in the UK have confirmed. Furthermore, the common is also associated with a wide range of other practical problems that further cement its unsuitability to deal with compensation for diseases contrary to popular belief. An assessment of alternative options for compensating victims of disease is therefore not only important but also necessary. Among the available options, workers’ compensation is the most ideal for South Africa.Item A phytochemical and pharmacological investigation of South African Vitex species(2004-09-03) Nyiligira., Eric.As part of investigation of the biological activities of South African plant, a phytochemical and pharmacological investigation was carried out on five indigenous Vitex species; V. obovata ssp. obovata, V.obovata ssp. wilmsii, V. pooara, V. rehmannii and V. zeyheri . The chemical composition of the essential oils was determined using gas chromatography and mass spectrometry, and 1.8-cineole, a- copaene , caryophyllene oxide and y-muurolene were found to be the most abundant constituents in the essential oils of both V. obovatassp. obovataand V. obovata sssp. wilmsii.Item Phenotypic and genotypic characterisation of mycobacterium tuberculosi strains in relation to the transmission of tuberculosis in South African mines(2000) Muthivhi., Tshilidzi, Neleus.The prevalence of tuberculosis in South African miners is substantially higher than that of in the general population. Through exposure to dust which leads to different degrees of silicosis, and by working in enclosed spaces where coughed out bacilli can survive in droplet nuclei and be inhaled by other workers, miners are especially prone to to become infected with M. tuberculosis and develop the disease. It is not only the working conditions which promote transmission of M. tuberculosis, but the living conditions as well. Most miners live and sleep in rooms shared by up to eight other men, which increases the opportunity for transmission, leading to both primary and reinfection tuberculosis.Item Evaluation of high pressure water spray systems as a control measure to reduce silica exposure in underground gold mines(2017) Senekal, Hendrik JohannesGold mining has always played a major role in the South African economy. Unfortunately, workers’ health could be at risk as exposure to respirable quartz could cause silicosis. Silicosis has no cure or treatment and the only means to prevent silicosis is to reduce exposure to as low a level as possible. This study tested the effectiveness of a high-pressure water spray system as an engineering control measure, to reduce respirable dust and respirable quartz concentrations. This intervention produced a mean personal respirable quartz concentration reduction of 87% (p-value of 0.00003). In addition, a reduction of 53% (p-value of 0.04) was observed in the mean static dust concentration measurements taken upstream and downstream of the control measure. Significant improvement in respirable dust and respirable quartz concentrations was observed after the introduction of the high-pressure water spray system. The results from this study indicate that the health risk to underground mine workers could be reduced by implementing a high-pressure water spray system as an engineering control.Item Validation of biomarkers for improved assessment of exposure and early effect from exposure to crystalline silica(2015-09-16) Wilson, Kerry SidwellItem Living in the shadow of a dust cloud: occupational respiratory diseases in the South African mining industry, 1975 to 2009(2012) Nelson, GillianBackground 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.Item Exposure to respirable crystalline silica in central South Africa farm workers(2013-03-05) Swanepoel, Andrew JohnstoneIntroduction Personal exposure to respirable crystalline silica (commonly in the form of quartz) causes serious adverse health effects and has been well documented in industries formally known as the ‘dusty trades’. Very little information exists on personal quartz exposure in agricultural settings. Silica exposure is an important public health issue particularly in settings of high tuberculosis (TB) and Human Immunodeficiency Virus (HIV) rates. The mineral has contributed to serious epidemics of TB in southern Africa and other low and middle - income regions of the world because of the increased risk of pulmonary tuberculosis in silica exposed workers. It is well known that HIV infection increases the incidence of TB and the risk of tuberculosis in individuals with both HIV and silicosis is larger than the sum of each factor. Globally (especially in resource poor countries), agriculture employs a very large population that may be affected. Objectives The objectives of the PhD were to review the published literature on respirable quartz exposure and associated disease in agricultural related settings systematically; to measure personal time weighted average respirable dust and quartz on sandy, sandy loam and clay soil farms in the Free State and North - West provinces of South Africa; to ascertain whether soil type is a determinant of exposure to respirable quartz; to identify additional determinants of quartz exposure in farming; to estimate annual cumulative respirable quartz exposure; and to discuss some occupational health implications and research needs. Methodology Published studies on exposure to silica and quartz in agriculture and related settings as well as silica - associated disease in farming were searched systematically through “PubMed”; and, critiqued. Three farms, located in the Free State and North West provinces of South Africa, had their soil type confirmed as sandy, sandy loam and clay; and, from these, a total of 298 respirable dust and respirable quartz measurements were collected between July 2006 - November 2009 during periods of major farming operations. These measurements were collected using standard international measurement and analytical methods. Quartz determinations were done using X - ray diffraction by a quality - assured, accredited laboratory, and were verified by a leading external agency. Respirable quartz values below the limit of detection (22 μg.m-3) were estimated using multiple imputation. Non - parametric tests were used to compare quartz exposure from the three different soil types. Variables such as soil type, commodity farmed, activity (nature of work done), process (manual vs mechanical), quartz % and weather variables (e.g. wind and humidity during the week prior of and during sampling) were used in bivariate and multiple regression modeling to identify determinants of respirable quartz exposure. Logistic regression was done aiming to identify determinants of respirable quartz greater than 50 μg.m-3 and to deal with data points below the detection limit without including multiple imputation methods. The annual cumulative exposure was estimated for a typical farm worker on the sandy soil farm using activity - specific measurements and duration of each activity in a year. Particle sizes of respirable dust fraction were determined using laser light scattering. Results Literature review In total, 17 studies were identified: 11 investigated respirable dust and quartz exposure on farms and six quartz related disease in agricultural settings. They provided convincing evidence of a respirable quartz risk on sandy soil farms but scant evidence of associated disease. Exposure to respirable dust and quartz Respirable quartz measurements from the three South African farms ranged from not detectable to 626 μg.m-3 and confirmed the quartz hazard: some concentrations exceeded generally accepted occupational exposure limits in all activities evaluated, even though 278 (93.3 %) of the respirable dust concentrations were well below a commonly used occupational exposure limit of 2 mg.m-3. Fifty seven percent, 59% and 81% of the respirable quartz measurements on the sandy soil, sandy loam soil and clay soil farm respectively exceeded the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) of 25 μg.m-3. Twelve percent and 13% of respirable quartz concentrations exceeded 100 μg.m-3 on the sandy soil and sandy loam soil farms respectively, but none exceeded this level on the clay soil farm. Determinants of exposure The proportions of measurements greater than 100 μg.m-3 were not significantly different between the sandy and sandy loam soil farms (prop.test; p = 0.65), but both were significantly larger than for the clay soil farm (prop.test; p= 0.001). The percentage of quartz in respirable dust was determined for all three farms using samples of a size such that all measurements were well above the analytical detection limit. Percentages ranged from 0.5 - 94.4% with no significant difference in the median quartz percentages across the three farms (Kruskal - Wallis test; p = 0.91). Bivariate analyses showed that commodity (Kruskal - Wallis test; p = 0.001), activity (Kruskal-Wallis test; p = 0.001) and process (Wilcoxon test; p = 0.003) were associated with respirable quartz concentrations. Multiple linear regression showed that soil type, season, commodity, activity, process, quartz percentage, humidity on the morning of measurement and interactions between activity, respirable dust exposure and quartz percentage were significantly related to respitable quartz exposure. Logistic regression showed that, during univariate analyses, cereal planter operator, increased quartz % in respirable dust, decreased humidity on the day of measurement and increased respirable dust concentration were all significantly associated with quartz levels above 50 μg.m-3. Multivariate analyses showed that cereal planter operator remained a strong determinant of higher level of exposure relative to other activity (OR 3.76 95% CI 1.64 - 8.63). Increased levels of quartz % in respirable dust increased the ORs for exposure above 50 μg.m-3. Annual cumulative exposure The estimated annual cumulative exposure of a farm worker exposed at the highest concentration measured for each task exceeded the cumulative exposure had the worker been exposed at 100 μg.m-3 by 1.46 times. At median quartz exposures measured for each of the activities done during the year, the chances of exceeding the cumulative exposure if exposed at the South African OEL are small: the ratio of the estimated cumulative exposure indices to occupational exposure limit cumulative exposure = 0.29. Particle size The median D50 particle size of the 30 respirable dust samples measured in this study was 5.53 μm with the smallest D50 value reported by the laboratory being 3.39 μm. Conclusion Despite its ubiquity, little is known about quartz exposure in the agricultural industry. This thesis not only demonstrates significant potential for overexposure in some settings, it also may be the biggest study of its kind: it is the first study to have measured a large number (298) of personal respirable quartz concentrations across various activities on three farms known to have different soil types. It is also the first study in farming that attempted to relate personal respirable quartz exposures to possible determinants, to consider potential modifiers of quartz exposure and to estimate annual cumulative quartz exposure. The study adds considerably to the evidence that over - exposure to quartz may be a risk in farming and has identified the need for practical interventions and research gaps. In addition, this study makes it possible to use the detailed analyses of silica exposure determinants in farming in other settings with similar conditions. Soil type may determine whether exposure is greater than 100 μg.m-3, but the job type and the manner in which the task is performed (e.g. mechanical or manual) may be important determinants of exposure. Identifying quartz exposure determinants (e.g. type of job) and modifiers will be of value to focus implementation of controls, which is of particular importance in developing countries. The nature of farming and weather variables may add information about exposure risk and should be included with soil type in future farming exposure assessment studies. Given the large numbers of farm workers possibly exposed to silica and the seriousness of silica - associated diseases, some dust - related occupational health interventions should be considered in South African farming, particularly because during the course of the studies none of the South African farms had medical surveillance programmes in place and few, if any, dust control measures were observed. Practitioners working in farming areas should be aware that silica - associated diseases may occur in farm workers; therefore despite limited evidence for silica associated disease, occupational health interventions appear justified. No study previously has defined the burden of silica – associated diseases in farming. A starting point may be to perform radiological surveys on long service farm workers (possibly more than 20 years service and performing dusty activities) on a sandy soil farm, as sandy soils are likely to produce the highest silica levels. An effort should also be made to define the duration and intensity of silica exposure in farming over the annual cycle. Lastly, cost - effective methods to reduce respirable dust and silica exposure in farming should be identified.