Dust exposure and pneumoconiosis in mines

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Mchaina, David Mhina
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Attempts to develop Threshold Limit Values together with the correlation between results of various sampling instruments are described. The main objectives of the investigations were: to establish the relationship between dust exposure and the development of pneumoconiosis, to study the effect of free silica content of dust on the development of silicosis, to study the concentration of respirable dust encountered in various mining occupations and to establish acceptable limits based on the gravimetric dust samplers. A subsidiary objective was to establish a correlation between mass and particle number concentrations. The miners involved in the study were those suffering from pneumoconiosis. Their stages of pneumoconiosis were related to cumulative dust doses to which the progression of pneumoconiosis was determined on the basis of ILO u/c International Classification of Radiographs of Pneumoconiosis, of 1971 using 1968 standard films for comparison. The cumulative doses to which the individual miners were exposed were compared with the profusion categories and the Nodule size progression. The hazard of silicosis was evaluated by determining the free silica content of the respirable portion of dust breathed by mine workers. Dust samples were collected from the breathing zones of miners with the use of gravimetric samplers. These samples were then analysed using X-ray diffraction. Free silica was determined, both qualitatively and quantitatively. The amount of quartz was determined by comparing the intensities of diffraction peaks of quartz in the samples with those of corundum. It is concluded that the maximum allowable concentrations of 350 particles per cubic centimeter in force on the Zambian Copperbelt and 2 mgm-3 adopted at Wankie Colliery can be considered as adequate standards for guarding against the hazards of pneumoconiosis.Cumulative doses for total dust of 275 mgmonthm -3 and 700 mgmonthm -3 are recommended for the Zambian Copperbelt and Wankie Colliery respectively. Cumulative dose for free silica of 55 mgmonthm-3 was set for the Zambian mines.The comparison between the results of the sampling instruments showed that the particle concentration measured by the Konimeter did not correlate with the mass concentration measured by gravimetric dust samplers. Of all sampling instruments, MRE 113A was found to be reliable and for control purposes this instrument should be used as a standard sampler.
Mine and Mineral resources(pneumoconiosis) , Mine Dusts