Descriptions of coal associated diseases and coal dust concentrations in Mpumalanga coal mines

Du Toit, Andreas Zacharias
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Introduction Coal mine workers are exposed to a mixture of dusts including coal dust and silica (as alpha quartz), in this respect the mixture of dusts is termed mixed coal dust. The illnesses commonly associated with the inhalation of mixed coal dust are (1) coal workers’ pneumoconiosis, (2) silicosis, and (3) chronic obstructive pulmonary disease. Objectives The main aim of this research report is to determine whether current dust levels in Mpumalanga coal mines were above generally recommended standards and to review information on the burden of coal associated diseases in the coal miners of Mpumalanga. The objectives of this research project are (1) to describe the coal dust and silica concentrations as measured by personal breathing zone sampling in Mpumalanga coal mines over the period 2003 to 2006 and (2) to describe the burden of coal-associated diseases reported by autopsy examinations received from NIOH Pathology Department and in the SAMODD data base in Mpumalanga coal mines over the period 2002 to 2006. Page 4 of 71 Methods Dust Personal breathing zone sampling data were obtained from gravimetric sampling programmes established according to the DMR – SAMOHP from fifty three coal mines in the Mpumalanga region. During the time of the study, the sampling programme strategies were co-ordinated by a central laboratory services: “Colliery Environmental Control Services”. The raw data were obtained from this laboratory for the periods 2003 to 2006 in Microsoft excel spread sheet format. Burden of disease NIOH - PATHAUT The annual reports of the NIOH on the autopsy data for the coal mining sector were obtained from the web site of NIOH. Sample data sheets were drawn up to extract only relevant information from the reports. DMR - SAMODD The DMR collects medical information from coal mines across South Africa, and this information was obtained from the local inspectorate. The data contained in the report were of all the mines in South Africa, a filter was applied in a Microsoft Excel spread sheet to extract the relevant information for Mpumalanga coal mines. Page 5 of 71 Results Dust There was a reduction in the recorded concentration of respirable dust levels in the collieries over the four year period 2003 to 2006. The average coal dust exposures fell from 1.9 mg/m³ in 2003 to 1.3 mg/m³ in 2006. The Department of Mineral Resources places emphasis on the 90th percentile and most of the sampling strategies are centred on this figure. Although the 90th percentile decreased from 4.82 mg/m³ to 3.02 mg/m³ (i.e. 1.8 mg/m³) over the four year period, this level is still unacceptable as it is above the required statutory limit of 2.0 mg/m³. Silica exposures also showed a reduction from an average of 0.047 mg/m³ in 2003 to 0.034 mg/m³ in 2006. Disease burden: PATHAUT Pulmonary tuberculosis - the number of employees at autopsy with pulmonary tuberculosis (PTB) decreased from 12 in 2002 to 8 in 2006, but there is not enough information to establish a trend over the five year period. Silicosis: - the number of employees at autopsy with silicosis was between 3 to 4 cases per year except in 2004 where there was an outlier of 11, but in general the cases stayed constant over the five year period. The rate of silicosis per 1000 Page 6 of 71 autopsies however indicates an increase over the five year period as the rate increased from 37 to 52. Emphysema: - the number of emphysema cases stayed fairly constant with 32 cases in 2002 and 30 cases in 2006, but with an increase in 2003 and 2004 to 42 and 43 respectively. The rate per 1000 autopsies increased from 294 in 2002 to 390 in 2006. Coal workers’ pneumoconiosis: - there was a decrease in coal workers’ pneumoconiosis from 2002 to 2006 from 10 to 2 cases, but there were 11 and 15 cases in 2003 and 2004. SAMODD Coal workers’ pneumoconiosis: - the total number of employees reported with Coal Workers Pneumoconiosis (CWP) decreased for the period 2003 to 2006, from 12 in 2003 to three in 2006. Chronic obstructive pulmonary disease: - No useful information was available for this illness. Silicosis: - One case was reported in 2002, and 2 cases in 2003 and 2004, no cases were reported for 2005. Tuberculosis: - with initially only three cases in 2002, cases increased during 2003 to 2005 to 53, 44 and 50 respectively. A reduction was observed in 2006 to 13 cases. Page 7 of 71 Conclusion There may be an overall reduction in the dustiness of the coal mining industry in Mpumalanga province as the arithmetic mean of the samples collected decreased from 1.9 to 1.3 mg/m³ over the four year period 2003 to 2006. The level of exposures to silica might be lower because the exposures reduced from a mean of 0.047 in 2003 to a mean of 0.034 mg/m³ in 2006. The recorded data suggest a decline in CWP; this is in line with international data from the United Kingdom, USA, Australia, Germany, France and Belgium. Pulmonary tuberculosis - was constant over the five year period based on limited autopsy data, but the SAMODD data base indicates a decline for the year 2006 but overall shows an increase in the number of tuberculosis cases in Mpumalanga coal mines. Silicosis cases were fairly constant, but the rate per 1000 autopsies increased by 15/1000 over the five year period. The number of recorded cases from the DMR SAMODD is too few to make any useful deductions. Emphysema numbers were constant, but the rate per 1000 autopsies increased by 96/1000 over the five year period. No useful interpretation can be made from the data received from the DMR on chronic obstructive pulmonary disease.
MPH, Occupational Hygiene,School of Public Health, Faculty of Health Sciences, University of the Witwatersrand
coal mine dust, diseases