Document R23NDx04wmaYkKRROGkRBYxJE

Elimination of silicosis in the SA mining industry By D Rowe, Principal Inspector: Occupational Hygiene, DME, South Africa 1. Introduction The ILO-WHO Global Programme on Elimination of Silicosis was established in 1995 and has the objective that every country develop its own national silicosis elimination programme. The immediate objective is to reduce signifi cantly the incidence rate of silicosis by the year 2010. Furthermore the elimination of silicosis as an occupational health problem is targeted for the year 2030. Estimates made by the World Health Organisation (WHO) show that during each year 0,75 million people die as a result of work related diseases and 160 million new cases of work-related diseases are reported. Economic losses result ing from occupational diseases amount to 3,3% of world gross national product whereas 0,7% of the world GDP is attributed to occupational injury. Available statistics show that the burden of human suffer ing and economical costs in the SA Mining industry are untenable and in dire need of being addressed in a more comprehensive manner. Several studies have shown that occupational ill-health is associated with lower levels of pro ductivity, poor work motivation and low levels ofjob satisfac tion. Incentives for improving conditions in SA mining indus try and in particular the gold mines are certainly there. The magnitude of the problem of silicosis facing the SA mining industry is reflected in available statistics and poses a priori ty challenge for a concerted remedial effort. 2. Exposure health performance statistics 2.1 Occupationally over exposed persons-airborne pollutants Evidence continues to highlight the limitations of current dust measurements for both control purposes and occupa tional exposure assessment. Conformance with maintaining levels of exposure below the occupational exposure limits (OEL) is used as an index of performance. The air quality (AQI) is used in this instance and is determined by dividing the concentration of pollutant (dust) by the OEL and should be no greater than unity. The results showing the percentage of overexposed per sons may be unreliable and do not reflect the true prevail ing conditions for a number of reasons, most notably that:- a) there is a varying response from mines who are expect ed to submit returns, and b) the exposure results are based on the old gravimetric sampling strategy which relied on averaging of results. With the advent of the new sampling strategy it is expect ed that the trends shown may well reverse dramatically. This phenomena was well demonstrated when a certain gold mine conducted a pilot study on the new sampling system. This study found that 15% of the work force previ ously not overexposed were now overexposed to quartz concentrations above the OEL of 0,1 mg/m3. Also shown was that where previously the highest recorded exposure was 50% of the OEL, persons were now being exposed to 3 to 4 times the OEL! From this information one can appreciate why no improvements in the containment of silicosis has been achieved which is due mainly to poor environmental engi neering control. Also notable from the table below is that the gold mining industry alone, is accountable for 81 % of total payments made for compensatable diseases in mining. 2.2 Silicosis diagnosed at autopsy The overall rate of silicosis diagnosed at autopsy has remained much the same since 1975 as depicted in Figure 1. In spite of efforts being made since the early 1900s to reduce the incidents rates, autopsy data show a fairly constant level of 15% to 20% of silicosis in autopsied gold miners. Exposure to silica and ultimately the development of sili cosis are high risk factors for tuberculosis (TB) particularly in the gold mining sector. 82 Journal of the Mine Ventilation Society of South Africa, July/September 2004 Commodity Gold Platinum Coal Asbestos Other Mines TOTAL Number of Mines 2002 (Number that submitted results) 52 (42) 15 (15) 73 (57) 0 140 (117) 280 (231) Number of exposed workers employed in 2002 109 843 80 221 37 178 0 18 523 245 765 % of workers exposed to AQI=1,0 2002 (2001) 4,75 (6,65) 0,17(0) 19,83 (28,92) 0(0) 6,46 (4,40) 5,66 (6,94) Compensation in R million 2002 (2001) R54,5 (104,50) R2,0 (2,50) R2,2 (3,3) R4,1 (24,2) R4,2 (8,1) R67,0 (142,60) Table 1 reflects employee exposure to airborne pollutants as well as total compensation paid per mineral commodity. Silicosis diagnosed at autopsy Tuberculosis diagnosed at autopsy Figure 1. Year Figure 2. 2.3 Tubercolosis diagnosed at autopsy The risk of developing TB increases with exposure to sili ca dust, even in the absence of silicosis. However the pres ence of silicosis aggravates the situation and increases the risk of TB nearly four fold. It is worthy to note that TB case rates among gold miners are approximately three times higher than those among coal and platinum miners. Furthermore the mortality rate in gold mining is 2,5 per 1000 workers per annum. This rate is over twice as high as the current accident fatality rate for gold miners over the last decade. The steadily rising prevalence of HIV infection has led to a doubling in new TB cases. The increase in TB inci dence mirrors the increase in prevalence of HIV which cur rently stands at 30% in gold mines. Results of autopsies performed under the Occupational Diseases in Mines and Works Act (ODMWA 1973) show that over a period of 26 years, the rate of TB diagnosed has risen from below 40 to 200 per 1000 autopsies as shown in figure 2. 3. South African national programme on silicosis elimination A national programme on silicosis elimination is not in position currently. ' Discussions have however, taken place in 2003 between the Departments of Labour, Health and Minerals and Energy. 3.1 Mining sector's initiative The mining sector has undertaken, through the Safety in Mines Research Advisory Committee (SIMRAC) and the Mining Occupational Advisory Committee (MOHAC), to give more prominence to research initiatives aimed at the elimi nation of silicosis by addressing occupational hygiene issues. In 2002 SIMRAC established a long term project to elimi nate silicosis which consisted of two phases. The 1st phase was to define the scope of the research project in phase 2 by holding nation-wide workshops with industry profession als and experts. The outcome of these workshops culminat ed in the development of an appropriate and coherent long term research programme. Phase 2 is a 5 year project subdivide into three major components with a total budget of R24 million:- a) Dust measurement and reporting The scope of this component requires information to be Journal of the Mine Ventilation Society of South Africa, July/September 2004 83 obtained on the current practice for the determination of exposure to respirable silica dust through visits to a select ed sample of mines and to all laboratories in S.A. conduct ing quartz-on-filter analysis; assessment of current practice in developed countries compared to S.A. practice; and the compilation of best practice manuals which would guide the mining industry towards the elimination of silicosis in mining. - b) Environmental engineering / dust control The scope of this component requires information to be obtained on current local and international practice for dust control through visits to a selected sample of mines and communication with dust control experts; assessment of current practice in developed countries compared to SA practice; pilot potentially cost effective dust control methods and the implementation of the recommendations of the best practice manuals on pilot mines and the assessment of workers' exposures. Compilation of all these best practice materials including manuals would also be necessary. c) Human resource training and management The scope of this component requires obtaining and evaluating current local and international practice for dust minimization campaigns; and the development of appropri ate training and educational material for a range of person nel. Assumption is made that occupational sample concen trations are log-normally and independently distributed both within any particular workshift and over many exposure averages. In view of this it is proposed that in future the 90th percentile value of recordings made, shall be used for a more accurate dose allocation. This action may also sup port the view that short term exposure to high silica concen trations may account for occurrences of silicosis of low cumulative or average exposure levels. d) Air quality index (AQI) The AQI is derived by dividing the concentration of the pollutant by the occupational exposure limit (OEL) of that pollutant and should be no greater than unity. Determining the concentration of respirable quartz in a certain dust sample is dependent on accurate composition al analysis. Hence the recommendation previously made to employ XRD. % qtz mine dust mg/m3 10 15 20 25 30 40 1,00 0,67 0,50 0,40 0,33 0,25 Dust Concentrations for an AQI of 1,0 Table 2 illustrates the impact percentage quartz content has on dust concentration values. 4. Current occupational hygiene practices In a programme such as that for the elimination of silico sis it is important to identify the problem at source in order to institute remedial measures and to evaluate the out comes. It is thus necessary that dust monitoring, control and disease (outcome) measurement be considered. 4.1 Monitoring of workforce exposures The introduction to the mining industry of the Guideline for the Compilation of a Mandatory Code of Practice for an "Occupational Health Programme on Personal Exposure to Airborne Pollutants" in September 2002, plays a vital role in the elimination of silicosis. The correct application of this guideline, by dedicated and committed professionals, is essential for any data so gathered to be of any meaningful value. Some pertinent issues that are in need of further clarification have been highlighted since the implementation of the guidelines by the gold mining industry and are as folI'ows:- a) Selecting the correct personal samplers A recommended direct-on-filter quartz analysis method ology using X-Ray Diffractometry (XRD) dictates that per sonal sampling pumps with cyclones only be employed. These cyclones are expected to operate with an air flow rate of 2,21/m to conform with the ISO/CEN/ACGIH res pirable particle deposition curve. b) Accurate, meaningful samples It is important that samples of exposures are representa tive of all full working shifts. c) Reporting and recording of sampling results The current reporting of averaged results in a Homogeneous Exposure Group (HEG) for dose allocation is questioned. The dust concentrations shown above for the various quartz contents are values that should not be exceeded. Action levels, i.e. 50% of these values, should be used by management to initiate an environmental engineering con trol intervention, e.g. for 30% quartz, an action level dust concentration of 0,17mg/m3 is suggested. The current practice of waiting for analysis results to eventually set dust level targets, delays the need for inter vention if required. A more proactive method to timeously remedy overexposures, is to use the highest analysis result of past sampling to set dust concentration targets. Personal sampling results and in particular the AQI, are lead indicators showing the effectiveness or otherwise of the environmental engineering control measures in place. 4.2 Environmental engineering control sampling strategy When personal sampling results indicate the necessity for an engineering intervention, the source of the problem needs to be located. Additional sampling, employing a dif ferent strategy to that of personal sampling is called for. This strategy could be one of deploying strategically posi tioned stationary samplers around a suspect activity or with in a workplace to ascertain the efficient utilization and man agement of appliances and systems in place. 5. Conclusion It is clearly evident that silicosis in gold mining in SA in particular is not under control. The implementation of the COP for Airborne Pollutants will hopefully assist mines in identifying areas in need of correction. The only recourse to improve occupational exposures to silica dust is to employ best practice methods in environmental engineer 84 Journal of the Mine Ventilation Society of South Africa, July/September 2004 ing control. Employment of best practice alone is insuffi cient if it is not supported by a well structured maintenance management programme. Employers will also be well advised to employ the full-time services of dedicated, quali fied and experienced mine occupational hygienists, in their quest to achieve the ultimate goal of eliminating silicosis from mining in SA. The findings of the envisaged research programme, which is anticipated in the future, should not be allowed to unduly delay the introduction of any innovative measures to improve the working environment. Concurrent with the research initiative it is timeous for the mining industry to consider the introduction of a silica dust awareness campaign. The gold mines in particular, who have the most to gain from such a programme, should be committed to the launching of it. All aspects of the subject should be covered, from effects (medical outcomes) through to sources and elementary, practical dust control measures. Incentives for eliminating silicosis are aplenty, from an economic viewpoint in compensation payments and most importantly for the prevention of human suffering. The chal lenge and responsibility to achieve these ideals rest square ly on the shoulders of all stakeholders. 6. Acknowledgement Sincere gratitude is extended to members of my staff of the Directorate Occupational Hygiene in the preparation of this paper. Thanks are also due to the Chief Inspector of Mines and the Department of.Minerals and Energy for permission to present this paper. 7. References "Global Strategy on Occupational Health For All" WHO. Geneva 1995 Annual Report (year 2001-2002) - Mine Health and Safety Inspectorate Mining Methods and Occupational Hygiene for the New Millennium from Dust to Dust by Mr. Des Wrigley 2001 Journal of The Mine Ventilation Society of SA - Volume 54.3 PATHAUT Statistical Database: National Centre For Occupational Diseases: Silicosis and Tubercolosis Autopsies Research Reports: SIMRAC Handbook Occupational Health Practice in the SA Mining Industry Guideline for the Compilation of a Mandatory Code of Practice for an Occupational Health Programme on Personal Exposure to Airborne Pollutants - Department of Minerals and Energy Occupational Exposure Sampling Strategy Manual NIOSH RCocco: The long and Winding Road from Silica Exposure to Silicosis and other Health Effects Sound - Noise - Vibration SOUNDp'V) NOISED* Sound Level Meter Noise D< eters jquency Analyser Type 1 / Type 2 1/1 and 1/3 Filters Touch Style PDA Colour Screen Digital Signal Processing USB, Infra Red Wireless Ethernet Back Erase Drawing Pad Voice Notes I- SABS Intrinsically Safe Impulse Integrating Data Logging Infra Red Downloading 80 Hours Run Time .^ m / Wh< . ' Vibration Analyser All Instruments integrate with f# QuestSuite Professional Application Software Hand Held TriAxial Accelerometer Datalogging Simultaneous X,Y,Z Axis : ''Mir' environmental and occupational hygiene instruments T: 011 4767323 sales@envirocon.co.za www.envirocon.co.za