Document M7oXDD2E5gnw894KBrOdjeZx

SAFETY IN MINES RESEARCH ADVISORY COMMITTEE SIMRAC Draft Final Project Report Title: PERSONAL GRAVIMETRIC DUST SAMPLING AND RISK ASSESSMENT Author/s: A D Unsted Research Agency: CSIR : Division of Mining Technology Project No.: GAP 046 Date: March 1996 EXECUTIVE SUMMARY The Government Mining Engineer (GME) introduced a personal gravimetric dust sampling programme for gold mines in 1990 and allowed a two year moratorium period during which anomalies and difficulties encountered were discussed and resolved in committee. The sampling strategy, as prescribed by the GME, was considered, inevitably, to have been based on conservative statistical considerations. It was thus considered to be unnecessarily costly and onerous in terms of the definition of statistical populations, the cost of sample analysis, and the increased organisational workload on mine technical and administrative staff. Experience gained in the statistical determination of health risks in other areas such as heat, noise and biological contamination in South African mines indicated a potential to simplify dust sampling strategies thereby providing scope for cost and effort savings. In a very general air contamination scenario an atmospheric contaminant is emitted by a source. It may mix with and be diluted by ambient air and it travels to a target person, object or area where it has the potential to exert an effect, usually after being deposited. The physical dimensions involved in this process may be millimetres to kilometres and the times may be milliseconds to virtually years. Air sampling may be performed near the source, in the ambient air, or near the target to characterize the source emission, identify the source, or predict the quality and quantity of contaminant reaching the target. Since the GME's dust sampling programme is aimed only at determining personal exposures, sampling is undertaken only on personnel, i.e. the target receptors. An aerosol consists of particles and the gas in which they are suspended. All aerosols are temporally unstable, i.e. they experience change with the passage of time. Some important aerosol characteristics which can change are: total mass concentration of a contaminant (sum of mass concentrations in the vapour and particle phases), the fraction of a contaminant in the particle or vapour phase, and particle size distribution. Size distribution is of prime importance because the particle size governs the length of time for which the particle will remain suspended in the air, the manner in which it will settle and the air velocity required to remove the particles from the workings. The unpredictable and somewhat surprising results obtained in this investigation are indicative of a wide variety of aerosol instabilities that may be encountered when sampling for airborne dust. A widely held view that dust concentrations in the workings are homogenous in nature as well as in composition was disproved. At the outset of gravimetric dust sampling agreement was reached with the GME that mines need only implement personal gravimetric sampling (for risk assessment and the determination of levies) and that exemption from previous statutory requirements - quarterly dust surveys using konimeters - would be granted across the board. In the early stages of implementing the GME's sampling strategy, Industry noted that sampling five percent of the workforce was onerous and that it would be considerably simpler to collect a single sample, at a representative place, in a workplace as an indication of worker exposure. The origins of the project, SIMGAP Project GAP046, were rooted in the Industry's need to establish the viability of such a simplification of sampling procedures. Extensive investigations were conducted at three underground sites and one surface installation. The first underground site was a highly mechanized, shallow mine, the second site was a shallow mine with conventional minHongwalls and the third site was a deep mechanized mine. The fourth site was an assay and sample preparation laboratory. At each location sampling was undertaken over a number of days and all working shifts. Sampling pumps were attached to personnel and the same personnel, as far as possible, were sampled during each investigation. All sampling was conducted for the full working shift. At the same time stationary samples were set up at representative places. At all the sampling sites extremely large variations in dust concentrations were measured on a day to day and shift to shift basis. Correlation of dust concentrations between personal and stationary samples was very poor as was the correlation between quartz fractions. In addition there was very poor correlation between personal samples in the same area during the same shift. Also, the correlation between dust and quartz concentrations was found to be poor. Thus, the possibility of replacing personal samples with representative, stationary samples could not be justified nor recommended. As part of this project, but not part of the original proposal, possible reasons for large variations in dust and quartz concentrations were investigated. Regular checks were made with the South African Bureau of Standards (SABS) on analytical results and highly satisfactory agreement in analyses were always obtained. Analyses of in-situ samples were compared with airborne concentrations and little agreement was found. Sampling pumps were set up to sample in parallel. Pumps of the same make gave very good agreement in dust concentrations but very poor correlation in quartz levels. Although this phenomenon has been noted in overseas literature no satisfactory explanation has been advanced and re-inforced the perception that aerosol behaviour is far from being fully understood or predictable. Sampling pumps of different types i.e. conventional cassette and cyclone, and rotating sponges yielded different results when set to sample in parallel. The sponge type always gave predictably lower, but extensively scattered, results than the conventional type and this is a cause for concern because it is estimated that approximately 50 percent of the gold, platinum and base metal mines are using this type of sampler and hence results reported would also inadvertently have erred on the low side. Data from reports submitted by gold mines to the GME were compiled in a data base and examined for trends. Mines were divided into six geographical regions, namely East (Eastern Transvaal), Elsburg, Klerksdorp, North Free State, South Free State and West Wits. Reports of half-yearly results for the period January 1992 to June 1994 were analysed. Results were further classified into three broad activity groups - underground stopes and development, underground roving, and surface. Large variations in dust concentrations and also in quartz concentrations were found in individual statistical populations, from one statistical population to another and from one sampling area to another for any given six month sampling cycle for a given mine. Furthermore, results differed significantly between successive sampling cycles for a given mine. Quartz concentration in a given statistical population for five individual samples could vary very litUe but could also typically vary from 4 to 72 percent, or 17 to 98 percent. It was also found that quartz percentages have been based on the total mass of particulate on filters, no allowance having been made for carbon particles or salts. Reported quartz concentrations are thus likely to have been in error and on an industry basis airborne quartz concentrations reported could inadvertently have been too low. No significant differences were found in either dust levels or quartz concentrations between the three activity classifications or between the regions, ie all were equally wide in distributions/ranges. The industry eight-hour Time Weighted Average (TWA) quartz content was found to be in the range 10 20 percent Due to possibly under-reporting an industry level of 20 percent for quartz should be used when evaluating exposures. In this case an eight-hour TWA of 0,5 mg/m3 would have equated to an Air Quality Index (AQI) of one, and could be adopted as a standard but which would, however, be very difficult to test for compliance. The adoption of this procedure would simplify the evaluation of working place conditions for control purposes as well as provide management with information with regard to likely worker exposure levels with a minimum of delay since the dust samples would not need to be analysed for quartz content. This could represent a significant, but valid, simplification in the risk assessment process. No detailed analyses of the reports submitted to the GME have been made. However, from the original records the potential exists to extract information pertaining to occupational dust exposure. There is a considerable volume of data which has thus far only been used to calculate levies but which could be put to more meaningful use. Although it would take considerable effort, occupational dust exposure levels could be extracted from these data. Industry at last has the sampling equipment and infrastructure to advance our knowledge in dose/response studies and to eliminate reliance on 40 year old data. Industry expressed the concern that dust exposure levels and measures instituted to control exposure levels are not adequately reflected in the risk formula as defined at present. It was found that the quartz content of the airborne dust greatly influences the outcome of a risk calculation. It can, however, be shown that if both the quartz and the non-quartz fraction of the airborne dust are incorporated in the risk evaluation the formula would become more equitable. Nevertheless, because of the highly variable and nonrepeatable dust and quartz levels, risk assessment, as defined at present, would still be being based on very random variables. This uncertainty would be exacerbated by fie inclusion of additional pollutants such as diesel soot, etc. There is a growing awareness that aN dust and not just the toxic fraction can impact on a persons' healtii. The so-called nuisance dust or particles not otherwise classified (PNOC) is suspected to contribute to increasing numbers of occupational asthma cases. In addition, the short duration high peak concentrations or transient high peak concentrations of dust are now suspected to play an important role in physiological impairment in conjunction with the average concentration of the dust. These peaks could trigger a physiological response, such as an asthma attack, and also overwhelm the body's natural defence mechanisms thereby leading to a more permanent type of impairment. These transient high peak exposures together with the 8 hour TWA exposures could then constitute the more significant risk. Risk assessment for levy purposes through the GME's dust sampling programme should be discontinued and levies, which are to pay compensation for past events, should be based on other criteria as defined by the Commissioner for Compensation (COID). At present, mines are required to implement the GME's gravimetric dust sampling programme to determine personal exposure levels on which a risk levy is calculated. Some mines have abandoned all sampling for engineering control purposes, there being no legal obligation for such sampling. Others, in addition to the gravimetric sampling, have continued with konimeter sampling to identify and rectify unsatisfactory dust concentrations in the workings. There was thus an opportunity to investigate the use of a single set of sampling equipment, viz gravimetric samplers, to fulfill both requirements. Furthermore, it was noted in the Leon Commission of Enquiry into Health and Safety in Mines' that high and unsatisfactory dust concentrations are not being identified and addressed. This remark refers to the eight-hour TWA dust concentrations where high dust concentrations are averaged and therefore go largely undetected and untraceable. Initial trials have indicated the feasibility of using a conventional gravimetric dust sampling pump with a small diameter filter (13mm) for short sampling periods. The small filter gives a superior dust mass/filter mass ratio compared to a bigger filter (25mm diameter). These short duration samples (12-15 minutes) have been found to be effective in evaluating workplace conditions and identifying places or operations where high dust concentrations are generated. The results of such sampling can be entered in a standard environmental report form for use by management. It can be assumed that if high dust levels are brought under control then exposure of the workforce to unsatisfactory dust levels will also be controlled. It is correct that there is a delay in obtaining the mass of dust on the filters and that conditions may have altered by the time management receives this report. Nevertheless, this is a common procedure for many occupational hygiene measurements, such as gas samples, that need laboratory evaluation and as such is an internationally practised technique. In any event, delayed results are better than no results and can still alert management to the need for corrective action. In general, where analyses are required for pollutants other than quartz, it will be necessary to collect two samples since the respirable fraction is used for quartz determination but a total dust sample is needed for other pollutants such as lead. This double sample collection is not considered to be cost effective. Using a conventional sampling system, i.e. filter, cassette, separating cyclone and pump and not a rotating sponge system, both the respirable and non-respirable fractions of the airborne dust are collected separately. After analyses of the respirable fraction, the two fractions could be recombined for a total dust analysis. Trials were held in which weighed thimbles were inserted in the catchpots of the separating cyclones from which the non-respirable fraction could be recovered. However, these trials were discontinued because the thimbles proved to be too difficult to extract from the catchpots. Instead, the residue from the catchpot was carefully deposited onto the already analysed filter through a system of flushing and vacuum deposition. Strict quality controls are necessary to prevent either contamination or loss of sample but, nevertheless, the technique is viable and would make multiple analyses possible, at least where x-ray diffraction is used for analyses. This method is not viable for the rotating sponge samples. The ultimate objective of dust sampling is to reduce exposure levels to those that may be considered to be in compliance with good health and safety practices. The present programme of sampling has been used only to compute numbers on which dust levies can be based. The strategy is not suitable to gauge the dustiness of working places and individual unsatisfactory exposures remain difficult to detect or trace. This could also be a meaningless exercise if such an attempt were to be made after a lapse of several months. In addition, the present programme provides no useful input to engineering control which would in turn assist with the reduction of personal exposure levels. It is evident that the current sampling programme and strategy should be reviewed as a matter of urgency and that it be replaced by a two pronged approach, one aimed at determining exposure for dose/response and epidemiological studies and the other at engineering control. Both strategies should be viewed in pursuance of an understanding of personal exposure. PREFACE A fundamental element of any occupational hygiene initiative of merit is, in terms of Olishifski's well-known definition, the implied logic of evaluating a hazard in a manner conducive to control. It is immaterial if such control is achieved by engineering means (preferably), or by personal protection (last resort), or by a combination of both. The ultimate objective is to reduce exposure to levels consistent with sustained good health and safety. It follows that if this objective cannot be fulfilled, the entire process of hazard anticipation, recognition and evaluation be subjected to serious review. The present project deals with dust as an occupational health hazard. More realistically it should be regarded as taking stock of the personal (gravimetric) dust sampling programme recently introduced in the South African mining industry. The findings of this study make it eminently clear that, despite the enormous potential of the method to come to grips with this insidious hazard, the specific application reduces the programme to a meaningless exercise: pooled data lack relevance to individual exposure while concurrently providing no useful input to engineering control. The following extracts from the `Leon Report' summarise the prevailing situation : ` -- failure (on the part of mines) to measure actual exposures in the workplace accurately --' (p40). The widespread practice of averaging - for example. The average dust level for an entire mine - serves only to confuse `(p60)' The report also draws attention to several unfounded assumptions, as well as unanticipated problems, for example - The lack of correlation between dust and quartz, - The incongruity of compliance testing in highly variable environments, - The lack of consistency in findings, and consequently `risk assessment', when using different instruments, and - The fact that the procedure of combining samples and averaging the results renders the entire programme insensitive to dangerously high personal exposures. As argued at the outset, the present process of evaluation is not conducive to engineering control or to personal exposure for the purpose of epidemiology. Clearly, a major review is indicated as a matter of priority and in this respect the point of departure should be to obtain a detailed understanding of personal exposure to dust. This, in fact, is the real purpose of the methodology. A.J. KIELBLOCK Occupational Hygiene Consultant CONTENTS (i) LIST OF TABLES..................................................................................................................................... (iv) LIST OF FIGURES ................................................................................................................................. (vi) 1 INTRODUCTION ............................................................................................................................... 1 PART 1 COMPARISON OF STATIONARY (AREA) SAMPLES WITH PERSONAL (ROVING) SAMPLES................................................................................................................................... 2 2 TEST SITE 1: Shallow highly mechanized mine ............................................................................ 2 2.1 Description of Test Site .......................................................................................................... 2 2.2 Measurement Strategy............................................................................................................ 4 2.3 Instrumentation........................................................................................................................ 4 2.4 Quartz Determination.............................................................................................................. 5 2.5 Monitoring Procedures............................................................................................................ 5 2.6 Quality Control .........................................................................................................................6 2.7 Results from and Analysis of Measurements........................................................................ 6 2.7.1 Comparison of representative place samples and main return samples, stationary samplers and roving samplers and between roving samplers..........11 3 TEST SITE 2: Shallow mine - conventional "mini" longwall section.............................................. 30 3.1 Description of Test Site ........................................................................................................ 30 3.2 Measurement Strategy.......................................................................................................... 32 3.3 Instrumentation, Monitoring Procedures and Quality Control ............................................ 32 3.4 Results from and Analysis of Measurements...................................................................... 32 4 TEST SITE 3: Deep mine, mechanized section .............................................................................. 38 4.1 Description of Test Site ........................................................................................................ 38 4.2 Measuring Strategy and Procedures.....................................................................................40 4.3 Results from and Analysis of Measurements...................................................................... 40 5 TEST SITE 4: Surface locality.......................................................................................................... 46 5.1 Assay Laboratory and Sample Preparation ........................................................................ 46 5.2 Measuring Strategy and Procedures..................................................................................... 47 5.3 Results from and Analyses of Measurements 48 CONTENTS (continued) (ii) 6 DISCUSSION: .................................................................................................................................. 54 6.1 Personal vs Stationary Samples.......................................................................................... 54 6.2 Variations in Dust Concentrations........................................................................................58 6.3 Variations in Quartz Concentrations ....................................................................................58 6.4 Correlation Between Dust and Quartz Levels .................................................................... 60 6.5 Air Quality Index.................................................................................................................... 61 6.6 Personal Samplers : Quartz, Quartz andDust, AQIs........................................................... 62 7 CONCLUSIONS AND RECOMMENDATIONS................................................................................ 62 PART 2 8 ASSESSMENT OF GRAVIMETRIC DUST SAMPLING DATA FROM SIX SAMPLING CYCLES SUBMITTED BY GOLD MINES, MEMBERS OF THE CHAMBER OF MINES, TO THE GOVERNMENT MINING ENGINEER.............................................................................................. 64 8.1 Methodology.......................................................................................................................... 64 8.2 Results .................................................................................................................................. 65 8.2.1 8.2.2 8.2.3 8.2.4 8.2.5 8.2.6 Overall industry results............................................................................................ 65 Overall industry quartz analyses............................................................................ 73 Overall industry population dust exposure ............................................................ 80 Industry trends in quartz concentrations................................................................ 83 Regional and industry average dust concentrations............................................ 85 Regional and industry quartz concentrations ........................................................ 90 9 DISCUSSION.................................................................................................................................... 96 9.1 Results Submitted to the GME.............................................................................................. 96 9.2 Impact of Quartz Content on Risk........................................................................................99 9.3 Risk........................................................................................................................................ 99 9.4 Investigation of Quartz Variations ...................................................................................... 101 9.5 Comparison of Sampling Pumps ...................................................................................... 101 9.6 Quartz Concentrations Obtained in Parallel Sampling...................................................... 104 10 CONCLUSIONS AND RECOMMENDATIONS............................................................................... 104 PART 3 11 TECHNIQUES TO RECOMBINE RESPIRABLE AND NON-RESPIRABLE DUST FOR TOTAL POLLUTANT ASSESSMENT............................................................................................ 107 CONTENTS (continued) PART 4 12 EXPOSURE AND ENGINEERING CONTROL MONITORING.....................................................110 12.1 Description ...........................................................................................................................110 12.2 Preliminary Results .............................................................................................................112 12.3 Discussion.............................................................................................................................114 12.4 Conclusions .........................................................................................................................114 13 OVERALL CONCLUSIONS AND RECOMMENDATIONS .......................................................... 115 13.1 Recombination of Respirable and Coarse Fractions of Dust for Complete Analysis................................................................................................................................. 115 13.2 Investigation of the possibility of Replacing 'Personal Sampling' with Stationary Area or Representative Place Sampling............................................................................ 115 13.3 Assessment of Data from the GME's Sampling Programmeon Gold Mines....................116 13.4 Recommendations for a more Equitable Risk Formula....................................................117 13.5 The GME's Dust Sampling Programme ............................................................................ 117 13.6 Exposure Monitoring and Monitoring for Dust Control Purposes......................................118 14 REFERENCES................................................................................................................................. 118 APPENDIX A TWA AND QUARTZ CONCENTRATION DATA EXTRACTED FROM REPORTS SUBMITTED BY MINES TO THE GOVERNMENT MINING ENGINEER FOR THE EAST, ELSBURG, KLERKSDORP, NORTH FREE STATE, SOUTH FREE STATE AND WEST WITS REGIONS .................................... 120 LIST OF TABLES (iv) 1 Shallow mining section. Trackless mining tests. Vehicles(roving)..................................................7 2 Shallow mining section. Trackless mining tests. Personnel(roving)................................................ 8 3 Shallow mining section. Trackless mining tests. Fixed stations : Intake ........................................ 9 4 Shallow mining section. Trackless mining tests. Fixed stations : Returns.....................................10 5 Conventional longwall section. Personnel (roving).........................................................................33 6 Conventional longwall section. Personnel (roving)........................................................................ 34 7 Conventional longwall section. Fixed stations : Representative places........................................ 36 8 Deep level trackless stoping section. Trackless mining tests. Vehicles (roving) ........................ 41 9 Deep level trackless stoping section. Trackless mining tests. Stationary samplers :Intake ... 42 10 Deep level trackless stoping section. Trackless mining tests. Fixed stations : Returns............43 11 Assay laboratory dust sampling - first survey....................................................................................48 12 Assay laboratory dust sampling - second survey............................................................................ 48 13 Industry stoping and development population TWA dust distribution ..............................................65 14 Industry underground roving population TWA dust distribution...................................................... 65 15 Industry surface population TWA dust distribution.......................................................................... 66 16 Industry total underground population TWA dust distribution ........................................................ 66 17 Industry overall TWA dust distribution...............................................................................................66 18 Industry stoping and development population quartz per cent distribution.................................... 73 19 Industry underground roving population quartz per cent distribution...............................................73 20 Industry surface population quartz per cent distribution.................................................................. 74 21 Industry total underground population quartz per cent distribution .................................................74 22 Industry overall quartz per cent distribution ..................................................................................... 75 23 Industry overall TWA distribution, 0 to 0,4 mg/m3 (dust) ................................................................. 80 24 Industry overall TWA distribution, 0,4 to 0,6 mg/m3 (dust)............................................................... 81 25 Industry overall TWA distribution, > 0,6 mg/m3 (dust) ..................................................................... 81 26 Industry overall quartz distribution, 0 to 10 per cent......................................................................... 83 27 Industry overall quartz distribution, 10 to 20 per cent....................................................................... 83 28 Industry overall quartz distribution, > 20 per cent............................................................................. 83 LIST OF TABLES (continued) (V) 29 Simple arithmetical and person weighted cyclic average dust exposure levels (TWA) (excluding surface results) ............................................................................................................ 86 30 Simple and arithmetical and person weighted cyclic average quartz concentrations (excluding surface results) ............................................................................................................ 91 31 The influence of quartz concentrations on risk.............................................................................. 99 32 The effect of quartz content on AQI and risk and proposed changes to Risk evaluation.......... 100 LIST OF FIGURES (vi) PART 1 1 Layout of test site (1) ...........................................................................................................................3 2 Comparison of dust loads, return air and representative place.......................................................11 3 Comparison of area samplers : dust concentrations at representativeplaceand main return ..12 4 Comparison of intake and return air dust concentrations - intake, representative place, main return......................................................................................................................................... 13 5 Comparison of intake and return air dust concentrations all intakes, representative place, main return......................................................................................................................................... 13 6 Variation in quartz content - representative place ...........................................................................14 7 Dust load and quartz content - representative place.......................................................................14 8 Comparison of quartz content - return air and representative place.............................................. 15 9 Stationary and roving samples - dust at representative place, team leader.................................. 16 10 Stationary and roving samples - dust at representative place, construction worker ..................... 16 11 Comparison of quartz content - representative place, team leader ............................................... 17 12 Comparison of quartz content-representative place, construction worker.................................. 17 13 Air quality index : representative place "D".......................................................................................19 14 AQI : comparison of fixed samplers : main return "E" and representativeplace "D"......................19 15 AQI : comparison : fixed to roving samples : representative place "D" and team leader.............. 20 16 AQI : comparison fixed to roving samples : representative place "D" and dump truck ................ 20 17 AQI : comparison fixed to roving samples : representative place "D" and LHD............................ 21 18 AQI : comparison fixed to roving samples : representative place, team leader, dump truck, LHD.....................................................................................................................................................21 19 Variation in dust exposure - scaler and roof bolter............................................................................22 20 Comparison of dust loads - roving : team leader and construction worker .................................. 23 21 Comparison of dust loads - roving : LHD and team leader............................................................ 23 22 Variation in dust exposure - roving : LHD and dump truck.............................................................. 24 23 Comparison of roving samplers : LHD and dump truck.................................................................. 24 24 Variation in quartz content - roving : team leader............................................................................ 25 25 Variation in quartz content - roving : construction worker .............................................................. 25 26 Variation in dust and quartz levels : roving - LHD............................................................................ 26 LIST OF FIGURES (continued) (vii) 27 Comparison of quartz content roving : team leader and construction worker .............................. 26 28 Dust load and quartz content - roving : teamleader ........................................................................27 29 Dust load and quartz content - roving : construction worker.......................................................... 27 30 Air quality index - roving : team leader ............................................................................................ 28 31 Air quality index - roving : dump truck...............................................................................................28 32 Air quality index - roving : LHD .........................................................................................................29 33 Comparison of AQI - roving : LHD and dump truck.........................................................................29 34 AQI comparison of roving samplers : team leader, dump truck, LHD ...........................................30 35 Layout of test site (2).........................................................................................................................31 36 Comparison of stationary samplers : representative place and main return (dust) ...................... 35 37 Stationary samplers vs roving (dust) : representative place and roving 1W.................................. 37 38 Comparison of representative places (dust) : representative place 1E and representative place 1W ...........................................................................................................................................37 39 Comparison : stationary and roving (dust): main return and personal 1W .................................. 38 40 Layout of site (3)................................................................................................................................. 39 41 Comparison of representative places and return (dust).................................................................. 44 42 Comparison of LHDs and return (dust).......................................................................... 44 43 Variations of dust and quartz levels LHD T41 ................................................................................ 45 44 Variations of dust and quartz levels main return H.......................................................................... 46 45 Layout of assay laboratory and sample preparation building ........................................................ 47 46 Stationary vs personal samples (dust) : test 1 ................................................................................ 49 47 Stationary vs personal samples (dust): test 2 ................................................................................ 49 48 Quartz concentrations : personal samples - test 1........................................................................... 50 49 Quartz concentrations : fixed samplers - test 1 ............................................................................... 51 50 Fixed vs personal quartz concentrations - test 1 ............................................................................ 51 51 Quartz concentrations : personal samples - test 2.......................................................................... 52 52 Quartzconcentrations : fixed samplers - test 2 ............................................................................... 52 53 Fixed vs personal quartz concentrations - test 2 ............................................................................ 53 LIST OF FIGURES (continued) (viii) 54 Comparison of roving and area samplers .......................................................................................54 55 Comparison of dust levels : two stationary and four personal........................................................ 55 56 Comparison of roving and area samplers ...................................................................................... 55 57 Stationary and roving samples (Team Leader) .............................................................................. 56 58 Stationary and roving samples (Construction Worker) .................................................................. 56 59 Comparison of dust loads (LHD).......................................................................................................57 60 Comparison of dust loads (dump truck)...........................................................................................57 61 Variation in dust exposure (return air): shift to shift basis .............................................................. 58 62 Comparison of roving and area samplers (all vehicle drivers) ...................................................... 59 63 Variation in quartz content (return air)...............................................................................................59 64 Stationary sampling position (main return): dust and quartz levels .............................................. 60 65 Variation in dust and quartz levels (main return) ............................................................................ 60 66 Dust load and quartz content (return air) .........................................................................................61 67 Air quality index (return air "E") .........................................................................................................61 68 Industry stoping and development population TWA dust distribution (half yearly cycles January to June 1994)..................................................................................................................... 67 69 Industry total stoping and development population TWA dust distribution .................................... 68 70 Industry underground roving populations TWA dust distribution (half yearly cycles January 1992 to June 1994) ......................................................................................................................... 68 71 Industry total underground roving population TWA dust distribution.............................................. 69 72 Industry surface population TWA dust distribution (half yearly cycles January 1992 to June 1994)....................................................................................................................................... 69 73 Industry total surface population TWA dust distribution.................................................................. 70 74 Industry total underground population TWA dust distribution (half yearly cycles January 1992 to June 1994) ......................................................................................................................... 70 75 Industry total underground population TWA dust distribution ........................................................ 71 76 Industry overall population TWA dust distribution (half yearly cycles January 1992 to June 1994)....................................................................................................................................... 72 77 Industry overall population TWA dust distribution............................................................................ 72 78 Industry stoping and development population quartz per cent distribution (half yearly cycles January 1992 to June 1994).......................................................................................................... 75 LIST OF FIGURES (continued) (ix) 79 industry stoping and development population quartz per cent distribution.................................... 76 80 Industry underground roving population quartz per cent distribution (half yearly cycles January 1992 to June 1994) .......................................................................................................... 76 81 Industry underground roving population quartz per cent distribution.............................................. 77 82 Industry surface population quartz per cent distribution (half yearly cycles January 1992 to June 1994)....................................................................................................................................... 77 83 Industry surface population quartz per cent distribution.................................................................. 78 84 Industry total underground population quartz per cent distribution (half yearly cycles January 1992 to June 1994).......................................................................................................... 78 85 Industry total underground population quartz per cent distribution ................................................ 79 86 Industry overall population quartz per cent distribution (half yearly cycles January 1992 to June 1994)....................................................................................................................................... 79 87 Industry overall population quartz per cent distribution ...................................................................80 88 Percentage of total population exposed to TWA levels below 0,4 mg/m3 (dust).......................... 81 89 Percentage of total population exposed to TWA levels between 0,4 and 0,6 mg/m3 (dust) .... 82 90 Percentage of total population exposed to TWA levels greater than 0,6 mg/m3 (dust)................82 91 Percentage of total population exposed to quartz levels between 0 and 10 per cent..................84 92 Percentage of total population exposed to quartz levels between 10 and 20 per cent................84 93 Percentage of total population exposed to quartz levels greater than 20 per cent ......................85 94 East region dust averages.................................................................................................................87 95 Elsburg region dust averages ...........................................................................................................87 96 Klerksdorp region dust averages .....................................................................................................88 97 North Free State region dust averages.............................................................................................88 98 South Free State region dust averages ...........................................................................................89 99 West Wits region dust averages.......................................................................................................89 100 Industry dust averages.......................................................................................................................90 101 East region quartz averages.............................................................................................................92 102 Elsburg region quartz averages .......................................................................................................92 103 Klerksdorp region quartz averages...................................................................................................93 104 North Free State region quartz averages 93 LIST OF FIGURES (continued) (x) 105 South Free State region quartz averages.........................................................................................94 106 West Wits region quartz averages ................................................................................................. 94 107 Industry quartz averages...................................................................................................................95 108 Variation in quartz concentration between statistical populations................................................. 97 109 Variation in quartz concentration between sampling cycles ........................................................... 97 110 Individual quartz concentration in a statistical population............................................................... 98 111 Variation in risk between statistical populations............................................................................. 98 112 Quartz content: rock and airborne dust.........................................................................................101 113 Gilian vs Gilian : dust (mg/m3).........................................................................................................102 114 Gilian vs rotating sponge : dust (mg/m3).........................................................................................102 115 Comparison of Gilian and rotating sponge samples (routinemeasurements)..............................103 116 Comparison of rotating sponge samplers.......................................................................................103 117 Gilian vs Gilian quartz per cent.......................................................................................................104 118 Present and possible techniques to determine AQI......................................................................106 119 Separate respirable and total dust sampling ............................................................................... 108 120 Proposed combined respirable and total dust sampling technique...............................................108 121 Continuous dust level trace.............................................................................................................Ill 122 Comparison of sampling techniques and registering of highdust levels ......................................Ill 123 Dust levels found for short duration sampling (1) .........................................................................112 124 Dust levels found for short duration sampling (2) ....................................................................... 113 1 INTRODUCTION 1 Shortly after the introduction of the Government Mining Engineer's (GME) programme of gravimetric dust sampling questions were raised by Industry with regard to an effective means of sampling, for engineering control purposes, possible reduction in sampling effort and reduction in analytical costs. It was also considered that the risk calculated for levy purposes was not equitable and did not accurately reflect any effort made to reduce dust concentrations and thus risk. The research programme was aimed at addressing the above concerns and extensive data sets were collected at each of three underground test sites, as well as at an assay laboratory where a repeat sampling exercise was conducted several months after the initial survey. The first underground test site was at a shallow, highly mechanised section of a gold mine in the West Wits Region, the second was a shallow conventional, mini longwall system (Elsburg Region) and the third test site was at a deep mechanised longwall section (Elsburg/Klerksdorp). The fourth test site was an Assay laboratory. The results of the separate monitoring exercises are set out below. The investigations were conducted using Gilian pumps. This should be seen as representative of the conventional pump and filter arrangement and not as an endorsement of the product. Rotating sponge type samplers were also used for the sake of completeness since a large number of mines use this system of sampling. Investigations into analytical techniques were carried out in the CSIR : Mining Technology's (Miningtek) GME approved air quality laboratory. (Now also approved by the Department of Labour). The possibility of using ah pollutants of airborne samples, instead of only quartz, to formulate an Air Quality Index and hence a risk, was also explored with a view to developing a more equitable risk formula. In-situ quartz concentrations were compared with airborne quartz concentration in investigating reasons for the variations encountered in levels of airborne quartz. During early 1995 copies of all available gravimetric dust sampling reports (compiled by the mines who are members of the Chamber of Mines) were forwarded to Miningtek by the office of the GME for compilation in a database and analysis to determine if "regional" and "Industry" 2 airborne quartz concentrations could be ascertained with a view to rationalizing these quartz concentrations. Preliminary trials were carried out using a modified sampling train of standard equipment to collect short duration dust samples that would provide indications of workplace dust concentrations. The results have been very encouraging, and could provide a technique to assist in the evaluation of engineering control methods to limit the liberation of dust into the working environment. PART 1 COMPARISON OF STATIONARY (AREA) SAMPLES WITH PERSONAL (ROVING) SAMPLES 2 TEST SITE 1 Shallow, highly mechanized section. 2.1 Description of Test Site The site was located 890 m below surface, approximately 5 km from the main shaft. The orebody was up to 9 m thick. Trackless mining took place in two lower development headings (Stations "A" and "B" in Figure 1), in an upper development heading (extension from "E") and in bord and pillar section "D". Typical dimensions of headings in this section were 8 m wide by 5 m high. In addition, conventional mining took place in a narrow reef mining section located between "B" and "D". The main tip for this mining section was outside the section approximately 0,5 km from "E". The workshop serving the section was 2 km away. 3 Figure 1 LAYOUT OF TEST SITE (1) Mining operations were conducted over three shifts every day i.e. morning, afternoon and night shift. The section under consideration was ventilated from a footwall cross-cut via two 75 kW booster fans (next to position "B") delivering 40 m3/s to the section. This provided the intake air, which was monitored at position "B". Some of this air was used to ventilate the lower development ends (monitored at positions "A" and "C") and some air was passed through the stoping section and a raise bored hole into the bord and pillar section. This air was mixed with some of the return air from the development heading extending from "B". The pollution levels of this air were monitored at position "C". Some of the air from the conventional stoping sections passed via a raise to the upper development end. The quality of air exiting from the bord and pillar sections was monitored at position "D" (representative place) and the major return was monitored at "E". Development headings were ventilated by 30 kW fan delivering 10 m3/s. 2.2 Measurement Strategy 4 Ideally, every person in the section should have been monitored simultaneously for any given monitoring shift, as well as the fixed stations at inlets, the representative place and the main return. Owing to limitations on available instrumentation and personnel this was not possible and as a next best alternative at least one person from each work category was monitored simultaneously with all the fixed position stations. Once personnel had been selected, the same . person was always monitored using the same instruments. The stationary points were monitored using the same instrument for each sampling shift. The purpose of these measurements was to establish whether measurements at fixed point (i.e. representative or main return) would give adequate information on personal exposures in the section, as these fixed point measurements would be easier to implement in any dust sampling strategy and could reduce the monitoring burden. Ventilation surveys were conducted by mine personnel during each monitoring shift to determine changes in local ventilation conditions, such as at representative place "D", which could be caused by fan stoppages, airway holings, installation of brattices, or partial blocking of airways by blasted rock. Monitoring was conducted for the full duration of the shift for each of the three shifts worked and each day of the week. The afternoon and night shifts were monitored in one continuous operation to reduce the unproductive set-up time requirements. The data for double shifts were, however, collected and analysed separately. At least two days were allowed between monitoring shifts to allow for down loading of the instruments, recharging of all instrument batteries, calibration checks, etc. The test period extended from the end of October to mid December 1993. Because the monitoring section had a significant diesel powered vehicle population it was necessary to separate the diesel soot particulate from mineral dust for the purposes of this investigation. 2.3 Instrumentation The dust sample collection method used was the standard gravimetric dust sampling technique as specified in Guidelines set out by the GME2. The technique makes use of pre-weighed 25 mm diameter cellulose nitrate filters, 0,8 pm porosity, for field and control filters. Air is drawn through the filters by a constant volume (1,9 fpm) pump and a 10 mm cyclone separator ensures that only the respirable particulates are deposited on the filters for evaluation. 5 Mineral dust and Diesel Particulate Matter (DPM) were collected on the sampling filters over the full shift. After stabilization the filters were reweighed and checked against the control filters and the total amount of particulate, i.e. mineral dust and DPM was ascertained. DPM was determined using a methodology developed at Miningtek. The method, described below, has been found to be simple and reliable, and can be compared with the one described by Rex and Gardiner3. Reweighed field filters are placed in pre-weighed mini platinum crucibles. Each crucible is numbered and has a corresponding numbered lid. When empty, crucibles and lids weigh in the region of 5 000 mg. After the field filter with particulates is placed in the crucible the lid is replaced and the entire ensemble is again reweighed. At this stage a control check is made: (Crucible + filter (+ dust) + lid) - (crucible (empty) + lid) = filter + dust (weighed separately when filters are returned to the laboratory). Discrepancies of five per cent or more resulted in sample rejection. The loaded crucible is placed in a suitable muffle and the temperature elevated to 200 C and held for one hour. Thereafter the temperature is further elevated to 600 C and again held for one hour. This process ensures complete combustion of all combustible matter (DPM + filter) and the lid ensures no loss of non-combustible (mineral) dust. After a suitable cooling period, usually overnight, the crucible and ash are reweighed and simple arithmetic gives the masses of DPM and mineral dust. 2.4 Quartz Determination Once combustible and non combustible particulate masses had been established, as described above, the ash content (mineral dust) was redeposited on a 25 mm diameter filter and subjected to X-ray diffraction examination to determine the quartz content. This was done for every filter used in the investigation. . 2.5 Monitoring Procedures The following routines were followed: the team, consisting of five to seven engineers and technicians proceeded underground an hour before the working shift (04:00 for the morning shift and 15:00 for the afternoon/night shift) to allow sufficient time to check and set up instrumentation before the arrival of the workforce. During this period all instrumentation for the vehicles to be monitored was installed. As the selected personnel arrived they were equipped with the relevant instrumentation. Thereafter members of the team manned the fixed position or stationary sampling points. 6 All instrument preparation and control, as well as filter preparation and mass determination were carried out at Miningtek in a GME approved laboratory using GME approved methods. The laboratory has recently also been approved by the Department of Labour. Quartz determination was performed using a direct on filter technique approved by the Sooth African Bureau of Standards and this equipment was maintained under contract by the manufacturer. Random samples were also sent to the SABS for evaluations. 2.7 Results from and Analysis of Measurements Measurements were taken during normal mining operations over a period of approximately two months. No attempt was made to control conditions to enable easier interpretation of results nor to obtain a greater volume of useful data, i.e. conditions were monitored as found. Details of all sampling results are set out in Tables 1 to 4. Table 1 gives data collected for vehicle operators (personal), Table 2 shows results of personal sampling (non vehicle), Table 3 features the results for stationary samples at the inlet position grouped together and Table 4, similarly, the results for the representative place and the main return. Table 1 SHALLOW MINING SECTION. TRACKLESS MINING TESTS VEHICLES fROVINGl <cyn "88888 11 i 31 7 <CuD < {N O ^ Kl < <N Date Test Actual Quartz Mineral AQl Risk Quartz Mineral AQl Risk Quartz Mineral Number Test Content Dust Content Oust Content Dust Number Cone Cone Cone. Per Cent mg/m3 Per Cent Per Cent mg/m3 Per Cent Per cent mg/m3 O Risk Quartz Minera AQl Risk Content 1Dust Per Cent Cone. Per Cent mg/m3 Per Cent d*7 rn-~ o 88 O -- cn o' o' o o o o o' o o o sss a o o' o o' o 8"a9 a 8882 2 :-ii " (oN t- o-- O CNO <N ^ 5 ? $ S3 o o o' o o 3888 8 r< $ Q a 8 \n 2 31 "Z *- ci n tt un 0.296 0 452 0 201 0.317 : 8 88 FCl t-' Nas- rOO O sr O Q Q 2 rn- 2 z CN 2 o o d o' o 32S2 8 o' o' o o' o' 0 01 007 0.00 0 13 005 oCN m-- --o T cn --r> -- n cd co CJ D N CO O) 2 Or> QO Ln0 8s cP3I 9<i o o o o' o o' 37.50 53.97 37.06 19.03 36 39 3 72 1 89 2.85 0.74 2.30 d c* CN <nN **- ICDl 38828 P CM R S v iun> -r o n'J 'nf IOj' o o' o o' o o' 3 $ J2 S3 R to d r-' o 0) 7 Ci nCl <ID3 nCD e*- 35 18 33.71 17.50 33 60 Q CD <N CD o' o' o o 0 964 45 63 0.231 1 05 44 0.92 3.36 57.64 0.150 0 87 , 3.03 1.81 13.04 23.63 0.656 1.88 14.14 0.7B 2.41 4 2 5 0 0.332 1.62 10.53 1.17 6 27 43.66 0.477 1.36 B.04 CM Tf IN 0) 2? -- <n n v in Minimum Maximum Average Std Dev Variance !T O ^ C> Is- ?r 5 a o o o *- o o 8 S 3 3K9SR (?N Unl n- k1/1 ^T N8i!|L| 8 S ti 82833 0 71 2 44 1.18 5.90 256 0.04 1.02 0.49 0.29 o.ce 0.02 5.90 206 1.56 2.43 ND : Less than detection limit of 20 pg rsi n-r7vjoj 8^ 2 Sn 8 asrh 8 P8 o o' o o -- o o' o 8SRF38 o o o o' o 0 033 0.197 0.125 0.137 1.09 008 059 0 02 11.97 4.19 480 23 09 17.13 69 37 33,75 15.11 228 24 ___________ L 9 283 a 2RR ooooo R8S25 o' o o d o 3 89S o'od 1403 0.61 0.64 511 26.47 12.43 1602 29.46 21.10 0.158 0.356 0.245 0.142 0.947 0.370 0.94 0 31 0.23 279 1.07 3.55 0.37 0.21 31.10 8.81 OIN N05 C7O (7a ON oNodo 88388 o o o o' o 0.39 2.05 1.19 0 62 0.39 0 61 16.87 7.22 612 37.42 ND 57.84 22.53 18.42 339.47 0.00 31.10 5.63 8 85 78.26 W| IsiisT CO CO U_J! cr o QUJ < O' 2 o I-- o UJ if) CD ~z. o < X V) CN jL> _rQo h- Date Morning 04/11/93 17/11/93 22/11/93 30/11/93 01 /12/93 Average Afternoon 27/10/93 01/11/93 09/11/93 12/11/93 25/11/93 Average Night 27/10/93 01/11/93 09/11/93 12/11/93 25/11/93 Average Test Number Actual Test Number ;inOc -r (N CO 'T ID CO to CO TM CD N CO ) O oj n oj ^2 T- (\1 CO TT )IT Minimum Maximum Average Std Dev Variance Quartz Mineral A Q I Risk Quartz Content Dust Content Cone. Per Cent mg/m3 Per Cent Per Cent 21.36 49.70 3.90 45.00 29.99 0.081 0.463 0.252 0.311 0.277 0.17 230 0.13 1.40 1.00 0.12 21.17 0.06 7.81 7.29 9.44 39.54 50.13 32.92 50.62 36.53 cn d d d 0 851888 dddddd 63.40 16.15 17.15 26.87 30.89 18.23 0.28 0.85 1.99 5.34 96.35 40.46 10.23 ND 36.76 ND 96.35 32.55 26.73 714.66 88828 ddddd 0.421 0.292 0.440 0.173 0.102 0.286 2 81 1.78 0.18 005 1.21 005 2.81 1 03 0.95 0.91 31.64 12.68 0.13 0.01 11.12 0.01 31.64 7.91 10.23 104.71 9.44 50.62 36.53 15.10 227.89 ND : Less than detection limit of 20 (jg o IC--O CO UHJ U2J UJ CL O' a: CO CO C(0O < zo Mineral Dust Cone. mg/m3 AQI b (N T- T- r- 0.404 0.391 0.537 0.407 0.237 0.395 0.24 0.54 0.40 0.10 0.01 0.38 2.69 1.43 0.74 0.55 1<" CO UzJ CD Z >o on h- Risk Per Cent 0.58 9.56 28.96 7.18 5.76 10.41 0.58 28.96 10.41 9.73 94.70 <}-- CD CO CO < 2o: DoIo--r zCooO Quartz Content Per cent 30.65 55.05 9.62 9.20 26.13 51.60 25.15 12.18 18.89 26.96 85.91 25.74 ND ND 27.91 ND 85.91 27.00 24.57 603.58 IDV Mineral Dust Cone. mg/m3 Risk Per Cent 0.438 i 1.34 0.401 2.21 0.348 0.33 0.420 0.39 0.402 1.07 7.22 19.53 0.45 0.60 6.95 33888 o' d o' d oddddd 83S2S ddddd 0.402 0.147 0.276 0.035 0.026 0.177 ro-ot-jr^IDcToT ^CrN d cni d d d CD t-- <N r- O (N N O O ID -1 d d d d 8888- CD CN O O 04 8.44 1.63 0.58 0.31 2.74 0.00 19.53 3.93 5.54 30.66 8 Table 3 SHALLOW MINING SECTION. TRACKLESS MINING TESTS FIXED STATIONS : INTAKE o o (<1---- CD Zo Ih<- if) TT CO CO O O (N o o o o' o' o 858888 oooooo zo H- < if) Nt-0Q<0t-N0M0C^O~ 6 o o o ci o' 9 Date Test Actual Quartz Mineral AQI Risk Quartz Mineral AQI Risk Quartz Mineral AQI Risk Number Test Content Dust Content Dust Content Dust Number Cone. Cone. Cone. Per Cent mg/m3 Per Cent Per Cent mg/m3 Per Cent Per cent mg/m3 Per Cent 588282 o o o' o o' o' Morning 04/11/93 17/11/93 22/11/93 30/11/93 01/12/93 Average 'r-- <M CO Tf 10 53.19 37.89 28.54 ND ND 23.92 0.066 0.081 0.099 0.177 0.106 0.106 30,80 8,28 ND ND ND 7.82 !? d o d o' o o 53858? o' o' o o o o' 858888 d o' d o d o' DmOQ 0.412 0.159 0.970 0.258 0.132 0.386 Afternoon 27/10/93 01/11/93 09/11/93 12/11/93 25/11/93 Average (D N CO 05 2 r- (0 CD CO LI 5,63 8.52 ND 51.54 16.42 0.369 0.167 0.232 0.182 0.211 0.232 0.09 0.20 0.09 1.09 0.37 0.04 0.16 0.03 4.73 1.24 3.55 42.89 8.52 ND 13.74 0.313 0.129 0.128 0.188 0.160 0.184 8828s o o o o o' d^ddo 828 88 odd do ND 25.75 33.33 19.69 0.07 0.66 0.64 0.46 0.02 1.76 1.64 1.14 VZi 90'E too 09 L 800 SP1822 TO- inlll(orrinOoi oodoo ooooo Night 27/10/93 01/11/93 09/11/93 12/11/93 25/11/93 Average t-- CN CO TT 10 n t Mj) ^ 2.76 21.83 ND 26.36 12.74 0.220 0.284 0.307 0,83 0.332 0.245 0,14 0.67 0,04 0.87 0.43 25.58 4 24 ND ND 7.46 0.401 0.124 0.432 0.105 0.241 0.260 040 0.19 0.01 0.06 0.17 0.278 ND 0.093 0.05 4.85 0.372 0.19 ND 1.62 0.211 0.11 0.239 0.12 0.01 0.14 0.04 0.06 Minimum Maximum Average Std Dev Variance ND 53.19 18.17 19.07 363.48 b-r^OQ-rOttr-QO o dodo 0 04 1.09 0.33 0.33 0.11 300 4.73 0.86 1.41 2.00 ND 42.89 9.53 13.68 187.24 89255 ooooo 0.00 1.21 0.19 0.32 0.10 ND 40.02 9.64 14.71 216.50 0.09 0.97 0.29 0.22 0.05 883PI8 ooood 0.01 1.76 0.41 0.63 0.40 ND : Less than detection limit of 20 pg Table 4 SHALLOW LONGWALL MINING SECTION. TRACKLESS MINING TESTS FIXED STATIONS : RETURNS Date Test Number Actual Test Number Quartz Content Per Cent Morning 04/11/93 17/11/93 22/11/93 30/11/93 01/12/93 Average in o J t-- CN CO TT 10 10.16 40.10 7216 75 77 58 95 51.43 Afternoon 27/10/93 01/11/93 09/11/93 12/11/93 25/11/93 Average co to co LI cd r- oo O) 2 48.95 25.76 38.71 52.79 41.55 Night 27/10/93 01/11/93 09/11/93 12/11/93 25/11/93 Average <N tT N- 0) 2 t-- m co 'T in 1703 39.83 6.69 55 26 29.72 mm* dddddd Mineral Dust Cone. mg/m3 1.425 1.308 0.281 90.692 0.994 0.940 0.215 0.214 0.475 0.155 1,070 0.426 ---------------- ------------------ , 11 AQI Risk Quartz Mineral Content Dust Cone. Per Cent Per Cent mg/m3 0.31 0.65 3.13 2.97 1.68 1.75 0.38 1.70 39.06 32.27 11.31 17.54 18.03 53.35 45.00 33.12 37.38 0.382 0.414 0.241 0.239 0.319 ^ o' o o o o' S28WS cd o c\i in co 163.84 2.09 28.70 110.23 76.22 97.85 27.49 17.18 38.57 45.27 0.37 1.89 0.10 5.91 2.07 0.54 14.31 0.04 139.88 38.69 ---------------- 1 67.29 49.30 46.86 44.44 51.97 IDV Risk Per Cent 0.69 2.21 1.09 0.79 1.20 1.90 19.53 4.72 2.51 7.17 6.48 0.78 1.05 3.49 2.95 168.05 2.41 4.38 48.62 55.87 1.33 1.91 0.29 2.26 1.45 7.09 14.62 0.34 20.41 10.62 10 88 8 8 o d o d o d OrdO SSB o> SS8 8318 23$:= O CD (N CD ^ o oo $^R < H2 5 R E =3 c E 3 '5E? N. OD O) <D CO Q 0> TO < 00 (O t- Variance | 449.33 0.17 4.44 3034.52 447.68 0.15 2.66 2041.05 11 Shov/n in the Tables are the actual sampling dates and the order that the samples v/ere collected. However, for convenience, all the morning shifts have been grouped together. This has also been done for the afternoon and night shifts. Averages are shov/n for the three different shifts separately and averages, minimum, maximum, standard deviation and variance are shov/n for all variables for all shifts in a given category. Comparison of representative place samples and main return samples, stationary samplers and roving samplers and between roving samplers If a single stationary monitoring site can be used as an indicator of worker exposure within the section then some agreement could at least be expected between results obtained at possible representative sites. The results of the comparison between dust loads monitored at the main return, Station E, and at the representative place, Station D, are shown in Figure 2. In this instance there is some agreement and an equation can be fitted to the data as follows: Dust load for Station D = 0.78 (dust load for Station E)092 The coefficient of correlation is 0.86. OUST LOaO RETURN AiR m<g/m~3 Figure 2 COMPARISON OF DUST LOADS. RETURN AIR AND REPRESENTATIVE PLACE 12 However, reference to Table 4 shows that over the measuring period the average dust concentration at Station E was 0,5 mg/m3 with a standard deviation of 0,39 mg/m3 (78 per cent of the average value). Similarly, for Station D (representative place) the average dust concentration was found to be 0,56 mg/m3 with a standard deviation of 0,42 mg/m3 (75 per cent of the average value). The scatter in the data is illustrated in Figure 3*. So, although the correlation in readings appeared to be good, there was a large variation in dust levels with large standard deviations. Although 15 samples had been averaged, it would be necessary to collect many more samples to obtain a representative dust concentration. |\><1 REP PLACE |\N MAIN RETURN Figure 3 COMPARISON OF AREA SAMPLERS : DUST CONCENTRATIONS AT REPRESENTATIVE PLACE AND MAIN RETURN * Where shifts are shown on the x-axis the first five shifts are the morning shift results, the next five shifts are afternoon shift results and the last five shifts refer to the night shifts results. A comparison of dust concentrations at an intake air source and the representative place and main return is shown in Figure 4. Dust concentrations in the intake air are seen to be lower than those measured at the other two localities, but this was to be expected as intake air is supposed to be uncontaminated.The comparison is made in order to establish if any deviation in dust concentrations could be ascribed to mining activities, and not to contaminated intake air on any given day. An additional comparison is made in Figure 5 for all intake air sources, i.e. Stations A, B and C, and the representative place (Station D) and the main return (Station E). There were differences 13 between intake air dust levels and for some shifts the samples collected at the representative place and the main return were higher than those of the intakes. The differences in dust concentrations between the representative place and the main return recorded for some shifts can be clearly seen. Without a thorough investigation and the collection of a large number of samples the selection of a representative intake position, or representative return air position, would not be readily feasible. INTAKE AIR TEST NUMBER +- REP PLACE * MAIN RETURN Figure 4 COMPARISON OF INTAKE AND RETURN AIR DUST CONCENTRATIONS INTAKE REPRESENTATIVE PLACE, MAIN RETURN \6o6 OD [\\] MAIN RETURN Figure 5 COMPARISON OF INTAKE AND RETURN AIR DUST CONCENTRATIONS : ALL INTAKES, REPRESENTATIVE PLACE, MAIN RETURN 14 Changes in quartz content, on a shift-wise basis, are illustrated in Figure 6 v/here the quartz content is plotted for each monitoring shift at the representative place, A large scatter in quartz concentration was encountered: minimum 6,7 per cent, maximum 75,8 per cent with an average value of 41,7 per cent and a standard deviation of 21,2 per cent. Shift-wise fluctuations were unpredictable, large and unexplained. Figure 6 VARIATION IN QUARTZ CONTENT - REPRESENTATIVE PLACE An investigation into any possible relationship between actual dust concentration and quartz content revealed no acceptable correlation, as seen in Figure 7. U Cl Vz o o 5D Figure 7 no TOO 90 80 70 60 50 40 oo 20 10 0 CXJ5T LOAD RCPRESEKTATIVE PLACE mg/m~3 DUST LOAD AND QUARTZ CONTENT - REPRESENTATIVE PLACE 15 Although an acceptable correlation was found between dust concentrations measured at the representative place and main return (Figure 2) the same conclusion could not be drawn for a comparison of quartz concentrations evaluated for these two measuring stations. This is illustrated in Figure 8 and large variations and scatter are evident. TOO 90 - 0C V SO - l_ 70 V- 5H 60 Z oo M 50 -- 4+ 4 4 4 a 40 - + tou 30 4 20 + 4 10 -- + 4 0 >0 I lo | SO I 70 j iS r 40 GO SO 100 RETURN AIR QUARTZ CONTENT percent Figure 8 COMPARISON OF QUARTZ CONTENT - RETURN AIR AND REPRESENTATIVE PLACE One of the main reasons for this intense investigation was to establish if personal sampling could be replaced by area sampling. In Figure 9 the relationship between dust samples collected at the representative place are compared with those collected on a sampler attached to a team leader who roved throughout the mechanised section. As can be seen, dust concentrations for the team leader fall within a narrow range, 0,1-0,6 mg/m3 and those for the representative place in the range 0,1-1,5 mg/m3. The correlation is poor in that a single dust concentration at the representative place could correlate with two or three concentrations for the team leader. Similarly, Figure 10 shows a poor correlation between dust levels at the representative place and those to which a construction worker in the section were exposed. In Figures 11 and 12 quartz concentrations of airborne dust at the representative place were compared with those evaluated for samples collected on filters carried by the team leader and construction worker respectively. No correlations can be seen in these comparisons. 16 1(0 \e REPRESENTATIVE: PLACE SAMPLES mg/m- Figure 9 -STATIONARY AND ROVING SAMPLES - OUST AT REPRFRFMTatiwf PLACE. TEAM LEADER v REPRESENTATIVE; PEACE SAMPLES mg/m~3 FigUre1 -STATIONARY AND ROVING SAMPLES - DUST AT RFPRESFNTATIWP PLACE. CONSTRUCTION WORKER no 100 90 80 70 60 50 40 30 20 10 0 17 REP PLACE QUARTZ CONTENT percent Figure 11 COMPARISON OF QUARTZ CONTENT - REPRESHNTATIVF PI ACE. TEAM LEADER 90 80 70 30 20 10 0 REP PLACE QUARTZ CONTENT percent Figure 12 COMPARISON OF QUARTZ CONTENT - REPRESENTATIVE PI AC.F CONSTRUCTION WORKER 18 Because a good correlation was found between dust concentrations measured at the main return and the representative place, it can also be concluded that if results from the main return had been used, instead of those from the representative place, no meaningful correlations between stationary and roving samplers would have emerged for any of the comparisons discussed above. Ultimately, in the Government Mining Engineer's gravimetric dust sampling programme, dust and quartz concentrations are used to calculate an Air Quality Index (AQI) and "Risk" for each Statistical Population in a mine's sampling strategy. The AQI is calculated as follows: f dust concentration AQI Per cent Quartz X Too x 10'1 In effect the quartz fraction of the mineral dust is compared to a Threshold Limit Value (TLV) of 0,1 mg/m3. The TLV is considered to be a concentration to which most persons can be exposed for eight hours a day for five days a week without experiencing harmful effects over a working life time. Any AQI greater then a value of one should attract attention and an action level is considered to be half the TLV. The AQI may be considered to be a better measure of conditions than individual dust and quartz measurements since it incorporates both dust and quartz concentrations in the Index. Risk has been defined by the GME as 4 (AQI)2 and is used in calculations of dust levies. A plot of AQI evaluated for each monitoring shift at the representative place is shown in Figure 13. Very large shift-wise fluctuations are seen as well as a very large scatter in the data. Of the 13 valid data sets eight had AQIs in excess of unity. However, the scatter in the results, as seen in Table 4, shows that values varied from 0,1 to 6,4 with an average of 2,5 and a standard deviation of 2,1 (84 per cent of average). A comparison of AQIs for the main return (Station E) and the representative place (Station D) is illustrated in Figure 14. Once again, although it was seen in Figure 2 that a good correlation existed for dust concentrations measured at these two localities, no such correlation could be found for the AQIs calculated for these two monitoring stations. Against this criterion results from these two stationary samples' positions are no longer seen to be interchangeable. 19 t <n a c < 24 6 8 10 SHIFT NUMBER 12 14 Figure 13 AIR QUALITY INDEX : REPRESENTATIVE PLACE "D" AIR QUALITY INDEX 9 - + - -+ + 3 __ + 0 a a 9 a + + ____ 1__ 1- t > > j- _J____ !-- --i____ i-- , 1 ... _____ 1--_____ 1_____ 1 2 3 4 5 S 7 E 9 10 11 12131415 Shi FT NUMBER O MAIN RETURN "E" + REP PLACE "0" Figure 14 AQI: COMPARISON OF FIXED SAMPLERS : MAIN RETURN WEW AND REPRESENTATIVE PLACE mD' 20 A comparison for a stationary or fixed sampler (Station D) with a personnel (roving) sampler worn by the team leader is shown in Figure 15. No real correlation can be observed and a poor correlation is observed when AQIs for the representative place are compared with those of other roving samplers namely the dump truck driver (Figure 16) and the Load Haul Dump (LHD) driver (Figure 17). 7 sr 5h sr 2h 1h 0 l--- 0 1 2 3 4-5 6 7 REPR ESENTATtVZ PUCE "0" AQI O TEAM LEADER Figure 15 AQi : COMPARISON : FIXED TO ROVING SAMPLES ; REPRESENTATIVE PLACE "D" AND TEAM LEADER Figure 16 REPRESEWTATTVE PLACE "D" AQI DUMP TRUCK AQi : COMPARISON FIXED TO ROVING SAMPLES REPRESENTATIVE PLACE "DW AND DUMP TRUCK 21 REPRESENTATIVE PLACE "D" AQl LHD Figure 17 AQl : COMPARISON FIXED TO ROVING SAMPLES REPRESENTATIVE PLACE "D" AND LHD Figure 18 shows the last three comparisons on a single plot. AIR QUALITY INDEX P&yi TEAM LEADER DUMP TRUCK Z//X LHD Figure 18 AQl : COMPARISON FIXED TO ROVING SAMPLES REPRESENTATIVE PLACE. TEAM LEADER. DUMP TRUCK. LHD 22 Comparisons of exposures experienced by roving personnel were also evaluated. These are all persons engaged in the same working area, and, to some degree similarity in dust exposures could have been anticipated. Furthermore, if correlation proved to be good it may be possible to only sample one person and then be able to obtain representative exposure levels for other workers in this area. Potentially, this could save on sampling costs. In Figure 19 dust levels experienced by the scaler and roof bolter operators are compared and large shift-wise and individual differences were found. The range of dust concentrations measured for the scaler operator was found to be 0,2 to 0,56 mg/m3 with an average value of 0,34 mg/m3 and a standard deviation of 0,12 mg/m3 (35 per cent of the average). Although the average exposure for the roof bolt operator was also found to be 0,34 mg/m3 the scatter of dust concentrations was much higher and lay in the range 0,05 - 0,96 mg/m3 with a standard deviation of 0,29 mg/rrP (85 per cent). Dust loads for the team leader and construction worker are depicted in Figure 20, where once again it is seen that two persons working in the same section can experience different dust exposures which are largely unrelated. This is further illustrated in Figures 21 to 23 which compares dust exposures for the LHD operator with those of the team leader,as well as with those of the dump truck driver respectively. 1.1 i 0.9 - + 4- 0.5 0.7 9N 0.6 t + 0 yJ 0.5 ' 0 0.4 - + 0 + o 4- 0.3 - 02 Q a 4- + a + 4- + 0.1 t + 01 t 1' --l---I-.._J_____ 1 23 4 5 6 7 9 10 11 12 O 1 4 15 TEST NUMBER O SCALEH 4- ROOF 801TER Figure 19 VARIATION IN DUST EXPOSURE - SCALER AND ROOF BOLTER i 0.9 0.8 \ 0.7 0.6 0.5 0.4 0.3 23 OUST LOAD ROVING 0"L) mg/m~3 Figure 20 COMPARISON OF DUST LOADS - ROVING : TEAM LEADER AND CONSTRUCTION WORKER x O 0.2 04 06 OB 1 12 14 16 18 DUST LOAD LHO mg/m'3 Figure 21 COMPARISON OF DUST LOADS - ROVING : LHP AND TEAM LEADER 1.5 E 24 8 10 12 14 TEST NUMBER LHO + DUMP TRUCK Figure 22 VARIATION IN DUST EXPOSURE - ROVING : LHP AND DUMP TRIJCK DUMP TRUCK DUST CONC. m j/ m '. Figure 23 COMPARISON OF ROVING SAMPLERS : LHP AND DUMP TRUCK 25 The quartz content of airborne dust was also compared for roving samplers and some of the results are shown in Figures 24 to 26 where they are set out for the team leader, the construction worker and the LHD operator respectively. TOO 90 80 70 60 -- 50 - 4 40 50 20 - t 10 - 0 0 4 2* 4 * 4 1 ! ____ !________ 1------ , ___1____ 5 a io 4 CN 16 ROVING (TEAM LEADER) TEST NUMBER Figure 24 VARIATION IN QUARTZ CONTENT - ROVING : TEAM LEADER Figure 25 VARIATION IN QUARTZ CONTENT - ROVING : CONSTRUCTION WORKFR 26 C Vy Coi oZ p o N OD 0.140 .0.351 0383 0.441 OUST CONCENTRATION 0.701 0 992 Figure 26 VARIATION IN DUST AND QUARTZ LEVELS : ROVING - LHP Again, large shift-wise and individual fluctuations were found. A direct comparison of the quartz content of airborne dust experienced by the team leader and construction worker, respectively, is shown in Figure 27. Although there is a reasonable correlation in quartz content as seen in Figure 20 there was little agreement in dust concentrations, and consequently, large variations in AQI occurred (see Table 2). As in Figure 7, where the dust load was compared to the quartz concentration for a stationary sampler (representative place), the comparison is now made for roving samplers, namely, the team leader (Figure 28) and the construction worker (Figure 29). Once again no correlation was found. C v & G Oo9 N E O o o> (S (POVTNG) Ti QUARTZ CONTENT percent Figure 27 COMPARISON OF QUARTZ CONTENT ROVING : TEAM LEADER AND CONSTRUCTION WORKER 100 90 CVv BO <3 70 a Z 60 n oz 50 o Mw 40 o5D 50 20 10 0 27 DUST LOAD ROVING fTl) mg/m''3 Figure 28 DUST LOAD AND QUARTZ CONTENT - ROVING : TEAM LEADF.R QUARTZ CONTENT p e r ce n t A - A A -- A & -A A AA v I 1__________________ ____________________ ____________________ !____________________!_____ O 0.5 1 1.5 2 DUST LOO ROVING (CW) mg/m~3 Figure 29 DUST LOAD AND QUARTZ CONTENT - ROVING : CONSTRUCTION WORKER 28 The AQIs were investigated for roving samplers within the section. Figure 30 shows the variation in AQI levels observed for the team leader and Figure 31 shows the results obtained for the dump truck driver. The large shift-wise variations of AQI for the LHD operator are depicted in Figure 32 and a comparison of AQIs for the dump truck and LHD operators is shown in Figure 33. X 8 F 3DO <<r 24 6 5 10 SHIFT NUMBER 12 14 Figure 30 AIR QUALITY INDEX - ROVING : TEAM LEADER F 31O3 c < SHIFT NUMBER Figure 31 AIR QUALITY INDEX - ROVING : DUMP TRUCK 29 AIR QUALITY INDEX 24 6 8 10 SHIFT NUMBER 12 14 Figure 32 AIR QUALITY INDEX - ROViNG : LHP SHIFT NUMBER O IHO DUMP TRUCK Figure 33 COMPARISON OF AQI - ROVING : LHP AND DUMP TRUCK 30 Figure 34 shows a similar comparison but includes the results obtained for the team leader as well. A study of these Figures shows large shift-wise and individual fluctuations with little or no correlation. - TEAM LEADER SHIFT NUMBER a DUMP TRUCK X LHO Figure 34 AQI COMPARISON OF ROVING SAMPLERS : TEAM LEADER. DUMP TRUCK. LHD Discussion on these findings will be presented under this heading when the results of all the investigations have been set out. 3 TEST SITE 2 Shallow mine - conventional "mini" longwall section. 3.1 Description of Test Site This monitoring site was located approximately 1 100 m below surface and very close to the shaft The stoping width was 1,2 m. Mining took place over ten panels - five on the west and five on the east side of the original raise with the panels designated 1W, 2W etc. (See Figure 35). The stoping dip distance was about 200 m and the angle of inclination about 25. Approximately 12 m3/s entered the footwall cross-cut on 8 level, passed up a cross raise and was joined with 15 m3/s from the stoping section below to provide the ventilating air for the site under investigation. After passing through the test site 14 m3/s passed to the stoping section above and 13rrv7s 31 Figure 35 LAYOUT OF TEST SITE (2) returned on 6 level. A day shift and a cleaning shift were in force and dust samples were collected over both shifts for the full duration of the shift. Personnel involved during morning shift operations totalled 58 and during the night (cleaning) 32. 3.2 Measurement Strategy 32 Research personnel proceeded to the test site approximately one hour before commencement of mining activities to check instrumentation and set up the stationary monitors. Fixed position monitoring stations were established in the main return and at the top of 1W and IE panels respectively. These latter two monitoring positions were considered to be representative places and the same sampling pumps were always used in the same localities for these three sampling positions. As far as was possible pumps were attached to personnel in each working panel but the same panels were not always being worked. Due to different work allocation it was, therefore, not always possible therefore to always monitor the same personnel. Two Gilian pumps were placed at each of the fixed positions in very close proximity for each shift to sample at each of the fixed positions. Later it was possible to operate samplers with rotating sponges in parallel with the Gilian pumps. Each of the personnel selected for a given shift also carried two sampling pumps. This was done to test results for parallel personal sampling as well as for stationary sampling. Ventilation surveys and parallel dust sampling was carried out by mine environmental control personnel during each of the monitoring shifts. The purpose of all the measurements was to again compare results from stationary monitors with those obtained for personal or roving monitors. In addition, the performance and results of instruments sampling in close proximity to each other could be compared. Data were collected over the period 21 December 1993 to 21 February 1994 over 14 shifts. 3.3 Instrumentation. Monitoring Procedures and Quality Control These have all been described in Section 2. 3.4 Results from and Analysis of Measurements Details are set out in Tables 5 to 7. Table 5 CONVENTIONAL LONGWALL SECTION PERSONNEL (ROVINGI TT OO O) CO o5 5 ME ooO ECD 3C oo tr $ CN ; a oO CED <: ro ~ O oS ChO- CtoO oo in CO rf CN CN o o d o *- o N- CD Tt co CO CN CD CO CN CN ec co co to in r- N" co -- o: a o ion oCO oN" r <cd o I rr Tf d d - CO t-- ^r04 rr Tf co CO CO oo trcoo- ocr-*o* T CD CD Q oO in K oO CO CD cd cb o co CN CO CO CO in co CN Tib o t"CN rO 2 co in o co cb r- co co in do rr- in CO co od do oo in co co co IN CO co N- ,... r-- 'T co CN CD CN (N hin co in cb -- oo CN CN <r- CN oo CO o CO CO r- co tt r-CN <> CD CO 33 CN N* co r-~ do CdM a :2: o o co o o2 -- aa 22 19/01/94 24/01/94 28/01/94 1 01/02/94 04/02/94 | 09/02/94 14/02/94 | 17/02/94 21/02/94 CN CO io r- co CD o 9,21 3.61 5.67 0.19 [ 0.521 0.830 0.48 0.42 0.600 0.523 0.34 0.26 0.318 1 0.16 0.839 | 1 0.42 0.92 0.69 0.46 0.27 0.10 0.70 Maximum Average Std Dev Variance 12.85 4.76 4.24 17,98 0.84 0.87 3.03 0.66 0.45 0.96 0.14 0.19 0 82 0.02 0.04________ 067 ND : Less than detection limit of 20 pg 9.32 2.84 1.341 1.25 0.952 0.48 17.27 6.44 5.97 25.67 1.34 0.78 0.27 0.07 1.25 0.61 0.38 0.14 $o o r- o co d 6.25 0.91 aa QO 22 22 0.533 0.592 0.27 0.30 0.763 0.880 0.38 0.44 QO 22 ND 1.10 6.25 2.07 2.43 5.89 1.17 0.34 0.52 0.27 0.699 0.442 0.890 1.092 0.908 0.858 0.35 0.22 0.45 0.55 0.45 0.43 1.09 0.55 0.77 0.38 0.19 0.09 0.04 0.01 0.28 0.35 0.58 0.77 0.49 0.20 0.79 1.19 1.19 0.62 0.29 0.08 Table 6 CONVENTIONAL LONGWALL SECTION PERSONNEL CROVING) o: 2<c5: co 5 oe 2c DCO c a6 a: 1 OO CED Oo o c OO CED oa E D) E eg sc u oo zI Q oc o Tn "(c1) O (U CL OD zz 34 01/02/94 04/02/94 09/02/94 14/02/94 17/02/94 21/02/94 CD o - CM CO 2 84 3 81 0.810 0.761 0.41 0.38 0.66 0.58 3,18 ND 0.880 1.268 0.44 0.63 0.77 1.61 ccoo c<oo cp o- o ooooo co co o O' r^- CM CD CM o o' o' d d Minimum Maximum Average Std Dev Variance ND 3.81 2.46 1.46 2.13 ND : Less than detection limit of 20 pg o -r-' o' o' d c- -r- -- rr o CD <> co UO 0.632 0.316 0.483 0.242 0.40 0.23 0.48 1.03 0.68 0.21 0 04 1.26 ND 0.795 0.832 99 o' o' 690 90 090 09 0 CO 00 CO CM in co co m; d o' o Q Z 9$ o o' ao zz oo zz d ^ o' d o N o CO cm oCD) CinD n ND 1.58 ND 1.42 0.884 0.791 1.210 1.586 0.952 0.917 0.773 0.776 0.44 0.40 0.61 0.79 0.39 0.39 0.78 0.63 1.46 2.52 0.91 0.84 CD CDCD CO CM n nv o o oo o o o tJ t- o o CcoO cOo i(nN oTj- CM to 35 Tables 5 and 6 show the results obtained for personal monitoring conducted in panels 1W, 2W, 3W, 4W, 5W, IE, 4E and 5E. As far as possible maxima, minima, averages, standard deviations and variances have been calculated. Table 7 sets out the results for the representative samples and the main return samplers. The results of these monitoring exercises indicate that the range in dust concentrations and quartz concentrations were much lower than those obtained at the first test site. Nevertheless, standard deviations of up to 35 per cent of average values were calculated and, once again, these are much lower than those calculated for the first test site. A comparison of dust concentrations at Station 1W (representative place) and the main return, as shown in Figure 36, indicates no meaningful correlation. This result is totally different from that obtained at the first site where correlation was found to be good and could be expressed in a mathematical relationship. When the results of dust levels obtained for a representative place are compared with those for a personal sampler (roving) (1W), once again no meaningful correlation can be found. (Figure 37). Furthermore, a comparison of dust levels at the main return with those of representative place 1W (Figure 38) also displays no correlation. N REPRESENTATIVE PLACE mj/m'J Figure 36 COMPARISON OF STATIONARY SAMPLERS : REPRESENTATIVE PLACE AND MAIN RETURN (DUST) 36 Table 7 CONVENTIONAL LONGWALL SECTION FIXED STATIONS : REPRESENTATIVE PLACES IE Date Test Number Quartz Mineral AQI Risk Conlent Dust Cone. Per Cent mg/m1 Per Cent 21/12/93 1 ND 0.810 0.41 ND 0.760 0.38 0.66 0.58 28/12/93 2 ND 0.660 0.33 ND 0.630 0.32 0.44 0.40 05/01/94 3 4.06 ND 0.517 0.26 0.507 0 25 0.27 0.26 07/01/94 4 5.92 4.79 0.708 0.42 0.752 0.38 0.71 0.57 11/01/94 5 ND 0.562 0.28 ND 0.624 0.31 0.32 0.39 19/01/94 6 ND 0.609 0.30 ND 0.627 0.31 ND 0.690 0.35 ND 0.664 0.33 0.37 0.39 0.48 0.44 24/01/94 RS 7 RS ND 0.143 0.07 ND 0 476 0.24 ND 0.391 0.20 ND 0.450 0.23 ND 0 569 0.28 ND 0 205 0.10 0 02 0 23 0.15 0.20 0.32 0.04 28/01/94 RSM 8 RS ND 0.555 0.28 ND 0.575 0.29 ND 0.663 0.33 ND 0 567 0.28 ND 0016 0.01 0 31 0 33 0.44 0 32 0 00 01/02/94 9 RS ND 0 499 0 25 ND 0 310 0.16 ND 0.520 0 26 ND 0.587 0 29 ND 0 146 0.07 0.25 0.10 0 27 0.34 0.02 04/02/94 RSM 10 RS ND 0.517 0.26 ND 0 499 0.25 ND 0 622 0.31 ND 0.571 0 29 ND 0 462 0 23 0 27 0 25 0.39 0 33 0 21 09/02/94 RSM 11 ND ND 0 524 0 26 ND 0 725 0.36 ND 0516 0 26 0.574 0.29 0 27 0 53 0 27 0.33 14/02/94 12 ND 0 740 0.37 ND 0 255 0 13 ND 0.506 0 25 ND 0.494 0.25 0.55 0 07 0 26 0.24 17/02/94 13 RS ND ND ND ND 22.05 0.720 0.507 1.090 0.805 0.168 0.36 0 25 0 55 0.40 0.08 0.52 0.26 1.19 0.65 0 03 21/02/94 RSM 14 RS RSM ND 0 505 0.25 ND 0 503 0 25 ND 0.483 0 24 ND 0.518 0 26 ND 0.414 0 21 0.26 0.25 0 23 0 27 0.17 Minimum Maximum Average Std Deviation Variance ND 5.92 0.32 1.23 1.52 0 26 1 09 0 59 0 18 0 03 0 13 0 55 0 30 0 09 0.01 0 07 1 19 0 38 0 25 0 06 ND : Less than detection limit of 20 pg RS : Rotating Sponge Sampler RSM : Rotating Sponge Sampler - Mine sample Quartz Content Per Cent NC 5.23 ND 2.78 11.45 10.14 6 91 7.97 ND 2.46 4.25 4.15 ND 3.85 ND 4.36 ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND NO ND ND 11 45 1.41 2 85 8 13 1W Mineral Dust Cone. mg/m* AQI 0.640 0.650 0.32 0.34 0.640 0,32 0.720 0.36 0.594 0.68 0.690 0.70 0.695 0.48 0.715 0.57 0.672 0.934 0.44 0.47 0.659 0.626 0.556 0 624 0.33 0.31 0.28 0.31 0.126 0.596 0 611 0.749 0 409 0.231 0.06 0.30 0.31 0.37 0.20 0.12 0.562 0.28 0 549 0.27 0615 0 011 0 372 0.347 0.534 0 414 0.251 0.31 0.01 0 19 0.17 0.29 0.21 0.13 0.292 0 395 0.297 0.458 0.294 0.15 0 20 0.15 0.23 0 15 0.497 0.460 0 595 0 595 0.703 0 643 0 804 0 668 0 570 0 540 0 759 0.704 0.25 0 23 0 30 0 30 0 35 0.32 0.40 0.33 0 29 0 27 0.38 0 35 0 664 0.761 0 542 0 614 0 358 0.33 0.38 0 27 0.31 0 18 0.29 0 93 0 60 0 14 0 02 0 01 0 70 0 30 0 13 0 02 Risk Per Cent 0.41 0.46 0.41 0.52 1.85 1.96 0.92 1.30 0.76 0.87 0.43 0.39 0.31 0.39 0.02 0.36 0.37 0.56 0.17 0.05 0.32 0.30 0.38 0.00 0,14 0.12 0 34 0.17 0.06 0.09 0.16 0.09 021 0.09 0.25 0 21 0 35 0.35 0.49 0.41 0.65 0 45 0.32 0 29 0.58 0.50 0.44 0 58 0 29 0,38 0.13 0 00 1 96 0 43 0 39 0.15 Quartz Content Per Cent 4.60 ND ND ND 6.02 ND 13.20 9.12 ND ND ND ND ND ND ND ND ND 4.74 ND ND ND ND ND ND 26.14 ND ND ND ND ND ND ND ND ND ND ND 4.44 ND ND ND ND ND ND ND ND ND ND ND ND 6.66 ND ND ND ND ND ND 13.20 0.88 2 66 7.07 MAIN RETURN Mineral Dust Cone. mg/m' AQI 0.630 0.32 0.590 0.30 0.670 0.34 0.640 0.32 0.482 0.29 0.469 0.23 0.742 0.98 0.702 0.64 0.895 0.45 0.882 0.44 0.618 0.458 0.668 0.658 0.31 0.23 0.33 0.33 0.080 0.539 0.567 0.549 0.04 0.27 0.28 0.27 0.383 0.307 0.590 0.558 0.565 0.602 0.088 0.416 0.445 0.489 0.498 0.244 0.250 0.605 0.779 0.828 0.777 0.441 0.968 0.416 0.428 0.521 0.499 0.535 0.562 0.619 0.709 0.731 0.697 0.679 0.700 0.150 0.375 0.19 0.15 0.30 0.28 0.28 0.30 0.23 0.21 0.22 0.24 0.25 0.12 0.13 0.30 0.39 0.41 0.39 0.22 0.48 0.21 0.21 0.26 0.25 0.27 0.28 0.31 0.35 0.37 0.35 0.34 0.35 0.10 0.19 0.506 0.805 0.470 0.277 0.42 0.90 0.61 0.12 0.02 0.25 0.40 0.24 0.14 0.21 0.98 0.33 0.13 0.02 Risk Per Cent 0.40 0.35 0.45 0.41 0.34 0.22 3.84 1.64 0.80 0.78 0.38 0.21 0.45 0.43 0.01 0.29 0.32 0.30 0.15 0 09 0.35 0.31 0.32 0.36 0.21 0.17 0.20 0.24 0.25 0.06 0.06 0.37 0.61 0.69 0 60 0.19 0.94 0.17 0.18 0.27 0.25 0 29 0.32 0.38 0.50 0.53 0.49 0.46 0.49 0.04 0.14 0.26 0.65 0.22 0.08 0.17 3.84 0.50 0.57 0.33 37 \ 0.3 0.4 0.5 0.6 0.7 Q.8 REPRESENTATIVE PLACE mg/m~3 . Figure 37 STATIONARY SAMPLERS VS ROVING (PUSH REPRESENTATIVE PLACE AND ROVING 1W \(6 0 3' 05 REPRESENTATIVE PLACE IE mg/m-*3 Figure 38 COMPARISON OF REPRESENTATIVE PLACES (DUST) REPRESENTATIVF PLACE IE AND REPRESENTATIVE PLACE 1W 38 In Figure 39 dust levels for the main return are compared with dust levels of a personal sampler (1W). This comparison also shows no correlation. 1.6 1.4 ( E \ WAIN RETURN m<g/m~3 Figure 39 COMPARISON : STATIONARY AND ROVING (DUST): MAIN RETURN AND PERSONAL 1W The results of comparing monitoring results for the different matched pairs of instruments are discussed later in this report. 4 TEST SITE 3 Deep mine, mechanized section. 4.1 Description of Test Site Data were collected in a deep level mining operation which used LHD vehicles in roadways (reef drives) to move broken rock from the stope face to a boxhole tip. The site comprised a 5 500 tons/month production stope in Ventersdorp Contact Reef (VCR), 2 500 m below surface. The stoping width was 1,3 m and the dip of the reef 25 (similar to test Site 2). For reasons of ground control five of the six stopes were mined up-dip and the bottom stope was mined on breast. The distance between roadways in which the LHDs operated was 30 m. 39 Diagonal access connections between roadways enabled vehicles to move to the various roadways. The general layout of this test site is shown in Figure 40. The site had a labour complement of 40 persons per shift. Seven LHDs were available of which five to six were in operation. During the mining shift the LHDs were mainly used for the transport of materials to the stope face, and, during the night shift broken rock was transported either from the footwall development ends or from the stope face to the stope tips. Figure 40 LAYOUT OF SITE f3) 40 When not in use the vehicles were parked in the two workshops serving the site. The test site was ventilated by refrigerated intake air being supplied via two 55 kW booster fans forcing the cooled air into the section at Station D. In the bottom footwall drive airflow was split, allowing some air to ventilate the footwall drive while most of the air was directed towards the stope face, some was also directed via a diagonal access way to the upper roadways. Airflow rates and directions are shown in Figure 40. The airflow in the connection between the bottom of the section and the first roadway was controlled by means of a curtain. Fifty per cent of the air supplied was exhausted via two fans at the top access of the stope into Return Airway : F. A particular feature of this test site was the difference in airflow rates at the various locations, aggravated by many uncontrollable leakage paths. 4.2 Measuring Strategy and Procedures The quality of the intake air was monitored at Station D. Other fixed positions or stationary monitoring positions, were the bottom entry to the stopes; G, return positions at E and F and an important intermediate return at H. Stations K and J were entrances to stopes and used for comparison with worker exposure in the stopes. Sampling trains were also fitted to three LHDs operating in the lower part of the stope and a sampling pump was sometimes fitted to an LHD operating in the uppermost part of the section and sometimes to the team leader. Once again the same instruments were used for any given sampling position for each shift. Personnel from the mine environmental control department assisted with manual determination of airflow rates. 4.3 Results from and Analysis of Measurements Results are tabulated in Tables 8, 9 and 10. As was found at test site 2, a conventional miniiongwall, no correlation could be found between dust concentrations measured at representative places and returns, or between the different representative places and different returns. This is shown in Figure 41. Also seen in this bar chart plot are the fluctuations in dust concentrations at these localities on a shift-wise basis. Table 8 DEEP LEVEL TRACKLESS SECTION. TRACKLESS MINING TESTS. VEHICLES (ROVING) 41 Table 9 DEEP LEVEL TRACKLESS STOPING SECTION. TRACKLESS MINING TESTS. STATIONARY SAMPLERS : INTAKE 42 43 Table 10 DEEP LEVEL TRACKLESS STOPING SECTION. TRACKLESS MINING TESTS FIXED STATIONS : RETURNS Date Test Number 24/03/94 1 29/03/94 2 11/04/94 3 15/04/94 4 21/04/94 5 02/05/94 6 05/05/94 7 Minimum Maximum Average Std Deviation Variance Quartz Content Per Cent 10.33 5.90 5.50 8.26 7.63 7.27 9.16 5.50 10.33 7.2 1.59 2.52 STATION E Mineral Dust Cone. mg/m3 AQI 0.165 0.17 0.077 0.05 0.082 0.05 0.121 0.10 0.053 0 04 0.107 0.08 0 091 0 08 0 05 0.17 0 10 0.03 0.00 0.04 0.17 0.08 0 03 0 00 Risk Per Cent 0.12 0.01 0.01 0.04 0.01 0.02 0 03 0.01 0.12 0 03 0 04 0.00 STATION H : MAIN RETURN Quartz Content Per Cent Mineral Dust Cone. mg/m3 AQI Risk Per Cent 6.80 0.183 0.12 0.06 6.70 0.152 0.10 0.04 3.80 0.167 0.08 0.03 6.73 0.169 0.11 0.05 8.47 0.075 0.06 0.02 9.94 0.044 0.04 0.01 7.07 0,091 0 06 0 02 3.80 9.94 7.07 1.74 3.03 0.04 0.18 0.13 0.05 0.00 0.04 0.12 0.09 0.03 0.00 0.01 0.06 0.03 0.02 0.00 44 n( z o H (DOA REP K |^\>j REP J TEST NUMBER KX| RETURN E |\\| WAIN RETURN Figure 41 COMPARISON OF REPRESENTATIVE PLACES AND RETURN IPUST) The bar chart, Figure 42, shows the relationship between dust concentrations monitored at LHD operators compared with each other and also with levels obtained at the main return. No clear correlation can be observed and the shift-wise fluctuations are again very evident, up to 400 per cent in some cases. Ega T4i TEST NUMBER tjo 22127 K3128 3 ""n return Figure 42 COMPARISON OF LHDs AND RETURN (DUSTI Dust concentration (mg/m3) 45 A typical variation in dust levels and quartz concentrations for these particular exposures is shown in Figure 43 for an LHD operator. A similar comparison is made for a stationary sampler, at main return H, and is illustrated in Figure 44. Whereas the dust concentration remained quite steady for the first four shifts the associated quartz concentrations did not. The highest quartz concentration was measured on shift six and is associated with the lowest dust level. The AQIs were all low owing to low dust concentrations and relatively low quartz content. Nevertheless, as assessed at the first two test sites, dust and quartz levels varied independently of each other on a shift-wise basis and no meaningful correlations could be found between dust/quartz concentrations measured at stationary samplers and those measured at roving samplers, nor between samplers in the same categories, e.g. stationary. Test number Figure 43 VARIATION OF DUST AND QUARTZ LEVELS LHD T41 Dust concentration (mg/m3) 46 0,20 0,15 0.10 0.005 6,80 It n 6,70 H II Quartz percent 3,80 Q73) \\\\ \V\\ i! I nil nn 8,47 Main return H 7,07 Knn 9,94 ft If i if \N 345 7 Test number Figure 44 VARIATION OF DUST AND QUARTZ LEVELS MAIN RETURN H 5 TEST SITE 4 Surface locality 5.1 Assay Laboratory and Sample Preparation Gravimetric dust sampling is implemented in surface operations as well as underground operations. It was therefore considered appropriate to investigate results obtained in a typical surface installation and dust sampling was conducted in an assay laboratory/sample preparation operation. There were obvious difficulties in selecting an effective representative place or stationary sampling position in an "open" reduction works, where wind currents could substantially influence results, and it is also possible that personal samplers would also have been affected in this way. It was therefore considered that a dust sampling exercise conducted in an enclosed environment was more likely to yield useful data and hence an investigation was conducted in an assay laboratory/sample preparation operation. Dust control equipment and appliances in the laboratory were operational during both tests. Measuring Strategy and Procedures 47 In all, ten stationary (representative) sampling positions were selected in the different work areas. These are shown in Figure 45 and denoted by SI, S2 etc. Corresponding personal samples, PI, P2 etc., were collected in these work areas although persons being sampled did not spend the entire shift in the area only. All samples were collected over the full eight hour shift. Standard sampling pumps and 25 mm diameter cellulose nitrate filters with 10 mm diameter separating cyclones were used to collect the samples. Figure 45 ASSAY LABORATORY AND SAMPLE PREPARATION 48 3 Results from and Analyses of Measurements Results of the two investigations carried out are set out in Tables 11 and 12. Table 11 ASSAY LABORATORY DUST SAMPLING - FIRST SURVEY X-Ray Milling Crushing Milling Splitting Balance Personal Reference PI P2 P3 AV P4 P5 P6 P7 AV P8 Dust Cone. Per Cent mg/m3 Quartz 0.415 0.343 0.274 23.5 ND 15.6 0.344 13.03 6.274 23.5 0.326 0.512 2.513 36.6 1.4 32.2 1.117 23.73 0.272 8.1 Stationary Dust Cone. Per Cent AQI Reference mg/m3 Quartz 1.0 SI 0.2 S2 0.4 S3 0.142 0.534 0.279 11.3 19.0 11.6 0.5 AV 0.318 13.97 14.7 S4 3.302 34.1 1.2 S5 0.3 S6 8.1 S7 0.078 0.151 0.155 ND 23.6 10.3 32 AV 0.128 11.30 0.2 S8 0.11 ND S9 0.106 ND AQI 0.2 1.0 0.3 0.5 11.3 0.0 0.4 0.2 0.2 0.1 0.1 ND: Less than detection limit of 20 pg Table 12 ASSAY LABORATORY DUST SAMPLING - SECOND SURVEY X-Ray Milling Crushing Milling Splitting Balance Personal Reference PI P2 P3 AV P4 P5 P6 P7 AV P8 AV Dust Cone. Per Cent mg/m3 Quartz 0.340 1.150 0.240 25.1 38.6 34.3 0.577 32.7 0.770 27,9 0.500 0 270 0.310 15.3 18.3 29.4 0 360 21.0 0.230 25.3 Stationary Dust Cone. AQI Reference mg/m3 0.9 SI 44 S2 08 S3 0 090 0.190 0.190 2.0 0.157 2.1 S4 0.200 0.8 S5 0.5 S6 0.9 S7 0.070 0.110 0 110 0.7 AV 0.097 06 S8 0.160 S9 0.090 S10 0,120 0.11 Per Cent Quartz 13.9 53.1 18.2 28.4 10.0 28.5 18.2 18.2 21.6 25 6 22.2 16.7 19.5 AQI 0.1 1.0 0.3 0.5 0.2 0.2 0.2 0.2 0.2 0.4 0.2 0.2 0.2 49 The relationship between stationary samples and corresponding personal samples is shown in Figure 46 for the first investigation. Figure 47 shows the results obtained in the second exercise at this establishment. In both cases correlation was found to be poor and, thus, similar to results obtained for the underground investigations. Although actual dust concentrations were found to be lower in the second exercise at the assay laboratory, the scatter in results is still evident. 0 05 1 15 2 25 3 3.5 STATIONARY DUST CONCENTRATION mg/m~3 Figure 46 STATIONARY VS PERSONAL SAMPLES (DUST): TEST 1 i .2 1.1 i 0.9 N o.s tDOo 0.7 0.6 Z o 0.5 V) 5a 0.4 0.3 0.2 0.1 0 OB *0.1 0.12 0.14 0 16 Q.lB 0.2 STATIONARY DUST mg/m~3 Figure 47 STATIONARY VS PERSONAL SAMPLES (DUST) : TEST 2 50 In the first investigation airborne quartz concentrations were found to vary from less than the detectable limit of 20 pg to 36,6 per cent for personal samples and up to 34,1 per cent for stationary samples, although these maxima occurred in different parts of the building. In fact, the maximum personal quartz exposure correlated with the minimum stationary concentration. In the second survey quartz concentrations ranged from 15,3 per cent to 38,6 per cent for personal samplers and from 10 per cent to 53,1 per cent for stationary samplers. The relationship between personal dust and quartz concentrations, stationary dust and quartz concentrations and stationary and personal quartz concentrations are shown in Figures 48 to 50 respectively. Figure 48 QUARTZ CONCENTRATIONS : PERSONAL SAMPLES - TEST 1 51 Figure 49 QUARTZ CONCENTRATIONS : FIXED SAMPLERS - TEST 1 STATIONARY QUARTZ CONCENTRATION percent Figure 50 FIXED VS PERSONAL QUARTZ CONCENTRATIONS - TEST 1 52 These same aspects were examined for the second dust survey conducted at the assay laboratory and are presented in Figures 51 to 53 respectively. Although dust levels generally appeared to be lower for personal samplers during the second survey, quartz concentrations were, if anything, higher. 4Q DO Figure 51 QUARTZ CONCENTRATIONS : PERSONAL SAMPLES - TEST 2 STATIONARY OUST mg/nr~3 Figure 52 QUARTZ CONCENTRATIONS : FIXED SAMPLERS - TEST 2 53 STATIONARY QUARTZ CONCENTRATION percent Figure 53 FIXED VS PERSONAL QUARTZ CONCENTRATIONS The same comments appear to hold for the second survey as noted for the first. The two surface surveys have displayed the same behaviour patterns for dust and quartz concentrations as was found in the underground surveys. Several very high, and thus unacceptable, AQls were found during the first survey but these were not repeated in the second survey. 6 DISCUSSION 54 6.1 Personal vs Stationary Samples One of the major aspects of this research was to establish if personal sampling could be reduced or even entirely replaced by stationary (fixed) or area samplers thereby reducing both sampling effort and costs. At all four test sites investigated, i.e. three underground and one laboratory, there was strong evidence that correlation between dust levels obtained at fixed positions samplers and personal samplers was very poor. This means that it would not be possible to only collect dust samples at fixed position sites, either main returns or representative places, and expect to be able to obtain results that could represent exposure levels of personnel working in the area. At three of the four test sites no correlation could be found between dust levels measured at main returns and those measured at representative places. Figures 54 and 55 below show the relationship between dust concentrations measured at stationary sampling positions and those obtained for some of the roving personnel at test Site 1. A comparison of dust levels for the major stationary and personal samplers is shown in Figure 56. < \S ? z0 t- t1so z ou H<DQ/> TEAM' IDR CONSTR ASST V//\ LHO [\N) main return D\)^ DUMPER Figure 54 COMPARISON OF ROVING AND AREA SAMPLERS 55 \ z o sozoo Fw3o REP PLACE I^XN LHD MAIN RETURN mg/m'-J |'//A OUWPER KXI T LDR |\\| CONSTR WKR Figure 55 COMPARISON OF DUST LEVELS : TWO STATIONARY AND FOUR PERSONAL n DUST CONCENTRATION _ j TEAM LDR TEST NUMBER CONSTR ASST |\N MAIN RETURN Figure 56 COMPARISON OF ROVING AND AREA SAMPLERS 56 Comparisons of dust levels with the return air station levels are shown in Figures 57 to 60 for a team leader, construction worker, LHD and dump truck drivers respectively. n < _bi a2 Oz> oa.: RETURN AIR SAMPLES mg/m Figure 57 STATIONARY AND ROVING SAMPLES (TEAM LEADER) N I RETURN AIR SAMPLES mg/m*3 Figure 58 STATIONARY AND ROVING SAMPLES (CONSTRUCTION WORKERS DUST LOAD LHD m g /m ' 57 2 1.9 1.8 1.7 1.6 tfo 1.5 1 .4 1.5 12 1.1 1 09 O3 0.7 06 0.5 04 0.3 02 0.1 0 0 0.2 04 06 03 1 12 14 16 IS 2 DUST LOAD RETURN AIR mg/nv'3 gure 59 COMPARISON OF DUST LOADS (LHD1 DUST LOAD D U M P TR U C K m g / m " 3 III DUST LOAD RETURN AIR mg/m-3 Figure 60 COMPARISON OF DUST LOADS (DUMP TRUCK1 6.2 Variations in Dust Concentrations 58 It was also found that dust concentrations varied from day to day as illustrated in Figure 61, which is also based on data from test site 1. Very often substantial differences in dust levels were found from shift to shift. For example, referring to Figure 61, shift 11 followed immediately after shift 6, and shift 12 followed immediately after shift 7 since, as explained, the night shifts were monitored back to back with the afternoon shifts. These shift-wise changes in dust levels were observed at all the test sites and at test site 4, the laboratory, and considerable differences in dust levels were measured from one monitoring exercise to the next, which were months apart. This is in agreement with results reported by mines and also in agreement with the literature4. Comparisons of all vehicle operators' exposure levels with each other and the main return are shown in Figure 62. The shift-wise variations are very apparent. 2 n< \EC6" o V-- <h<r o z ou IDo/) 05h O RETURN AiR TEST NUMBER Figure 61 VARIATION IN DUST EXPOSURE (RETURN AIR) : SHIFT TO SHIFT BASIS 6.3 Variations in Quartz Concentrations In addition to shift-wise variations in dust levels, quartz concentrations for the dust samples also varied on a shift-wise basis and was evidenced at all the test sites. A typical example is shown in Figure 63. Dust and quartz levels are shown together for this monitoring station and quartz concentrations are seen to vary from 17 to 98 per cent. Dust and quartz levels are shown together for this monitoring station and the randomness of quartz levels with respect to dust levels is clearly seen in Figure 64. 59 DUST CONCENTRATION m g / m ' [8X81 LHD KnSSI DUMPER TEST NUMBER W/A SCALER K^l R bolter |\N ma>n RETURN Figure 62 COMPARISON OF ROVING AND AREA SAMPLERS (ALL VEHCILE DRIVERS') 100 90 SO Va 70 50 oo SO N 4-0 ia 30 20 10 0 12 14 16 RETURN AIR TEST NUMBER L Figure 63 VARIATION IN QUARTZ CONTENT (RETURN AIR) 60 Morning Shift > Afternoon Shif^ ^ Night Shift ^ 1,8 FT 1,6 - "b) 1 >4 f,2 - Ito 1- d ^Quartz percent I 0'8 0,6 - o | 0,4 18 Q 0,2 __ 5.3 45 33 9.8 17 28 28 4*9 67 44 0 __ 0 ]__ 1__ 2 1__ 1---4 L J__ 1---- 1----1---- L 6 8 10 i i__ i__!--i-- 12 14 16 Test number Figure 64 STATIONARY SAMPLING POSITION (MAIN RETURN) : DUST AND QUARTZ LEVELS 6.4 Correlation Between Dust and Quartz Levels No correlation between dust levels and quartz concentrations could be found in any of the samples collected and analysed for this research project. A typical relationship is shown in Figures 65 and 66. S aV 5Da DUST CONCENTRATION mg/nv"3 MAIN RETURN Figure 65 VARIATION IN DUST AND QUARTZ LEVELS (MAIN RETURNS 61 DUST LOAD RETURN AIR mq/m'v3 Figure 66 DUST LOAD AND QUARTZ CONTENT (RETURN AIR) 6.5 Air Quality Index Dust samples are analysed to compile an Air Quality Index (AQI) which should provide a measure of the relative toxicity of a sample. It is therefore predictable that if dust and quartz concentrations vary on a shift-wise basis the AQI will also do so as shown in Figure 67. (An AQI greater than unity would be regarded as unsatisfactory). RETURN AIR "E" SHIFT NUMBER Figure 67 AIR QUALITY INDEX (RETURN AIR "E") 62 Reference to Figure 54 shows that little correlation was found between dust concentrations measured at personal samplers, but for different occupations within a working section this can be regarded as an expected result. 6.6 Personal Samplers ; Quartz, Quartz and Dust, AQIs In none of these investigations was a correlation found for personal samplers between' quartz concentrations, quartz concentrations and dust levels, and AQIs. Furthermore the tables of results indicate large differences in standard deviations and minima/maxima observations, which collectively indicates a need for a large number of samples to be collected to more accurately characterize typical or mean exposure values for the different work categories or even stationary sampling positions. This is not practical and defeats an objective of this project, namely to reduce the sampling effort. . 7 CONCLUSIONS AND RECOMMENDATIONS 7.1 Fixed Point, stationary or area samplers do not provide accurate or comparable Time Weighted Averages, quartz content, Air Quality Index or risk to be able to use data collected at such monitoring stations to substitute for personal samples. Variations in these parameters have been observed on a shift, daily, weekly and monthly basis. Results reported are very dependent on the day and the shift that is being sampled for the person being sampled. These are thus random results. - 7.2 Very large ranges in quartz concentration have been observed in five samples of a given Statistical Population and even bigger ranges have been detected in a large working section. Furthermore, although Gilian pumps sampling in parallel yielded very similar dust loadings, the quartz concentrations were uncorrelated. Overseas tests have confirmed this anomaly without offering any explanation. 7.3 Unpredictable variations in dust and quartz levels and, consequently, variations in AQI and risk, as well as the unexplained characteristics of quartz in suspension in the working atmosphere should be very carefully considered before any standards are set, i.e. legally required dust concentrations and AQI. Testing for compliance could require large numbers of samples and prove to be costly. 7.4 High dust counts and high quartz concentrations are lost in the permissible averaging system, and unsatisfactory personal exposures are difficult to trace and act upon because a quartz fraction is required before an AQI can be calculated. Often these calculations will only be performed at the conclusion of a sampling cycle when any action is meaningless. Thus, at 63 present, when the dust concentration of a sample is determined there are no indications on whether or not the result is acceptable. Moreover, the results of dust sampling, which are all of a personal nature, are not reported on any environmental assessment report, nor is this required. Any high "peak" dust concentrations during a shift cannot be identified by present sampling practices, and the shift average and Statistical Population average further conceals these aberrations. 7.5 The fact that quartz concentrations for parallel dust samples have not been found to be compatible is an indication that the quartz distribution within a moving airstream is not as homogeneous as had been assumed in the past. A bedrock of non-homogeneous nature, a variable rock breaking mechanism and different rock moving processes could all contribute to these differences. This can compound difficulties in testing for compliance with a set standard. 7.6 Poor correlation in sampling results obtained for different types of instruments must cast doubt on a large percentage of results submitted to the GME for risk assessment, since it is estimated that at least half of the gold mines, members of the Chamber of Mines, use rotating sponge type instruments for sampling. 7.7 It is apparent that there has been a misconception on the way in which airborne dust behaves, how it is liberated and the non-homogeneity of the composition of dust. These factors all contribute towards making the prediction of dust levels for given conditions all but impossible. There is a strong indication that considerably more research is needed to advance the understanding of dust, its behaviour and the minimum number of samples required to be able to certify acceptable representation both for personal and control samples. PART 2 64 8 ASSESSMENT OF GRAVIMETRIC DUST SAMPLING DATA FROM SIX SAMPLING CYCLES SUBMITTED BY GOLD MINES, MEMBERS OF THE CHAMBER OF MINES, TO THE GOVERNMENT MINING ENGINEER. 8.1 Methodology Following a project report back meeting in November 1994, in which attention was drawn to variable dust and quartz concentrations encountered in extensive monitoring exercises, Miningtek was requested to investigate the feasibility of regional and/or an industry average quartz concentration for airborne dust. Individual dust sampling reports for six sampling cycles submitted by gold mines, members of the Chamber of Mines, to the Government Mining Engineer, were compiled in a database for analysis. In addition, dust sampling reports compiled by Miningtek were studied in detail and, where appropriate, used in the analyses. Mines were grouped into geographical areas for purposes of compiling regional dust (eight hour Time Weighted Average) and quartz concentrations. The regions were defined as East (Transvaal), Elsburg, Klerksdorp, Northern Free State, Southern Free State and West Wits. All data were used for Industry analyses. The mines in the different regions were as follows: East Elsburg Klerksdorp Northern Free State Southern Free State West Wits Leslie, Winkelhaak, Kinross, Grootvlei, ERPM. Randfontein Estates, Western Areas, Durban Deep. Buffelsfontein, Flartebeestfontein, Vaal Reefs West, Vaal Reefs East, Vaal Reefs South. Free State Geduld, Western Holdings, Freddies, Loraine, Harmony, President Brand, President Steyn, Free State Saaiplaas. H J Joel, Beatrix, Oryx, Unisel, St Helena. Leeudoorn, Libanon, West Driefontein, Elandsrand, East Driefontein, Deelkraal, Doornfontein, Western Deep Levels, Blyvooruitzicht, Kloof. Furthermore, the results were separated, for each region, into categories of underground stoping and development, underground roving (i.e. other than stoping and development) and surface. For any meaningful results to emerge it became apparent that simple averages could not be used. Consequently, all TWAs and quartz concentrations were weighted according to the numbers of persons exposed to specific levels (as reported in data for Statistical Populations in 65 the returns submitted). A full understanding of TWAs is complicated because different sampling pumps were used throughout Industry and, as will be shown, different pumps did not produce compatible results. 8.2 Results 8.2.1 Overall industry results Overall industry results are presented in Tables 13 to 17 for eight-hour Time Weighted Averages broken down into stoping and development, underground roving, surface, total underground and overall (underground and surface). Data for all six sampling cycles are presented. TABLE 13 INDUSTRY STOPING AND DEVELOPMENT POPULATION TWA DUST DISTRIBUTION Dust Cone. Grouping (mg/m3) 0-0,2 0,2-0,4 0,4-0,6 0,6-0.8 0,8-1,0 Persons Cycle 1 3264 28973 42786 25433 11910 Persons Cycle 2 3349 28175 40568 21982 14892 Persons Cycle 3 4876 46230 42326 22331 6609 Persons Cycle 4 Persons Cycle 5 5700 53789 40530 22050 1724 7720 60732 43208 17230 3085 Persons Cycle 6 7329 46340 51099 17044 4559 1.0-1,2 >1,2 2569 3744 6365 2252 1520 656 1354 286 942 1430 821 508 TABLE 14 INDUSTRY UNDERGROUND ROVING POPULATION TWA DUST DISTRIBUTION Dust Cone. Grouping (mg/m3) 0-0,2 0,2-0,4 0,4-0,6 0,6-0,8 0,8-1,0 1,0-1,2 >1,2 Persons Cycle 1 7294 40510 24353 10013 4852 2267 1268 Persons Cycle 2 5711 38098 28132 12349 1855 1069 686 Persons Cycle 3 9390 43964 27749 5134 3262 149 0 Persons Cycle 4 9353 45621 21426 10076 3551 515 Persons Cycle 5 17896 43698 22143 12229 4952 1071 311 Persons Cycle 6 14790 50905 23785 10249 3611 2318 1366 66 TABLE 15 INDUSTRY SURFACE POPULATION TWA DUST DISTRIBUTION Dust Cone. Persons Persons Persons Persons Persons Grouping (mg/m3) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 0-0,2 3843 3835 4714 5376 9594 0,2-0,4 6960 8110 9034 10712 12274 0,4-0,6 7761 4770 7044 4667 7084 0,6-0,8 2167 2679 2815 1931 2991 0,8-1,0 2046 1482 744 642 1269 1,0-1,2 331 401 824 723 381 >1,2 1377 865 327 615 847 Persons Cycle 6 3798 8509 6276 2277 803 120 920 TABLE 16 INDUSTRY TOTAL UNDERGROUND POPULATION TWA DUST DISTRIBUTION Dust Cone. Persons Persons Persons Persons Persons Persons Grouping (mg/m3) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-0,2 10558 9060 14266 63142 25616 22119 0,2-0,4 69483 66273 90194 86151 104430 97245 0,4-0,6 67139 68700 70075 43476 65351 74884 0,6-0.8 35446 34331 27465 11800 29459 27293 0,8-1,0 16762 16747 9871 4905 8037 8170 1,0-1,2 4836 7434 1669 801 2013 3748 >1,2 5012 2938 656 0 1132 1874 TABLE 17 INDUSTRY OVERALL TWA DUST DISTRIBUTION Dust Cone. Persons Persons Persons Persons Persons Persons Grouping (mg/m3) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-0,2 14401 12895 18980 68518 35210 25917 0,2-0,4 76443 74383 99228 96863 116704 105754 0,4-0,6 74900 73470 77119 48143 72435 81160 0,6-0,8 37613 37010 30280 13731 32450 29570 0,8-1,0 18808 18229 10615 5547 9306 8973 1,0-1,2 5167 7835 2493 1524 2394 3868 >1,2 6389 3803 983 615 1979 2794 67 Data for stoping and development are presented graphically in Figures 68 and 69, where Figure 69 is a statistically smoothed curve of Figure 68 and shows actual numbers of persons not percentage of the working population. Based on data submitted by mines the largest percentage of underground workers in this category are exposed to dust concentrations in the range 0,2 0,4 mg/m3 although in the last sampling cycle analysed there was an upward shift whereby the majority of workers in this category were exposed to dust concentrations in the range 0,4 to 0,6 mg/m3. The significance of this shift will be discussed later. There is a positive skewness for the frequency distribution which may be considered to be normal5. In Figures 70 and 71 the results of the analyses for the underground roving population (industry) are presented and it is clear that the exposure levels for the majority of the workers in this category are in the range 0,2-0,4 mg/m3. Once again positive skewness is displayed. TWA (mg/m1) grouping Figure 68 INDUSTRY STOPING AND DEVELOPMENT POPULATION TWA DUST DISTRIBUTION (HALF YEARLY CYCLES JANUARY TO JUNE 19941 68 Figure 69 INDUSTRY TOTAL STOPING AND DEVELOPMENT POPULATION TWA DUST DISTRIBUTION Figure 70 INDUSTRY UNDERGROUND ROVING POPULATIONS TWA DUST DISTRIBUTION (HALF YEARLY CYCLES JANUARY 1992 TO JUNF 1994\ 69 Figure 71 INDUSTRY TOTAL UNDERGROUND ROVING POPULATION TWA DUST DISTRIBUTION Data collected for surface workings are presented in Figures 72 and 73 and although the mean exposure level remains in the range 0,2-0,4 mg/m3 it is also evident that a larger proportion of this particular sector of the workforce is exposed to dust concentrations in excess of 1,2 mg/m3 than was found for the two underground categories. This aspect will also be discussed later. Positive skewness is again displayed. TWA (mQ/m*) grouping Figure 72 INDUSTRY SURFACE POPULATION TWA DUST DISTRIBUTION (HALF YEARLY CYCLES JANUARY 1992 TO JUNE 1994) 70 Figure 73 INDUSTRY TOTAL SURFACE POPULATION TWA DUST DISTRIBUTION The results for all underground work categories were grouped and the analyses are shown in Figures 74 and 75. 00.2 0.2-0.4 0.4-0.4 ' 0.6-C.a TWA (mg/m*) grouping 0&-10 1.01.2 >1.2 Figure 74 INDUSTRY TOTAL UNDERGROUND POPULATION TWA DUST DISTRIBUTION (HALF YEARLY CYCLES JANUARY 1992 TO JUNE 1994) 71 Figure 75 INDUSTRY TOTAL UNDERGROUND POPULATION TWA DUST DISTRIBUTION Positive skewness is displayed and the mean exposure levels are seen to lie in the range 0,2 0,4 mg/m3. Once the surface results are added to those just presented the picture is found to remain unchanged except for the elevation of the number of persons exposed to dust concentrations greater than 1,2 mg/m3. Shown in Figures 76 and 77 are the overall (surface plus underground) TWA distributions and the overall industry population TWA distribution. Taking into account the surface and underground results, the majority of the workforce is seen to be exposed to dust concentrations in the range 0,2-0,4 mg/m3. Percentage of population C 72 TWA ^mg/m*) grouping 76 INDUSTRY OVERALL POPULATION TWA DUST DISTRIBUTION (-HALF YFARI Y CYCLES JANUARY 1992 TO JUNE 1994) Figure 77 INDUSTRY OVERALL POPULATION TWA DUST DISTRIBUTION Population 8.2.2 Overall industry quartz analyses 73 Overall industry quartz analyses are set out in Tables 18 to 22 in which are the quartz concentrations for stoping and development, underground roving, surface, total underground population and industry overall (surface and underground) are shown. TABLE 18 INDUSTRY STOPING AND DEVELOPMENT POPULATION QUARTZ PER CENT DISTRIBUTION Quartz Persons Persons Persons Persons Persons Persons Grouping (%) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-5 5259 4550 5287 8194 7709 8188 5-10 15225 14639 27865 23926 23959 38612 10-15 32708 34274 44410 37218 41606 38389 15-20 31866 32351 22560 31209 30494 32079 20-25 19159 17443 11794 7066 14405 6869 25-30 4476 6610 7231 8501 7094 2163 30-35 3704 2080 2826 2684 3394 1738 35-40 3456 3747 1944 1260 925 249 >40 1824 1897 1316 1602 353 475 TABLE 19 INDUSTRY UNDERGROUND ROVING POPULATION QUARTZ PER CENT DISTRIBUTION Quartz Persons Persons Persons Persons Persons Persons Grouping (%) 0-5 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 9112 10018 12474 11811 13998 17332 5-10 19550 18555 28309 28794 29212 32365 10-15 24745 24730 22038 24082 29493 31126 15-20 17165 19716 12932 13158 19695 18761 20-25 7874 8898 7224 7425 5465 3395 25-30 3809 3393 4111 3012 2662 1966 30-35 3817 4281 647 685 288 230 35-40 1843 1795 1086 287 165 181 >40 2680 2802 885 740 1151 766 74 TABLE 20 INDUSTRY SURFACE POPULATION QUARTZ PER CENT DISTRIBUTION Quartz Persons Persons Persons Persons Persons Persons Grouping (%) 0-5 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 4619 4143 5422 5708 6233 6120 5-10 5042 4719 7857 7205 6098 7064 10-15 6520 5487 5945 6278 6634 4658 15-20 3253 3359 2570 2680 4804 1586 20-25 2396 2313 1713 683 1639 2529 25-30 1406 1036 1337 1009 1397 910 30-35 178 203 625 426 769 397 35-40 87 39 85 146 77 192 >40 1227 1122 251 130 135 TABLE 21 INDUSTRY TOTAL UNDERGROUND POPULATION QUARTZ PER CENT DISTRIBUTION Quartz Persons Persons Persons Persons Persons Persons Grouping (%) 0-5 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 14371 14568 17761 20005 21707 25520 5-10 34775 33194 56174 52720 53171 70977 10-15 57453 59004 66448 61300 71099 69515 15-20 49031 52067 35492 44367 50189 50840 20-25 27033 26341 19018 14491 19870 10264 25-30 8285 10003 11342 11513 9756 4129 30-35 7521 6361 3473 3369 3682 1968 35-40 5299 5542 3030 1547 1090 430 >40 4504 4699 2201 2342 1504 1241 75 TABLE 22 INDUSTRY OVERALL QUARTZ PER CENT DISTRIBUTION Quartz Persons Persons Persons Persons Persons Grouping (%) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 0-5 18990 18711 23183 25713 27940 5-10 39817 37913 64031 59925 59269 10-15 63973 64491 72393 67578 77733 15-20 52284 55426 38062 47047 54993 20-25 29429 28654 20731 15174 21509 25-30 9691 11039 12679 12522 11153 30-35 7699 6564 4098 3795 4451 35-40 5386 5581 3115 1693 1167 >40 5731 5821 2452 2342 1634 Persons Cycle 6 31640 78041 74173 52426 12793 5039 2365 622 1376 Figures 78 to 87 show the graphical analyses of the above. All graphs, with the exception of underground roving, indicate mean quartz concentrations in the range 10-15 per cent. Underground roving results display a mean of between 5 to 10 per cent for airborne quartz, but with a shift to a higher range (10-15 per cent) for the last two sampling cycles. All graphical analyses display positive skewness with a detectable population being exposed to dust concentrations where quartz levels are greater than 40 per cent. Figure 78 INDUSTRY STOPING AND DEVELOPMENT POPULATION QUARTZ PER CENT DISTRIBUTION (HALF YEARLY CYCLES JANUARY 1992 TO JUNE 19941 76 Figure 79 INDUSTRY STOPING AND DEVELOPMENT POPULATION QUARTZ PER CFNT DISTRIBUTION Figure 80 INDUSTRY UNDERGROUND ROVING POPULATION QUARTZ PER CFNT DISTRIBUTION (FIALF YEARLY CYCLES JANUARY 1992 TO JUNE 19941 77 Figure 81 INDUSTRY UNDERGROUND ROVING POPULATION QUARTZ PER CENT DISTRIBUTION Figure 82 INDUSTRY SURFACE POPULATION QUARTZ PER CENT DISTRIBUTION (HALF YEARLY CYCLES JANUARY 1992 TO JUNE 1994) 78 Figure 83 INDUSTRY SURFACE POPULATION QUARTZ PER CENT DISTRIBUTION Fi9ure 84 INDUSTRY TOTAL UNDERGROUND POPULATION Ol JARTZ PFR r.PMT DISTRIBUTION (HALF YEARLY CYCLES JANUARY 199? TO JUNE 1994) 79 Figure 85 INDUSTRY TOTAL UNDERGROUND POPULATION QUARTZ PER CENT DISTRIBUTION Figure 86 INDUSTRY OVERALL POPULATION QUARTZ PER CENT DISTRIBUTION (HALF YEARLY CYCLES JANUARY 1992 TO JUNE 1994) 80 Figure 87 INDUSTRY OVERALL POPULATION QUARTZ PER CENT DISTRIBUTION 8.2.3 Overall industry population dust exposure Overall trends in Industry Time Weighted Averages are summarised in Tables 23 to 25 and graphically interpreted in Figures 88 to 90. These trends indicate that an increasingly greater percentage of the mine workforce is being exposed to increasingly lower levels of dust. The fraction of the workforce exposed to dust concentrations less than 0,4 mg/m3 has increased by approximately 15 per cent, while the fraction of the workforce exposed to dust concentrations greater than 0,6 mg/m3 has decreased by approximately the same amount over the six dust sampling cycles evaluated. TABLE 23 INDUSTRY OVERALL TWA DISTRIBUTION, 0 TO 0,4 mg/m3 (Dust) Dust Cone. Persons Persons Persons Persons Persons Persons Grouping (mg/m3) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-0,2 14401 12895 18980 68518 35210 25917 0,2-0,4 76443 74383 99228 96863 116704 105754 81 TABLE 24 INDUSTRY OVERALL TWA DISTRIBUTION, 0,4 TO 0,6 mg/m3 (Dust) Dust Cone. Persons Persons Persons Persons Persons Persons Grouping (mg/m3) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0,4-0,6 74900 73470 77119 48143 72435 81160 TABLE 25 INDUSTRY OVERALL TWA DISTRIBUTION > 0,6 mg/m3 (Dust) Dust Cone. Grouping (mg/m3) Persons Cycle 1 Persons Cycle 2 Persons Cycle 3 Persons Cycle 4 Persons Cycle 5 Persons Cycle 6 0,6-0,8 37613 27010 30280 13731 32450 29570 0,8-1,0 18808 18229 10615 5547 9306 8973 1,0-1,2 5167 7835 2493 1524 2394 3868 1,2+ 6389 3803 983 615 1979 2794 Jun-92 Jan-93 Jun-93 Cycles Jan-94 Jun-94 Figure 88 PERCENTAGE OF TOTAL POPULATION EXPOSED TO TWA DUST LEVELS BELOW 0.4 mci/m3 82 Percentage of population Percentage of PPulation Cycles ure 89 PERCENTAGE OF TOTAL POPULATION EXPOSED TO TWA DUST LEVELS BETWEEN 0.4 AND 0.6 ma/m] 40 - 30 u 20 10 0 Jan-92 Jun-92 Jan-93 Jun-93 Cycles Jan-94 Jun-94 Figure 90 PERCENTAGE OF TOTAL POPULATION EXPOSED TO TWA DUST LEVELS GREATER THAN 0,6 mci/m3 8.2.4 83 Industry trends in quartz concentrations A similar analysis was performed to examine industry trends in quartz concentrations to which the working population is exposed. These results are shown in Tables 26 to 28 and Figures 91 to 93. There is a shift towards exposure to lower quartz concentrations. TABLE 26 INDUSTRY OVERALL QUARTZ DISTRIBUTION, 0 TO 10 PER CENT Quartz Persons Persons Persons Persons Persons Persons Grouping (%) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-5 18990 18711 23183 25713 27940 31640 5-10 39817 37913 64031 59925 59269 78041 TABLE 27 INDUSTRY OVERALL QUARTZ DISTRIBUTION, 10 TO 20 PER CENT Quartz Persons Persons Persons Persons Persons Persons Grouping (%) 10-15 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 63973 64491 72393 67578 77733 74173 15-20 52284 55426 38062 47047 54993 51426 TABLE 28 INDUSTRY OVERALL QUARTZ DISTRIBUTION, >20 PER CENT Quartz Persons Persons Persons Persons Persons Persons Grouping (%) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 20-25 29429 28654 20731 15174 21509 12793 25-30 9691 11039 12679 12522 11153 5039 30-35 7699 6564 4098 3795 4451 2365 35-40 5386 5581 3115 1693 1167 622 >40 5731 5821 2452 2342 1634 1376 84 Figure 91 PERCENTAGE OF TOTAL POPULATION EXPOSED TO QUARTZ LEVELS BETWEEN 0 AND 10 PER CENT Cycles Figure 92 PERCENTAGE TOTAL POPULATION EXPOSED TO QUARTZ LEVELS BETWEEN 10 AND 20 PER CENT 85 Figure 93 PERCENTAGE OF TOTAL POPULATION EXPOSED TO QUARTZ LEVELS GREATER THAN 20 PER CENT The reason for the shifts to lower dust concentrations and for more persons to be exposed to lower concentrations of airborne quartz is not clear. As seen in Part 1 no relationship was found between dust levels and quartz concentrations. 8.2.5 Regional and industry average dust concentrations Regional and Industry average dust concentrations, both simple arithmetic and person weighted, are presented in Table 29 and corresponding graphs in Figures 94 to 100. Table 29 86 SIMPLE ARITHMETICAL AND PERSON WEIGHTED CYCLIC AVERAGE DUST EXPOSURE LEVELS (TWA) (EXCLUDING SURFACE RESULTS') East Simple Ave mg/m3 0.52 0.55 0.54 0.57 0.53 0.58 Std Dev 0.34 0.28 0.25 0.25 0.25 0.26 Weighted Ave mg/m3 0.54 0.59 0.55 0.58 0.51 0.57 Klerksdorp Simple Ave mg/m3 0.59 0.59 0.50 0.48 0.50 0.39 Std Dev 0.29 0.23 0.21 0.18 0.25 0.19 Weighted Ave mg/m3 0.64 0.61 0.53 0.49 0.53 0.43 SOFS Simple Ave mg/m3 0.61 0.52 0.49 0.51 0.44 0.63 Std Dev 0.30 0.25 0.21 0.27 0.21 0.20 Weighted Ave mg/m3 0.62 0.64 0.50 0.46 0.43 0.63 Industry Total Simple Ave mg/m3 0.50 0.48 0.43 0.41 0.41 0.43 Std Dev 0.46 0.25 0.21 0.20 0.22 0.25 Weighted Ave mg/m3 0.54 0.54 0.46 0.46 0.43 0.46 Elsburg Simple Ave mg/m3 0.54 0.45 0.46 0.50 0.47 0.57 Std Dev 0.26 0.22 0.24 0.22 0.25 0.22 NOFS Simple Ave mg/m3 0.37 0.43 0.39 0.37 0.35 0.38 Std Dev 0.16 0.21 0.17 0.18 0.17 0.18 W Wits Simple Ave mg/m3 0.54 0.44 0.39 0.39 0.37 0.40 Std Dev 0.71 0.26 0.18 0.19 0.21 0.30 Weighted Ave mg/m3 0.55 0.54 0.58 0.72 0.51 0.63 Weighted Ave mg/m3 0.48 0.55 0.46 0.44 0.41 0.45 Weighted Ave mg/m3 0.51 0.46 0.38 0.38 0.36 0.41 87 A -4-STD DEV SAMPLING CYCLE x AVERAGE -STD DEV Figure 94 EAST REGION DUST AVERAGES TWA m g / n r A -fSTD DEV SAMPLING CYCLE X AVERAGE -STD DEV Figure 95 ELSBURG REGION DUST AVERAGES 88 n < 'c* E A. +STO OEV SAMPLING CYCLE X AVERAGE -STO oev Figure 96 KLERKSDORP REGION DUST AVERAGES u i/ B uj VMJ. Figure 97 NORTH FREE STATE REGION DUST AVERAGES 89 A +STD DEV SAMPLING CYCLE X AVERAGE v -Syd Dev Figure 98 SOUTH FREE STATE REGION DUST AVERAGES n <e A +STD DEV SAMPLING CYCLE x AVERAGE -STD DEV Figure 99 WEST WITS REGION DUST AVERAGES 90 A +STD DEV SAMPLING CYCLE X AVERAGE T .-STD DEV Figure 100 INDUSTRY DUST AVERAGES Exposure levels in the East and Elsburg regions appear to be similar, as do levels in the Klerksdorp, West Wits and Northern Free State regions. The Southern Free State region apparently has the highest average exposures. However, when comparisons between regions are made, no statistical differences in results obtained for the different regions could be demonstrated and an industry average of 0,4 mg/m3 is indicated. 8.2.6 Regional and industry quartz concentrations In a similar fashion regional and industry quartz concentrations, simple and person weighted, were compiled and are set out in Table 30. The graphic interpretations are shown in Figures 101 to 107. In recognition of the variability of airborne quartz concentration and its unpredictability, Industry requested available data to be examined to determine what single value could be used, representatively, either for each region or for Industry in general. The system of report compilation wherein averages are averaged, with possible compounded errors and masking of high values, precludes any possibility of determining statistical differences in quartz concentrations in the various regions. However, an industry average of 10 to 20 per cent is indicated. Table 30 91 SIMPLE ARITHMETICAL AND PERSON WEIGHTED CYCLIC AVERAGE QUARTZ CONCENTRATIONS (EXCLUDING SURFACE RESULTS1 East Simple Ave Per Cent 15.52 15.61 9.36 10.32 11.06 8.79 Std Dev 7.98 8.00 4.65 5.99 6.72 3.93 Weighted Ave Per Cent 15.56 14.64 10.28 10.98 11.23 8.89 Klerksdorp Simple Ave Per Cent 19.23 19.37 19.46 17.68 16.12 12.89 Std Dev 7.65 7.75 8.74 5.89 7.16 7.13 Weighted Ave Per Cent 18.98 19.36 19.15 18.06 16.84 13.82 SOFS Simple Ave Per Cent 9.29 9.70 9.31 9.77 11.25 9.05 Std Dev 3.84 3.82 3.09 6.12 5.08 6.91 Weighted Ave Per Cent 9.31 9.72 9.69 9.30 10.50 8.36 Total Industry Simple Ave Per Cent 15.41 15.22 13.05 12.89 12.87 11.71 Std Dev 13.36 8.52 7.80 7.14 8.82 6.90 Weighted Ave Per Cent 16.21 16.37 14.37 13.75 13.69 12.42 Elsburg Simple Ave Per Cent 14.88 14.77 14.30 14.67 15.63 13.34 Std Dev 8.50 9.05 7.48 7.62 10.73 6.37 Weighted Ave Per Cent 16.08 15.91 16.77 16.02 16.61 16.62 NOFS Simple Ave Per Cent 14.22 14.20 13.22 13.30 12.90 11.69 Std Dev 7.29 7.30 8.00 7.60 5.69 5.01 Weighted Ave Per Cent 14.99 15.61 15.29 15.65 13.94 12.52 W Wits Simple Ave Per Cent 15.52 14.69 10.97 11.64 11.30 11.91 Std Dev 20.20 9.61 6.06 6.43 6.63 8.78 Weighted Ave Per Cent 16.80 16.60 10.96 11.98 11.94 11.85 In the above two analyses surface data were excluded. Actual TWA and quartz concentration data for the East, Elsburg, Klerksdorp, North Free State, South Free State and West Wits Regions are appended in Appendix A in Tables 1 to 12 and Figures 1 to 72. 92 QUARTZ percent -VSTD DEV S4WPUNG CYCLE + AVERAGE --STD DEV Figure 101 FAST REGION QUARTZ AVERAGES Figure 102 ELSBURG REGION QUARTZ AVERAGES 93 QUARTZ p e rc e n t 1st 2nd H +STD OEV 3rd 4th 5th SAMPLING CYCLE + AVERAGE 4 -STD DEV 6th Figure 103 KLERKSDQRP REGION QUARTZ AVERAGES c V oa. F 5OD 1st 2nd +STD DEV 3rd 4th 3th SAMPUNG CYCLE + AVERAGE 4 -STD DEV 6th Figure 104 NORTH FREE STATE REGION QUARTZ AVERAGES 94 QUARTZ p e rc e n t Tat 2nd B +5TD DEV 3rd 4th 5th SAMPLING CYCLE + AVERAGE --STD DEV 5th Figure 105 SOUTH FREE STATE REGION QUARTZ AVERAGES -f-STD DEV SAMPLING CYCLE + AVERAGE * -STD OEV Figure 106 WEST WITS REGION QUARTZ AVERAGES 95 QUARTZ p e rce n t 1st 2nd +STO DEV 3rd 4th SAMPUNG CYCLE + AVERAGE 5th -STO DEV 6th Figure 107 INDUSTRY QUARTZ AVERAGES 9 DISCUSSION 96 9.1 Results Submitted to the GME An inspection of the results forwarded to the GME by mines shows not only large variations in dust concentrations from one Statistical Population to another in a given sampling area for a mine, but also large variations in quartz content for these Statistical Populations. Typical examples are shown in Figure 108. In addition, the quartz concentration for a given Statistical Population can also vary from one sampling cycle to the next (Figure 109). In terms of the GME's guidelines for gravimetric dust sampling it is permissible to combine up to five samples of a Statistical Population for a single analysis. It is also only required to analyse for quartz once a year. The quartz concentrations thus reported are from combined analyses and still display wide variations. For research purposes each individual sample was analysed and typical variations of quartz concentrations for five individual samples are shown in Figure 110. An average value is meaningless with such large variations, and the reporting system is such that the very high individual quartz concentrations will go undetected and the person exposed to the high quartz concentration will not be identified. As reported above quartz concentrations in a working section, not necessarily a Statistical Population, have shown variations from 17 to 98 per cent. Dust concentrations greater than the mean could be indicative of specific occupations or work places giving rise to high or unsatisfactory dust levels. This has not been investigated in the current report or in the reporting system. Industry statistics tend to mask workplaces and work categories, where attention should be focused for action. There are obviously work categories and workplaces where exposure to dust should be of concern. 97 Sampling Cycle 1 Stat. Pop.1 0% Stat. Pop. 2 Sampling Cycle 2 Stat. Pop.1 1% Stat. Pop. 2 Stat. Pop. n 22,5% Stat. Pop. n 50,8% Figure 108 VARIATION IN QUARTZ CONCENTRATION BETWEEN STATISTICAL POPULATIONS CYCLE 1 Statistical Population 1 30,5 % CYCLE 2 Statistical Population 1 55,8 % Figure 109 VARIATION IN QUARTZ CONCENTRATION BETWEEN SAMPLING CYCLES 98 *T /O r # /O Figure 110 INDIVIDUAL QUARTZ CONCENTRATION IN A STATISTICAL POPULATION Depicted in Figure 111 are typical ranges in Risk from one Statistical Population to the next for a mine for sampling cycle A and for the next sampling cycle, B, after mass and quartz analyses. These are very large changes, but, because of the permissible averaging system in reporting, personnel exposed to unsatisfactory dust and quartz levels cannot readily be identified, and at best these levels could only be detected at the end of a sampling cycle once quartz analyses have been completed. This system is ineffective in timeously identifying unsatisfactory conditions with a view to implementing controls. First Sampling Cycle Stat. Pop.1 0% Stat. Pop. 2 Second Sampling Cycle Stat. Pop.1 1% Stat. Pop. 2 Stat. Pop. n 1,44% Mine 0,23% Stat. Pop. n 139,5% Mine 7,5% Figure 111 VARIATION IN RISK BETWEEN STATISTICAL POPULATIONS 9.2 Impact of Quartz Content on Risk 99 Table 31 shows the results of typical returns from a mine. Table 31 THE INFLUENCE OF QUARTZ CONCENTRATION ON RISK TWA mg/m3 Si02 % AQI Risk % Cycle 1 5,0 7,0 3,5 49,0 Cycle 2 1,5 30,0 4,5 81,0 During the first cycle a "high" TWA was reported for a low quartz concentration which resulted in an AQI of 3,5 and a risk of 49 per cent. During the next cycle dust exposure levels had reduced substantially, which should inherently produce better working conditions, but because of a more than 400 per cent increase in quartz content, something which no mine can control, the resulting AQI increased to 4,5 and the risk to 81 per cent. This system of evaluation must be considered to be flawed when airborne dust concentrations have been reduced but a mine is likely to be penalized for a risk based on a factor over which it has no control. Furthermore, in sampling only to produce results for risk calculations, remedial actions are unlikely to be implemented timeously. 9.3 Risk The way risk is presently defined and assessed does not adequately reflect any measures taken to reduce concentrations of airborne dust, and mines may be penalised for something over which they have no control, namely the quartz content of the airborne dust. In a recent study6 the author suggests that attention should be paid to occupational asthma which is defined by the American Lung Association as a disease in which the airways overreact to dusts, vapours, gases or fumes. When these irritants are inhaled, the airway muscles tighten, the tissues swell, and excess mucous is produced, all of which make breathing difficult. It is also suggested that eight-hour TWA exposure limits may not be appropriate for controlling asthma resulting from irritant exposures, as the asthma may be induced by transient peak exposures rather than by sustained exposure levels10. Furthermore, the study points to important evidence of the role that all dusts, not just specific dusts such as silica, play in the causation of occupational disease. 100 Table 32 THE EFFECT OF QUARTZ CONTENT ON AQI AND RISK AND PROPOSED CHANGES TO RISK EVALUATION TWA mg/m3 5,0 1,5 5,0 1,5 SiOj PI PNOC PI AQI % mg/m3 PNOC 7 3,5 - - 3,5 30 4,5 - - 4,5 PROPOSED CHANGE : INCLUDE PNOC IN ASSESSMENT 7 3,5 4,65 0,93 4,43 30 4,5 1,05 0,21 4,71 RISK 49,0 81,0 78,5 88,7 PI PNOC PI PNOC : Pollutant Index (Pollutant Content/Threshold Limit Value) : Particles Not Otherwise Classified (Non Respirable Dust) : Pollutant Index for Non Respirable Dust The old concept was that there were nuisance dusts that didn't matter too much and therefore they were regarded as harmless as they did not have specific effects like silica or asbestos. However, this concept needs to be re-evaluated. Global exposure, the importance of everything inhaled, not just individual agents, is an important concept to recognize. In South African mines the present risk calculation does not take into account the non-quartz fractions or Particles Not Otherwise Classified (PNOC). Table 32 illustrates the impact of including PNOC in the risk calculation. Although the risks for both situations would increase, the disparity between taking PNOC into account, which can be justified as pointed out above, or by totally omitting it (as done at present) is considerably reduced. This approach would make risk assessment more equitable but the risk would still largely be based on "random" quartz concentrations, which would still be unacceptable. If diesel soot is to be included in any risk calculation, it could be taken into account by dividing the soot fraction (obtained as described in Part 1) by a TLV. A TLV for soot has not yet been set for South African mines, but in a separate study7 soot levels were also shown to fluctuate considerably and this may, in turn, exacerbate the evaluation. 9.4 Investigation of Quartz Variations 101 The anomalies and large variations in dust and quartz levels were reported at a progress meeting and Miningtek was asked to investigate possible reasons for large differences in airborne quartz. This was a deviation from the original research proposal. Consequently, several working places were visited and rock samples were chipped from the hangingwall, working face and footwall, and, during the in-situ sampling airborne samples were collected. The in-situ samples were pulverized and analysed for quartz and the airborne samples were X-rayed for quartz content. The results are presented in Figure 112. No correlation could be found between in-situ quartz concentrations and airborne quartz concentrations. Figure 112 QUARTZ CONTENT : ROCK AND AIRBORNE DUST 9.5 Comparison of Sampling Pumps Several investigations were carried out with different types of sampling pumps, i.e. Gilian type and rotating sponge type in parallel. The results of a comparison made between Gilian pumps is shown in Figure 113 where a very good correlation is demonstrated. The results of a controlled test where Gilian pumps sampled in parallel with rotating sponge type pumps is presented in Figure 114. In this field test the rotating sponge pumps consistently undersampled the Gilian pumps. At test site 2 Gilian pumps were routinely operated in parallel with rotating sponge pumps. As is the case with the controlled test the rotating sponge pumps consistently undersampled the Gilian pumps. This is seen in Figure 115. Dust concentration (mg/m3) Rotating sponge (mg/m3) zi 102 ure 113 G1LIAN VS GILIAN : DUST (mci/m3) Figure 114 GILIAN VS ROTATING SPONGE : DUST fmq>m!) Rotating sponge (mg/m3) 103 Figure 115 COMPARISON OF G1LIAN AND ROTATING SPONGE SAMPLES (ROUTINE MEASUREMENTS) At the same test site a comparison was made with rotating sponge pumps sampling in parallel and the poor correlation obtained is presented in Figure 116. 0,1 0,2 0,3 0,4 0,5 Rotating sponge sampler (mg/m3) Figure 116 COMPARISON OF ROTATING SPONGE SAMPLERS 104 9.6 Quartz Concentrations Obtained in Parallel Sampling Although a good correlation was obtained between dust concentrations for Gilian pumps sampling in parallel, the quartz content of the parallel samples displayed very poor correlation as shown in Figure 117. This result was surprising but has been noted in the literature8 9. In one study8 185 samples including 25 paired samples were evaluated. The 25 paired samples had differences of percentage of silica values ranging from less than 0,1 to 19,2. The magnitude of percentage of silica content of samples collected from the same section ranged from differences of 7,5 to 88. The findings in this SIMRAC report are very similar. Attention is drawn to the implications of these findings for any tests for adherence to or compliance with pre-set standards. No explanations for these anomalies were advanced in the literature nor were any forthcoming as a result of this investigation. Figure 117 GILIAN VS GILIAN QUARTZ PER CENT 10 CONCLUSIONS AND RECOMMENDATIONS 10.1 The impact of quartz on risk calculation has been shown to be very considerable. The way risk is presently defined and assessed does not adequately reflect any measures taken to reduce airborne concentrations of dust and mines are penalised for something over which they have no control, namely the quartz content of the airborne dust. In risk assessment the non-quartz fraction or Particles Not Otherwise Classified (PNOC) (nuisance dust) is not taken into consideration at all. Although the risks for both situations would increase the disparity between taking PNOC into account and totally omitting it, as at present, is considerably reduced. This approach could make 105 risk assessment more equitable but it would still largely be being based on "random" quartz concentrations, which would still be unacceptable. The inclusion of diesel soot in a risk formula would introduce another element of uncertainty. 10.2 The present dust sampling programme, sample analysis and reporting system features eight-hour TWA results by "activity" and not by occupation. These results make any study of dose response very difficult, and, furthermore some form of averaging random quartz concentrations is incorporated. Exposure levels are calculated for the time that the sampling pump operates, whether or not the wearer was in dusty conditions, for example, while travelling to and from the working place. This is said to enable a "dose" for the working shift to be calculated. However, it could be argued that the full 24-hour period should be considered to evaluate daily dose. In reality it is the dose at the working place which should be evaluated in order to be able to study a dose-response relationship. The logistics of determining workplace dose has militated against this approach but this matter should be reconsidered for future studies. 10.3 Dust sampling for control purposes is not readily accomplished using gravimetric dust sampling equipment. Presently, the only use to which gravimetric samples are put is to calculate an AQI and then a risk from which a dust levy is then calculated. The flow charts, as set out in Figure 118 show that if this is indeed the main purpose of the present dust sampling effort then this effort can be considerably reduced, as it is not necessary to weigh any filters to determine an AQI. An AQI can be determined from the volume of air sampled and the analytical mass of the quartz in the sample. This technique, which achieves the same objective, completely eliminates all precision weighing of filters before and after field sampling, and could represent considerable savings in terms of labour used to perform these operations. Serious consideration should be given to this approach. 10.4 Results extracted from reports submitted to the GME do not show any significant differences in dust and quartz levels in the six geographical regions investigated. On an industry basis a slight shift is indicated over six sampling cycles that would place a greater working population being exposed to lower concentrations of dust with a lower quartz content. These indicated changes cannot be adequately explained. It is feasible to abolish all quartz analysis in view of what has been stated in this report, and to use an industry value of 20 per cent. This would be within one standard deviation of the average values reported. Should this be accepted, then a dust concentration of 0,5 mg/m3 would give an AQI of one (and a risk of four per cent). This approach would also allow an immediate evaluation of dust levels in terms of being satisfactory or not - any dust level in excess of 0,5 mg/m3 would be unsatisfactory. 106 A noticeable Industry shift for the stoping and developing category from 0,2-0,4 mg/m3 to the next range, i.e. 0,4-0,6 mg/m3, would be moving results towards an Industry AQ1 of one. When surface dust sampling results are added to the overall analysis of dust exposures for the six sampling cycles the number of persons exposed to dust concentrations in excess of 1,2 mg/m3 is increased. This means, with an industry quartz concentration of 20 per cent, more persons would be exposed to an AQI in excess of two and on an industry basis this should elicit an investigation. 10.5 If the original data are still available on mines there is the potential to extract information pertaining to occupational dust exposure levels. This could form the basis of a research project that can link with epidemiological studies. The issue of different sampling systems yielding results that could be different would need to be addressed. CONTROL FILTERS NUMBER WEIGH FIELD FILTERS NUMBER WEIGH ---S-A-M-P-L-E-- DETERMINE AIR VOLUME SAMPLED CONTROL FILTERS WEIQH FIELD FILTERS WEIGH DETERMINE MASS OF DUST OUST MASS AIR VOLUME SAMPLED ---------/ DUST I LABORATORY CONCENTRATION / ! mg/m1 , ANALYSE LABORATORY ANALYTICAL MASS QUARTZ ANALYTICAL MASS QUARTZ OUST MASS SAMPLED > @ MINE: % QUARTZ X /DUST CONCENTRATION/- % QUARTZ | qUARTZ concentration! mg/m1 , f, [quartz concentration] [$3 i, I AIR QUALITY INDEX) FIEL0 FILTERS NUMBER POSSIBILITY SAMPLE ------------------ DETERMINE AIR VOLUME SAMPLED -L-A-B-O-R-A-T-O-R^Y ANALYSE LABORATORY ANALYTICAL MASS QUARTZ ANALYTICAL MASS QUARTZ * AIR VOLUME SAMPLED 1 Figure 118 PRESENT AND POSSIBLE TECHNIQUES TO DETERMINE AQI PART 3 107 11 TECHNIQUES TO RECOMBINE RESPIRABLE AND NON-RESPIRABLE DUST FOR TOTAL POLLUTANT ASSESSMENT Analytical techniques for quartz are based on analysing a deposition of particulates in as even a bed as possible. The particulate size should not exceed 10 pm diameter. Analysis of other pollutants is based on "total" sample evaluation, that is the full sample and not only a fraction of the sample. It was anticipated that the GME would request mines to analyse all airborne pollutants so that future risk could be based on all airborne pollutants. This could have meant that mines could have been faced with double sampling, one set of samples to evaluate quartz and another set of samples, based on total dust sampling techniques as outlined in the guidelines for gravimetric dust sampling, for other airborne pollutants. If a way could be devised to be able to perform quartz and other pollutant analyses from a single sample, mines could save on both effort and cost of collecting the samples. As shown in Part 1 this is already possible for mineral dust and diesel soot (RCD). Initially, experiments were conducted with small thimbles which fitted inside the catch or grit pots of the Gilian 10 mm diameter cyclones. It was visualised that if these thimbles could be dissolved and redeposited with the respirable dust, by now X-rayed for quartz content, the sample would be made available for further analysis. These thimbles weighed between 125 and 170 mg and the technique for catching the coarse fraction of the dust in a catchpot lining worked well. The major difficulty was that the thimbles were only available in fibreglass, and not cellulose nitrate, and could, therefore, not be cleanly dissolved. In addition, the thimbles had to be cut to the correct size and were difficult to remove from the catchpot. The next development was to flush the contents out of the catchpot into the redepositing distilled water with the respirable fraction of the sample, again after the respirable fraction had been X-rayed for quartz content. It is necessary to weigh all filters used in the redepositing process to determine how much coarse dust, if any, has been added to the f nal sample. The total mass of dust is needed to calculate pollutant percentage (if required). Furthermore, it is necessary to weigh three control filters and to pour distilled water through the controls and then, after drying, to reweigh the controls as a check on the cleanliness of the distilled water. Any substantial gain in weight on the controls would invalidate the sample under consideration. 108 Figure 119 shows the usual, separate sampling techniques for the required analyses but would entail a double sampling requirement, i.e. one sample would have to be collected for respirable dust and a second sample for total dust. Figure 120 shows the proposed technique. Respirable Dust Sample Total Dust Sample (discarded) Figure 119 SEPARATE RESPIRABLE AND TOTAL DUST SAMPLING Rosoirablc Figure 120 PROPOSED COMBINED RESPIRABLE AND TOTAL DUST SAMPLING TECHNIQUE 109 Although the proposed technique works for a conventional sampling train, care has to be taken so that the catchpot is not dislodged during the sampling shift and that the sampling train is transported with care to the laboratory. It is also a matter of not only submitting a filter for analysis, but also its relevant catchpot. This recombination technique is unlikely to work on samples that are analysed with an infra-red technique. Recombination has not been tried with CIP 10 samplers. During the experimental work carried out in this investigation the possible influence of water soluble salts and carbon particulates on quartz concentrations was examined. Although these contaminants do not affect the quartz scan,* and therefore the analytical mass of the quartz, their presence can result in an incorrect percent quartz being reported. In the redeposition technique practised by CSIR/Miningtek, the filters, with the samples deposited on them, are dissolved in acetone, the residue ashed, and then washed in triple distilled water. The ashing and washing processes would get rid of carbon particles and water borne salts. This treatment is similar to that to which konimeter slides were subjected in order to ensure that only the mineral dust of the samples was evaluated. It is clear that if percent quartz is reported in terms of all particulates captured in the filter medium, considerable errors could arise. This could have affected the results reported in Part 2, and, in fact, true quartz levels could be significantly higher. However, since the present quartz is only used for re-determining the analytical mass of this quartz to enable calculations of AQI and Risk to be done the determination of AQI and Risk would not have been affected. * The presence of large amounts of diesel soot do, however, affect the results and must be taken into account. PART 4 110 12 EXPOSURE AND ENGINEERING CONTROL MONITORING 12.1 Description An eight-hour sample or a sample collected over several hours, although it collects dust when high levels are generated, cannot indicate adverse conditions once the total dust load is divided by the air volume sampled because the high level, which may be of relative short duration, is being averaged with the rest of the sample. Konimeter sampling was of very short duration, approximately 0,2 seconds, and very useful in indicating high concentrations of dust, but could hardly be regarded as providing reliable data on full shift exposures and could not, of course, be analysed for quartz content. It was also a criticism of the Leon Report' that high dust levels were not being identified and subsequently being investigated. This part of the project was aimed at testing the feasibility of worker exposure monitoring and engineering control monitoring, using equipment already in use on the mines. It was realised that for reporting on workplace conditions and control purposes a short duration sample was needed. Because it was anticipated that the dust mass collected over a period of about 10-15 minutes would be low, giving a very unfavourable dust mass/filter mass ratio, a 13 mm cellulose nitrate filter size was selected for a trial series. A typical trace of dust concentration with time from a tyndallometer (aerosol monitor) would look like the trace presented in Figure 121. The eight hour average dust concentration, including the high level of 20 mg/m3 which lasted for 10 minutes, was 0,7 mg/m3 and did not give any hint of any unsatisfactory condition during the shift. Shown in Figure 122 are the possibilities when making use of short duration samples. For example: Mode 1 shows the conventional eight hour average dust concentration, Mode 2 shows the result if the 10 minute sample was collected only during the peak dust level, Mode 3 indicates the result that would be obtained if only half of the peak dust level had been sampled; the 10-minute average would exceed the eight-hour average considerably and alert those in charge to a need for action, ill Figure 121 CONTINUOUS DUST LEVEL TRACE 34 Mode Figure 122 COMPARISON OF SAMPLING TECHNIQUES AND REGISTERING OF HIGH DUST LEVELS Dust concentration (mg/m) 112 Mode 4 is again, effectively, the result of the eight-hour sampling; instead of a 10 minute sampling period a 60 minute sampling period could be considered. Mode 5 shows the effect of sampling the peak dust and 50 minutes of the average dust, the result would again indicate a need for action when compared with the eight hour result, and Mode 6 shows the result of sampling only five minutes of the peak dust, yet again the result would indicate the need for action. It is, of course possible, that even with short duration sampling the peak dust levels could be missed entirely. The desirability of evaluating transient peak dust levels has also been discussed in section 3.9. 12.2 Preliminary Results Two underground trials were held using the short duration technique. The first short duration samples were collected over 10-12-minute intervals. After each sample was collected an unused cassette was fitted to the pump. Samples were collected over the period that the environmental officer made all his other observations, e.g. temperature, air velocity, etc. In addition, a standard sampling train was started as the stope was entered and stopped when the stope was exited. The duration of the sample was 69 minutes. An eight-hour personal sample was also collected for comparison of results. The results of this exercise are depicted in Figure 123. 69 minute travelling sampler = 1.297. mg/m3 (start at top of stope and stop at bottom of stope) ] Figure 123 DUST LEVELS FOUND FOR SHORT DURATION SAMPLING (11 113 It is obvious that the short duration samples are able to indicate places of concern with respect to dust levels. The 69-minute travelling sampler yielded a result almost twice as large as the eight-hour personal sampler, i.e. 1,3 mg/m3 compared to 0,7 mg/m3. A second trial was held at another mine and additional measurements were made. In addition to the travelling sampler (this time 121 minutes), a conventional sampling pump was used by starting and stopping it with the short duration pump but not changing cassettes. Thus, the dust collected at the environmental monitoring stations was deposited on a single filter and gave an integrated sample. This gave a much higher result than the continuously operated pump, and although it compares well with the short duration samples, it does not give detail. A Hund tyndallometer was also used and two full shift samples were collected, one with a Gilian pump and the other with a CIP 10 pump worn by the same person. All the results are shown in Figure 124. Figure 124 DUST LEVELS FOUND FOR SHORT DURATION SAMPLING (2) 12.3 Discussion 114 At both test sites the short duration samples returned results higher than the eight-hour or full shift sampling results. This illustrates the potential to assist in identifying localities and operations where unsatisfactory dust conditions may exist. Whilst useful in providing a dust level "index" for a working place, the continuous workplace sample ( 121 minutes) is unlikely to be of assistance in pinpointing either unsatisfactory working conditions or "dusty" operations. The stop/start sample gave a value which more closely approximated dust levels found with the short duration samples but would also not be useful for isolating either unsatisfactory work environments or practices. The tyndallometer (Hund), which gives real-time readings of aerosol levels, could be used with effect to locate high aerosol levels without being able to indicate actual dust concentrations. Elevated dust levels, as found with the short-duration samples, correlated with elevated aerosol concentrations. However, this may not always be the case. As can be seen from Figure 124 the full shift samples gave no indication of high dust levels caused by specific mining operations. 12.4 Conclusions Of the methods checked, the greatest detail was provided by the short term samplers and the tyndallometer. The full shift samplers give no indication of any abnormalities and would not be of any use for engineering control purposes. The method is very promising and can address the problem of locating and identifying areas with unsatisfactory dust levels. The method is being further investigated in a 1996 SIMRAC project. 115 13 OVERALL CONCLUSIONS AND RECOMMENDATIONS 13.1 Recombination of Respirable and Coarse Fractions of Dust for Complete Analysis After X-ray analysis of a conventional sample, i.e. dust collected on a filter, it was found that the coarse fractions can be recombined with the respirable fraction by redepositing both fractions on a second filter. The combined sample is then available for further analysis of additional airborne pollutants. This technique cannot be used with samples collected on a rotating sponge filter, nor is it possible with infrared analysis because the original filter paper is destroyed in the preparation of the necessary wafer. Where pollutants other than quartz have to be assayed in addition to quartz, this technique offers cost savings in that only one sample needs to be collected for complete analysis, as opposed to a respirable sample for quartz analysis and a total dust sample for other airborne pollutants. As, and when, the Government Mining Engineer (GME) requires analyses of other pollutants in addition to quartz, this technique can be used. It is already feasible to analyse for diesel soot and mineral dust, and thereafter the quartz fraction of the mineral dust, on a single conventional filter. Hence, multiple analyses from a single filter is already possible and the technique discussed in this report can be adopted. 13.2 Investigation of the Possibility of Replacing 'Personal Sampling' with Stationary, Area or Representative Place Sampling Field investigations were conducted at three underground test sites and one assay/sample preparation laboratory, which was repeated after several months. Dust samples were collected over full shifts at stationary samplers at main returns and/or representative places simultaneously with samples collected on roving (personal) samplers. It was found that no correlation could be seen between stationary samplers placed at different positions, i.e. main returns or representative places, between stationary samplers and roving samplers, or between roving samplers. This latter result was expected because dust samples collected for different occupations have been shown to differ. This lack of correlation, as outlined above, has been demonstrated for dust levels, quartz concentrations, Air Quality Indexes and "risk", and was common to all the test sites. Only two exceptions were found at two different test sites and for different parameters. 116 Dust levels, quartz concentrations, AQIs and risk have been found to vary from day to day and even from shift to shift for samples collected at the same site or at the same person. Furthermore, dust levels, quartz concentrations, AQI and risk were found to vary from Statistical Population to Statistical Population and from one dust sampling cycle to the next. Moreover, very large ranges in quartz concentrations (4-72 per cent) were found for individual dust samples of a Statistical Population, and a range of 17 to 98 per cent was found for dust samples in a single working section. No correlation could be found at any position at any test site between dust concentration and quartz concentration. It is also clear from the investigation that any results obtained could depend largely on the day and the shift when the samples were collected3. Because of the very considerable impact that quartz concentrations bring to bear on the calculation of risk additional investigations were conducted to try to establish any possible reasons for the large variations in quartz concentrations found for airborne dust. The matter was not resolved and has not been resolved in overseas countries undertaking similar investigations. It can be clearly concluded that on the evidence acquired at the four test sites, personal sampling cannot be replaced by area sampling. In essence, it would not be possible to reduce the sampling effort required by mines and still achieve the same personal sampling results. 13.3 Assessment of Data from the GME's Sampling Programme on Gold Mines Mines were divided into six geographical regions, namely East (Eastern Transvaal), Elsburg, Klerksdorp, North Free State, South Free State and West Wits. Reports of half-yearly results for the period January 1992 to June 1994 were analysed. Results were further classified into underground stopes and development, underground roving, and surface. No significant differences were found in either dust levels or quartz concentrations between the three activity classifications or between the regions. As pointed out in Part 3, unless carbon particles and water borne contaminants are taken into account, then quartz concentrations could be in error. On an industry basis airborne quartz levels reported could thus inadvertently have been too low. The industry eight-hour TWA dust concentration was found to lie in the range 0,2 to 0,4 mg/m3 and the quartz concentration in the range 10 to 20 per cent. It is recommended that an Industry figure of 20 per cent for quartz should be used when evaluating exposures. In this case a dust 117 concentration of 0,5 mg/m3 would have an AQI of one. The adoption of this procedure would simplify the evaluation of working place conditions for engineering control purposes, as well as provide management with information with regard to likely worker exposure levels with a minimum of delay, since the dust samples would not need to be analysed for quartz content. Also, Air Quality Indexes, based on eight-hour TWA exposures and "fixed" quartz concentrations, can be used to gauge worker exposure with minimal delays. Routine analyses for quartz concentration no longer needs to be carried out. Nevertheless, there may still be occasions when the analysis of a sample may be required, for whatever reason, and this can then be done. If the original records are still available on mines there is the potential to extract information with respect to occupational dust exposures. This could be the basis of a research project that could be linked to epidemiological studies. The considerable volume of data, used only to calculate levies, could, in this way, be put to more meaningful use. 13.4 Recommendations for a more Equitable Risk Formula From research work conducted and reports to the GME it is obvious that the present risk formula is not equitable and does not reflect steps taken to reduce dust levels. The formula would become more equitable if all dusts are incorporated into its evaluation. However, because of the highly variable dust and quartz levels, risk assessment is being based on very random variables. The position would be exacerbated by the inclusion of more and more pollutants, such as diesel soot, etc. It is recommended that risk assessment for levy purposes through the GME's dust sampling programme should be discontinued and that levies, which are to pay compensation for past events, should be based on other criteria formulated by the Commissioner of Compensation. 13.5 The GME's Dust Sampling Programme Dust sampling is undertaken by mines to determine a risk for levy purposes. Dust sampling for control purposes using gravimetric dust sampling equipment is rarely undertaken. Mines prefer to use konimeters for control sampling, if at all. The results of the dust samples collected for the GME reports are not used by mines nor can they be used to tie in with medical surveillance. In general, from results submitted to the GME it would be difficult to trace an individual sample or locate an individual working place where an unsatisfactory dust sample was recorded. With a time lapse of several months possible before 118 submission of results to the GME any meaningful official action for an unsatisfactory dust sample is also not possible. Furthermore, persons may have left their employment or working places closed down. This type of sampling strategy has thus been found to provide little use in locating or controlling unsatisfactory dust conditions in work places. Therefore, there seems to be little purpose in continuing with the sampling programme. If levies can be determined, as recommended in Section 13.4, then mines should be permitted to sample dust for control purposes by whatever means is found to be acceptable and useful until research can point the way to an enhanced technique. Mines should, however, assist with occupational dust sampling, which would be for research purposes, and not for the determination of a levy. In such a sampling programme all pollutants sampled would be used to gauge relative and total toxicity. This is in keeping with a recommendation in the literature. 13.6 Exposure Monitoring and Monitoring for Dust Control Purposes Initial trials have indicated the feasibility of gravimetric dust sampling with small diameter filters for short time periods to evaluate working conditions and to determine if control measures are necessary. These samples can be used to check on effectiveness of controls. It can be assumed that if techniques are made available to monitor the control of dust emissions so that dust can be brought under control then exposure levels will also be controlled. However, there is still a delay in obtaining the mass of dust on the filters for evaluation of the samples and the need for a direct reading instrument that can exclude all unwanted aerosols such as water vapour and oil mist is indicated. There is, nevertheless, a need for occupational sampling on an industry basis in which dust levels (all dusts) and the toxicity of the dusts is evaluated for risk of a particular occupation group. These data can then gainfully be integrated with medical surveillance to investigate dose response relationships. Occupational dust sampling and short duration sampling for engineering control purposes are the subject of another research project (SIMRAC 1996). 14 REFERENCES . 1. Commission of Enquiry into Safety and Health in the Mining Industry. Report - Volume 1 (1995). 2. Guidelines for gravimetric dust sampling. Department of Mineral and Energy Affairs. November 1992. 119 3. Method Development for the Gravimetric Determination of Respirable Combustible Dust (RCD) in Air. Rex, D A and Gardiner, L R. Chamber of Mines Research Organization, Project No. GE2P, March 1989. Internal Report No. 580. 4. Exposure Variability in the Workplace : Its implications for the Assessment of Compliance. Eltjo Buringh, Roel Lanting. Am Ind. Hyg. Assoc. J. (52), January 1991, pp 6-13. 5. Elementary Statistics. Elizabeth Harris in Environmental Engineering in South African Mines. The Mine Ventilation Society of South Africa. Cape and Transvaal Printers 1982, pp 819-846. 6. The Changing Face of Respiratory Illness. Stephen G Minter. Occupational Hazards, February 1995, pp 43-44. 7. SIMRAC Final Project Report : Control of Diesel Exhaust Emissions in Underground Workings. Test Results from Exposure Measurements in South African Mines. Haase, H. And Unsted, A D. Project GEN 010, March 1995. 8. Regulatory Implications of Airborne Respirable Free Silica Variability in Underground Coal Mines. Jacqueline M Viilnave, Morton Corn, Marcie Francis, Thomas A Hall. AM Ind. Hyg. Assoc. J. (52)/March 1991, pp 107-112. 9. Respirable Dust and Free Silica Variability in Mine Environments. Thomas A Hall, Morton Corn, S Zeger, CC Law. Strategies for Mine Dust Measurement, pp 1151 -1159. 10. Untersuchungen zur Auspulbarkeit von Makrophagen. Rehn, B, Zou, Tong-Tong, Hobusch, G and Bruch, J. Ergebnisse von Untersuchungen auf dem Gebiet der StaubSilikosebekampfung im Steinkohlenbergau. BAND 17. Arbeitsgemeinschaft Staub-und Silikosebekampfung. 1989. 120 APPENDIX A TWA AND QUARTZ CONCENTRATION DATA EXTRACTED FROM REPORTS SUBMITTED BY MINES TO THE GOVERNMENT MINING ENGINEER FOR THE EAST, ELSBURG, KLERKSDORP, NORTH FREE STATE, SOUTH FREE STATE AND WEST WITS REGIONS. 121 TABLE 1 EAST STOPING AND DEVELOPMENT POPULATION TWA DISTRIBUTIONS Dust Cone. Persons Persons Persons Persons Persons Persons Grouping (mg/m3) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-0,2 0,2-0,4 0,4-0,6 1233 1373 2451 738 2066 3402 1126 3191 3317 662 2448 3085 1799 2665 2280 1273 2945 1281 0,6-0.8 1309 810 1126 601 600 36 0,8-1,0 610 60 281 258 52 1,0-1,2 50 271 140 >1,2 EAST UNDERGROUND ROVING POPULATION TWA DISTRIBUTIONS Dust Cone. Persons Persons Persons Persons Persons Persons Grouping (mg/m3) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-0,2 807 911 470 284 436 479 0,2-0,4 3236 2754 3126 2707 4074 2375 0,4-0,6 2159 1312 2089 2918 1138 941 0,6-0,8 300 2296 963 1272 394 1541 0,8-1,0 420 222 534 152 519 1,0-1,2 >1,2 173 332 160 247 55 304 223 272 55 124 EAST SURFACE POPULATION TWA DISTRIBUTIONS Dust Cone. Grouping (mg/m3) Persons Cycle 1 Persons Cycle 2 Persons Cycle 3 Persons Cycle 4 Persons Cycle 5 Persons Cycle 6 0-0,2 189 256 114 241 470 8 0,2-0,4 250 216 385 515 296 546 0,4-0,6 270 47 265 151 317 1315 0,6-0,8 182 334 280 268 307 568 0,8-1,0 293 618 239 1,0-1,2 40 48 228 >1,2 218 57 57 303 122 TABLE 2 EAST STOPING AND DEVELOPMENT POPULATION QUARTZ DISTRIBUTION Quartz Persons Persons Persons Persons Persons Persons Grouping (%) 0-5 5-10 1 10-15 15-20 Cycle 1 0 711 1954 2464 Cycle 2 0 646 2599 3130 Cycle 3 384 4396 2381 437 Cycle 4 608 3613 1424 685 Cycle 5 Cycle 6 1321 2163 2114 1229 1405 2318 1078 1117 20-25 25-30 1183 1215 769 621 382 0 0 503 272 268 52 0 30-35 54 36 0 0 0 0 35-40 0 0 0 125 125 0 >40 0 0 0 0 0 0 EAST UNDERGROUND ROVING POPULATION QUARTZ DISTRIBUTION Quartz Persons Persons Persons Persons Persons Persons Grouping (%) 0-5 Cycle 1 311 Cycle 2 314 Cycle 3 1413 Cycle 4 2575 Cycle 5 2280 Cycle 6 1671 5-10 1713 2080 2373 2331 1869 3046 10-15 1586 1781 1336 1816 1277 1386 15-20 20-25 183 2327 234 783 619 108 538 562 132 132 25-30 464 581 259 130 130 30-35 153 28 35-40 165 165 >40 242 296 EAST SURFACE POPULATION QUARTZ DISTRIBUTION Quartz Persons Persons Persons Persons Persons Persons Grouping (%) 0-5 Cycle 1 438 Cycle 2 566 Cycle 3 462 Cycle 4 428 Cycle 5 626 Cycle 6 543 5-10 65 64 501 537 90 1961 10-15 423 358 339 150 317 236 15-20 358 381 17 17 216 20-25 150 103 25-30 158 100 237 30-35 35-40 >40 123 TABLE 3 ELSBURG STOPING AND DEVELOPMENT POPULATION TWA DISTRIBUTION Dust Cone. Grouping (mg/m3) Persons Cycle 1 Persons Cycle 2 Persons Cycle 3 Persons Cycle 4 Persons Cycle 5 Persons Cycle 6 ` 0-0,2 87 167 196 127 603 0,2-0,4 1692 148 195 1642 1586 0,4-0,6 4273 2131 2675 2655 2676 0,6-0.8 2284 3641 2294 4696 1909 0,8-1,0 1227 1033 706 101 216 1,0-1,2 206 130 >1,2 373 ELSBURG UNDERGROUND ROVING POPULATION TWA DISTRIBUTION Dust Cone. Persons Persons Persons Persons Persons Persons Grouping (mg/m3) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-0,2 183 245 346 648 1025 65 0,2-0,4 860 536 665 1105 169 824 0,4-0,6 791 389 119 142 199 241 0,6-0,8 157 129 66 286 0,8-1,0 88 66 1,0-1,2 127 130 >1,2 7 7 133 ELSBURG SURFACE POPULATION TWA DISTRIBUTION Dust Cone. Persons Persons Persons Persons Persons Persons Grouping (mg/m3) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-0,2 183 245 346 648 1025 65 0,2-0,4 860 536 665 1105 169 824 0,4-0,6 791 389 119 142 199 241 0,6-0,8 157 129 66 286 0,8-1,0 88 66 1,0-1,2 127 130 >1,2 7 7 133 124 TABLE 4 ELSBURG STOPING AND DEVELOPMENT POPULATION QUARTZ DISTRIBUTION Quartz Persons Persons Persons Persons Persons Persons Grouping Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 (%) 0-5 1008 659 92 127 131 5-10 1072 230 689 734 232 219 10-15 2331 1907 700 1006 509 1349 15-20 3082 2241 3465 4523 2255 2065 20-25 1577 1275 1055 1712 2568 1692 25-30 1033 30-35 1072 184 67 216 1148 932 35-40 >40 147 ELSBURG UNDERGROUND ROVING POPULATION QUARTZ DISTRIBUTION Quartz Persons Persons Persons Persons Persons Persons Grouping (%) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-5 98 499 94 553 479 516 5-10 1046 1489 150 1013 1326 2087 10-15 1388 1957 1005 2580 736 1437 15-20 725 1915 235 1271 4456 4850 20-25 363 653 631 925 593 25-30 431 367 610 135 30-35 916 35-40 233 240 o A ELSBURG SURFACE POPULATION QUARTZ DISTRIBUTION Quartz Persons Persons Persons Persons Persons Grouping (%) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 0-5 254 182 492 734 381 5-10 599 324 110 215 290 10-15 87 94 650 15-20 312 66 178 514 20-25 462 390 87 78 130 25-30 100 160 234 145 30-35 35-40 9 240 242 10 >40 168 181 Persons Cycle 6 426 291 357 275 126 140 125 TABLE 5 KLERKSDORP STOPING AND DEVELOPMENT POPULATION TWA DISTRIBUTION Dust Cone. Persons Persons Persons Persons Persons Persons Grouping (mg/m3) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-0.2 114 224 1184 0,2-0,4 1065 713 3929 4052 2754 7483 0,4-0,6 5578 8656 10919 7182 16125 15224 0,6-0.8 0,8-1,0 1,0-1,2 8789 5465 351 9681 3762 1336 6428 1680 1460 2614 922 508 4084 959 249 1342 122 813 >1,2 1500 435 806 KLERKSDORP UNDERGROUND ROVING POPULATION TWA DISTRIBUTION Dust Cone. Persons Persons Persons Persons Persons Persons Grouping (mg/m3) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-0,2 509 13 715 197 1369 1946 0,2-0,4 0,4-0,6 6768 7911 6867 9740 7666 11390 6817 5314 8135 8891 13299 7784 0,6-0,8 5070 4281 1189 1517 1617 843 0,8-1,0 1532 887 854 325 3085 1,0-1,2 1469 688 631 8 >1.2 547 69 178 KLERKSDORP SURFACE POPULATION TWA DISTRIBUTION Dust Cone. Grouping (mg/m3) Persons Cycle 1 Persons Cycle 2 Persons Cycle 3 Persons Cycle 4 Persons Cycle 5 Persons Cycle 6 0-0,2 485 524 58 212 494 232 0,2-0,4 0,4-0,6 952 1728 1280 611 1827 1602 746 2702 2131 890 1989 2509 0,6-0,8 0,8-1,0 1,0-1,2 327 1246 623 356 705 144 221 247 493 232 55 218 140 58 25 7 >1,2 505 262 456 248 126 TABLE 6 KLERKSDORP STOPING AND DEVELOPMENT POPULATION QUARTZ DISTRIBUTION Quartz Persons Persons Persons Persons Persons Persons Grouping (%) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-5 766 2143 5-10 223 234 1876 493 1128 5863 10-15 2409 3304 5089 2751 5287 4883 15-20 9787 9734 6109 4536 8535 8920 20-25 6629 6933 7006 521 6536 2858 25-30 1763 1869 2315 2148 1998 1364 30-35 1975 1158 1399 662 479 35-40 351 523 639 652 >40 446 507 418 136 KLERKSDORP UNDERGROUND ROVING POPULATION QUARTZ DISTRIBUTION Quartz Persons Persons Persons Persons Persons Persons Grouping (%) 0-5 5-10 10-15 Cycle 1 672 2111 7688 Cycle 2 532 2026 6632 Cycle 3 965 1506 5980 Cycle 4 342 1601 5109 Cycle 5 1323 3837 8407 Cycle 6 2322 6467 5810 15-20 7387 6967 6545 3197 6288 7066 20-25 2704 2997 2938 2620 2196 1356 25-30 1950 1756 2217 631 1758 746 30-35 325 324 432 470 86 35-40 905 1266 1086 >40 45 45 145 11 113 KLERKSDORP SURFACE POPULATION QUARTZ DISTRIBUTION Quartz Persons Persons Persons Persons Persons Persons Grouping (%) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-5 289 289 328 189 797 886 5-10 455 365 836 365 571 975 10-15 1333 1422 1240 1294 1703 1308 15-20 609 820 571 320 1379 150 20-25 243 203 579 258 504 1100 25-30 571 459 414 193 821 544 30-35 171 196 201 505 132 35-40 38 85 136 77 >40 497 569 243 130 57 127 TABLE 7 NOFS STOPING AND DEVELOPMENT POPULATION TWA DISTRIBUTION Dust Cone. Persons Persons Persons Persons Persons Persons Grouping (mg/m3) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-0,2 900 1357 1117 1315 590 2059 0,2-0,4 12411 10980 16747 23229 23367 18464 0,4-0,6 15572 13180 12872 10929 9958 14261 0,6-0.8 3061 3502 5023 7083 4710 6786 0,8-1,0 346 1670 1079 16 16 65 1,0-1,2 2092 435 >1,2 15 75 NOFS UNDERGROUND ROVING POPULATION TWA DISTRIBUTION Dust Cone. Persons Persons Persons Persons Persons Persons Grouping (mg/m3) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-0,2 3339 3479 5462 6546 7516 6236 0,2-0,4 15731 11982 14973 16130 14724 14958 0,4-0,6 3455 5286 4278 3113 2871 4691 0,6-0,8 898 1880 887 1328 1874 2149 0,8-1,0 120 556 247 293 77 146 1,0-1,2 164 49 94 >1,2 23707 23232 25941 27410 27062 28180 NOFS SURFACE POPULATION TWA DISTRIBUTION Dust Cone. Persons Persons Persons Persons Persons Persons Grouping (mg/m3) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-0,2 716 690 878 1264 1756 1334 0,2-0,4 1432 899 1382 1987 2209 1339 0,4-0,6 623 692 1118 588 554 902 0,6-0,8 138 330 934 625 193 722 0,8-1,0 659 16 215 10 222 180 1,0-1,2 87 135 376 329 66 94 >1,2 253 412 145 551 147 180 128 TABLE 8 NOFS STOPING AND DEVELOPMENT POPULATION QUARTZ DISTRIBUTION Quartz Grouping (%) 0-5 Persons Cycle 1 Persons Cycle 2 Persons Cycle 3 Persons Cycle 4 Persons Cycle 5 Persons Cycle 6 1744 1757 1246 1910 316 1506 5-10 10-15 15-20 20-25 25-30 30-35 2072 9910 11230 4560 2378 399 2081 10309 11299 4577 2359 399 6510 12208 8342 1717 4031 581 7507 12758 10547 2431 4401 846 5168 15881 12506 2417 1020 1234 9592 15454 12610 1178 443 806 35-40 >40 1305 898 1020 1602 99 121 NOFS UNDERGROUND ROVING POPULATION QUARTZ DISTRIBUTION Quartz Grouping (%) Persons Cycle 1 Persons Cycle 2 Persons Cycle 3 Persons Cycle 4 Persons Cycle 5 Persons Cycle 6 0-5 5-10 3393 5774 3332 5784 2193 7795 2220 8602 2148 9413 2426 10614 10-15 15-20 5969 4514 5361 4564 6838 5083 7788 4390 8211 5801 10552 3457 20-25 25-30 1877 1911 2408 2827 659 926 269 269 1290 1049 628 30-35 314 414 215 215 202 205 35-40 289 289 122 >40 1308 1308 79 79 NOFS SURFACE POPULATION QUARTZ DISTRIBUTION Quartz Grouping (%) 0-5 Persons Cycle 1 Persons Cycle 2 Persons Cycle 3 Persons Cycle 4 Persons Cycle 5 Persons Cycle 6 1402 1043 966 836 967 632 5-10 1069 783 1381 1528 1526 1389 10-15 573 589 1245 1390 1164 1080 15-20 20-25 273 278 744 798 1032 1056 470 477 390 266 703 594 25-30 225 193 30-35 89 89 35-40 40 >40 61 75 8 129 TABLE 9 SOFS STOPING AND DEVELOPMENT POPULATION TWA DISTRIBUTION Dust Cone. Grouping (mg/m3) Persons Cycle 1 Persons Cycle 2 Persons Cycle 3 Persons Cycle 4 Persons Cycle 5 Persons Cycle 6 0-0,2 36 151 0,2-0,4 0,4-0,6 1246 1839 349 2761 1886 3876 2045 4051 2115 3229 932 2610 0,6-0.8 0,8-1,0 1,0-1,2 >1,2 2152 841 1439 345 1213 1351 331 996 1699 690 1887 84 812 2573 495 1217 226 SOFS UNDERGROUND ROVING POPULATION TWA DISTRIBUTION Dust Cone. Grouping (mg/m3) Persons Cycle 1 Persons Cycle 2 Persons Cycle 3 Persons Cycle 4 Persons Cycle 5 Persons Cycle 6 0-0,2 0,2-0,4 325 1957 423 1601 63 1096 196 1616 537 1878 16 622 0,4-0,6 1067 639 1412 1111 900 948 0,6-0,8 0,8-1,0 1,0-1,2 259 556 144 567 187 77 1259 198 334 >1,2 594 107 SOFS SURFACE POPULATION TWA DISTRIBUTION Dust Cone. Persons Persons Persons Persons Persons Persons Grouping (mg/m3) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-0,2 68 148 331 41 190 159 0,2-0,4 0,4-0,6 0,6-0,8 681 1042 581 1247 981 637 654 605 1840 558 344 403 467 214 133 104 84 0,8-1,0 397 545 6 72 184 1,0-1,2 4 5 26 >1,2 89 191 130 TABLE 10 SOFS STOPING AND DEVELOPMENT POPULATION QUARTZ DISTRIBUTION Quartz Persons Persons Persons Persons Persons Persons Grouping (%) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-5 5-10 1064 3973 632 3572 830 3811 2749 1804 2312 876 875 4710 10-15 2346 2413 4305 2009 2393 1594 15-20 335 343 241 1240 1221 379 20-25 144 41 199 25-30 30-35 35-40 66 >40 SOFS UNDERGROUND ROVING POPULATION QUARTZ DISTRIBUTION Quartz Persons Persons Persons Persons Persons Persons Grouping (%) 0-5 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 633 853 288 334 489 1766 5-10 2696 1660 1588 3062 998 777 10-15 367 607 596 201 1522 633 15-20 99 99 243 383 20-25 25-30 30-35 35-40 >40 201 SOFS SURFACE POPULATION QUARTZ DISTRIBUTION Quartz Persons Persons Persons Persons Persons Persons Grouping (%) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-5 1040 1048 766 1357 665 812 5-10 421 867 1271 444 110 599 10-15 780 515 678 139 282 13 15-20 85 101 257 103 554 65 20-25 30 12 13 25-30 4 30-35 35-40 >40 131 TABLE 11 WEST WITS. STOPING AND DEVELOPMENT POPULATION TWA DISTRIBUTION Dust Cone. Grouping (mg/m3) Persons Cycle 1 Persons Cycle 2 Persons Cycle 3 Persons Cycle 4 Persons Cycle 5 Persons Cycle 6 0-0,2 2277 1878 3527 4258 5427 4086 0,2-0,4 11326 15966 22347 22159 29249 18188 0,4-0,6 14151 15085 8793 13265 7584 15172 0,6-0.8 6696 3389 2570 2685 1062 1668 0,8-1,0 2722 1066 1328 0 799 765 1,0-1,2 573 763 0 0 0 339 >1,2 1526 646 171 0 0 293 WEST WITS. UNDERGROUND ROVING POPULATION TWA DISTRIBUTION Dust Cone. Grouping (mg/m3) Persons Cycle 1 Persons Cycle 2 Persons Cycle 3 Persons Cycle 4 Persons Cycle 5 Persons Cycle 6 0-0,2 2229 800 2530 2077 6672 0,2-0,4 10274 12350 16661 16114 13974 0,4-0,6 9751 11155 7830 7200 6873 0,6-0,8 3369 3219 1951 4829 4778 0,8-1,0 2593 190 1388 995 954 1,0-1,2 461 0 0 211 217 >1,2 561 370 0 0 78 WEST WITS. SURFACE POPULATION TWA DISTRIBUTION 5983 17588 6992 2536 540 377 1242 Dust Cone. Grouping (mg/m3) Persons Cycle 1 Persons Cycle 2 Persons Cycle 3 Persons Cycle 4 Persons Cycle 5 Persons Cycle 6 0-0,2 0,2-0,4 0,4-0,6 0,6-0,8 0,8-1,0 2202 2785 3695 896 553 1972 4137 2426 769 74 2987 4194 2100 635 268 2970 5112 2338 549 67 3659 2885 2866 1024 210 2000 3032 906 592 366 1,0-1,2 149 0 80 205 180 0 >1,2 312 0 125 0 181 56 132 TABLE 12 WEST WITS. STOPING AND DEVELOPMENT POPULATION QUARTZ DISTRIBUTION Quartz Grouping (%) 0-5 Persons Cycle 1 Persons Cycle 2 Persons Cycle 3 Persons Cycle 4 Persons Cycle 5 Persons Cycle 6 1443 1502 2735 2800 2863 2259 5-10 10-15 15-20 20-25 7174 13758 4968 5066 7876 13742 5604 3402 10583 19727 3966 1247 9775 17270 9678 1582 14392 15422 4748 2502 15910 14031 6988 1089 25-30 30-35 335 2382 382 647 3808 356 204 303 779 960 533 0 35-40 >40 3105 1378 3224 1390 49 49 128 206 339 WEST WITS. UNDERGROUND ROVING POPULATION QUARTZ DISTRIBUTION Quartz Persons Persons Persons Persons Persons Persons Grouping (%) Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 0-5 4005 4488 6521 5787 7279 8631 5-10 6210 5516 14897 12185 11769 9374 10-15 7747 8392 6283 6588 9340 11308 15-20 4257 3844 592 3517 2148 3280 20-25 2392 2775 1247 1846 1553 520 25-30 695 420 345 592 146 1085 30-35 3025 2599 25 35-40 416 181 >40 1085 1153 661 661 1140 653 WEST WITS. SURFACE POPULATION QUARTZ DISTRIBUTION Quartz Persons Persons Persons Persons Persons Persons Grouping (%) 0-5 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 1196 1015 2408 2164 2797 2821 5-10 2433 2316 3758 4116 3511 1849 10-15 3324 2509 2443 3305 2518 1664 15-20 1616 1713 803 928 1623 40 20-25 1191 1093 657 69 186 835 25-30 577 577 538 289 194 362 30-35 7 7 95 95 264 139 35-40 39 52 >40 501 297 233 78 133 Figure 1 Eastern region stoping and development population TWA distribution (half yearly cycles Jan. 1992 to Jun. 1994) N)OOO OO o o Population 0OOO0 134 14000 Figure 2 Eastern region stoping and development population TWA distribution N)O O H $ > CQS' 3 <o o "czO Q* CQ 70 - Figure 3 Eastern region underground roving population (half yearly cycles Jan. 1992 to Jun. 1994) 135 136 Population KJ 20000 Figure 4 Eastern region total underground roving population TW A distribution 137 Percentage of population ocnooiocnocnooio v k) Figure 5 Eastern region surface population TW A distribution (half yearly cycles Jan. 1992 to Jun. 1994) oO oOOo ooO OO cn N) O --* cn Population 3000 Figure 6 Eastern region total surface population TW A distribution --* o 138 cn 139 Percentage of population ) C*> cno DO O o MD V M CoO o CO o o> o Mo o "coO 3' CQ CQ CQ 3u > Figure 7 Elsburg region stoping and development population TW A distribution (half yearly cycles Jan. 1992 to Jun. 1994) Population 20000 Figure 8 Elsburg region total stoping and development population TW A distribution 140 100 Figure 9 Elsburg region underground roving population TW A distribution (half yearly cycles Jan. 1992 to Jun. 1994) 141 14000 - Figure 10 Elsburg region total underground roving population TW A distribution 142 [ 09 143 Percentage of population -* n) co cn ooooo o Figure 11 Elsburg region surface population TW A distribution (half yearly cycles Jan. 1992 to Jun. 1994) o ooooooo CJ C/1 o CJ o o NJ cn o Population K) o o 144 4500 Figure 12 Elsburg region total surface population TW A distribution _k C/l o _k o o cn o 145 PERCENTAGE OF POPULATION i8 k 70 , Figure 13 Klerksdorp region stoping and development population TW A distribution (half yearly cycles Jan. 1992 to Jun. 1994) L o o o To Population 70000 7 Figure 14 Klerksdorp region total stoping and development population TW A distribution 146 147 Figure 15 Klerksdorp region underground roving population distribution (half yearly cycles Jan. 1992 to Jun. 1994) 00009 </! o o o o & o oo OJo oo o Population o o o o 148 OO o Figure 16 Klerksdorp region total underground roving population TW A distribution 149 Figure 17 Klerksdorp region surface population TW A distribution (half yearly cycles Jan. 1992 to Jun. 1994) o o o o CO o o o Population 12000 - Figure 18 Klerksdorp region total surface population TW A distribution o o 150 OO o Figure 19 NOFS region stoping and development population TW A distribution (half yearly cycles Jan. 1992to Jun. 1994) oO8 o CD o 8 o O o o o o Population 120000 Figure 20 NOFS region stoping and development population TW A distribution s o o o 152 fO o o o o ca3 o "cO o' CO 153 Percentage of population --i 3 CO co CZ3Q* CO o ) ] oI k> V K) Figure 21 NOFS region total underground roving population TW A distribution (half yearly cycles Jan. 1992 to Jun. 1994) 00006 154 Population Figure 22 NOFS region total underground roving population TW A distribution 155 Percentage of population H > t3o 3 to o "cO o` CO Figure 23 NOFS region surface population T W A distribution (half yearly cycles Jan. 1992 to Jun. 1994) 10000 Figure 24 NOFS region total surface population TW A distribution 156 157 Percentage of population Figure 25 Southern OFS region stoping and development population TW A distribution (half yearly cycles Jan. 1992 to Jun. 1994) 20000 Figure 26 Southern OFS region stoping and development population TW A distribution 158 155 Figure 27 Southern OFS underground roving population TW A distribution (half yearly cycles Jan. 1992 to Jun. 1994) 10000 Figure 28 Southern OFS region total underground roving population TW A distribution 160 161 Figure 29 SOFS surface population TW A distribution (half yearly cycles Jan. 1992 to Jun. 1994) 162 Population MOOO COooo ooo 5000 - Figure 30 Southern OFS region total surface population TW A distribution --k ooo 163 Percentage of population Figure 31 W est Wits, stoping and development population TW A distribution (half yearly cycles Jan. 1992 to Jun. 1994) 140000 Figure 32 W est Wits, region total sloping and development population TW A distribution 164 165 Percentage of population ooiocnocnocnocno cn OO H > c3a 3 co T3 (O V ro Figure 33 W est Wits, region underground roving population TW A distribution (half yearly cycles Jan. 1992 to Jun. 1994) 90000 Figure 34 W est Wits, region underground roving population TW A distribution 166 167 Figure 35 W est Wits, surface population TW A distribution (half yearly cycles Jan. 1992 to Jun. 1994) 25000 Figure 36 W est Wits, region total surface population TWA distribution 168 Population 169 ? CO o to cn & Figure 37 Eastern region total stoping and development population quartz distribution (half yearly cycles Jan. 1992 to Jun. 1994) O6 K> o8 ooo 03o oo Population 16000 Figure 38 Eastern region total stoping and development population quartz distribution 0>ooo 170 NJOoo 171 Figure 39 Eastern region underground roving population quartz distribution (half yearly cycles Jan. 1992 to Jun. 1994) o o 8 o O o N) & o> 00 o Population 14000 Figure 40 Eastern region total underground roving population quartz distribution 172 8 O O o 173 Figure 41 Eastern region surface population quartz distribution (half yearly cycles Jan. 1992to Jun. 1994) 174 Population Qc)O 'Co 0s C--Qi o C3O 3500 Figure 42 Eastern region total surface population quartz distribution 175 Figure 43 Elsburg region sloping and development population quartz distribution (half yearly cycles Jan 1992 to Jun. 1994) 176 Population AO 18000 - Figure 44 Elsburg region total stoping and development population quartz distribution 177 Figure 45 Elsburg region underground roving population quartz distribution (half yearly cycles Jan. 1992 to Jun. 1994) o oo o o Population oo o o o 178 12000 Figure 46 Elsburg region total underground roving population quartz distribution o o OO 179 Percentage of population ro M cj cu -t* ocnocnoqnocno ] u> cn k] cCOo -fc. Figure 47 Elsburg region surface population quartz distribution (half yearly cycles Jan. 1992 to Jun. 180 3000 Figure 48 Elsburg region total surface population quartz distribution 181 Percentage of population D Figure 49 Klerksdorp region stoping and developm ent quartz distribution (half yearly cycles Jan. 1992 to Jun. 1994) - 00009 182 Population Figure 50 Klerksdorp region total stoping and development population quartz distribution CO cno cnotnocno N) W --- --* NJ Percentage of population 183 P o Figure 51 Kierksdorp region underground roving population quartz distribution (half yearly cycles Jan. 1992 to Jun. 1994) 45000 Figure 52 Klerksdorp region total underground roving population quartz distribution 184 cno Percentage of population ocnocnocnoc/io 185 Figure 53 Klerksdorp region surface population quartz distribution (half yearly cycles Jan. 1992 to Jun. 1994) o o o o o o tn cn$OO oo Population 186 8000 - Figure 54 Klerksdorp region total surface population quartz distribution o o M CJ Oo O O 187 Figure 55 NOFS region stoping and development population quartz distribution (half yearly cycles Jan. 1992 to Jun. 1994) 80000 Figure 56 NOFS region total stoping and development population quartz distribution 188 189 Percentage of population V O Figure 57 NOFS region underground roving population quartz distribution (half yearly cycles Jan. 1992 to Jun. 1994) 60000 Figure 58 NOFS region total underground roving population quartz distribution 190 191 Figure 59 NOFS region surface population quartz distribution (half yearly cycles Jan. 1992 to Jun. 1994) 0009 -oood oooo conoo 6 oo Population CJOoO 192 N)OOO ooo Figure 60 NOFS region total surface population quartz distribution 193 Figure 61 SOFS region stoping and development population quartz distribution (half yearly cycles Jan. 1992 to Jun. 1994) 194 Population 20000 Figure 6Z S 0F S region total stoping and development population quartz distribution 195 Figure 63 SOFS underground roving population quartz distribution (half yearly cycles Jan. 1992 to Jun. 1994) 12000 Figure 64 SOFS region total underground roving population quartz distribution 196 6 197 Figure 65 SOFS region surface population quartz distribution (half yearly cycles Jan. 1992 to Jun. 1994) 6000 Figure 66 SOFS region toyal surface population quartz distribution 198 199 Percentage of population O ficJ P- N CO --iO c "2. Z3* CO Figure 67 W est Wits, region stoping and development population quartz distribution (half yearly cycles Jan. 1992 to Jun. 1994) I 00008 200 Population & Figure 68 W est Wits, region total stoping and development population quartz distribution 201 Percentage of population N) N) CJ W -JX ocnotnocnocno cn h 3 Figure 69 W est Wits, region underground roving population quartz distribution (half yearly cycles 1992 to Jun. 1994) 202 Population O -Oc 030. N CQ gco. 3' (Q 60000 - Figure 70 W est WITS, region total underground roving population quartz distribution 203 Figure 71 W est W its, region surface population quartz distribution (half yearly cycles Jan. 1992 to Jun. 1994) 204 Population 20000 Figure 72 W est Wits, region total surface population quartz distribution