Document MMNoJG35rJdEew9JRbZN8e4Qy

CRITERIA FOR A RECOMMENDED STANDARD Occupational Exposure to Respirable Coal Mine Dust U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service Centers for Disease Control and Prevention National Institute for Occupational Safety and Health Education and Information Division Cincinnati, Ohio September 1995 For sale by the Superintendent of Documents; U.S. Government Printing Office, Washington, D.C. 20402 DISCLAIMER Mention of any company name or product does not constitute endorsement by the National Institute for Occupational Safety and Health. Copies of this and other NIOSH documents are available from National Institute for Occupational Safety and Health Publications Dissemination 4676 Columbia Parkway Cincinnati, OH 45226-1998 1 -800-35-NIOSH (1-800-356-4674) Fax number: (513) 533-8573 To receive other information about occupational safety and health problems, call 1-800-35-NIOSH (1-800-356-4674), or visit the NIOSH Home Page on the World Wide Web at http://www.cdc.gov/niosh/homepage.html DHHS (NIOSH) Publication No. 95-106 FOREWORD In the Federal Mine Safety and Health Act of 1977 (Public Law 95-164) and the Occupational Safety and Health Act of 1970 (Public Law 91-596), Congress declared that its purpose was to assure, insofar as possible, safe and healthful working conditions for every working man and woman and to preserve our human resources. In these Acts, the National Institute for Occupa tional Safety and Health (NIOSH) is charged with recommending occupational safety and health standards and describing exposure levels that are safe for various periods of employment, including but not limited to the exposures at which no worker will suffer diminished health, functional capacity, or life expectancy as a result of his or her work experience. By means of criteria documents, NIOSH communicates these recommended standards to regulatory agencies (including the Occupational Safety and Health Administration [OSHA] and the Mine Safety and Health Administration [MSHA]) and to others in the community of occupational safety and health. Criteria documents provide the scientific basis for new occupational safety and health standards. These documents generally contain a critical review of the scientific and technical information available on the prevalence of hazards, the existence of safety and health risks, and the adequacy of control methods. In addition to transmitting these documents to the Department of Labor, NIOSH also distributes them to health professionals in academic institutions, industry, organized labor, public interest groups, and other government agencies. This criteria document reviews available information about the adverse health effects associated with exposure to respirable coal mine dust. Epidemiological studies have clearly demonstrated that miners have an elevated risk of developing occupational respiratory diseases when they are exposed to respirable coal mine dust over a working lifetime at the current MSHA permissible exposure limit (PEL) of 2 mg/m3. The exposure limit of 1 mg/m3 recommended in this document is based on an evaluation of health effects data, sampling and analytical feasibility, and techno logical feasibility. However, this recommended exposure limit (REL) does not ensure that miners exposed at this concentration over a working lifetime will have a zero risk of developing occupational respiratory diseases. Therefore, NIOSH recommends additional measures to protect miners' health: (1) keeping worker exposures as far below the REL as feasible through the use of engineering controls and work practices, (2) frequent monitoring of worker exposures, and (3) participation of miners in the recommended medical screening and surveillance program. Future research may provide new and more effective methods for minimizing occupational health risks among coal miners, including new methods for controlling exposures to respirable coal mine dust, more accurate and reliable measures of worker exposures, improved methods for earlier detection of disease, and new medical interventions to halt or reverse disease progression. iii If future developments permit a lower exposure limit that is both technologically feasible and prudent for the public health, NIOSH will revise its recommended standard. Until then, adherence to the REL of 1 mg/m3 will minimize the risk of developing occupational respiratory diseases. Linda Rosenstock, M.D., M.P.H. Director, National Institute for Occupational Safety and Health Centers for Disease Control and Prevention IV ABSTRACT This document examines the occupational health risks associated with exposures to respirable coal mine dust over a working lifetime. Such exposures are associated with the development of occupational respiratory diseases, including simple coal workers' pneumoconiosis (CWP), pro gressive massive fibrosis (PMF), and chronic obstructive pulmonary disease (COPD). Epidemi ological studies have clearly demonstrated that miners have an elevated risk of developing simple CWP, PMF, or deficits in lung function when they are exposed to respirable coal mine dust over a working lifetime at the current Mine Safety and Health Administration (MSHA) permissible exposure limit (PEL) of 2 mg/m3. Coal miners who are exposed to respirable crystalline silica are also at risk of developing silicosis or mixed-dust pneumoconiosis. The National Institute for Occupational Safety and Health (NIOSH) recommends that exposures to respirable coal mine dust be limited to 1 mg/m3 as a time-weighted average (TWA) concen tration for up to 10 hr/day during a 40-hr workweek, measured according to current MSHA methods. NIOSH recommends that sampling be conducted with a device that operates in accordance with the NIOSH accuracy criteria and the international definition of respirable dust. The 1-mg/m3 REL is equivalent to 0.9 mg/m3 when measured according to these NIOSH recommended sampling criteria. The NIOSH REL represents the upper limit of exposure for each worker during each work shift and shall not be adjusted upward to account for measurement uncertainty. To minimize the risk of adverse health effects, exposures shall be kept as far below the REL as feasible using engineering controls and work practices. Recommendations are made for minimizing the occupational health risks encountered by under ground and surface coal miners. These recommendations pertain to respirable coal mine dust sampling to monitor worker exposures, use of personal protective equipment (including training and fit-testing for the use of respirators), and medical screening and surveillance examinations (including preplacement and periodic chest X-rays and spirometry). v CONTENTS Foreword..........................................................................................................................................iii Abstract.............................................................................................................................................. v Abbreviations.................................................................................................................................. xvi Glossary......................................................................................................................................... xviii Acknowledgments.......................................................................................................................... xxii 1 RECOMMENDATIONS FOR A COAL MINE DUST STANDARD.................. 1 1.1 Definitions......................................................................................................................1 1.1.1 1.1.2 1.1.3 1.1.4 1.1.5 1.1.6 Miner or Coal Miner..........................................................................................1 Ex-Miner............................................................................................................ 1 Coal Mine ......................................................................................................... 1 Mine Operator.................................................................................................. 2 Surface Coal Mine............................................................................................ 2 Surface Work Area of an Underground Coal Mine....................................... 2 1.2 Recommended Exposure Limits (RELs) for Respirable Coal Mine Dust and Respirable Crystalline Silica....................................................2 1.2.1 RELs.................................................................................................................. 2 1.2.2 Sampling and Analysis...................................................................................... 3 1.3 Exposure Monitoring......................................................................................................3 1.3.1 1.3.2 1.3.3 1.3.4 1.3.5 Initial Exposure Monitoring Survey................................................................ 3 Periodic Exposure Monitoring..........................................................................3 Sampler Performance Criteria..........................................................................3 Worker Notification......................................................................................... 3 Intake Air Concentrations................................................................................4 1.4 Medical Screening and Surveillance Program for Underground and Surface Coal Miners ................................................................... 4 1.4.1 General...............................................................................................................4 1.4.2 Preplacement and Periodic Medical Examinations.......................................... 4 1.5 Posting........................................................................................................................... 5 vii Coal Mine Dust 1.6 Engineering Controls and Work Practices....................................................................5 1.7 Respiratory Protection...................................................................................................5 1.7.1 General Considerations...................................................................................... 5 1.7.2 Respiratory Protection Program.......................................................................6 1.7.3 Respirator Selection......................................................................................... 6 1.8 Informing Workers of the Hazards................................................................................ 7 1.8.1 Notification of Hazards...................................................................................... 7 1.8.2 Training ............................................................................................................ 7 1.9 Sanitation and Hygiene...................................................................................................7 1.9.1 Smoking............................................................................................................ 7 1.9.2 Drinking Water...................................................................................................7 1.9.3 Showering, Changing, and Toilet Facilities....................................................7 1.10 Recordkeeping............................................................................................................... 8 1.10.1 Records of Exposure Monitoring.......................................................................8 1.10.2 Medical Records................................................................................................8 1.10.3 Availability of Records...................................................................................... 8 1.10.4 Transfer of Records ......................................................................................... 8 2 INTRODUCTION ............................................................................................................. 9 2.1 Purpose............................................................................................................................9 2.2 Scope...............................................................................................................................9 2.3 NIOSH Activities and Programs for Coal Miners..................................................... 10 2.4 Health Effects Studies................................................................................................. 10 2.5 Other Standards and Recommendations..................................................................... 11 2.5.1 2.5.2 2.5.3 2.5.4 2.5.5 MSHA..............................................................................................................11 OSHA ..............................................................................................................12 ACGIHTLV.................................................................................................... 12 WHO Exposure Limit.....................................................................................12 Limits in Other Countries .............................................................................. 12 3 PROPERTIES, PRODUCTION, AND POTENTIAL FOR EXPOSURE..............14 3.1 Chemical and Physical Properties of Coal Mine Dust.............................................. 14 vm Contents 3.1.1 Coal and its Characteristics.............................................................................. 14 3.1.2 Composition of Coal Mine Dust.....................................................................14 3.2 Coal Production and Mining Methods.....................................................................18 3.2.1 Underground Coal Mining Methods...............................................................18 3.2.1.1 Room-and-Pillar Mining ................................................................. 21 3.2.1.2 Longwall Mining..............................................................................22 3.2.1.3 Additional Underground Coal Mining Methods ............................22 3.2.1.4 Roof Supports.................................................................................... 23 3.2.1.5 Control of Gases and Airborne Dust............................................23 3.2.2 Surface Coal Mining Methods....................................................................... 23 3.2.2.1 Drilling ............................................................................................. 26 3.2.2.2 Blasting............................................................................................. 26 3.2.2.3 Overburden Excavation (Stripping)..................................................26 3.2.2.4 Coal Loading ....................................................................................27 3.2.2.5 Coal Haulage ....................................................................................27 3.2.2.6 Reclamation....................................................................................... 27 3.2.2.7 Coal Preparation.................................................................................27 3.2.2.8 Transportation to Consumers........................................................... 28 3.3 Number of Miners Potentially Exposed in U.S. Coal Mines.................................. 29 3.3.1 Occupational Exposures in U.S. Coal Mines..................................................29 3.3.1.1 Exposures to Respirable Coal Mine Dust........................................ 29 3.3.1.2 Exposure to Respirable Crystalline Silica........................................ 30 3.3.2 Occupational Exposures in Small Mines........................................................ 30 4 HEALTH EFFECTS OF EXPOSURE TO RESPIRABLE COAL MINE DUST....................................................................................................32 4.1 Description of Occupational Respiratory Diseases in Coal Miners......................32 4.1.1 Historical Perspective .................................................................................... 32 4.1.2 Simple CWP and PMF.................................................................................... 33 4.1.2.1 Radiographic Classification of Simple CWP and PMF................33 4.1.2.2 Pathological Classification of CWP and PMF ............................... 36 4.1.2.3 Relationship Between Chest X-Rays, Pathology, and Lung Dust Content.....................................................................37 4.1.3 Silicosis............................................................................................................. 38 4.1.3.1 Chronic Silicosis.................................................................................38 4.1.3.2 Complicated Silicosis........................................................................39 4.1.3.3 Accelerated Silicosis ........................................................................39 IX Coal Mine Dust 4.1.3.4 Acute Silicosis..................................................................................39 4.1.4 Mixed-Dust Pneumoconiosis........................................................................ 39 4.1.5 COPD..............................................................................................................40 4.2 Epidemiological Studies..............................................................................................41 4.2.1 Studies of Simple CWP, PMF, and Silicosis..................................................41 4.2.1.1 U.S. Studies from the 1960s.............................................................. 41 4.2.1.2 U.S. Studies from 1970 to Present .................................................. 42 4.2.1.3 Studies Outside the United States..................................................... 47 4.2.1.4 Studies of the Rapid Development of PMF...................................49 4.2.1.5 Studies of the Role of Silica............................................................50 4.2.1.6 Radiographic Small Opacities Among Nonminers......................... 51 4.2.2 Studies of COPD in Coal Miners.....................................................................51 4.2.2.1 Chronic Bronchitis ...........................................................................52 4.2.2.2 Emphysema....................................................................................... 52 4.2.2.3 Decreased Lung Function..................................................................53 4.2.3 Predicted Prevalence of Simple CWP, PMF, and Decreased Lung Function Among U.S. and U.K. Coal Miners.................................. 57 4.2.3.1 Predicted Prevalence of Simple CWP and PMF ............................ 57 4.2.3.2 Predicted Prevalence of Decreased Lung Function......................... 57 4.2.4 Surface Coal Miners....................................................................................... 60 4.2.4.1 Health Hazard Evaluations Among Drillers at U.S. Surface Coal Mines ........................................................................60 4.2.4.2 Medical Evaluations of Miners at U.S. Bituminous Surface Coal Mines, 1972-73 ..................................................... 61 4.2.4.3 Medical Evaluations of Miners at U.S. Anthracite Surface Coal Mines, 1984-85 ..................................................... 61 4.2.4.4 Study of U.K. Surface Coal Miners.................................................. 61 4.2.5 Studies of Mortality Among Coal Miners..................................................... 62 4.2.5.1 Mortality Related to Exposure to Respirable Coal Mine Dust .............................................................................. 63 4.2.5.2 Studies of Lung Cancer and Stomach Cancer Among Coal Miners.................................................................................... 64 4.3 Animal and Human Studies of Lung Dust Burden and Cellular Mechanisms................................................................................................................ 65 4.3.1 4.3.2 4.3.3 Alveolar Clearance Mechanisms.....................................................................65 Studies of Alveolar Clearance in Animals and Relevance to Dust-Exposed Workers........................................................................... 67 Biological Factors in Individual Susceptibility to Fibrosis............................ 67 x Contents 5 ENVIRONMENTAL MONITORING ........................................................................70 5.1 Current Sampling Criteria.......................................................................................... 70 5.1.1 Characteristics of the Currently Approved Sampling Device......................70 5.1.2 Current Regulations for Sampler Certification...............................................70 5.1.3 Construction of the Sampling Device........................................................... 71 5.2 Recommended Sampling Criteria..............................................................................71 5.3 Basis for Particle-Size-Selective Sampling .............................................................. 73 5.3.1 5.3.2 5.3.3 Early Definitions of Particle-Size-Selective Sampling.................................. 73 Deposition and Clearance of Particles in the Human Respiratory Tract.......................................................................................... 75 Deposition-Based and Penetration-Based Sampling Criteria ......................76 5.4 Conversion Factor for Comparing Current and Recommended Sampling Criteria.......................................................................................................77 5.5 Current Sampling Program.......................................................................................... 82 5.5.1 MSHA Inspector Sampling............................................................................. 82 5.5.2 Coal Mine Operator Sampling........................................................................82 5.5.3 Ventilation System and Methane and Dust Control Plan ............................ 84 5.6 Sampling Recommendations....................................................................................... 85 5.6.1 Sampling Strategy Issues................................................................................. 85 5.6.2 5.6.3 5.6.1.1 Frequency of Sampling.....................................................................85 5.6.1.2 Number of Exposure Measurements ............................................85 5.6.1.3 Validity of Exposure Measurements ...............................................86 5.6.1.4 Representative Exposure Measurements.........................................86 5.6.1.5 Reliable Classification of Work Environments as Acceptable or Unacceptable........................................................... 87 5.6.1.6 Additional Personal Monitoring........................................................ 87 Single, Full-Shift Sampling ...........................................................................87 Types of Environmental Monitoring.............................................................. 88 5.6.3.1 Personal Sampling.............................................................................. 88 5.6.3.2 Studies Comparing Personal and Area Monitoring......................... 89 5.6.3.3 Area Sampling.................................................................................... 90 5.7 Analytical Methods.......................................................................................................90 6 MEDICAL SCREENING AND SURVEILLANCE ............................................... 92 6.1 Objectives of Medical Screening and Surveillance .................................................92 xi Coal Mine Dust 6.1.1 Definitions....................................................................................................... 92 6.1.2 Criteria for Medical Screening and Surveillance Tests ............................... 92 6.2 Current Medical Surveillance Program and Recommended Revisions................93 6.2.1 6.2.2 6.2.3 6.2.4 Current Chest X-Ray Program....................................................................... 93 Spirometry Recommendations........................................................................94 Recommendations for Surface Coal Miners..................................................94 Current and Recommended Option to Work in Low-Dust Environment .................................................................................................94 6.3 Recommended Medical Screening and Surveillance Program for Underground and Surface Coal Miners............................................................95 6.3.1 Worker Participation....................................................................................... 95 6.3.2 NIOSH-Approved Facilities...........................................................................96 6.3.3 Smoking.......................................................................................................... 96 6.4 Interpretation of Medical Screening Examinations ............................................... 96 6.4.1 6.4.2 6.4.3 6.4.4 Evidence of Pneumoconiosis on Chest X-Rays........................................... 96 Evaluation of Spirometric Examinations........................................................ 97 Worker Notification....................................................................................... 97 Medical Followup and Intervention.............................................................. 98 6.5 Lung Function Tests for Medical Screening and Surveillance................................98 6.5.1 6.5.2 6.5.3 6.5.4 6.5.5 6.5.6 Determining Obstructive and Restrictive Ventilatory Defects......................98 Quality Control and Instrumentation.............................................................. 99 ATS Acceptability and Reproducibility Criteria for Spirometry Tests..................................................................................... 102 Cross-Sectional Spirometry Testing......................................................... 103 Longitudinal Spirometry Testing............................................................... 104 Additional Medical Tests of Lung Function............................................ 105 6.6 Other Issues Pertaining to Recommendations for Medical Screening and Surveillance................................................................................. 105 6.6.1 6.6.2 Evaluating the Work-Relatedness of COPD Among Coal Miners.............................................................................................. Medical Intervention Strategies............................................................... 105 106 7 BASIS FOR THE RECOMMENDED STANDARD ....................................108 7.1 The NIOSH REL for Respirable Coal Mine Dust............................................... 108 7.2 Basis for the Current U.S. Standard..................................................................... 108 xu Contents 7.3 Basis for the NIOSHREL.................................................................................... 109 7.3.1 Epidemiological Studies Evaluated ........................................................ 109 7.3.2 Estimated Risks of Occupational Respiratory Diseases......................... 115 7.3.2.1 Background Prevalence...................................................................115 7.3.2.2 Excess Risk in U.S. Coal Miners............................................... 116 7.3.2.3 Risk Estimates at Low Exposures............................................... 119 7.3.2.4 Excess Risk of PMF at Age 65 by Duration and Intensity of Exposure........................................................ 119 7.3.3 Expected Long-Term Average Exposures When Work-Shift Exposures Are Below the REL......................................... 122 7.3.4 Factors Considered in Determining the REL............................................ 124 7.3.4.1 Strength of Evidence .................................................................. 7.3.4.2 Limitations of the Risk Estimates............................................... 7.3.4.3 Statistical Models Evaluated ..................................................... 7.3.4.4 Comparison of Predicted and Observed Prevalences of Simple CWP..................................................... 7.3.4.5 Cumulative Exposure As the Metric of Exposure...................... 7.3.4.6 Coal Rank.................................................................................... 7.3.4.7 Additional Measures to Minimize the Risk of Adverse Health Effects........................................................ 124 124 125 126 127 127 127 7.4 Sampling and Analytical Feasibility..................................................................... 128 7.5 Applicability of the REL to Workers Other Than Underground Coal Miners ................................................................................. 128 7.5.1 Surface Coal Miners................................................................................. 128 7.5.2 Workers Exposed to Coal Dust in Occupations Other Than Mining ........................................................................................... 129 7.6 Recommended Exposure Limit for Respirable Crystalline Silica................................................................................................. 129 7.7 Technological Feasibility of Keeping Worker Exposures Below the REL for Respirable Coal Mine Dust ............................................... 130 7.7.1 7.7.2 Percentage of Samples Below the REL .................................................. Sources of Dust and Control Methods Used in Underground Coal Mines........................................................................ 130 131 7.7.2.1 Sources ....................................................................................... 131 1.1.22 Controls....................................................................................... 131 xiii Coal Mine Dust 1.13 Feasibility of Keeping Exposures Below the Current MSHA PEL for Respirable Coal Mine Dust......................................... 133 7.7.4 Economic Considerations for Keeping Exposures Below the REL . . . 134 8 METHODS FOR PROTECTING COAL MINERS................................................135 8.1 Informing Workers About Hazards ..................................................................... 135 8.1.1 Training Programs..................................................................................... 135 8.1.2 Posting....................................................................................................... 135 8.2 Establishing Written Emergency Procedures......................................................... 136 8.3 Engineering Controls.............................................................................................. 136 8.3.1 Dust Control.............................................................................................. 136 8.3.2 Ventilation................................................................................................. 136 8.4 Work Practices....................................................................................................... 137 8.4.1 Worker Isolation........................................................................................ 137 8.4.2 Sanitation and Hygiene.............................................................................. 137 8.5 Personal Protective Equipment.............................................................................. 138 8.5.1 Protective Clothing and Equipment........................................................ 138 8.5.2 Respiratory Protection.............................................................................. 138 8.5.2.1 The Need for Respiratory Protection......................................... 138 8.5.2.2 Selection of Respirators............................................................... 138 8.5.2.3 Respiratory Protection Program.................................................. 139 8.6 Exposure Monitoring.............................................................................................. 140 8.7 Medical Screening and Surveillance..................................................................... 140 8.8 Smoking Cessation................................................................................................. 143 8.9 Recordkeeping....................................................................................................... 143 8.10 Protecting Contract Miners..................................................................................... 143 9 RESEARCH NEEDS....................................................................................................144 REFERENCES ................................................................................................... 147 PUBLICATIONS EXAMINED........................................................................................ 185 xiv Contents APPENDICES A. Concentrations of Respirable Coal Mine Dust and Respirable Crystalline Silica in Underground and Surface Coal Mines..................................................... 219 B. Concentrations of Respirable Coal Mine Dust and Respirable Crystalline Silica in Samples Required by 30 CFR 90 ........................................................... 256 C. Optional Dust Control Techniques for Coal Mining Environments...................... 268 D. Methods for Controlling Respirable Coal Mine Dust from Overburden Drilling at Surface Coal Mines ........................................................ 278 E. Interpretation of Pulmonary Function Tests: Spirometry......................................286 F. NIOSH Occupational History Questionnaire from the Coal Workers' X-ray Surveillance Program........................................................................................ 299 G. Technical Considerations in the Use of Spirometry in Screening and Surveillance of Mineral-Dust-Exposed Workers......................................................302 H. The Black Lung Benefits Program...............................................................................306 I. Confidence Limit on Minimum Accurately Quantifiable (MAQ) Concentration of Respirable Coal Mine Dust........................................................ 311 J. Variability in Sampling and Analytical Methods......................................................... 318 K. Estimates of Exposure Variability and Exposure Parameters for Selected Designated Occupations.............................................................................................. 323 L. Validation of Predictions of Small Rounded Opacity Prevalence from Attfield and Morring [1992] ..................................................................................... 331 xv ACGIH AEC ANOVA ATS BAL BMRC BOM Btu CEN cfm CFR Cl CO CO2 COPD CPSU CWP DLCO Fed. Reg. FEVi FVC gh gh/m3 GSD HHE hr ILO ISO L L/min LLN XVI ABBREVIATIONS American Conference of Governmental Industrial Hygienists U.S. Atomic Energy Commission Analysis of variance American Thoracic Society Bronchoalveolar lavage British Medical Research Council U.S. Bureau of Mines British thermal unit Comite Europeen de Normalisation Cubic feet per minute Code of Federal Regulations Confidence interval Carbon monoxide Carbon dioxide Chronic obstructive pulmonary disease Coal mine dust personal sampler unit Coal workers' pneumoconiosis Diffusing capacity of the lung for carbon monoxide Federal Register Forced expiratory volume in 1 second Forced vital capacity Gram hour(s) Gram hour(s) per cubic meter Geometric standard deviation Health hazard evaluation Hour(s) International Labour Office International Standards Organization Liter(s) Liter(s) per minute Lower limit of normal LOD LOQ MAQ MCE mg/m'* mg-yr/m3 min ml MMD MMU MRE MSHA MW NIOSH n OSHA PEL psi PMF PMNs PVC REL RV SAR SCBA SCSR SD SIP SMR TLC TLV TNF TWA UCL UK use VC Abbreviations Limit of detection Limit of quantitation Minimum accurately quantifiable concentration Mixed cellulose ester Milligram(s) per cubic meter Milligram year(s) per cubic meter Minute(s) Milliliter(s) Mass median diameter Mechanized mining unit Mining Research Establishment of the National Coal Board, London, England Mine Safety and Health Administration Maximum voluntary ventilation National Institute for Occupational Safety and Health Nanoliter(s) Occupational Safety and Health Administration Permissible exposure limit Pounds per square inch Progressive massive fibrosis Polymorphonuclear leukocytes Polyvinyl chloride Recommended exposure limit Residual volume Supplied-air respirator Self-contained breathing apparatus Self-contained self rescuer Arithmetic standard deviation Spot inspection program Standardized mortality ratio Total lung capacity Threshold limit value Tumor necrosis factor Time-weighted average Upper confidence limit United Kingdom United States Code Vital capacity xvu GLOSSARY Active workings: Any place in a coal mine where miners are normally required to work or travel [30 CFR 70.2]. Aerodynamic diameter: The diameter of a sphere with a density 1 g/cm and with the same stopping time as the particle. Particles of a given aerodynamic diameter move within the air spaces of the respiratory system identically, regardless of density or shape. Black lung: A common term used to refer to occupational respiratory disease in miners [Weeks and Wagner 1986]. Chronic obstructive pulmonary disease (COPD): Includes chronic bronchitis, impaired lung function, and emphysema. COPD is characterized by the irreversible (although sometimes variable) obstruction of lung airways. Clearance: The translocation, transformation, and removal of deposited particles from the respiratory tract [Lioy et al. 1984]. Coalface: The exposed area of a coalbed from which coal is extracted [ElA 1989]. Coalfines: Coal with a maximum particle size that is usually less than one-sixteenth of an inch and rarely above one-eighth of an inch [EIA 1989]. Coal rank: A classification of coal based on the fixed carbon, volatile matter, and heating value of the coal. Coal rank indicates the progressive geological alteration (coalification) from lignite to anthracite [EIA 1989]. Coal type: A classification of coal based on physical characteristics or microscopic constituents [EIA 1989]. Coal workers' pneumoconiosis (CWP): A chronic dust disease of the lung arising from employment in an underground coal mine [30 USC 902]. In workers who are or have been exposed to coal mine dust, diagnosis is based on the radiographic classification of the size, shape, profusion, and extent of opacities in the lungs. Coefficient of variation (CV): The CV is a measure of relative dispersion; it is also known as relative standard deviation and defined as the standard deviation/mean [Leidel et al. 1977]. xvm Glossary Concentration: The amount of a substance contained per unit volume of air [30 CFR 70.2]. Confidence interval (Cl), confidence limits (CLs): A range of values (determined by the degree of presumed random variability in the data) within which a parameter (e.g., a mean) is believed to lie with the specified level of confidence. The boundaries of a Cl are the CLs [Last 1983]. These include the lower confidence limit (LCL) and the upper confidence limit (UCL). Continuous mining: A mining method used in room-and-pillar mining in which the coal is removed from the coal face in one operation using a continuous mining machine. Conventional mining: A mining method used in room-and-pillar mining in which the coal face is cut so that it breaks easily when blasted (with either explosives or high-pressure air). The broken coal is then loaded onto conveyors or into shuttle carts for removal to the surface. Crystalline silica (orfree silica): Silicon dioxide (Si02). "Crystalline" refers to the orientation of SiC>2 molecules in a fixed pattern as opposed to a nonperiodic, random molecular arrangement defined as amorphous. The three most common crystalline forms of free silica encountered in general industry are quartz, tridymite, and cristobalite [NIOSH 1974]. In coal mines, the predominant form is quartz. Culm: Fine anthracite. Culm bank: The hillside where waste from anthracite mines is dumped. Deposition: The collection of inhaled airborne particles by the respiratory tract and the initial regional patterns of these deposited particles [Lioy et al. 1984]. District manager: The manager of the Coal Mine Safety and Health District in which the mine is located [30 CFR 70.2]. Geometric mean (GM): The GM is a measure of central tendency for a log-normal distribution [Leidel et al. 1977]. Geometric standard deviation (GSD): The GSD is a measure of relative dispersion (variability) of a lognormal distribution. Gob area: The area of subsidence that occurs when roof supports are removed during longwall mining and the area caves in. The gob area then supports the overlying strata. Engineering controls: Hazard controls designed into equipment and workplaces. Highwall: The unexcavated face of exposed overburden or coal in a strip pit. Inby: Toward the workings of a mine. Incidence: The frequency of occurrence of new cases of a disease for a given period. xix Coal Mine Dust Incidence rate: The rate at which new events occur in a population. The number of new events (e.g., new cases of a disease diagnosed or reported during a defined period) is divided by the number of persons in the population in which the cases occurred [Last 1983]. Inhalable dust: The particulate mass fraction of dust in the mine environment that is hazardous when deposited anywhere in the respiratory tract [ACGIH 1994]. Longwall mining: A system of mining in which long sections of coal (also called panels) up to 1,000 ft are removed by a cutting machine without leaving pillars of coal for support. A movable, powered roof support system is used to support the roof in the working area; when these supports are moved, the area (gob area) caves in and supports the overlying strata. Mechanized mining unit (MMU): A unit of mining equipment (including hand-loading equip ment) used for the production of material [30 CFR 70.2]. MRE instrument: The gravimetric dust sampler with a four-channel horizontal elutriator developed by the Mining Research Establishment of the National Coal Board, London, England [30 CFR 70.2]. Normal production shift: A production shift during which the amount of material produced in an MMU is at least 50% of the average production reported for the last set of five valid samples; or, the amount of material produced by a new MMU before five valid samples are taken [30 CFR 70.2]. Outby: Toward the shaft or entry of a mine. Overburden: Any material, consolidated or unconsolidated, that overlies a coal deposit. Over burden ratio refers to the amount of overburden that must be removed to excavate a given quantity of coal [EIA 1989]. Prevalence: The frequency of all current cases of a disease (old and new) occurring within specific populations at a particular time. Prevalence rate (ratio): The total number of all individuals who have an attribute or disease at a given time or during a given period divided by the population at risk of having the attribute or disease at this point in time or midway through the period [Last 1983]. Progressive massivefibrosis (PMF): Coal workers' complicated pneumoconiosis. Diagnosis is based on radiographic determination of the presence of large opacities of 1 cm or larger. Quartz: Crystalline silicon dioxide (Si02) not chemically combined with other substances and having a distinctive physical structure [30 CFR 70.2]. Regression analysis: Given data on a dependent variable Y and an independent variable X, regression analysis involves finding the best mathematical model (within some restricted form) to describe Y as a function of X or to predict Y from X. Most commonly, the model is linear. The xx Glossary logistic model is also common in epidemiology. Multiple regression analysis considers Y as a function of more than one independent variable [Last 1983]. Respirable coal mine dust: That portion of airborne dust in coal mines that is capable of entering the gas-exchange regions of the lungs if inhaled; by convention, a particle-size-selective fraction of the total airborne dust; includes particles with aerodynamic diameters less than approximately 10 pm. Respirable convention (Er): The target sampling curve for instruments approximating the respirable fraction. Er is defined at aerodynamic diameter D by ISO [1993], CEN [1993], and ACGIH [1994] in terms of the cumulative normal function <I> as: Er = Ej <J>[ln[DR/D]/cjR] where the indicated constants are Dr = 4.25 pm and or = ln[l.5], and the inhalable convention Ei is defined by Ej = 0.50 (1 + exp[-0.06 D]), D <100 pm Retention: The temporal distribution of uncleared particles in the respiratory tract [Lioy et al. 1984]. Room-and-pillar mining: A system of mining in which the mine roof is supported primarily by coal pillars that are left at regular intervals [EIA 1989]. Spoil: Overburden removed in gaining access to the coal during surface coal mining. Thoracic dust: The particulate mass fraction of dust in the mine environment that is hazardous when deposited anywhere within the lung airways and the gas-exchange region [ACGIH 1994]. Time-weighted average (TWA): Exposure of a worker over an 8-hr work shift as defined in 29 CFR 1910.1000(d)(1). Work practices: Procedures followed by employers and workers to control hazards. xxi ACKNOWLEDGMENTS This document was prepared by the staff of the National Institute for Occupational Safety and Health (NIOSH). Principal responsibility for this document rested with the Division of Standards Devel opment and Technology Transfer (DSDTT), Richard W. Niemeier, Ph.D., Director, and the Division of Respiratory Disease Studies (DRDS), Gregory R. Wagner, M.D., Director. Eileen D. Kuempel (DSDTT) was the project manager and developed the document. The contributions of the following NIOSH staff are gratefully acknowledged: Rochelle Althouse, Michael D. Attfield, Ph.D.; David L. Bartley, Ph.D.; Patricia L. Brower; Vincent Castranova, Ph.D.; Henry S. Chan; Christopher C. Coffey; Barbara L. Dames; Clayton B. Doak; John M. Dower; John L. Hankinson, Ph.D.; Paul A. Hewett, Ph.D.; Janet Hale; Michael Jacobsen, Ph.D. (visiting scientist); John E. Parker, M. D.; Laurence D. Reed; Thomas B. Richards, M.D. (formerly of NIOSH); Randall J. Smith; Sidney C. Soderholm, Ph.D.; and Kenneth C. Weber, Ph.D. We also thank the following NIOSH staff for their critical review of the document: Heinz Ahlers, J.D.; David D. Bayse, Ph.D.; M. Eileen Birch, Ph.D.; Joseph D. Bowman, Ph.D.; Robert M. Cas tellan, M.D.; Joseph C. Cocalis; Laurence Doemeny, Ph.D.; Peter M. Eller, Ph.D.; Jerome P. Flesch; Steven Galson, M.D.; Dennis W. Groce; Frank Hearl; Rick Homung, Ph.D.; Nelson A. Leidel, Sc.D.; Richard A. Lemen, Ph.D.; Charles D. Lorberau; Bonita Malit, M.D.; Robert W. Mason, Ph.D.; Michael A. McCawley, Ph.D.; Faye Rice; Leslie T. Stayner, Ph.D.; David M. Votaw; Martha Waters, Ph.D.; John Whalen; and Ralph D. Zumwalde. Anne Hamilton performed editorial review and coordinated production. Ruth Grubbs performed editorial review. Vanessa Becks and Susan Kaelin provided editorial assistance and produced camera-ready copy. Pamela Graydon, Marsha Striley, and Jane Weber provided editorial assistance. JoAnne Hamons assisted in producing draft copies. Judith G. Curless produced the final draft. Participants on the panel at the External Peer Review meeting in Cincinnati, Ohio, on July 30-31, 1993, include: John P. Gibbs, M.D. Corporate Medical Director Kerr-McGee Corporation 123 Robert S. Kerr Avenue Oklahoma City, Oklahoma 73102-6425 Robert Jankowski U.S. Bureau of Mines Pittsburgh Research Center P.O. Box 18070 Pittsburgh, Pennsylvania 15236 XXll A cknowledgments Donald Rasmussen, M.D. Southern West Virginia Clinic 250 Stanaford Road Beckley, West Virginia 25801 Michael Jacobsen, Ph.D. Division of Respiratory Disease Studies National Institute for Occupational Safety and Health James H. Vincent, Ph.D. University of Minnesota Division of Environmental and Occupational Health Box 807, Mayo 420 Delaware Street, S.E. Minneapolis, Minnesota 55455 James L. Weeks, Ph.D. George Washington University Medical Center Division of Occupational and Environmental Medicine 2300 K Street, N.W., Suite 201 Washington, D.C. 20037 We wish to thank the following consultants for their written comments on this document: John A. Knebel National Mining Congress 1920 N Street, N.W., Suite 300 Washington, D.C. 20036 Gordon Strickland Chemical Manufacturers Association 2501 M Street, N.W. Washington, D.C. 20037 R.V. Ramani, Ph.D. Generic Mineral Technology Center for Respirable Dusts c/o Pennsylvania State University 104 Hosier Building Univeristy Park, Pennsylvania 16802 Joseph J. Schwerha, M.D. General Manager of Health Services and Medical Director U.S. Steel Corporation 600 Grant Street, Room 2581 Pittsburgh, Pennsylvania 15219-2749 Agnes B. Kane, M.D., Ph.D. Associate Professor Department of Pathology and Laboratory Medicine Brown University, Box G Providence, Rhode Island 02912 Noah Seixas, Ph.D. School of Public Health and Community Medicine Department of Environmental Health University of Washington Seattle, Washington 98191 Jan M. Mutmansky, Ph.D. Department of Minerals Engineering Pennsylvania State University 120 Hosier Building State College, Pennsylvania 16802 Annette Haag American Association of Occupational Health Nurses 50 Lenox Pointe Atlanta, Georgia 30324-3176 Paul Morrow, Ph.D. Department of Environmental Medicine University of Rochester Rochester, New York 14642 Mine Safety and Health Administration Ballston Town No. 3 4015 Wilson Boulevard Arlington, Virginia 22203 xxiii Coal Mine Dust Jonathan M. Samet, M.D. Professor and Chairman Department of Epidemiology School of Hygiene and Public Health Johns Hopkins University 615 N. Wolfe Street, Suite 039 Baltimore, Maryland 21205 Mary Townsend, Ph.D. 289 Park Entrance Drive Pittsburgh, Pennsylvania 15228 Robert L. Vines (Retired) Vice President, Health and Safety Bituminous Coal Operators' Association, Inc. 918 Sixteenth Street, N.W., Suite 303 Washington, D.C. 20006-2971 Hermann Enzer Deputy Director U.S. Bureau of Mines Twin Cities Research Center 5629 Minnehaha Avenue, South Minneapolis, Minnesota 55417 Bruce Watzman Vice President Safety, Health, and Human Resources National Coal Association 1130 17th Street, N.W. Washington, D.C. 20036-4677 John H. Johnson, Ph.D. Michigan Technical University E M Department 1400 Townsend Drive Houghton, Michigan 49931 James L. Whittenberger, M.D. Professor Emeritus University of California, Irvine College of Medicine Department of Community and Environmental Medicine Irvine, California 92717 Australian Environmental Health Services PTY LTD. P.O. Box 159 Figtree, NSW 2525 Australia Edward Emmett Worksafe Australia National Occupational Health and Safety Commission 92 Parramatta Road Camperdown NSW 2050 GPO Box 58 Sydney, NSW 2001 Australia Marcus B. Bond, M.D. 1711 Arbutus Street Golden, Colorado 80401 Mr. Peter A. Hernandez American Iron and Steel Institute 1101 17th Street, N.W., Suite 1300 Washington, D.C. 20036-4700 Glen A. Zumwalt ANR Coal Company P.O. Box 1871 Roanoke, Virginia 24008 xxiv