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Silicosis in Metal Mining

SILICOSIS IN THE METAL MINING INDUSTRY A Revaluation • 1958-1961 U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE PUBLIC HEALTH SERVICE o° 1 Robert H. Flinn, M.D.; Hugh P. Brinton, Ph. D.; Henry N. Doyle, - •q Lewis J. Cralley, Ph. D.; Robert L. Harris, Jr. '9 1 U.S. DEPARTMENT OF THE INTERIOR 9 0 m I BUREAU OF MINES ~ ~ Yames Wesoeld; ,J. Howard Bird; Lawrence B. Berger

Study Coordinator, Bureau of Mines : James Westfield Study Coordinator, Public Health Service : Henry N. Doyle Director of Medical Studies : Robert H. Flinn, M.D. Director of Environmental Studies : J. Howard Bird INTERAGENCY TECHNICAL COMMITTEE Public Health Service Bureau of Mines LEWIs J. CRALLEY, PH. D. LAWRENCE B. BERGER W. CLARS COOPER, M.D. J. HOWARD BIRD HENRY N. DOYLE JoHN A. JOHNSON ROSERT H. FISxN, M.D. JAMES WESmFIELD RosERT L. HARRIS, JR., Secretary PANEL OF ROENTGENOLOGISTS BENJAMIN FEL6oN, M.D., University of Cincinnati, College of Medicine GEORGE JACOBsON, M.D., University of Southern California, School of Medicine EUGENE P. PENDERGRASS, M.D., Hospital of the University of Pennsylvania Public Health Service Publication No. 1076 U.$. GOVERNMENT PRINTING OFFICE WASHINGTON t 1963 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C., 20402 - Price $1.25 (Paper Cover) Foreword Throughout the history of mining, silicosis has been a major health problem. Efforts to control the disease did not begin in the United States until shortly after the turn of the 20th century, when the Pub- lic Health Service and the Bureau of Mines embarked on a series of joint investigations which contributed much basic knowledge on the etiology, pathology, and control of silicosis. However, it was not until about 1935 that the mining industries began major efforts to control the disease. Because of the long period involved in the devel- opment of silicosis, these efforts were not expected to lead to a de- monstrable reduction in the prevalence of silicosis until many years later. In 1956, a study of compensation and other records pointed up the disease as a continuing problem of industrial, social, and eco- nomic significance. The present study was an outgrowth of hear- ings on mine health and safety held by the Committee on Education and Labor, House of Representatives, 84th Congress. Because of the inadequacy of retrospective data on dust concen- trations in the mines and silicosis prevalence rates due to the dearth of mine studies during the period 1940-61, it was not possible to an- swer all of the questions proposed in the objectives of the study. The study, however, should form the basis for others which could mate- rially assist in ultimately eliminating silicosis as a serious threat to the health of metal miners. qa4v a-~ 011n^m MARLING J. ANKENY HARRY HEIMANN, M.D. Director, Bureau of Mines Chie f, Division of Occupational Department of the Interior Health Bureau of State Services Public Health Service Department of Health, Educa- tion, and Welfare V

Acknowledgments I Appreciation is expressed to the participating mining companies and labor unions for their excellent cooperation. Likewise, valuable assistance in organizing the study was given by the American Mining Congress and the various State mining associations. Without the assistance and cooperation of the State health departments and the State mining agencies it would have been impossible to carry out the study. In addition, the success of a comprehensive study of this type depends upon the specialized skills of many individuals. The au- thors wish especially to acknowledge the following contributions in the environmental and medical aspects of the study. Bureau o f[llines-Members of the Health and Safety Activity of the Bureau of Mines performed as an effective team in both field and laboratory activities. Field studies were accomplished as sched- uled, and laboratory production of analytical results kept pace with field operations. Particular acknowledgment is made of the contributions to this report by Floyd G. Anderson, who participated in preparation of the section on History of Dust Sampling and Comparison of Methods; by Arthur L. Franks, Jr., Leslie Johnson, and Paul Schapiro, who analyzed field data and prepared material for the report; and by Joseph B. Stepan, who prepared the section entitled "Review of Environmental and Historical Records." Leslie Johnson was in charge of field operations, and Arthur L. Franks, Jr., and Paul P. Schapiro served as team leaders. Others who took part in the field studies at various times were E. F. Allen, Walter Bank, R. C. Bates, C. J. Beecroft, R. L. Ber- nard, J. L. Brandt, W. B. Brogoitti, R. Capps, R. C. Derzay, A. M. Evans, R. L. Evans, G. B. Fritts, J. A. Fulmer, J. P. Harmon, T. Jolley, R. G. Peluso, H. G. Plimpton, E. J. Podgorski, H. E. Poland, R. O. Pynnonen, R. L. Rock, K. U. Russell, H. L. Schell, A. Schrader, D. K. Walker, M. L. Williams, and G. D. Winans. Laboratory operations were conducted at Bureau of Mines stations at Pittsburgh, Pa., and Denver, Colo. At Pittsburgh, Floyd G. Ander- son supervised particle-size determinations by optical microscopy, and i I t vn

Peter J. Colbassani supervised X-ray diffraction and spectrographic determinations. At Denver, Russell Faddis and Harrison Hudson participated in operations pertaining to assessment of airborne dust, and Albert Maxian supervised analyses of all samples of mine air collected during the study. Public Health Service=Staff members of the Division of Occupa- tional Health located both at the Occupational Health Research and Training Facility at Cincinnati, Ohio, and at the Occupational Health Field Station, Salt Lake City, Utah, participated in the medical studies. Special appreciation is due to the following medical officers who conducted the examinations of miners: Mike Hayes, M.D.; Thomas H. Milby, M.D.; George H. Franck, M.D.; Raymond T. Moore, M.D.; Rodger K. Farr, M.D.; Robert Collier, M.D.; Nicholas P. Sinaly, M.D.; Patrick J. Hennelly, M.D.; Neely E. Pardee, M.D.; Willard P. Johnson, M.D.; and L. Bruce Bachman, M.D.; in addi- tion, Victor E. Archer, M.D., conducted the medical examinations reported herein from the Uranium Miners' Survey of 1960. Likewise, appreciation is extended to Roy J. Hanna and Rickard D. Hutchison, who participated in the special engineering studies; to Darrell E. Anderson who participated` in both the medical and environmental studies; to Robert G. Keenan, Frances Hyslop, and David A. Fraser, Ph. D., for special analytical work on selected field samples; and to Louis Pecora, Ph. D., for his work on physiology. Mr. Nicholas E. Manos is responsible for the development of the methodology and analyses of the field data obtained from the tests of pulmonary ventilatory function described in Appendix A. Much credit goes to Duncan Holaday for his assistance in get- ting the field work underway; to James Mueller and Frances E. Brogan for their help in the administrative phases of the study; and to Norma L. Egnew, Pius Zimmer, Helen McCool, and Mary Gabriel for their assistance with the statistical analyses. Miss Victoria Trasko has rendered valuable service in the final editing and collating of the manuscript. The material presented as a retrospective study of a major sili- cosis control program was made possible by the enthusiastic coop- eration extended by Dr. George W. Wright and Mr. Robert Downs of the Saranac Laboratory, and officials of the cooperating mining companies in the Lake Superior district, especially those of the Oglebay Norton Mining Co. and its Montreal mine, located at Mon- treal, Wis. vIn Contents Page FOREWORD- - --- --------------- -- --- ------- -- V .. CKNOWLEDOMENTS------------------- ------------------- Vn CHAPTER I INTRODUCTION-------------------------------------------- Background----------------------------------------- Methodology---------------------------------------- References------------------------------------------ CHAPTER II 1 1 4 8 SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS------------ 11 Summary------------------------------------------- 11 EnvironmentalStudy---------------------------- 12 Medical Study---------------------------------- 15 C.onclusions----------------------------------------- 19 Recommendations------------------------------------ 21 General---------------------------------------- 21 The Working Environment----------------------- 22 Medical Services-------------------------------- 23 CHAPTER III REVIEW OF PAST STUDIES-------------------------------- 27 References----------- I ------------------------------ 30 CHAPTER IV THE ENVIRONMENTAL STUDY-------------------,.--------- 33 Part A-Field Investigation-------------------------- 33 Purpose and Scope----------------------------------- 33 Geography and Geology of Ore Deposits------------------ 35 Mining Methods------------------------------------- 36 Survey Methods------------------------------------- 36 Field Procedures-------------------------------- 39 Threshold Limit Values-------------------------- 42 ix

THE ENVTRONMENTAL STUDY-Continued Page CHAPTER V Results of Environmental Study------------------------ Particle Size------------------------------------ 45 45 ~ I MEDICAL STUDY----------------------------------------- Page 99 Free Silica Content of Dust---------------------- 47 General Procedures----------------------------------- 99 Dust Concentrations------------------------------ 48 Personnel and Facilities----.---------------------- 99 Mines Studied 100 Underground-General-------------------------- 53 ---------------------------------- Underground Operations------------------------- 53 , Examination Procedures------------------------- 100 The Population Sample Examined------ 101 Man Trips--------------------------------- 56 ----------- Procedure of Medical Examinations--------------------- 104 Slushing------------------------------------ 56 Medical History and Symptoms- ----------------- 104 Mucking----------------------------------- 56 Occupational History---------------------------- 105 Timbering---------------------------------- 56 Chest Roentgenograms--------------------------- 106 Drilling and Loading Holes------------------- 56 Pulmonary Ventilatory Function 7.'ests 107 Tramming ----------- - - ----- - - 58 I ------------ - Forced Expirogram -- 107 - - - - - -------- - Loading and Dumping Cars------------------ 58 I i ---- -----------.--------- Maximum Forced Expiratory Flow Rate------- 107 Skip Tenders------------------------------- Between Operations------------------------- 58 58 i i Conditions of Testing------------------------ Characteristics of Workers Examined------------------- 108 108 Age and Occupation 108 Eating Lunch------------------------------- 58 ~ ----------------------------- Years in Principal Occupation 112 Concrete and Gunite Crews------------------- 59 -------------------- Rock Bolting 59 r Years in Present Occupation -------------------- 112 ------------------------------- Analysis of Medical Findings-------------------------- 117 Mobile Equipment Operators----------------- 59 Analysis of Chest Roentgenograms---------------- 117 Barring Down------------------------------ 59 General Procedure--------------------------- 117 Breaking Boulders--------------------------- 59 Classification of Roentgenograms-------------- 117 Mills and Crushers------------------------------ 60 Roentgenograms Classified as Silicotic--------- 118 Mills-------------------------------------- 60 History of Past Illnesses------------------------- 126 Crushers----------------------------------- 60 ChestIllnesses------------------------------ 126 Assayers in Mills.--------------------------- 62 r Tuberculosis-------------------------------- 127 Shops and Other Surface Locations---------------- 62 Heart Trouble------------------------------ 132 Shops-------------------------------------- 64 Rheumatic Fever---------------------------- 132 Assay Laboratories-------------------------- 64 Rheumatism-------------------------------- 132 Dust on Lungs 133 Concentrate Loaders------------------------- 64 ------------------------------ History of Lead Poisoning 133 Concrete Plants----------------------------- 64 -------------------- History of Mercurial Poisoning - 134 Other Operations---------------------------- 64 --- ------------ Frequency of Present Symptoms------------------ 134 Dust Control----------------------------------- 70 ChestIllness-------------------------------- 134 VentiIation------------------------------------- 71 ~ Shortness of Breath-------------------------- 135 Composition of Mine Atmospheres-----,.---------- Conclusions on Dust Production and Control------- 72 76 Silicosis Related to Type and Duration of Exposure-- Years in Metal Mining----------------------- 140 140 i References------------------------------------------ 76 Age of Workers----------------------------- 141 Part B-History of Dust Sampling and Comparison of Methods----------------------------------------- References------------------------------------------ 77 94 Age and Years in Metal Mining--------------- Years in Metal Mining and Principal Occupa- tion------------------------------------- 144 144 I: Present Occupation-------------------------- 152 Present Occupation Compared With Principal Occupation------------------------------- 152 x xi

MEDICAL STUDY-COntmued APPENDIX Analysis of Medical Findings-Continued, Silicosis Related to Type and Duration of Exposure- Continued Geographical Location_______________________ Page 156 EFFECTS OF SILICOSIS AND OTHER FACTORS ON PULMONARY F_UNCTION---- ---------------------------------------- Page 231 Silicosis According to Commodity Produced_ ___ 156 Introduction---------------------------------------- 231 Workers With Experience at One Mine Only Effects of Silicosis on Pulmonary Function_____________ 232 and at Two or More Mines_________________ 159 Effects of Other Factor~ on Pulmonary Function-------- 236 Silicosis Among Workers Excluded Because of ~ Correlation Between Four Measurements of Pulmonary Other Dusty Work________________________ 162 Function------------------------------------------ 237 Silicosis by Periods of Work Experience Before ~ - and After 1935____________________________ Comparison of Present With Past Studies---------------- 162 164 TABLES Case Histories--------------------------------------- 169 Table IV.1.-Data on mines included in the dust study------ 33 Health Services-------------------------------------- 180 Table IV.2.-Host rock and alpha quartz correlation---_--_- 35 References------------------------------------------ 181 Table IV.3.-Distribution of 67 mines according to principal mining method ------------ - -- 36 CHAPTER VI A RETROSPECTIVE STUDY OF A SILICOSIS CONTROL PROORAM__ 185 ------------------------ - -- Table IV.4.-Number of midget impinger samples collected for determination of airborne dust concentrations____-_--_- 41 Background----------------------------------------- 185 Table IV.5.-Samples collected during the study------------ 41 The Study of Medical Records From One Mine _ _ _ _ _ _ _ _ _ _ _ Description of the Members of the Study Group____ 188 190 Table IV.6.-Comparison of 55 particle-size analyses by elec- tron and optical microscopy____________________________ 45 Workers With Silicosis___________________________ Work History, Subsequent to 1933, of Employees 192 Table IV.7.-Particle-size characteristics of 481 samples exam- ined by optical microscopy_____________________________ 46 With Silicosis--------------------------------- 194 Table IV.8.-Free silica content of settled dust at 67 mines_-_ 48 Presilicotic Changes_____________________________ The Review of Environmental and Historical Records------ 196 199 Table IV.9.-Distribution of weighted average exposures that exceeded threshold limit values-------------------------- 51 History of Operations and General Information___-_ 199 I Table IV.10. Occupational dust exposures, underground, Geology----------------------------------------- 200 weighted averages-------- .----------------------------- 56 Total and Free Silica Determination----------- 202 ~ Table IV.11.-Midget impinger samples collected at surface Mining Methods________________________________ 202 and underground mills and crushers_____________________ 60 History of Organized Safety Activity-------------- Ventilation------------------------------------- 204 206 Table IV.12.-Midget impinger samples collected at Surface locations---------------------------------------------- 62 Other Ventilation Improvements--------------- History of Dust Control__________________________ 210 210 Table IV.13.-Occupational dust exposures, surface and under- ground, ,.,rithmetic avelages____________________________ 65 Wet Drilling-------------------------------- 210 Table IV.14.-Dust concentrations in underground operations_ 66 Other Use of Water To Control Dust---------- Other Improvements or Dust Control Measures-_ 211 211 Table IV.15.-Occupational dust exposures, surface and under- ground-------- --------------------------------------- 67 Company Dust Counts___________________________ 213 Table IV.16.-Measures to reduce dust exposures----------- 70 Table IV.17.--Practices that caused dusty conditions-------- 71 CHAPTER VII Table IV.18.-Ventilation rates at 53 mines with mechanical ventilation------------------------------------------- 72 THE USE OF THE NEW INTERNATIONAL RADIOLO(31CAL CLAS- SIFICATION OF THE PNEUMOCONIOSES (GENEVA-1958) IN place.s------------------------------------------------- Table IV.19.-Methods of ventilation in underground working 72 THE STUDY OF SILICOSIS________________________________ 219 Table IV.20.-Composition of mine atmospheres------------ 74 References------------------------------------------ 230 Table IV.21.-Methods for determination of dust in air------ 79 xii i I ;F

Table IV.22.-Comparison of dust concentrations from midget impinger samples with concentrations from companion Page samples by other methods------------------------------ 89 Table IV.23.-Settled dust samples------------------------ 92 Table IV.24.-Comparison of free silica content of screened and air elutriated fractions of settled dust with that of com- panion electrostatic precipitator samples of airborne dust_- 93 Table V.1.-Workers at 36 metal mines eligible for a medical examination and those examined according to age and place where working---------------------------------------- Table V.2.-Principal occupation of workers at 50 metal mines 102 according to age--------------------------------------- 110 Table V.3.-Present occupation of workers at 50 metal mines according to age--------------------------------------- 111 Table V.4.-Principal occupations of workers at 50 metal mines according to years worked at metal mines---------------- 114 Table V.S.-Present occupation of workers at 50 metal mines according to years in present occupation----------------- 116 Table V.6.-Distribution of 50 metal mines according to prevalence of silicosis__________________________________ 122 Table V.7.-Percent of metal mine workers with X-ray evidence of silicosis according to size of mine and number of years worked at 50 metal mines and uranium mines------- 123 Table V.8.-Frequency distribution of metal mines by size showing percent of workers with silicosis----------------- 126 Table V.9.-Percent of workers at 50 metal mines with certain present symptoms and past illnesses for silicotic and non- silicotic workers by age and years worked at metal mines--_ 128 Table V.10.-Shortness of breath among workers at 50 metal mines according to lung field markings and years at metal mines------------------------------------------------ 137 Table V.11.-Shortness of breath among workers at 50 metal mines according to detailed lung field markings, age and years at metal mines_- -------------------------------- 139 Table V.12.-Shortness of breath among workers at 50 metal mines according to elevation of mine and age, workers with or without silicosis------------------------------------- 140 Table V.13.-Number and percent of metal mine workers with X-ray evidence of silicosis according to years at metal mines-- 142 Table V.14.-Number and percent of metal mine workers with X-ray evidence of silicosis according to age--------------- 142 Table V.15.-Number and percent of metal mine workers with X-ray evidence of silicosis according to age and years at metal mines------------------------------------------ 145 i t Table V.16.-Percent of workers with 'evidence of silicosis at 50 metal mines according to principal occupation and years Page at metal mines---------------------------------------- 147 Table V.17.-Silicosis among metal mine workers by principal occupation and years at metal mines__ __________________ 150 Table V.18.-Workers at 50 metal mines according to occupa- tion at time of medical examination_____------------------- _ 153 Table V.19.-Present occupation compared with principal occupation of workers at 50 metal mines according to percent with silicosis-------------------------------------------- 154 Table V.20.-Silicosis among metal mine workers according to commodity produced, by years at metal mines----------- 157 Table V.21.-Silicosis among metal mine workers with ex- perience of 10 years or more at one mine only and at two or more mines by principal occupation and years at metal mines- 160 Table V.22.-Silicosis among metal mine workers with exposure in other dusty trades of 5 years or over according to total years in all dusty work________________________________ 162 Table V.23.-Silicosis among workers at metal mines by period of work experience and total years worked at metal mines_ ___ 164 Table V.24:-Silicosis in western lead-zinc mine workers ex- mined in 1958-61 compared with Utah metal mine workers examined in 1939 according to years at metal mines--------- 167 Table V.25.-Weighted average dust concentrations (mppcf) at comparable occupations in 12 lead-zinc mines studied in 1958-61 compared with Utah metal mines studied in 1939____ 167 Table V.26.-Number of 50 metal mines having specified health services according to size of mine------------------- 180 Table VI.1.-X-ray film classification (Saranac) of employees working in iron mines with contracts with the Saranac Laboratory by period examined------------------------- 186 Table VI.2.-Distribution of workers in the study group ac- cording to number at work Jan. 1, 1933, and number who began working in subsequent periods by number of years on company payroll----------------------------------- 191 Table VI.3.-Metal mine workers with silicosis according to age and years in mining when employment with the company wasterminated---------------------------------------- -- 193 Table VI.4.-Mining experience previous to 1933 of workers who had silicosis in 1933 by years worked in one mine only andin twoormoremines------------------------------- 194 Table VI.5.-Mining experience after 1933 of workers who had silicosis in 1933 which did not progress, according to job status and years worked------------------------------- 195 I i i i xiv xv

Table VI.6.-X-ray film readings by the Saranac Laboratory poe of workers with experience before and since 1933 by years in metal mines________________________________________ 197 Table V1.7.-Presilicotic changes in X-ray interpretation of men with 10 years or more of employment who began work in 1933-42, and 1943-52-Montreal mine------------------ 198 Table VL8.-Statistical data on company operations in Mon- treal mine-------------------------------------------- Table VI.9.-Average company dust counts for operations in 201 orein Montreal mine---------------------------------- 214_ Table VI.10.-Average company dust counts for operations in rock in Montreal mine_________________________________ 215 Table VIL1.-I.L.O. radiological classification of silicotic chest films in study group of 14,076 metal mine workers--------- 227 Table VII.2.-I.L.O. categorization of lung field markings by years of work at 50 metal mines_________________________ 228 Table VII.3.-I.L.O. detailed classification of all 14,858 chest roentgenograms taken in metal mines study including 671 employees with exposure in other dusty trades------------ 229 Fiourm Figure I.1.-States in which mine studies were made-------- 7 Figure IV.1.-Acceptable counts for two cells from the same sample----------------------------------------------- 39 Figure IV.2.-Frequency distribption of geometric mean par- ticle sizes--------------------------------------------- 47 Figure IV.3.-Percentage distribution of midget impinger samples by range of free silica content___________________ 49 Figure IV.4. Distribution of weighted average exposure under- ground in respect to threshold limit values---------------- 50 Figure IV.5.-Average of midget impinger samples collected in each mine in respect to dust concentration and free silica content---------------------------------------------- 54 Figure IV.6.-Distribution of midget impinger samples col- lected in respect to dust concentration and free silica con- tent -------------------------------------------------- 55 Figure IV.7.-Ranges and percentages of dust concentrations underground------------------------------------------ 57 Figure IV.8.-Distribution of midget impinger samples col- lected in mill and crusher locations in respect to dust con- centration and free silica content________________________ 61 Figure IV.9.-Distribution of midget impinger samples col- lected in shops and surface locations in respect to dust con- . centration and free silica content________________________ 63 t i i I i r Page Figure V.1.-Medical examination form___------------------ 104 Figure V.2.-Occupational history form____________________ 106 Figure V.3.-International radiological classification of chest films modified for Public Health Service metal mines survey__ 119 Figure V.4.-Definition of terms used in Public. Health__Service modification of I.L.O. radiological classification of chest films for metal minessurvey---------------------------------- 120 Figure V.5.-Frequency distribution of 50 metal mines showing number of cases of simple and complicated silicosis-------- 125 Figure V.6.-Shortness of breath among workers with and without silicosis according to years worked in 50 metal . mines------------------------------------------------ Figure V.7.-Percent of all metal mine workers with silicosis 138 by age----------------------------------------------- 143 Figure V.8.-Percent of metal mine workers. with silicosis according to age and years worked in metal mines--------- 146 Figure V.9.-Percent of metal mine workers with silicosis according to principal occupation and years worked in metal mines--------------------------- --------------------- Figure V. 10..Percent of metal mine workers with silicosis 149 according to commodity produced----------------------- 158 Figure V:11.Dilicosis among metal mine workers with ex- posure of 10 years or more in one mine only, and in two or more mines------------------------------------------- Figure V.12.-Percent of metal mine. workers with silicosis according to period of experience and years worked in metal 161 mines------------------------------------------------ 165 Figure V.13.-Simple silicosis_____________________________ 170 Figure V.14.-Simple silicosis---------------------- -------- 171 Figure V.15.-Siznple silicosis_____________________________ 172 Figure V.16.-Simple silicosis_____________________________ 173 Figure V.17.-Simple silicosis----------------------------- 174 Figure V.18.-Complicated silicosis________________________ 175 Figure V.19.-Complicated silicosis------------------------ 176 Figure V.20.-Complicated silicosis. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ 177 Figure V.21.-Complicated silicosis------------------------ 178 Figure V.22.-Complicated silicosis________________________ 179 Figure VI.1.-Orders to Captains and Bosses-Use of Respira- tors Underground (prepared in 1935 for Montreal mine)__-_ 212 Figure VI.2.-The Montreal Mining Co. Rules for Dust Pre- vention (prepared in 1936)----------------------------- 213 Figure VII.1.-Radiological classification of chest films for Public Health Service metal mines survey_ _ _ _ ___ _ _ 222

PHOTOGRAPHS Page Frontispiece. View of Homestake Mining Co., Lead, S. Dak_ ii Richest Hill on Earth. Butte, Mont. Plumes are from surface fans------------------------------------------ 9 Bishop Mine-Union Carbide Nuclear Co., Bishop, Calif----_ 25 Two-stage 500-horsepower main surface fan-direct expulsion tyPe------------------------------------------------- 32 Sprinkler tank car for wetting haulageways. Rear view------ 37 i Miner operating electric tugger in slushing operation--------- 44 Miner wetting down muck pile and faces prior to mucking op- eration. Note overhead vent tubing and method of ground support----------------------------------------------- I 52 Compressed air and water mist spray used during blasting cycle in headings-------------------------------------- 73 Airlock door and fan on main adit------------------------- 75 Underground dust collector------------------------------- 78 The medical survey unit---------------------------------- 97 Physician interviewing a miner----------------------------- 103 A miner performing a pulmonary function test-------------- 109 The occupational history interview------------------------- 113 Taking the chest X-ray film------------------------------- 141 Smooth lining in airway to reduce frictional resistance and permit increased airflow--------------------------------- 184 Air shaft discharge stack with acoustical lining to reduce noise------------------------------------------------- 217 i xviu CHAPTER I Introduction IN 1956, THE Committee on Education and Labor, House of Rep- resentatives, held a series of hearings on bills introduced in the 84th Congress relating to inspections and investigations in metallic and nonmetallic mines and quarries for the purpose of obtaining infor- mation relating to health, safety conditions, accidents, and occupa- tional diseases therein. Testimony relating to the silicosis problem in the metal mining industry was presented at the December 1956 hearings by representatives of the Public Health Service and the Bureau of Mines. Although the committee did not recommend favorable action on the bills, as an outgrowth of the hearings, the Congress appropriated funds to the Public Health Service and the Bureau of Mines to revaluate the silicosis problem in the metal • --- = mmes. This report presents the major findings of the environmental and clinical studies conducted by the two agencies between March 1958 and September 1961 on the nature and scope of the silicosis problem in the metal mining industry. Also included is a retrospective study of a long-term silicosis control program and a discussion of the use of the International Radiological Classification of the Pneumoconioses in the study of silicosis. _ $ACKGRO.UND The classic studies of the Public Health Service and the Bureau of Mines relating to dust diseases conducted between 1913 and 1940 made several important contribut.ion_ s_ to our knowledge of silicosis. They served to confirm the findings of many independent investiga- tors and assisted in determining the etiology and pathology of the disease. The studies helped immeasurably in the assay of _ dust exposure and in defining the role of such factors as particle size, composition of the dust, and duration of exposure, and led ultimately to the adoption of 5 million particles per cu_bic foot-of air_ as a maxi- I I