Document DD8wmVkedNkNXORQEp7bnKVRN

FILE NAME: National Safety Council (NSC) DATE: 1935 Oct DOC#: NSC163 DOCUMENT DESCRIPTION: Transactions of the NSC - 24th Annual Safety Congress - Presentations - Occupational Diseases & Safety Equipment 1935 TRANSACTIONS N ational Safety C ou n cil Incorporated TWENTY-FOURTH ANNUAL SAFETY CONGRESS Louisville, Kentucky October 14 to October 18, 1935 The Brown, Kentucky and^Seelbach Hotels Copyright, 1936, National Safety Council, Inc. Foreword ' HE TRANSACTIONS of the Twenty-Fourth Annual Safety Congress, National Safety Council, 1935, are published in two volumes. This volume, first, contains the general sessions, the special subject sessions, and the .ustrial Section sessions. It is supplemented by a smaller volume containing sessions of the Street and Highway Traffic Section, the Child Education tion and Home Safety. All industrial members of the Council automatically receive the large volume, e smaller is sent to members believed to be chiefly interested in the sessions :overs. It may, however, also be secured by other Council members upon uest. Many members have found it worth while to distribute copies of these msactions to supervisors, foremen and others in an administrative or superory. position who may make practical use of them for reference purposes, r the benefit of those who desire extra copies the following quantity prices are ated: One to ten copies of the large volume, $1.50 each; eleven copies and er, $1.25 each; copies of the smaller volume, 50c each. T ACCORDANCE with the plan of publication followed for the past several years the Transactions are published again this year as a condensed record the proceedings at th National Congress. The papers of each session or ision of the Congress have been edited carefully to eliminate extraneous matand to abbreviate the less essential portions because of space limitations. In er words, the material herein presented is not a verbatim report of all the eches presented at the Congress, but rather an abridged version, made as mpact as possible, yet without any injury to the technical aspects of any iress. The original manuscripts arc on file in the library of the National fety Council, where they are available for additional reference. In several ;es,' where illustrations were sent by the speakers to the Council, these also oh file. The National Safety Council at its Congresses seeks to eliminate from dis,sion matters which are not pertinent to the aim of the Congress or which are itrary to Council policies, but it cannot accept responsibility for the views pressed either in the papers presented or in the discussions based upon the ners. NATIONAL SAFETY COUNCIL, INC. 20 North Wacker Drive, Chicago CONTENTS Page Council Officers and Directors................................................................................ 4 Council Purposes and Policies................................................................................ 9 Annual Meeting of Members......................................................................... Annual Banquet............................................................................................................ 27 Subject Sessions-- Finding and Correcting Accident Causes............................................................. 29 Fire Prevention in Industry................................................................................... 33 First Aid and Health Service in Industry........................................................... 51 Heat Exhaustion.............................................................................................. Industrial Nursing.................................................................................................... 73 Industrial Safety Lectures-- Public Speaking in Safety W ork....................................................................... 79 Selling Safety in Foremanship............................................................. Industry and Its Motor Vehicle Problem............................................................103 Maintaining Interest in Safety............................................................................ HI Occupational Diseases............................................................................................ 117 Safety Equipment.................................................................................................... 133- Safety in the Small Plant...................................................................................... 145 Safety Training....................................................................................................... 147 Accident Prevention Equipment Manufacturers' Section.................................. 153 Aeronautical Section.................................................................................................. 159 A.S.S.E.--Engineering Section................... ............................................................ 107 Automotive and Machine Shop S e c tio n .............................................................. 109 Cement Section...........................................1............................................................... 177 Chemical Section........................................ 1...................................................... 193 Construction Section................................. I.............................................................. 209 Food Section.............................................. . j .............................................................. 223 Marine Section........................................... i .............................................................. 237 Meat Packing, Tanning and Leather Industries Section.................................... 265 Metals Sectioh................................................................................................................283 Mining Section................................ 301 Paper and Pulp Section.............................................................................................. 321 Petroleum Section...................................................................................................... 345 Power Press Section.................................................................................................. 373 Public Utilities Section.............................................................................................. 391 Quarry Section............................................................................................................ 411 Refrigeration Section.................................................................................................. 423 Rubber Section............................................................................................................ ` - ' J Safety Section, A.A.R.--Steam RailroadSection, N.S.C....................................... 459 Textile Section............................................................................................................. 485 Transit Section................................ 495 Vehicle Fleet Section.................................................................................................. 513 Wood Products S e c tio n ......................................................................................... 529 I n d e x ...................... 537 National Safety Council Incorporated HONORARY MEMBERS A ssociation o r I ron- and Steel E lectrical E ngineers R obert W. Camrbrix Arthur W illiams OFFICERS (1935-1936) D r. C. H. W atson', President. D. D. F ennell. Vice-President for Public Relations. Dr. H art E. F ishf.r, Vice-President for Health. John IF Gibson, Vice-President for Community Safety Councils. Hox. I I aroi.u G. H offman, Vice-President for Public Safety. A lbert S. R kcui.a, Vice-President for Engineering. A. V. R onweber, Vice-President for fmlustrial Safety, R. T. Soi.knstkn, Vice-President fur Membership. A lbert W. W h itn ey , Vice-President for Education. W. E. W orth, Vice-President for Finance and Treasurer. \V. H. Camf.ron, Secretary and Managing Director. EXECUTIVE COMMITTEE (1935-1936) A. L. A rmstrong, Chemical Section. C. B. A uel, Past President. J. I. Ba n a s ii, Past President. C. W. B f.rcquist, Past President. H arold S. B utteNHF.im , The American City Magazine. W. II. C ameron, National Safety Council. Robert W. C ampbell, Past President. Robert I. Catlin, Aetna Casualty & Surety Company. L ewis A. D f.Blois, Past President. C. W. D f.mpesy, Food Section. Marcus A. Dow, Past President. D. D. F ennell, Consulting Engineer. Donald A. F inkbf.inf.r, Toledo Safety Council. D r. H art E. FTsher, Chicago Rapid Transit Company. E. W. F iskk, J r., Marine Section. R. B. F ortuin, Lehigh Valley Safety Council. ' Joiix B. G ibson, Western Electric Company. E. E. Grant, Paper & Pulp Section. H arry G uilbf.rt, The Pullman Company. H on. H arold G. H offm an. Governor of New Jersey. E dwin A. K ayser, St. Louis Safety Council. W alter G. K in g , Past President. 4 Officers and Directors W ilmam C. K noelk, Street & Highway Traffic Section. C. F. L arson, Association of American Railways. J ohn E. L ong, Past President. T iios. H. M acD onald, U. S. Department of Agriculture. E. J. M ehrf.n, Portland Cement Association. I. W. M illard, Industrial Gloves Corporation. A rthur T. M orey, Past President. Lew R. P almer, Past President. C. E. P ettibone, Past President. J A. P urdy, Wood Products Section. Albert S. R egula, Industrial Relations Counselors, Inc. Lt. Col. H enry A. R eningf.r, Past President. A. V. R ohweder, Duluth. Missahe & Northern Railway Co. George E. S anford, General Electric Company. R orf.rt I.. S chm itt, Louisville Safety Council. Gf.n. J ohn IT. S herburne, Massachusetts Safety Council. C harles B. S cott, Past President. C. W. S m ith , Standard Oil Company (Ind.). W alter Dent S m it h , Delaware Safety Council. R. T. Solensten, Elliott Service Company. J ames M. S trike, St. Joseph Safety Council. C. P. T olman, Past President. Dr. C. II. W ats,on, American Telephone & Telegraph Co. A. W. W hitn ey, National Bureau of Casualty & Surety Underwriters. C. T. W inegar, Automotive & Machine Shop Section. W . E. W orth, International Harvester Company. A rthur H. Young, Past President, j DIRECTORS (1935-1936) J. W. A lt, Mining Section. i N elson R. A nderson, Seattle Traffic & Safety Council. F rederick A rcher, Child Education Section. A. L. A rmstrong, Chemical Section. J. I. B an as H, Consulting Engineer. E rnest W. Beck, United States Rubber Products, Inc. C. W. Bergquist, Western Electric Company. P ercy D. Betterly, Worcester Safety Council. D avid S. B eyer, Liberty Mutual Insurance Co. Clifford M. B isho p, Brooklyn Safety Council. E. F. B lank, Jones & Laughlin Steel Corp. C. F. Borkeniiagen, Kenosha Safety Council. S. D. Boyd, York County Safety Council. W. A. B rown, Transit Section. S. W. B urchiel, Automobile Club of Rhode Island. H arold S. B uttenh eim , The American City Magazine. P reston D. Caelum, Baltimore Safety Council. W. H. Cameron, National Safety Council. Twenty-fourth Annual Safety Congress-- National Safety Council . Carney, Chicago Safety Council. ckt I. Catlin, Aetna Casualty & Surety Company. -. Cody, Evanston Safety Council. B. Coleman, Cement Section. H erbert Corson, Safety Dept., Nashville Chamber of Commerce. nk E mery Cox, Berkeley Traffic Safety Commission. Culliney, Bethlehem Steel Company. W. D arr, Metals Section. i.i.iAM G. D eaner, Rochester Safety Council. vis A. DeBlois, Consulting Engineer. E. Decker, Mason City Safety Council. W. D empesy, Food Section. M. D ietz, Rubber Section. mes B. D ouglas, The Philadelphia Gas Works Co. . Touts I. D ublin, Metropolitan Life Insurance Co. D. F ennell, Consulting Engineer. >N.\r.ti A. F inkbeiner, Toledo Safety Council. . I I art E. F isiier, Chicago Rapid Transit Co. W. F isk e, J r., Marine Section. ios. F itzgerald, Western Pennsylvania Safety Council. ward B. F onda, Burroughs, Wellcome & Co. (U. S. A.), Inc. B. F ortuin, Lehigh Valley Safety Council. F oster, J r., Quarry Section. iin B. Gibson, Western Electric Company. >v M. Godwin, Public Utilities Section. . F. G rant, Paper & Pulp Section. arry Gu ii.dert, The Pullman Company'. atA11 IIale, The Atchison, Topeko & Santa Fe Ry. Co. Tajor Bolling II. H andy, Richmond Safety Council. . T. H arrington, U. S. Bureau of Mines. . C. H aven, Vehicle Fleet Section. I. W. Hniss, Textile Section. . T. I I ellm utii, Chicago, North Shore & Milwaukee R. R. Co. ijari.es E. H ill, New York Central Lines. o n . H arold G. H offman, Governor of New Jersey. laude J. H olding, Albany Safety Council. unviN A. K ayser, St. Louis Safety Council. iiomas P. K earns, Industrial Commission of Ohio. .. T. K eller, Detroit Industrial Safety Council, aa V. Ivepner, Pennsylvania Salt Mfg. Co. Villi am C. K noelk, Street & Highway Traffic Section. '. L. L aF ountaine, Great Northern Railway Co. '. F. L arson, Missouri Pacific Railroad Company. mon L azarus, Safety Council of Columbus (O.) Chamber of Commerce. E. L ong, The Delaw are. & Hudson Railroad Corp. V. R. Loyd, Safety Div. Birmingham Chamber oE Commerce. : nos. II. M acD onald, U. S. Department of Agriculture. .. T. M cArthur, Peoria Safety Council. K. J. M cCa n n , Meat Packing, Tanning & Leather Industries Section. Officers and Directors M iller M cClintock, Harvard University. T. H. McKennf.y, Carnegie-Illinois Steel Corp. A. D. McW horter, Safety Div., Memphis Chamber of Commerce. H. T. Martin, Fisk Rubber Company F. W. M atson, Minnesota Safety Council. J ames R. M ays, Elizabeth Safety Council. E. J. M eiiren, Portland Cement Association. I. W. M illard, Industrial Gloves Corporation. J ames K. M iller, Grand Rapids Safety Council. L eslie W. M iller, Superior Safety Council. H arold L. M iner, E. I. du Pont de Nemours & Co. L awrence M. M oore, Eastbay Safety Council. R. B. M ouley, Industrial Accident Prevention Assus. George C. A. Opp, The Detroit Edison Company. G eoroe O ppenheim er, Kansas City Safety Council. L ew R. P almer, Equitable Life Assurance Society. D avid A. P atton, Newark Safety Council. C harles W. P endock, Safety Div., Milwaukee Assn, of Commerce. C. E. P ettibone, American Mutual Liability Insurance Co. Gen. George B. P illsbury, United States Engineer Office. A rthur P otterton, Hudson County Safely Council. W. D. P rice, Employees' Publication Section. ). A. P urdy, Wood Products Section. Alrert S. R gula, Industrial Relations Counselors, Inc. Lt. Col. H enry A. R eninger, Lehigh Portland Cement Co. M arinus R iter, Paterson Safety Council. R. B. R oaper, Petroleum Section. A. V. R oiiwf.der, Duluth, Missabe & Northern Ry. Co. George E. S anford, General Electric Company. H enry G. S ciiaffner, Erie Safety Council! R obert L. Schmitt, Louisville Safety Council. K arl G. Sciioeffler, Rahway Safety Council. H arry A. S chultz, United States Steel Corp. E arl S. S iiartzer, Utica Safety Council. R ay H. S heets, Madison County Safety Council. Gen. J oh n II. S herburne, Massachusetts Safety Council. Dr. L. A. S iioudy, Bethlehem Steel Company. E rnest L. S imonds, New Haven Safety Council. J udge L ee E. S keel, Cleveland Safety Council. C. W. S m it h , Standard Oil Company (Ind.). E dwin C. S m ith , Blackstone Valley Safety Council. W alter Dent S m it h , Delaware Safety Council. W. A. S now, Construction Section R. T. S olensten, Elliott Service Company. E. C. S pring, Lansdale, Penna. George R. Stephens, Safety Bureau, Buffalo Chamber oi Commerce. J ames M. S tiuke, St. Joseph Safety Council. A rthur M. T ode, Consulting Marine Engineer. H arold M. T oombs, Refrigeration Section. T he Nati< the first, Industria the sessi Section ; All! The sm; it cover request. Ma Transai visory For th< quoted over, $ TN A yea of the divisio ter an other speeci comp addre Safet 8 Twenty-fourth Annual Safety Congress-- National Safety Council W. W. T rench, Schenectady Safety Council. W. D. T urbeville, San Antonio Safety Council. E. J. W allman, Power Press Section. Dr. C. H. W atson, American Telephone & Telegraph Co. H arry M. W ebber, Illinois Bell Telephone Co. A lbert C. W hite, J r., Springfield Safety Council. S. F.. W hiting, Liberty Mutual Insurance Company. A. W. W hitney, National Bureau of Casualty & Surety Underwriters. T. A. W illson, Accident Prevention Equipment Manufacturers' Section. W. H. W in a n s, Union Carbide & Carbon Corp. C. T. W inegar, Automotive & Machine Shop Section. H arry W ise, Sr., Chattanooga Safety Council. J. M. W oltz, The Youngstown Sheet & Tube Co. W . E. W orth, International Harvester Company. E. J. Zauft, Safety Bureau, Duluth Chamber of Commerce. E arl W. Zimmerman, Safety Div., Syracuse Chamber of Commerce. ncil rtl to the croup to p took it <1 a year maintain iterature, 'ins. sheets of .-eivecl a . to save mg lucky depart10 days ulditional icularly : trolley reduction ice of a a coal ers, but solely -.rhaps I d be re- .lployee mpaign ust give displays .rnittee- Occupational Diseases Occupational Diseases FRIDAY MORNING SESSION October 18, 1935 The session *vas called to order by Mr. W. Dean Keefer, director. Industrial Division, National Safety Council. Dr. C. H. Watson, newly-elected President of The National Safety Council and Medical Director, American Telephone and Tele graph Company, New York City, presided. Present and Prospective Occupational Disease Legislation By F. ROBERTSON JONES f General Manager, Association of Casualty and Surety Executives New York, N. Y. Since the prevention of diseases is, to some degree, a community problem, the state ought to do its part toward the prevention of occupational diseases, along with all others. The. public health authorities should study the causes oi such dis eases, their prevalence, virulence and the means for their prevention. They should advise as to such means of control, and, as a last resort, appeal to legislatures tor power to order compliance with their rules. Statutory regulations for prevention, emanating from other sources, such as are common in ``labor" or "factory" laws, have too'serious drawbacks to be efficient. Tliey are apt to be inflexible and quickly become "out of date"; and they arc too apt to he perverted for the establishment of fictitious ' . liases for wasteful and demoralizing damage-suit litigation. Scientific bureaus oi occupational hygiene, under direction of public health authorities, are the best public instrumentality. Efficient bureaus of that character are now to be found in several i ! states; but, generally, such public health organizations are inadequately manned and equipped. Therefore the primary need in occupational disease legislation is for measures to improve our public health services. , Emphasis should be placed on prevention, not merely because "an ounce of pre- 1 , vention is worth a pound of cure," but because public measures for the assurance c.f relief to victims arc perilously susceptible of being so perverted that those affected will tend to rely upon and abuse the protection afforded as a substitute for, instead of as a supplement to , means for sclf-protcction. Expert opinion now calls strongly for the entire elimination of employers' liability for "damages" for occupational injuries--by disease as well ns by accident--based upon negligence. That remedy is too uncertain in operation, litigious, demoralizing and wasteful: it furnishes relief to too few of the victims unless it be so liberalized as to be grosslv unjust and financially perilous to employers--and thereby harmful to industry and all dependent upon industry. Losses from ill-health among workmen are primarily subjects for seli-providencc or for "social insurance"--for "sickness insurance" to lieln out during brief illnesses, and for "invalidity." "old age" and "widows' and orphans' " Insurance where illnesses or infirmities result in long or permanent disability or untimely dealth. The cost of these insurances against the common misfortunes of life cannot rightly or expediently be imposed wholly upon industry, but needs to be distributed somewhat in proportion 117 118 Tzventy-fourth A vv ita i Safely Congress-- National Safety Council to responsibility. And benefits, at a high scale of maximum earnings, as in workmen's compensation, simply cannot he provided for all such workmen's misfortunes. In invalidity, old-age and life insurance, at least, the benefits must he graded, more or less, in proportion to the individual workmen's contributions to the requisite reserves; and the right to benefit must be conditioned upon some minimum number of contribu tions. It is only for some relatively small proportion of the injuries and physical ills to which workmen are subject that it is reasonable and practicable to impose the full responsibility on industry. From its beginnings, the workmen's compensation law has covered all injuries to health resulting from occupational accidents. Further it has now, in this country and abroad, been extended to cover many specified diseases, not resulting from accidents, classified as "occupational." And in a few states in this country and I.atin America it has been extended indefinitely further to cover "all inclusively" all injuries to health "arising out of and in the course of the employment" or all "occupational diseases," undefined, "arising out of the employment." In this country there is strong political pressure in favor of this "all inclusive" coverage of injuries by disease based upon the contention that there is no difference in principle between "injuries by accident" and "injuries by disease" ; therefore, indus try ought to be liable for both classes of injuries on the same terms and conditions. This contention is fallacious. The fundamental principles of the compensation law are that industry shall he held responsible and liable to compensate for the losses from those injuries only which arc caused by "trade risks", resulting from employment and which the employer can control; and that the liability for such risks shall he suffi ciently well defined as to be insurable at practicable and equitable rates, fixed in advance. The standard compensation laws have been framed to carry out those prin ciples in application to injuries by accident. Rut the factual conditions relative to injuries by disease are so different from those relative to injuries by accident as to necessitate different treatment. The crucial difference between accidents and diseases is the time factor. An accident is a sudden event, happening at a definite time and place. Generally the causa! relation between the employment and the accident and between the accident and the resulting injury can he traced with reasonable certainty. Generally the employer is automatically identified. And there is a clear-cut event from the date of which time-limits on notices, claims, etc., can he measured. In contrast, many diseases attributable to occupational risks are of slow' contraction, and may be of equally slow progress to harmful results. In silicosis there may be an interval of as much as twenty or thirty years between the first exposure and disability or death. In the meantime, many causes for disablement or death, other than the occupational disease may have operated. Often it is a matter of extreme difficulty to determine whether disability or death really has resulted from an occupational disease or from other causes. Medical diagnosis of the mere existence of a particular disease is often uncertain ; yet for the proper operation of compensation for occupational diseases it is essential to obtain true medical diagnoses, not merely of the existence of the disease, but also of its causes and consequences. A further difficulty is that, where the disease is of slow contraction, it may be contracted by a workman under several different employers or insurance carriers. In such cases it is essential for the protection of the workman that some one existent employer or insurance carrier shall be directly liable for the entire compensation. That is a highely vicarious and harsh liability to impose upon an employer or insurer --whether or not accompanied by a right to claim contribution from earlier employers and insurers- - and. in all fairness, should he subject to strict limitations. .Moreover there is a difficulty incidental to the provision of new insurance for ' compensation for such diseases of slow' contraction as silicosis, finder such conditions, the liability imposed upon the employer includes a liability for disability or death in the future; in other words, a liability, not merely for future risks but also for the cost of a volume of physical impairments already incurred though the liability therefor is not yet matured, fit insurance parlance, these are termed "accrued liabilities." Such accrued liabilities, under a law newly imposing a liability to compensate for silicosis, would, it is estimated, in a state such as New' York, aggregate many millions of dollars. This mst is additional to losses from current risks; and how to meet it and how to fix. reasonable charges for insuring it is a complex financial problem. Occupational Diseases 119 The situation, then, in 1113' opinion, is this: The principle of compensation, re gardless of fault, may well be extended to cover those disabling diseases that are characteristic of and peculiar to and have their origin in the occupation or process in which a person is engaged. This would exclude the diseases of ordinary life, and would be applicable only to the specific hazards which arise nut of and because of industrial processes and occupations. The provisions for such coverage should be separate and distinct from the provisions of law applicable to compensation for acrj- dcntal injuries, and these distinctions should be constantly emphasized. The probl&rrF5 of formulating such provisions is relatively simple with reference to those recognized diseases set. forth in the older occupational disease laws, since such diseases are reliably diagnosable, of quick contraction and non-progressive. Bnf it is difficult in respect to such progressive diseases of slow contraction as silicosis and asbestosis-- now generally regarded as heing truly "occupational." Fortunately, however, there are promising models for our guidance in some of the foreign compensation laws, whereas experience under indefinite, "all inclusive" coverage in Connecticut, Massa chusetts, Wisconsin and California is helpful with lessons of faults to avoid. In my opinion, a law for the compensation of occupational diseases should contain provisions to the following effect : 1. Diseases to be made "compensable" should be distinctly specified--by listing in a "schedule" or otherwise. They should include all those diseases, but only those, to b found in the state, which, according to prevailing medical opinion, can be traced, in individual cases, to origins in "trade-risks"--f. c.. risks, not of ordinary life, but created by special practices or processes in industrial occupations. 2. There should be a special regime for expert adjudication of medical questions in occupational disease cases. 3. There should be definite periods of exposure required as a condition to the right to compensation for various occupational diseases; the time within which, in order to be compensable, disability' or death must follow exposure should be limited; and cases resulting from exposures prior to the effective date of the compensation coverage, or in industries wholly outside the particular state, should be excluded. 4. Prompt notice either of the first manifestation of the disease or of disablement --the time of such event to be determined as a medical question--should he strictly required; and every presumption shoidd.be against the validity of a claim not made as promptly as practicable. j 5. In case an occupational diseasej merely aggravates, prolongs or accelerates disability or death due primarily or proximatcly to a lion-occupational disease or infirmity or, above all, to old age, the qompensation should be reduced to be propor tionate to the degree to which the occupational disease contributes to the disability or accelerates death. 6. The employer, as of the time of the workman's last substantial exposure to hazards of the disease, and the insurance carrier then on the risk should he liable for the entire compensation--with or without right to contribution from earlier employers and insurers. But all such liabilities! whether directly for compensation or for con tribution to the compensation payable by others, should he subject to brief time limitations. 7. I11 incurable diseases, especially silicosis, the obligatory medical benefits should be specially limited in time and kind. 8. In silicosis and other diseases of slow contraction, there should be special provisions for limited compensation to workmen laid off before actual disablement, with the alternative, under some conditions, of waiver of compensation by such work-* men for aggravations resulting from heing allowed to continue in the hazardous occupation. , 9. A law newly imposing liability to compensate for silicosis and other diseases of slow contraction should leave a substantial interval for preparation between the date of its enactment and that when it shall take effect; the compensation for such diseases should be specially reduced and limited below what would otherwise he appropriate until the "accrued liabilities" are worked off. 10. Compensation for occupational diseases should he insurable separately from compensation for accidents: and, in the initial stage, at least, of a regime of com pensation for such diseases as silicosis, the rating practices now imposed upon insur ance carriers need to be radically modified. -0 7 ivcnty-fourth Annual-Safety Conyvess---National Safety Coimcii The above program is sound and would be highly conducive to occupational -asc prevention. But I am not so confident that it would he safe. The pressure is mg for "liberality" in compensation laws. Merely a few among a large number i.reliable slight diversions from what I suggest would convert compensation for ipntional diseases into indefinite health, old-age and life insurance for workmen in .y industries. The cost might ruin the industries, and, at least, would be so deniable as to make the risks "uninsurable," except on the unlimited assessment jn, with all its financial perils and uncertainties. In regard to prevention, there arc still some practices to be decided upon in freting a regime of .compensation for occupational diseases about which there ins much doubt. For example: Such a regime will practically compel employers, living, employment, to discriminate against all the ailing or aging--against all pt the most healthy and robust. That seems to be desirable in occupations when occupational disease hazards are great. But is it desirable otherwise? Again, an ideal common to those of us who emphasize prevention is to require prompt removal from exposure of workmen manifesting the first symptoms of an 'ipational disease. But for the. elderly or skilled workman the loss of his trade-job i be worse, in every respect, than the danger of continuing his exposure. How , should such cases be defined and treated and how should the law be framed to ct or induce such treatment? Political impatience is the chief obstacle to a just and equitable settlement of the \ .ipational disease problem. If those thoroughly informed as to this complex sub- \ '. w h o have sincerely at heart the welfare of workers could be delegated the an- \ -itv to devise a solution, some progress might be made. But when political j -Uganda is injected into the situation there is little chance for an adjustment j factory to all concerned. The greatest need today is the divorcement of occupa- / ial disease legislation from politics or political considerations. Some Practical Considerations in Dust Control By J. J. BLOOM FIELD Sanitary Engineer, United States Public Health Service, Washington, D. C. The prevention of occupational diseases due to the inhalation, of industrial dust primarily an engineering problem. Until recently, however, little attention had devoted to the control of dust, accounting for the paucity of fundamental data he subject. The consequences of the neglect to furnish adequate protection from - hazards are now being felt, and the cost is becoming a serious drain on industry. now well established that exposure to certain kinds of dust, such as those con ing considerable amounts of quartz, has increased the morbidity and mortality s from respiratory diseases; wliile metallic dusts, such as lead and its compounds, c been associated with general systemic poisoning of workers. It is obvious, 'fore, that any serious attempt to control the dust hazard should, in time, result - only in the improvement of the health of workers, hut also he of definite economic fit to industry. The benefits of a preventive program in the field of accidents are well known. "dry is fast realizing the need of a similar preventive program with respect to national diseases. Evaluation of the Dust Hazard The first step in the evaluation of the dust hazard is the determination of the 'national exposure to the dust in question. A typical example of such a study serve to clarify the methodology involved. Table 1 shows the various occupations in a granite quarry and the number of tors employed in each occupation. Drillers are the only persons using pneu:c tools, known to. produce considerable quantities of dust. In other words, 38 cent of the quarry personnel are shown to he exposed to a potentially dangerous hazard. The occupational analysis at once indicates that the dust investigation .x* Occupational Diseases 121 Table 1--Occupational Classification of Granite Quarriers Occupation Drillers: Lcyncr ......................... Plug and jack hammer. Ollier quarry employees: Superintendent . . . . . . . Foremen ...................... Compressor engineer .. Hoisting engineers Locomotive engineer .. Locomotive fireman . .. Steam-shovel man Crane' operator ........... Derrick men .............. Muckers ..................... Blacksmiths ................ Tool boys .................... Water boys ................ Machinists .................. Air-line repairers ....... Pipe fitte rs .................. Number in Each . Occupation 17 37 1 7 1 12 1 1 1 1 24 24 6 2 1 3 1 2 Total 142 Table 2--Occupational Dust Exposure of Granite Quarriers 1 I 1 Occupation ; Lcvncr drillers ......................................................... Plug and jack-hammer drillers (quarry-hole).... Plug drillers (yard)......................................1......... All other workers...................................................... Number in each occupation 17 37 88 Dust counts in millions of particles per cubic foot of air. Weighted Average 144.4 112.1 36.9 5.8 should especially concern itself with these workers. The next step involves the determination of the occupational dust exposure. Table 2 shows the results of such a study. It is apparent in this table that the drillers arc exposed to high dust concentra tions, especially the Lcyncr and jackhammer drillers working in the quarry hole. From a further analysis of the occupational dust exposure of drillers it is possible to determine which activities are responsible for the dust. For example, experience has taught us that the various activities comprising the processes of most dusty occupations are usually associated with dissimilar dust exposures. For this reason it is essential to estimate the amount of time spent in each activity in any one occu pation and to determine the dust exposure for each. Table 3 shows the results of such a study in the case of a Lcyncr driller. It will be seen that a Lcyncr driller has five different dust exposures. A differ ential analysis, as presented in Table 3, yields several valuable findings. First, it enables one to obtain a true average dust exposure for workers engaged in the occu pation of Leyner drilling. (In this case the weighted average is 144.4 as contrasted with 213.4 million particles per cubic foot found during drilling operations only.) Second, it enables one to determine which activity, or activities, contribute most to the 22 Twenty-fourth Annual Safety Congress--National Safety Council Table 3--Summary of Dust Exposure of Leyner Drillers in a Granite Quarry Activity illincr ........................................ nnging drills ............................. . .'itching drills ................................. v.aching ....................................... 'wing off boles.......................... Avcra.ee dust exposure in millions of particles per cubic foot of air (a) 213.4 9.8 8.0 6.0 1,085.0 Number of lintirs spent in cadi activity (b) 4 1 2 A 'A Particlc-Iiours in millions per cubic foot (a X b) 853/. 9.8 16.0 4.5 271.3 T o ta l....................................... 8 1,155.2 155.2 particle-hours in millions per cubic foot =~ 144.4 million particles per cubic foot 8 boors -.st hazard. It^is evident that the practice of blow-ins off boles by means of inserting compressed air line into each bole is attended with a great amount of dust; and "Ugh this activity lasts but 15 minutes of the 8-hour working (lay, it is responsible r 23 per cent of the total dust exposure. It is evident that 23 per cent of the l.evncr miller's dust exposure may be at once eliminated by prohibiting this practice. And vastly, such an analysis indicates the necessity for devoting all one's efforts to the enioval of dust during the drilling process, since this activity accounts for 74 per cent f the total dust exposure, although a l.evncr driller spends but one-half of the rbine day at bis drill. So far wc have dealt with an industry in which the workers, as a rule, do not bange their occupation. Often workers have bad several occupations, either in the nine industry or in several different kinds of establishments. If the worker has been mplnycd in various occupations in the industry, it is a simple matter to determine us total dust exposure in that industry. This is important from the viewpoint of orrclating a worker's dust exposure and his clinical condition. A typical example is ''own in Table 4. Table 4--Total Occupational Dust Exposure of an Anthracite Coal Worker Occupation late picker .............. ............. . . , atcher '.......................................... mile driver ................................... ' .tier's laborer ............................ . in e r .............................................. 'ction foreman ............................ Number of years in each occupation ? 3 3 15 5 Dust concentra tion in millions of particles per cubic foot 380 71 71 480 480 7 Millions of particlerears pci cubic foot 700 142 213 1,440 7.200 35 Total................ ...................... 30 9.790 790 millions of particle-years per cubic foot --------------= 326 n niHions of particles r>er cubic foot hi Table 4 the worker's occupations are arranged in the order of employment, lasf.one living his present occupation, ft is.obvious that had one considered this u npation only, the dust exposure would not have yielded a true state of affairs, Occupational Diseases 123 nor would it have been possible to correlate this dust exposure with the man's clinical picture. In the above technic, correct weight is given to the number of years spent in each occupation and the dust exposure associated .with each. Only by such an analysis is it possible to arrive at a fair estimate of a worker's dust exposure and his proper designation. Such an analysis is justified by the fact that results obtained with this technic yield excellent correlations with the clinico-ruentgcnological studies conducted on anthracite coal miners.2 It is thus apparent that there is more to engineering dust surveys than the taking of dust samples-and their analysis. Owing to the fact that the making of dust studies is rapidly being adopted in industry, it has seemed necessary to emphasize the impor tant factors in such investigations. Although the making of dust counts, per sc, is not a difficult.-procedure, the collection of dust samples in industry ami their proper interpretation should he done by a thoroughly trained investigator. The examples Just given show the value of this technic in the subsccjncnt steps to be taken in the control of the industrial dust hazard. General Dust Control Methods The selection of any method of dust suppression will depend primarily upon its effectiveness in reducing a given hazard and its adaptability. A large percentage of reduction in dust docs not necessarily indicate that the method used is efficient, unless the reduction has actually been sufficient to bring the exposure below the safe limit, and does not interfere with the industrial operations involved. In general, there arc four methods of dust control: ( 1) substitution of nomlnst-producing or harmless sub stances; (2) isolation of the dusty operation; (3) wetting the dust at its source; (4) local exhaust ventilation. These methods may be supplemented by personal respiratory protection. Tiie first method has a 1united application. One example is the use of a nonsilica parting compound for a silica compound in connection with the making of foundry molds. Table 5 shows that although the use of parting compound, in this particular study, only necessitated an exposure of 34 minutes of the 340 minutes of a mofder's work day (10 per ccntj, actually this activity accounted tor approximately 5S per cent of the molder's total exposure. It is obvious that the employment of a parting compound, which is not as harmful as one composed of free silica, will lessen the dust hazard in this instance to a considerable extent. Activity Table 5---Dust Exposure of Molders i Average Dust ' Exposure in Millions Time of Expo- of Particles sure in minutes per Cubic Foot (a) (b) ParticleMinutes in Millions (a X b) Use of Farting Compound......... 54 Remaining tasks in molding....... 412 Pouring ...................................... 58 Dumping molds ("shake-out" ) .. 16 63.8 3,445 4.4 1.813 3.1 180 32.5 520 T o tal.................................... 5,958 5958 million particle-minutes 540 minutes 11.0 million particles (per cu. ft.) In the case of abrasive cleaning with steel instead of sand, we have the example of the substitution of a substance involving a lesser dust exposure as well as the use of a material not as toxic as sand.2 Table 6 shows the improvement effected by this type of substitution. Not only is the dust concentration reduced from an average of 969 to 135 million particles per cubic foot, but the potential exposure to quartz dust is diminished from 42-99 to 3 per cent. M Twenty-fourth Annual Safety Congress-- National Safety Council Me 6--Showing Reduction in Concentration and Quartz Content of Dust in Sandblast Rooms With the Substitution of Steel for Sand Abrasive poof 'rasivc Average dust concentration in lnillions of particles Percentage per cubic foot of Quartz :id ................................................................................ %p cl ................................................................................ 155 -12-08 3 The second method of dust control, isolating the dusty process, possesses many Abilities, hut unfortunately is not widely used. The theory underlying isolation to concentrate the dust sources to one locality or to a single closed space. In this y. a minimum number of employees are exposed. At present, many foundries, durc shake-out expose workers who normally are engaged in occupations with low -t concentrations. Thus, tnolders in a foundry may he exposed to a dust concenction of 3 million particles per cubic foot under normal occupational conditions, but ten shake-out'operations are carried on close by. their exposure may be increased more than 50 million. The same condition exists when annealing flasks containing und sing arc emptied in malleable iron foundries, exposing grinders and tumbling cl attendants at work close by. Perhaps the best example of isolation of a dusty process is the abrasive cleaning m. This completely encloses a hazardous process and exposes only the blaster who generally ccpiippcd with a protective helmet. The room is also exhausted, which other reduces the dust concentration. Processes which arc isolated require good ntilation. Other examples of isolation are the automatic turntable for abrasive ailing, tumbling barrels, and batch-mixing rooms found in some pottery cstablish- ots. The third method, perhaps the oldest known, is the practice of wetting the dust its source. In Table 7 an example is depicted in connection with the drilling and ding of rock in anthracite coal mine operations. Tt is apparent that a tremendous 'action in dust has been effected by this method. However, as already pointed out. less a particular method is attendant with a reduction of the dust to a safe limit, cannot he considered successful. In the present instance, the workers engaged in :iiing are still exposed to unsafe concentrations of a highly dangerous dttsU and more positive method.of controlling tiie dust in drilling operations by dust traps dd he indicated. For drilling and loading operations involving an exposure to dusts toxic than those containing high amounts of free silica, as in the case of coal or tain talcs, the reduction shown by the use of wet methods may be considered live. Me 7--Contrasting "Wet" and "Dry" Methods of Rock Drilling and Loading 1esses No. of Samples Average dust count in millions of particles per cubic foot "Dry" "W et" 'ling ............................................ 23 568 33 ding ............................................ 10 636 32 The fourth method--exhaust ventilation--is perhaps the most effective, and one the widest application. We cannot discuss here the details of the theory and e->n of local exhaust systems, except to point out there is a real need for more 'nmental studies of the type conducted by DallaValle with reference to the design Meal exhaust hoods, which he has presented in Public Health Bulletin 217. Th-k of Hatch and his colleagues4 on the control of the silicosis hazard in the hard industries is another example of a scientific approach to the dust elimination Mem. i Occupational Diseases 125 Table 8--Summary of Results Contrasting the Dust Exposure of Mine Workers Under Controlled and Uncontrolled Working Conditions Operation Dust Concentration in millions of particles per cubic foot of air Controlled Uncontrolled Remarks OC -U hiring charge . ........... 40 Loading coal or rock.. 32 Loading coal . . ...........4-26 D rilling........... ........... 33 Hauling coal in mines. 1.2 Preparation of coal. . . 24 636 291-1138* 568 17 380 Unless at least IS minutes elapsed after tiring a charge, miners found to be exposed to high dust concentrations. By wetting the loaded material the dust count is reduced as shown. Mechanical loading decreases the dust ex posure as indicated. Wet drilling is effective in reducing tlic dust concentration. Further reduction would necessitate exhaust ventilation. Wetting coal and empty cars reduces dust in haulngeways. Wet breakers reduce dust counts as shown. * T h e lower result is asso ciated wilii the h an d loading of wet coal while th e h ig h er average is based on the hand loading of dry coal. It is apparent that there are no set roles for the mechanical protection of workers from the industrial dust hazard. Specific conditions in an industry, or a plant, will determine the type of protection to be employed. The present discussion lias empha sized the importance of approaching the problem from the standpoint of the occupa tional exposure. Studies in representative plants of an industry often reveal the various methods which may he employed in dontrolling the dust hazard. The follow ing two examples indicate the value of such investigations. Table 8 indicates the various control nieasurcs which were found in use in the anthracite coal mines investigated in the study referred to earlier. Although no single mine practiced all of the control measures shown in this table, by an occupational study in several representative mines it was possible to show that methods are not known and practiced for the elimination of the dust hazard in this industry. Another example is indicated in the results of a study now in progress in connec tion with mercurialism among workers in the hatters' fur cutting industry. Table 9 shows the exposure to mercury dust and vapor of sonic of the workers in this industry Table 9--Exposure of Hatters' Fur Workers to Mercury Dust and Vapor Under Controlled and Uncontrolled Conditions Occupation Total Mercury Exposure in Milligrams per 10 cubic meters Uncontrolled Controlled Method of Control Blowers ........................................ 4.6 .. None practiced Shippers ...................................... 7.2 .. Cutters ................................. 4.0 1.8 " " Bocal exhaust ventilation Sorters ........................................ 3.8 1.7 *' Brushers ..................................... 3.1 1.2 Drummers .................................. 2.5 0.6 " Segregation Clippers . .. ........... 1.5 0 . 7 __________ J]______ 126 Twenty-fourth Annua! Safety Congress--lYaiioiitii Safety Council under controlled and uncontrolled working conditions. It is apparent that where some measure of control is practiced by such methods as segregation or local exhaust ventilation, a material reduction in the exposure to mercury has been effected. It Is our belief that in the case of the blowers' exposure, a reduction may be effected by mechanical enclosure and local exhaust ventilation, and that the shippers' exposure to mercury vapor may be lessened by a general system of ventilation sufficient to change the air in the store room frequently enough to bring the mercury concentratration to a lower level. Unfortunately, in the present investigation, it has been im possible to find a plant in which an attempt has been made to reduce the exposure lor these two occupations. In some dusty occupations the methods of controlling dust have not been devel oped. In fact, operations such as removing the cores from very large foundry' castings, sand-blasting, handling of used storage battery plates, paint chipping, and cadmium oxide manufacture appear to offer no practical means of adequately controlling the dust generated. In such cases, it is therefore necessary to furnish the worker with personal respiratory protection devices to prevent his exposure to the harmful effects of the dusts present. These devices consist of various types of respirators, masks, and helmets. It is important to hold in mind the limited use of personal protection devices. Because a worker cannot with comfort wear a mask or helmet continuously, such devices must be employed intermittently. Their use is generally extended to those operations where all other methods have failed or supplementary to them, as in storage battery repair where the exposure to small amounts of lead breathed is known to be detrimental to health. It should be pointed out that the U. S. Bureau of Mines is equipped to conduct approval tests of respirators used for protection against various dusts and fumes (Schedule 21). These tests are conducted against the dust for which the device is to be used and arc rated, not on an efficiency basis, but on the quantity of dust which actually passes the respirator. The results of a study of masks or helmets of the positive pressure type, made during the sandblast investigation conducted several years ago by the Public Health Service in cooperation with the National Safety Council." showed that the only practical safeguard to the worker inside the sand blast room was to provide him with a mask or helmet of the positive pressure type. In studying the efficiency of such devices it was found that a relationship existed between the amount of air supplied to the helmet and the concentration of dust inside the helmet during blasting. To determine the optimum air volume to be sup plied to such protective devices, it was necessary to obtain dust samples from inside the helmet while varying the air volume, at the same time maintaining the dust conentration in the sandblast room (outside the helmet) constant. The positive supply of 6 cu. ft. of dust-free air per minute will protect a worker under the operating conditions now in practice in sand-blast rooms. The ultimate criterion of protection, however, is the result of dust determinations of the air within the helmet, that is, the, air actually breathed by the worker and not the volume of air supplied. Too much emphasis cannot be stressed on the necessity of maintaining in good order the personal respiratory devices for the protection of the worker against various toxic dusts. Maintenance, of exhaust ventilation systems, and other types of protec tive equipment, should be a rule in industry rather than an exception, 'boo often the term "rood housekeeping" has been interpreted as signifying only tile periodic removal of dust collected on doors, rafters, etc. Although such practice contributes to the general state of cleanliness of a workroom and should .always be in force, the time has surely come when serious attention should be given to the installation and rigid naintenanee of all types of dust roufrol devices. In every plant there should be some responsible individual charged with the periodic inspection of all workrooms as to sanitation, ventilation, and maintenance of all dust removal and other protective devices. Perhaps the best criterion of the effectiveness of these devices is the periodic determination of the dust content of the air at the workers' breathing zone. tnly by constant vigilance and an approach to the. problem as outlined in this paper may one hope to make progress in the control of the dust hazard in industry, ( >fton the benefits of even .a most extensive program of dust control are not immediately realized. This is especially true in dealing with fibrosis producing dusts in plants where, some of the workmen have already inhaled sufficient quantities to Occupational Diseases 127 cause disability-. However, in dealing with such dusts as lead, cadmium, and mercury compounds, control measures may produce salubrious results in a relatively brief period. It is difficult, because of lack of sufficient reliable data, to indicate here the economic benefits resulting from a preventive program of dust control. It lias been estimated by Dean K. Brundajrc. statistician of this office, that the minimum expectancy in savings to employer and employee from an indicated reduction of the accident rate and of the time lost on account of illness (or an equivalent reduction in mortality), demonstrated as attainable, is $20,000 per year per 1.(100 employees. And this estimate is for plants whose accident rate is considcraldy below the average, in which there are no occupational health hazards. In plants where hazards are known to exist the savings should be far in excess of this conservative estimate. When one realizes that in this country there arc approximately 15 millions of workers engaged in manu facturing, mechanical, and mineral industries, then it is evident that the magnitude of the problem has not been overemphasized. References 1. B loo m fie ld , J . J . a n d D r e e s s e n , \ \ \ C . : S ili co sis a m o n g g r a n i t e q u a r r i e s P u b l i c H e a l t h R e p o r t s , Vol. 49, N o. 23, J u n e 8, 1934. 2. A n t h r n c o - S i l i c o s i s a m o n g h a r d coa l m i n e r s . P u b li c H e a l t h B u l l e t i n N o . 221, 1933. 3. B loo m fie ld , J . J . , a n d G r c e n b t i r g , L e o n a r d : S a n d a n d m e ta l li c a b r a s i v e b l a s t i n g a s a n i n d u s t r i a l h e a l t h h a z a r d . J o u r . l n d . 3 Iy g. , vol. 13, no. 4, J u l y , 1933. 4. H a t c h . T h e o d o r e , D r i n k e r , P h i l i p , a n d C h o a t e , S a r a h P . : C o n tr o l of t h e sil ic o s is h a z a r d in th e b a r d - r o c k in d u s tries . I. A . l a b o r a to r y s tu d y of the d esig n ot lust c o n tro l s y s t e m s for u s e w i t h p n e u m a t i c g r a n i t e c u t t i n g to ol s. J o u r . 1ml. H y g . , vol. 12, no. 3. M a r c h , 130. H atc h, Theodore, Kelley, G eorge S., and Fchnel, J. \V .: Control ot the Mlico-is h az a rd in th e h a r d - r o c k in d u s tries . I I . A n i n v e s t ig a t io n of the Kelley d u s t tr a p for i k c w ith p n e u m a t i c r o c k d r il ls of t h e " J a c k - h a n n n c r " ty p e ; J o u r . Jml. H y g . . vnl. 14. no. 2, l e b r u a r y , 132. H atch, Theodore, W a rre n , Henry,, ami Kelley, George S .: Control of the silicosis hazard in th e h a rd -ro c k in dustries. H I . D es ig n ami operation of a d u s t-c o n tro l s y ste m for use w ith p n e u m a t i c r o c k d r il ls i n o p en e x c a v a t i o n . J o u r . l n d . H y g . , vol. 14, n o . 7, S e p t e m b e r , 1932. Silicosis and Silico-Tuberculosis Medical Problems of an Important Industrial Disease l By EDGAR MAYER, M.D. i New York City A bidden element of tbc cost of production is industrial disease.' Industry lias reached a stage beyond tile concern only of wages and hours, bar more important is conservation of man power by preventive medicine and improved engineering. Disease preventive measures are not a cost, but, in the long run, a great economic saving. Incidence. In the United States it lias been computed that there are from 500,0(10 to a 1,000,000 people employed in occupations where a silicosis hazard exists. In New York City there tire about 65,000 such employees. In a ia presentativc group of granite workers in Massachusetts silicosis alone was present in about 15 per cent and silicosis complicated with tuberculosis in almost K per cent. Tuberculosis was the cause of dealli in over one-third of tbc granite workers which is four times the incidence for males of 20 years and over in this country. In foundry men studied in Massachusetts, silicosis was less freipient labout 0 per cent) and less advanced in degree than in granite workers. The duration of exposure in foundry workers with pneumoiioconiosts has averaged many more years than that required to produce silicosis in an industry such as gold mining. The tuberculosis hazard in foundries is nearly as great as that reported for some of the other dusty trades, but tbc figures are lunch lower than those of miners of gold, silver, copper and lead, among whom the mortality from tuberculosis is S to 1H times the general expectancy. Death rates for till noil-tuberculous infections have been reported higher among workers in siliceous dusts than in the general population. It is suggested that the worker in silica succumbs more often to acute pulmonary infrctioiis rather than survivma tbc chronic fibrosis. !S Twenty-fourth Annual Safety Congress-- National Safety Council r Silicosis is defined as a pathologic condition of the' lungs due to the inhalation -ilica, whether free or combined in such a state as to he capable of setting up its racteristic pathogenic effects. The principal factors that determine the incidence -ilicosis are ( 1) the percentage of free silica in the inhaled dust; (2) the conoration of silica particles less than 10 micra in diameter in the atmosphere; (3) duration of exposure to the dust, and (4) the susceptibility of the individual .posed as modified by age, complicating infections, etc. The occupational disease -ulting from such inhalation has been defined as "morbid results of occupational viity traceable to specific causes or labor conditions and followed by more or extended incapacity for work." .1fetabolism of Silica. Significant amounts of silica arc present in all body ues and fluids. It enters the body through the digestive tract and the lungs, t of that entering the stomach is eliminated in the stools, but a fairly large amt is absorbed into the blood as shown by the constant excretion of silica in urine. All vegetable foods contain silicon especially the hulls of grains, hay and aw. The low silica content of the liver, spleen and kidneys indicates the little iiition of the absorbed silica in the body. Silica content of the urine of animals be influenced at will by diet. The body possesses a very efficient mechanism the disposal of silica because of the low kidney thrcshhold. Silica entering lungs in particulate form is expectorated in part with its enveloping cells, but st of it is carried into the pulmonary lymph channels. Many such particles reach lymph nodes and even the spleen by way of the blood. The finest particles ..ever, may be dissolved in alkaline body fluids and carried away in solution, to excreted in the urine. There may be a constant drainage of silica from tbe g through the inhalation of extremely fine particles of silica in dusty atmospheres, small that they are not seen under the microscope. Attempts to influence the absorption of silica from the lungs by administration alkali have been inconclusive. Klimination of silica by way of tbe sputum from dents having deposits of silica in their lungs appears to be higher than those mg no history of exposure to dust. Only small amounts of silica are in the id and this level is little different in normals than in silicotics. Patlwlopy. This disease is essentially a fibrosis of the lungs developing espelly in such industries as hard-rock metal mining, granite cutting, metal grinding ; sand-blasting. The pathological changes are believed to result from two causes, blocking of the lung lymphatics by mononuclear cells laden with dust in addition the action of colloidal silica, the exact nature of which is in doubt. The small -deles under 10 micra are the only ones capable of penetrating the lung tissue. Although silica plays the dominant role in the production of silicosis, the ad.ture of other dusts tends to modify the pathological changes in the lungs so t these resemble then those of other forms of dust inhalation, and the modification rs some relation to the percentage of free silica in the mixture. Silicates, as in vstos, produce a definite change in the lung, as well as other dusts such as rblc, coal, etc. Such changes are represented by a fibrosis brought about because ilivcly insoluble minute particles of minerals in sufficient concentration have n brought by the activity of phagocytic cells into intimate contact with the bnonary connective tissue. This fibrosis is a diffuse cellular one that occurs in walls of the smaller bronchi and of all their finer divisions and extends to 'dve the supporting connective tissue of the adjacent blood vessels and to some m t also the walls of adjacent air spaces. However, when the great majority of inhaled particles are composed of or contain silica, there develops, in addition, a rific and localized type of fibrosis called the silicotic nodule--an orderly whorled angement of cells and fibres, and with sharp definition from the adjacent pareu nia. Many dusts create a generalized fibrosis hut only one, namely one combined ;h silicon dioxide produces the special fibrosis of silicosis. Sericitc, known as te mica, which is a hydrated silicate of aluminum and potassium, has not produced animal experiments the silicotic nodule, but instead generalized fibrosis resulted. Dusts must he differentiated into those which are chemically active and those h are inert when .inhaled into the respiratory tract. Silica is a chemically active : which must necessarily be soluble to a degree in the body fluids and its activity nds on its solubility. This activity which is manifested in the areas where dust :cles are tarried along the lymph stream by phagocytes, causes lesions of two Occupational Diseases 129 types, "toxic'' and "sclerotic" both of which have been reproduced experimentally. Toxic lesions depend upon local necrosis and slow death and appear to favor the growth of tubercle bacilli; the sclerotic lesions produce the nodular fibrosis. The inert dusts ace insoluble in body fluids and cannot exert chemical action in the lung tissue, but if they accumulate to a marked extent their effect is mechanical which may lead to a certain amount of diffuse fibrosis around the dust deposits. Certain dusts, such as carbon, may have physical effects, they may adsorb toxic substances and it has been suggested that on this basis there is a relatively lower incidence of active clinical tuberculosis in silico-anthracotics than in silicotic lungs. Other dusts may even protect, as in the case of certain clays, gypsum and aluminum oxide. Pure pneumonoconiosis may be only a laboratory disease, as the pulmonary fibrosis oi workers in dusty trades probably results hum the combined action of dust and infection, whether it be tuberculous or not. In silicosis it is not the mineral particles that arc breathed in during life that record the cause of disease, but the particles that have been dissolved. Risk to work, efficiency and health may be greatly accentuated through the inhalation of finely divided particles even of a chemically inactive dust when there has occurred a lymph stasis which is known to follow exposure to silica. This lymphatic blockage leads to retention and accumulation of the inert dust. In soft coal miners who get what is called "miner's asthma" we have this accumulation of carbon. Such patients arc very liable to have a high incidence of bronchitis with mechanical and physical changes due to retention of anthracotic dust. Furthermore, unequivocal cases of silicosis, with or without tuberculosis, can no longer be doubted. Tuberculosis. Most apical tuberculosis is acquired before the ago of 25 and so silicosis at the age of 30 makes a previous tuberculosis more serious. Most workers with tuberculosis going into the mines before the age of 30 die of tuberculosis by the age of 45. The silicotic develops a sputum that contains tubercle bacilli late in life and the children who arc contacts with tubercular silicotics develop very little clinical tuberculosis. It is impossible to say definitely that tuberculosis engrafts itself upon the silicotic or vice versa, for we sec apical tuberculosis in silicosis that spreads downward, while other silicotics show only the tuberculosis in the lower lobes. It has been found that most silicotics die of tuberculosis. The diagnosis of silicosis is made primarily on two findings, the proper history of occupational exposure to siliceous dust and, the presence of abnormal shadows on the pulmonary X-ray. The physical examination and the patient's symptoms are of less value. There are other diagnostic aids such as the finding of large quantities of silica particles in the sputum, quantitative determinations of silica in urine, and at post mortem, chemical analyses of the lung ash supplemented by petrographic examination, roentgen-ray spectrum analysis and special incinerating studies of lung tissue. We must at times rclj- on the pathologist to determine the amount and distribution of fibrosis due to silica and from microscopic studies give an opinion on the importance of this fibrosis as the ultimate cause of disease and death. Lung fibrosis may be present without any silica. Silica may he present in lung tissue or the pulmonary lymph channels without associated fibrosis. Finely divided siliceous particles from lung tissue may contain innocuous silicate which cannot he distinguished from harmful silica particles. Hydrated silica which is not doubly refractive cannot he demonstrated with prisms. Therefore in the pathological section the presence of siliceous fibrosis can he suspected blit cannot be specifically identified with the siliceous material that it may contain. Accordingly the niicroincincration method of Irwin with hydrochloric acid is now included in the microscopic examination of any lung as a means toward a surer diagnosis. Diagnostic difficulties in clinical medicine may be more obvious if we examine first tbc occupational bistory. Quartz grinders working under conditions of massive exposure may develop silicosis in acute form even in a period of months, whereas in other occupations it may take 25 years. Workers in tbc same industry, indeed in the same room, experience different degrees of exposure dependent upon perhaps the dust-lillcring capacity of the nose and functional condition of the lung as deter mined by constitutional characteristics and antecedent disease. The size and col loidal structure of tbc particles of silica, as well ns tbc dosage and total amount of silica, will influence the rate of development of the disease. Apparently particles that ue larger than 10 micra are not phagneytosed in the lung. So a definite 30 Twenty-fourth Annual Safety Congress-- National Safety Council 'lory <>{ exposure must lie established and in general hospitals where patients are gratory, conditions under which they worked arc very vaguely described and ere are not available data on dust counts and silica concentration, so that the history often misleading. As to symptoms, patients can perform strenuous labor despite extensive disease ind the symptoms of dyspnea and cough arc common to many diseases, bever is -.I-sent unless infection occurs, but most important is the great disproportion between patient's complaints and what is seen on the X-ray, the latter showing extensive i'normal shadows in comparison with the symptoms. On physical examination, extensive disease may be present and few abnormal hysical signs. The physical signs are merely those of a general pulmonary fibrosis . ith emphysema, such as restriction of costal and dispbragmatic movement, diminuion of or intensified breath sounds and a hyperresonant note. Rales are usually 'sent unless infection is present. As to the X-ray. there are 3 essential types of shadows described, linear strands, nail discrete shadows, and homogeneous shadows of varying sizes; these <?orrcnond to the fibrous strands, silicotic nodules, and the conglomerate masses i fibrosis. -The nodular shadows are usually characteristically around the iluni, or conglomerate nodular shadows of bat-wing appearance extend into both nper lung fields, or nodular shadows may he distributed in the upper two-thirdj f the lung fields, perhaps more pronounced on the right side, with the lower third pt clear by emphysema. With infection present, the shadows are less sharp or he linear strands interconnect or fuse. Large conglomerate shadows appearing ut from the hilum leaving the periphery of the lung clear throughout because of mphysema. The distribution of some of these lesions may he determined by the osture assumed by the workers, and infection may likewise determine an ultimate ifypical distribution. Many variations from these patterns tire seen in the X-ray, pecially under excessive exposure or when other dusts arc inhaled, or in the (sence of infection. Tt is probable that the main source of the diagnostic diliililies is caused by the emphysema which muffles the physical signs and is responith emphysema, such as restriction of costal and diaphragmatic movement, diniinui1le in great part for the absence of symptoms. It may blot out, even oil X-ray, he silicotic lesions of fine size. Examples of such difficulties in diagnosis as encounrvd by us arc the following: Case }--Mr. T. A forty-five year old man entered the New York hospital mplaining of mild cough and expectoration of four months' duration. lie appeared cutely ill. his fever was 103 degrees and respiration 28. Rales were elicited over i upper half of both sides of the chest. Examination of his eye grounds revealed 'literal retinal tubercles: his sputum Contained numerous acid-fast organisms, lie X-ray revealed fine mottled shadows distributed throughout both lung fields ad a small cavity at the left apex. A diagnosis of miliary tuberculosis was made. ; however, after one weeks' stay in the hospital, his temperature and pulse returned normal and during the following month he gained 18 pounds. The signs in his " s t now became confined to the left apex. In view of his unusual progress the aghosis of miliary tuberculosis was doubted. His occupational history revealed at up until three years before entrance to the hospital he had worked for 20 ars polishing leather on a sandpaper wheel. There were numerous machines in e work room and no precautions were observed to clear the very dusty air. ::s sputum was examined through the kindness of Dr. Burke of Ray brook, X. Y. iio found it laden with numerous doubly rcfractile silica particles. He expressed :r opinion that this was consistent with silicosis for he bad found such numerous articles only in cases of silicosis. The patient subsequently died of a tuberculous 'ningitis. Retinal tubercles were demonstrated on microscopic section. The holugist's report was miliary tuberculosis. Ashing of the lung showed increased 'ica content, consistent with undue exposure to dust (more than 2 mgm. silica per .im dried tissue). Case II--Mr. R., aged 54, entered the New York hospital complaining of mop:;, ses. dyspnea and chest pain. On physical examination there were rales 1 dullness over the upper third of the right chest anteriorly. He ran a low ole fever but was robust and felt quite well. The chest X-ray disclosed enlarged inn shadows, particularly on the right, and diffuse mottled discrete shadows Occupational Diseases 131 throughout both lung fields with a circumscribed density near the right apex. ' He gave a history of having worked for twenty-four years as a cutter and sizer of asbestos-containing paper box boards. The rooms were in a continuous cloud of dust. Examination of the dust revealed 5 per cent silica content. The hemoptysis, we felt, was to be explained on the basis of infection or neoplasm, but we did not know whether we were dealing with one of those processes alone or an associated silicosis or asbestosis. A small nodule in the neck was subsequently removed and - showed carcinoma. We arc inclined to believe that this does not explain the whole process, as the man is still alive and certainly, from the X-ray standpoint, wo cannot say that there is no silicosis. ' 1 Case III--Me. C. A dish-washer, aged -lb, entered Ilellevue hospital because of cough and expectoration, associated with dyspnea. There was some dullness and rales at the right base posteriorly. Chest X-ray revealed a homogeneous shadow at the right base. His sputum contained no tubercle bacilli and lipiodol study revealed no abnormalities. Bronchoscopic examination disclosed a bleeding mass in right main bronchus. Symptoms and disease progressed during the following four years. Discrete mottled shadows first appeared in the upper right lung field and the shadow at the right base cleared somewhat. Three years later extensive ab normal shadows were present throughout both lung fields, particularly on the right. Diagnosis of chronic pemunonia of unknown etiology was made. At no time was a diagnosis of silicosis entertained, because as far as could he determined he had no history of exposure. Furthermore if there were silicosis it behaved very atypically having the lesion confined practically to the right base at the beginning and then spreading to the left lung. Autopsy however, revealed a typical silicosis associated with a small degree of tuberculosis. A picture of the lung showed how much more extensive the silicotic process was in the right lung. There was stenosis of flic right middle lobe bronchus with bronchiectasis in this lobe. Chronic infection in the lung field probably accounted for the unusual localization. This ease illustrates how necessary it is to bare the history of dust exposure for without it here we are unable to even suggest a diagnosis. Cnsr IV --Mr. C., aged 45, complained of cough and dyspnea with slight expec toration and gave a history of having worked for many years repairing tires, using talc powder. It was difficult to obtain accurate details as to the possibility of silica exposure except that the rooms were (filled with clouds of dust. Rales were present at both apices and a few tubercle bacilli were found in the sputum. Discrete and stringy shadows were disseminated throughout both lung fields. We know from the positive sputum that tuberculosis is present. The patient has, however, been well for a period of two years. The doubtful history of exposure together with the numerous discrete nodular shadows in his lung, which arc con sistent with silicosis, makes this patient a problem. Is this tuberculosis alone or is this tuberculosis with silicosis? The patient is still living a year later and working. Conclusion. Cases such as these are exceptional, hut their existence must always he borne in mind. If occupational history is inadequate and X-ray, clinical and laboratory studies prove misleading, the diagnosis may present great difficulty. However, a comprehensive study of all possible data usually clears up the problem with reasonable certainty. ADJOURNMENT Safety Equipment Safety Equipment WEDNESDAY AFTERNOON SESSION October 16, 1935 The session was called to order by Chairman, Irwin \V. Millard, president. Industrial Gloves Corporation, Danville, 111. Chairman-Millard mentioned some of the problems of providing adequate safety equipment for industry. Respiratory Protective Devices (An interpretation of the U. S. Bureau of Mines, Schedule 21) By CARLTON E. BROWN, Chemist, and WILLIAM P. YANT, Supervising Chemist Gas Section, Pittsburgh Experiment Station, Pittsburgh, Pa. The respiratory protective devices of industrial hygienic importance arc those designed to protect against the inhalation of harmful solid, gaseous, or liquid atmos pheric contaminants, or the inhalation of air dciicit'ut in oxygen. The devices in common use arc the mechanical filter respirator (commonly re ferred to as respirator) for protection against the inhalation of dusts, smokes, fumes, and mists or what may be referred to collectively as atmospheric particulate matter; gas masks for protection against the inhalation of gases and vapors; oxygen breath ing apparatus, hose masks, and air-line respirators for protection against the inhalation of any atmosphere provided it -docs-not-contain harmful constituent which can he absorbed readily through the skin: and the abrasive blasting helmet or hood for pro tection against the inhalation of and the impact and abrasion irom the atmospheric particulate, matter generated in sand blasting or abrasive, blasting with steel shot. These devices are designed to furnish protection cither by making the wearer's inspired air safe to breathe or by supplying the wearer with safe air from a supply which ho carries or from outside the contaminated zone. The wearer of the first or air-purifying type, on inspiration draws air from his immediate surroundings through the device which either removes the contaminant, usually by chemical or mechanical filtration, or converts it into a harmless substance. This type, of course, offers no protection against atmospheres deficient in oxvgent as it does not add oxygen to the air. There arc two types of respiratory protective devices of the second type designed to supply the wearer with safe air. In one, the wearer receives his air supply from a cylinder of compressed oxygen, liquid oxygen, liquid air, or from a chemical which vields oxygen upon decomposition. This air supply is part of the self-contained unit, all of which is carried by the wearer. In the other type a hose, attached to a facepiece, is connected to a compressor or blower whose intake is located in safe air. Air is forced through the hose to the wearer. N o te : P u b lis h e d b y p e rm is si o n oi D irector, V . S. P u r e a u of M in es. (N o t su bje ct to c o p y right.) 133 Mi.-*;: J vY !' l l <-Ak 134 1 svcnty-fourth Annual Safety Congress-- National Safety Council 1here h ?ome confusion in the use of the term "respirator," to designate devices for protection against the inhalation of atmospheric particulate matter. Such devices were the first and for a long time were the only respiratory protective devices. They were logically called respirators, and as long as they were the only devices of this kind there was no confusion. The development of other devices of industrial hygienic importance and the development of devices for maintaining artificial respiration over long periods and for enabling men trapped in submerged submarines to reach the sur face safely, all called respirators, was responsible for the confusion. The Bureau of Mines suggests that the term "respirator" he retained for all of these devices, but that respiratory protective devices of industrial hygienic, importance he called indus trial respirators and that the different kinds of industrial respirators he assigned a name which will indicate their operating principle or field of use or both. Satisfac tory names in common use should he retained. .On this basis, the Bureau of Mines suggests the following classification for respiratory protective devices of industrial hygienic importance: Industrial Respirators 1. Supplied-Air Respirators a. Self-contained type (1) Oxygen breathing apparatus'1 b. Hose type (T) Hose mask (21 Air-line respirator'1 (3) Abrasive blasting respirator' 2. Air-Purifying Respirators a. Chemical filter respirator1* (1) Acid gas or type A" chemical filter respirator (2 ) Organic vapor or type B' chemical filter respirator (3) Ammonia or type C' chemical filter respirator (M) Carbon monoxide or type D ' chemical filter respirator b. Mechanical filter respirator* f l) Dust or type A ' mechanical filter respirator (2) Fume or type B' mechanical filter respirator (3) Mist or type C" mechanical filter respirator c. Chemical and mechanical filter respirator" Testing and Approving of Industrial Respirators by the U. S. Bureau of Mines Since its organization the U. S. Bureau of Mines has been interested in industrial respirators as a means of protecting workers in the mineral industry against harmful atmospheric contaminants. To this end the Bureau has developed an approval system, die purposes of which are: (1) To encourage and aid manufacturers in the develop ment and marketing of safe and suitable equipment: and (2) to encourage the ennmmer to use such equipment, to aid him in obtaining it and to instruct him in its ,.-agc. These purposes arc accomplished by establishing a schedule of the material and 'erforniance requirements that a safe and suitable device should meet; by making approval tests for conformance to such a schedule; and by informing the public of the a Sometimes called m ine rescue breathing apparatus. > Sometimes called paint-spray respirator or positive pressure respirator. e Sometimes called sand-blast helmet or hood. d C o m m o n l y calleirl g a s m a s k . * L e tte rs assigned to ca nisters of chem ical filter respirators. See U. S. P u re a u of M ines A p p r o v a l S c h e d . 14 P , P r o c e d u r e for T e s t i n g G a s M a s k s for P e r m i s s i b i l i t y , 17 p p ., 1935. f Comm only called respirator. Sometimes referred to as dust respirator or mechanical Iter-type respirator. o L e tte rs assigned to m echanical filter resp irato r filters. See U. S. P u reau of Mines A p p r o v a l S ched. 21, P r o c e d u r e for T e s t i n g F i l t e r - T y p e D u s t , F u m e , an d M is t .R es pira tors for f- r m i ss ib i lU y , 11 p p ,, ' 1934. HT he devices now referred to as Type X or All Service Gas Mask and the chemical .trtiMgc respirator fall under this heading. Safety Equipment 135 advantage- in the use of devices bearing Bureau of Mines approval. If the device is found by examination and test to meet the rcf|uircments of the schedule the Bureau of Mines gives the manufacturer a certificate of approval which he may display as evi dence of the quality of his product. The approved devices are marked in a manner which clearly distinguishes them and indicates the purpose for which they are ap proved and the limitations under which they may lie used. As an aid to the con sumer, the Bureau of Mines periodically issues a list of the devices which have met the requirements. The submission of equipment is entirely voluntary on the part of the manufac turer. On making application for tests, the manufacturer deposits a fee which is turned into the miscellaneous receipts of the treasury of the United States; none of the money accrues to the Bureau of Mines. The approval system is motivated en tirely by the desire of the manufacturers to produce and market good equipment, the interest of the Bureau of Mines in having safe equipment available commercially, and the demand of the consumer for such equipment. Approval schedules have been issued for oxygen breathing apparatus,' chemical filter respirators or gas masks,' hose masks' and mechanical filter respirators.* The schedule covering hose masks is being revised to include the other kinds of supplicdair respirators, namely, air-line and abrasive-blasting respirators. When this revision is completed, the Bureau of Mines will have approval schedules fur all types of respirators now in common use. The approval system undoubtedly is largely respon sible for the development of fundamentally safe and suitable devices, and the elimina tion of confusion in their selection and use. The general plan of the various schedules is similar. The requirements may he divided into 3 parts: ( 1) Pre-test requirements, or those with which the manufacturer must comply before examination and test of a device will he undertaken. For example, tho respirator must be in a fully developed form ready for market and available for pur chase if approval is granted. Also, the manufacturer must be prepared to test and maintain control of the essential characteristics of his device by a method which meets the approval of this Bureau. (2) Material, construction, and performance requirements which the equipment must meet by examination and test. | (3) Post-test requirements, or those fvith which the manufacturer must comply after the device is approved. From the viewpoint of the consumer the most important of these concern labeling and marking, provision of adequate instructions for proper use of the device, and maintenance of design and quality of the product marketed under the approval. As a check on the latter, the Bureau of Mines obtains samples of the device on the open market and subjects them to the various inspections and tests of the appropriate schedule. The Bureau reserves the right to withdraw its approval of any device for cause. Interpretation of U. S. Bureau of Mines Approval Schedule 21, Procedure for Testing Filter-Type Dust, Fume, and Mist Respirators for Permissibility Among the reasons for the development of Schedule 21. Procedure for Testing Filter-Type Dust. Fume, and Mist Respirators for Permissibility, was the realization by the Bureau of Mines and others that there was a definite need for mechanical filter respirators to protect workers against harmful atmospheric particulate matter in situa tions where better methods of control of dust production and removal were cither not available or practical, the inefficiency of existing mechanical filter respirators, and1*34 1 Bureau of Mines, P ro ced u re for E stab lish in g a List of PermisMtile Self-Contained Oxygen B r e a t h i n g . A p p a r a t u s ; F e e s , C h a r a c t e r of T e s t s , n n d C o n d i t i o n l.'itdcr w h ic h M i n e F e s c u e B r e a t h i n g A p p a r a t u s w il l b e T e s t e d : S c h e d . 13A, J a n u a r y 21, 1*730, 12 pp. . - B u r e a u of Mities, P r o c e d u r e for T e s t i n g flas M a s k s for P e rm issib ility : 9, 1935, 17 pp. Si bed. MI), M ay 3 B u r e a u of M i n e s , P r o c e d u r e for T e s t i n g H o s e M a s k s for P e r n i i s s i b i l i t v : S ch ed . 19, A p ril 28, V)27, 8 pp. 4 Bureau of Mines, Procedure for T esting Filter-Type Dust, Fume, and Mist Respirators for P e r m i s s i b i l i t y : Schorl. 21, A u g u s t 20, 1934, 14 pp. I urnty-foiirth Annual Safety Congress-- National Safety Council -ts from manufacturers and consumers that this bureau test and approve such -ihcdule 21 follows the general plan of the other bureau approval schedules for 'ini respirators: the pre-test and post-test requirements are quite similar, and -.neral principles of the test requirements are the same. The primary purpose of : aper is to explain the reasons for the various test requirements. Pre-Test Requirements The pre-test requirements of Schedule 21 require that the manufacturer submit mation, drawings, and samples of the device to be tested. The device must be i 'ctcly developed and ready' for release to the public, and the device when tested ire manufacturer or his agent must have passed tests of the nature described chcdulc 21. The reasons for the third requirement are: ( 1) To assure the au that the manufacturer is prepared to control the filtering characteristics of -espirator; (2 ) to eliminate any question of competition with private consulting vies in developing respirators; (3) to furnish evidence that the respirator really .ady for release to public market; and (4) to save the manufacturer's and the au's time. After the manufacturer has complied with all the above pre-test dements he must submit a fee for the examination and test of his device. fee is turned into the miscellaneous funds of the U. S. treasury and none of money reverts to the Bureau of Mines. Test Requirements In developing the tests for mechanical filter respirators consideration was given to the general requirements for a safe and suitable device. These requirements similar for all types of industrial respirators. The respirator must (1) give quate protection. (2) be reasonably comfortable and physically convenient to m. and (3) provide an acceptable service life. Adequate protection implies that the mechanical filter respirator when properly itained and worn must prevent the wearer from breathing enough particulate Uer to cause a harmful physiological response under the conditions of occupational sure for which it is designed to be used. Comfort and physical convenience factors arc equal in importance to adequate lection. Even though aware of the ultimate serious effect which will be produced r prolonged daily exposure, workmen arc inclined to be diffident and unwilling ilTer much daily inconvenience and discomfort from the respirator. Encumbrance and discomfort also increase fatigue, cause distraction, and in -al handicap the wearer's ability to take care of himself, thus increasing the 'bilily of accident. Important specific items include the weight of the respirator, arriage on the face or head, effect on vision, heating of the area of the skin i-r the facepiece, inability to expectorate, difficulty in talking, and resistance to ,idling. The importance of comfort and physical convenience cannot be over minted. The service life involves elements of practicability in the wearing and maintenance die, device, and indirectly the safety. This type of respirator is primarily not an agency device, but a part of the workman's equipment for doing his regular job iy. If the service life is short, the bother of changing of filter elements will reflected in the workman's attitude toward good maintenance and use. All mechanical filter respirators arc subjected to certain inspections and tests ihey must fulfill certain requirements. The general design and construction, ocularly as to facial fit, freedom from irritating facial contacts, weight, effect vision and the wearing of goggles, and ease of changing filler elements, and' mined. The materials are examined to determine if they are obviously suited the purpose for which they are designed. Rubber parts which come in contact '! the skin must not contain any skin-irritating constituent. . Resistance to Air Flow Requirements The requirements for resistance to air flow are the same for all approved memical filter respirators. At no time during or after the filter efficacy testing period st tho "resistance to air being drawn through the device at the rate of 83 liters Safety Equipment 137 (3 cubic Teel) per minute exceed 50 millimeters (1.97 inches) of water column height or the resistance to air being blown through the device at the same rate of flow exceed 25 millimeters of water column height. An air flow of 85 liters per minute is approximately equivalent to the respiratory rate of a man doing heavy work. The amount of particulate matter pulled to the device during the filter efficacy tests is roughly equivalent to the amount that would be pulled to the filter by a worker wearing the mechanical filter respirator in a moderately concentrated suspension of the particulate matter during an 8-hour period. Thus resistance to air flow of an approved mechanical filter respirator should not become excessive when worn for an 8-hour period in most suspensions of atmospheric particulate matter en countered in industry. The manufacturer is reuv'-ad to give instructions on cleaning or changing the filter elements when the resist::: n'- '> .dr ilnv noticeably increases. Direct Leakage and Man Test All mechanical filter respirators are subjected to a direct leakage and man test to determine facial fit. whether there is any direct leakage of unfiltered air, and to obtain information on the comfort of the device. Three of the mechanical filter respirators are worn for 30 minutes by 3 men with different facial features in an atmosphere containing a heavy suspension of bituminous-coal dust. At the end of the period the respirators are removed and that part of the face covered by the) facepiece is examined for evidence of any leak under the edge of the facepiece. Sticks a millimeter thick were wedged under the edges of the facepieces worn by subjects A and C to cause the leaks. The location and approximate magnitude of the leaks arc shown by the black streaks on that part of the face covered by the edges of the facepieces. The nasal passages and sputum of the subjects are also examined before and after the tests. Filtering-Efficacy Tests In the development of the filtering-efficacy tests, particular attention was given to the physical properties, especially particle size, of the significant kinds of atmos pheric particulate matter encountered in industry. . Previous studies of filtering materials had shown that, in general, filtering efficacy decreases with a decrease in particle size. It was decided that most of the significant industrially generated atmospheric particulate matter could be classified into the! following three groups in accordance with method of generation, physical state, am| particle size: 1. Mechanically generated dusts resultirig from the disintegration of a solid, such as the dust clouds produced in the various processes of mining, quarrying and tunneling and the grinding, crushing, and general processing of solid materials. This type of atmospheric particulate matter is referred to as Type A atmospheric particulate matter and mechanical filter respirators designed to furnish protection against these suspensions arc referred to as Type A mechanical filter respirators. 2. Fumes of various metals (usually their chemical compounds, as oxides or carbonates) such as lead, mercury (except mercury vapor) manganese, magnesium, aluminum, antimony, arsenic, copper, chromium, iron, cadmium, and zinc resulting from sublimation or the condensation of their vapor, or from the chemical reactions between their vapor and gases. This type of atmospheric particulate matter is re ferred to as Type B atmospheric particulate matter and mechanical filter respirators designed to furnish protection against these suspensions arc referred to as Type B mechanical filter respirators. 3. Mists as produced by spray-coating with paint and vitreous enamels, chromic acid mist as produced in chromium plating, and other mists of materials whose liquid vehicle docs not produce harmful gases or vapors. This type of atmospheric particulate matter is referred to as Type C atmospheric particulate matter and mechanical filter respirators designed to furnish protection against these suspensions are referred to as Type C mechanical filter respirators. The mechanically generated dusts and fumes consist of solid particles while the mists consist of liquid or liquid-coated solid particles. The particle size of me chanically generated dusts extends over a wide range, in some cases, from particles visible to the naked eye probably down to molecular dimensions. The range in particle size of fumes is much smaller. The upper limit is in the lower microscopic Twenty-fourth Annual Safety Congress-- National Safety Council nse (about 0.5 micron), while the lower limit probably approaches molecular 'pensions. The particles of some fumes, particularly zinc and magnesium. readily and form large tlocklike clusters. The clfcct is least pronounced in the ease lead. Mist particles are spherical and probably more uniform in particle size than sc of dusts and fumes. Suspensions of each of the types of industrially-generated atmospheric particle natter were selected for use in the filtering-efficacy tests. These suspensions were iioscn on the basis of their industrial hygienic significance and their physical roperties. such as particle-size distribution and tendency to aggregate, which have appreciable effect on filtration. It was desired to test the mechanical filter -pirators against the most common or widespread harmful suspensions of each pe: the test suspensions to have physical properties, such as particle size and gregation tendency, which would render them as difficult to remove by filtration any other suspension of the same type. The test suspensions selected are: (a) For testing Type A mechanical filter respirators or those designed to' 'iiisli protection against mechanically generated dusts a suspension generated from ry fine (99--f- per cent through 325 standard mesh sieve) silica dust consisting of -r per cent free silica (SiCk) is used. The suspension is generated in such a way hat all particles larger than about 3 microns are removed before the suspension iters the test chamber. The particle-size distribution of the test suspension must ut exceed a geometric mean of 0.6 micron and a standard geometric deviation of ''0. The particle-size determination is made by collecting samples of the suspension tlie Owens jet dust counter and determining tbc particle size distribution by a Icroprojection method developed by the bureau of Mines.0 (b) For testing Type B mechanical filter respirators or those designed to .nrnish protection against fumes, a lead oxide fume generated by tbc combustion of natural gas containing lead tetraethyl vapor is used. The particles of this fume are xtremely small and have about the least tendency to aggregate of any fume, lienee bey are very' difficult to remove from the air by' mechanical filtration. A suspension magnesium oxide is also used to determine tbc effect of a fume, whose particles .-lily aggregate in large clusters, on the resistance to air flow of the filter of the vice. (c) For testing Type C mechanical filter respirators or those designed to urnish protection against mists, three different suspensions are used. Chromic .id mist generated by electrolyzing an aipicous solution of chromic acid, as is done industrial chromium plating: lead paint mist generated by sprav-coaling with lead bit; and a water mist carrying silica dust generated by spraying a 2 per cent neons suspension of silica dust are used. The water-mist carrying silica dust is vd to simulate the mists generated in spray-coating with vitreous enamels. 1 The concentration of the particulate matter in the test suspensions was chosen represent more or less the higher concentrations found in industry. Since the nccnlrntion of mechanically generated dust found in industry varies over such ide limits it was decided to test Type A mechanical filter respirators against two nccnlrations; one to represent the more or less average dusty industrial condims, and the other to represent very dusty conditions. The complete mechanical filter, respirator is tested on a mechanical testing : paratus. The test suspension is pulled through the device at the rate of 32 liters 1.13 cubic feet) per minute, continuous flow. Tbc volume of air pulled through v mechanical filter respirator is 10 cubic meters in all cases except in some is against particular kinds of suspensions as mechanically generated lead dusts I in the high-silica dust-concentration test and the magnesium oxide test whose rimary object is to determine the increase in resistance to air flow of the filter ith the amount of particulate matter retained. Ten cubic meters is approximately piivalent to the volume of air breathed by a worker in 8 hours. The samples of articulate matter for concentration determinations are precipitated electrically mii the air of tbc test suspension both before and after it has passed through mechanical filter respirator. The samples are collected in containers which i be weighed readily on an analytical balance. For reasons of coiivenienre, speed, " 1!m,, vii. lb a n d Y n n t , W . I*. T h e 1 Mif-ropr,),*, In r for I I c l r n n i n i n g V a r t i r l r P i / c n i l , n o o n a n d N n i n l i c r O m c c n l r a u o n of A l i n o ^ p l i c r i e t) u M s . I f S. P u r e a u ol Mine*; K cp n rt l i iv e s tv u i ti o n i f ,t2X0, 1935. Safely Equipment . 139 and accuracy the samples of silica dust arc quantitated by weight rather than by count. Samples of the other ('articulate matter are quantitated chemically. The requirements as to the amount of particulate matter that the mechanical fdter respirators must remove from the air pulled through them is based on the best available information on the concentration of the particulate matter that is safe to breathe. These requirements are subject to change with the accumulation of knowl edge on the physiological effects of industrially generated atmospheric particulate matter. In other words, the filtering-efficacy requirement is that the air inhaled by the wearer of such a device must be safe to breathe, and not that the device have any particular percentage filtering efficiency. Mechanical filter respirators are not approved for any substance more harmful than the particulate matter in the test suspension against which they are tested. Thus Type A respirators are not approved for any substance more harmful than free silica (SiOs) dust. However, Schedule 21 provides for testing and approving' mechanical filter respirators against any kind of industrially generated atmospheric particulate matter. For example. Type A mechanical filter respirators arc not' approved for protection against poisoning by breathing dusts whose main harmful constituents are metals or their compounds. However, two mechanical filter respira tors have been submitted and approved for protection against the inhalation of mechanical generated lead dusts. Table 1 summarizes the details of the filtering-efficacy tests and lists the me chanical filter respirators which have been approved to date. (Pages 1-10-141.) Post-Test Requirements The manufacturer of an approved mechanical filter respirator is required to mark his device with the name of his company, the name letter, or number by which the type is designated for trade purposes, and the approval number assigned to the device by the Bureau of Mines; and the filter unit must be marked with the approval number and with the type or kind of atmospheric particulate matter for which it is approved. The mechanical filter respirator and replacement filter units must be provided with substantial and durable containers. Copies of the approval labels issued to the manufacturer by the Bureau of Mines muft he attached to these containers. The approval label gives the approval number, j shows to whom the approval is issued, states what the device is and is not approved for, and cautions the wearer to follow the manufacturer's instructions for the usd and care of the device. The following is a sample of the required instructions furnished by the manu facturer. These instructions are similar for all of the approved mechanical filter respirators. Instructions for Use of Mechanical Filter Respirator 1. Respirators will not protect unless placed on the face properly each time they are worn. Carelessness in face-fit means dangerous leakage. In general, a better fit is obtained if the mask is worn not too high on the nose. 2. To fit the respirator to the face hold the respirator, exhaust valve pointing downward, by the metal screw connection with cither hand, and hold the headstrap with the other hand. Tlacc the facepiece against the face and hold it in place while (lulling the headstrap over the head and below the cars. Then adjust the facepiece until a firm snug fit is obtained. The headstrap may be adjusted while the respirator is in place by holding the metal slide between the thumb and forefinger of one hand and pulling on the proper strap with the other hand. .1. To instruct the wearer in the proper adjustment of the he.adstraps and position of the respirator on the face a cardboard disc is enclosed. To use this disc unscrew the filter bag, place the disc against the felt washer in the metal connection on the felt bag, assemble the respirator, and put it on. The wearer should not be able to breathe through the respirator or feel any inward leakage of air under the edges of the facepiece. The presence or absence of dust streaks on the face inside the line of fit of the facepiece after wearing the respirator in a dusty atmosphere can also he used to tell whether a proper fit was obtained, 4. The recommended procedure for cleaning the filter bag is to insert loosely the nozzle of a high-pressure air hose into the bag opening and to blow several 140 7 U'cnly-foiirtli Animal Safety Congress-- National Safety Council TABLE 1. DETAILS OF FILTERING EFFICACY TESTS AND LIST Kind of mechanical iih cr-u pe : espir tor Industrially generated atmospheric particu late m a tte r against which the device is designed to furnish protection T est suspensions used J'ype A Mechanically generated dusts resulting principally from the d i s i n t e g r a t i o n of a solid, such as the dust clouds produced in inining. quarrying and tunneling, and the in d u s tr ia l o p eratio n s of g rin d in g , c r u s h in g , an d p ro c e s s in g of m in erals Air-suspended ground flint, which consists of 9 9 4 p e r c e n t fre e s ili ca ( S iO j) . O v e r 99 p e r c e n t of t h e d u s t p a s s e s t h r o u g h 325he.->b s t a n d a r d s ie v e l ype P. ! >pe(. F u m es of various m etals (usually their (a) h ead oxide fume produced by the dc- chemical compounds, as oxides or carbon- c o m p o s i t i o n a n d c o m b u s t i o n of le ad ates) such ns lead, m ercury (except mer- tetraethyl cury vapor), manganese, copper, chromium, iron, c a d m iu m , zinc, m agnesium , a lu m i num . antim ony, and arsenic resulting from su b lim atio n or condensation of their vapor, or from chemical reactions between their vapor and gases M ists as produced by spray-coating with (b) M agnesium oxide fume, freshly pro- p aim and vilrcmi- enamels, chromic acid duced by burning m agnesium ribbon m ist as produced in chromium plating, unu C h r o m i c acid m i s t p r o d u c e d b v el ec tr o - o t h e r m i s t s of m a t e r i a l s w h o s e li qu id v e- ' f v z i n g a n a q u e o u s s o l u t i o n ' (2(30-500 b id e does not produce harmful gases or r a in s of c h r o m ic ac id p er lite r) ot vapors chromic acid icall)Jed lead Mechanically generated dusts whose main h a rm fu l c o n s titu e n t is lead, such as lead dusts generated in manufacturing storage batteries; enameling; pottery making; mbber com pounding; sandpapering and chip ping painted surfaces; paintmaking; pre p aring lith u -tra n sfers; and mining, milling and processing lead tires (b) Head paint m ist produce! by spraying a paint having the following composi tion: white lead (paste having approxi m a t e l y 91 p e r c e n t w h i t e le ad a n d 9 p e r c e n t li n se e d oil by w e i g h t ) , 100 g r a m s ; l i n s e e d oil, 50 c u b i c c e n t i m e t e r s : a n d s t e a m - d i s t i l l e d t u r p e n t i n e , 25 cubic centimeters (c) Mist produced by spraying a 2 percent aqueous suspension of ground Hint, air- f lo a te d (994- p e i c e n t . t h r o u g h 325 s t a n d ayI m e s h s ie v e ) . T h e g r o u n d flint c o n sists of 9 9 4 percent free silica (SiOM. M ix tu r e u s e d in m a k i n g n e g a tiv e plates ol h a d s t o r a g e b a t t e r i e s . C o n t a i n s 72 p e r c e n t l i t h a r g e , T b O ; 25 p e r c e n t red lead, r b . ;0 < ; ami 3 percent lampblack " O n e m i l l i g r a m -- 0.015-1 g r a i n . ' O n e c u b i c m e t e r = 35.315 cu b ic feet. ' K a t e of s a m p l i n g :r r 32 l i t e r s (1.13 c u b i c feet) p e r m i n u t e . `M i n e m i l l i g r a m of t h i s s il i c a d u s t c o n t a i n s a p p r o x i m a t e l y 300 m e d b y t h e i m p i n g c r m e t h o d a s d e s c r i b e d b y t h e IJ. S. 1'uhli'c dijgrnni p e r c u b i c m e t e r of t h i s d u s t is a p p r o x i m a t e l y e q u i v a l e n t (ul-ic foot. Sc*- p r e v i o u s l i s t i n g of c o m p a n y fo r c o m p l e t e a d d r e s s . million particles as deterHealth Service. Hence. 1 to 8.5 millions of particles Safety Equipment 1 OF APPROVED MECHANICAL FILTER-TYPE RESPIRATORS Concentration of test suspension, milligrams per cubic^ m e te r b oi a ir ( a ) 50 10d 0) 5 2d 15 i 5 of lead V olum e of test suspension pulled through the device, cubic meters* M axim um am ount of particulate m atter permitted to pass through the device Milligrams Milligrams Per ct,hic m eter of air N am e and m a n u factu re r of mech icai filter-type re.-pirators appro to d a t e , S e p t e m b e r 25, 11/34 2.88 4 mg. for an y 1 of 3 devices, or an av erag e of 3 mg. for each of tbe 3 devices 1.0d M .S. A . G>mi<> R e s p i r a t o r . A p p r c N'o 210!, i ' iied to M in e S a f e t y , pliances Co. Willson Rag Respirator No. I A p p r o v a l No. 2102, is s u e d t o \V son Products, Inc. 9.98 12 m g. for any 1 l.(W W illson R ag R espira tor No. of 3 devices, or A p p r o v e d No. 2103, is s u ed to \V a n a v e r a g e of 10 o n J ' l o d l K ' t S , I n c . * n ig . for e a c h of the 3 I 'u l m o s n n M-15 P o u c h - T y p e Kill R e s p i r a t o r . A p p r o v a l No. 2104, med t o 1'ulmoMtn S a f e l y K q ui p in c Corp. Rievcr R esonator. Approval > 2105, isMicu to S t a n d a r d Safe Kquipmcnt Co. 9.98 1.5 0.15 W i l l s o n H a g R e s p i r a t o r No. 4. A p r o v a l No. 2KX. is s u e d t o Wills P r o d u c ts , Inc. 100 25 15 - 5 of chromic acid AOO-fjOO of lend 10 5*' of silica dust 1? 5 of lead 2 9.98 9.98 1.5 9.98 5 2.88 0.43 0.1 M.S.A. Comfn Respirator. Approv N o. 2101, is s u e d ' to M i n e Safei A p p l i a n c e s Co. 0.15 M .S.A. Cumin R e s p ira to r n ot aj p roved for lead c o n t a in i n g mi,st$. 0.5** M .S . A . C'omf) R e s p i r a t o r . A p p r o v e N o. 2101, is s u e d to M in e S a f e t y A p p l i a n c e s Co. 0.15 M.S.A. Coinfo Respirator with spe ria l filters for lead dust. Approve N o . 2107, is s u e d t o M in e S a f e l y A p p l i a n c e s Co. W i l l s o n H ag R e s p i r a t o r No. 4001. A p p r o v a l No. 2108, is s u e d t o Willson Products, Inc.*