Document 2JeQVEgO8634dQvEaDyQ8KyEp

FILE NAME: National Safety Council (NSC) DATE: 1935 Oct DOC#: NSC155 DOCUMENT DESCRIPTION: Transactions of the NSC - 24th Annual Safety Congress - Presentation - Occupational Diseases 1935 TRANSACTIONS National Safety Council Incorporated TWENTY-FOURTH ANNUAL SAFETY CONGRESS Louisville, Kentucky October 14 to October IS, 1935 The Brown, Kentucky and^Scelbach Hotels Copyright, 1936, Notional Safety Council, Inc. Foreword IIE T R A N SA C T IO N S of tJie Twenty-Fourth Annual Safety Congress, National Safety Council. 1035, 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 tovers. I t ntay, however, also be secured by other Council members upon ucst. 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, SI.25 each; copies of the smaller volume, 50c each. d A CCO RD A N CE with the plan of publication followed for the past several years the Transactions arc published again this year as a condensed record the proceedings at the National Congress. The papers of each session or ision of the Congress have been edited carefully to eliminate extraneous inntand to abbreviate the less essential portions because of space limitations. In cr words, the material herein presented is not a verbatim report of all the echcs presented at the Congress, but rather an abridged version, made as npact ns possible, yet without any injury to the technical aspects oi any Iress. The original manuscripts are on file in the library of the National fety Council, where they are available for additional reference. In several cs, where illustrations were sent by the speakers to the Council, these also on file. The National Safety Council at its Congresses seeks to eliminate from dis,sion matters which arc not pertinent to the atm of the Congress or which arc ltr.iry to Council policies, but it cannot accept responsibility for the views pressed either in the papers presented or in the discussions based upon the ,crs. NATIONAL SAFETY COUNCIL, INC. 20 North Waclccr Drive, Chicago CONTENTS Page Council Onicers and Directors................................................................................. 4 Cciinci! Purposes and Policies ............................................................................... 9 Annual Meeting of Members..................................................................................... 11 Annual Banquet........................................................................................................... 27 Subject Sessions-- Finding and Correcting Accident Causes............................................................ 29 Fire Prevention in Industry................................................................................... 33 First Aid and Health Service in Industry.......................................................... 51 Ilcat Exhaustion................................................................................... 61 Industrial Nursing................................................................................................... 73 Industrial Safety Lectures-- Public Speaking in Safety W o r k ...................................................................... 79 Selling Safety in Foremansliip.............................................. 89 Industry and Its Motor Vehicle Problem.......................................................... 103 Maintaining Interest in Safety............................................................................. 1H Occupational Diseases.......................................................... .................................. H~ Safety Equipment..................................................................................................... 133* Safety in the Small P la n t....................................................................................... 145 Safety Training........................................................................................................ 147 Accident Prevention Equipment Manufacturers' Section................................... 153- Acronnutical Section................................................................................................... 159 A.S.S.E.--Engineering Section................................................................................. 157 Automotive and Machine Shop Section.................................................................. 159 Cement Section..............................................1.............................................................. 177 Chemical Section.......................................... j..................................................... -- 193 Construction Section.................................. j .............................................................. 209 Food Section................................................................................................................. 223 Marine Section............................................................................................................. 237 Meat PacVnng, Tanning and Leather Industries Section..................................... 265 Metals Section................................................................................................................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...................................... : ............................................................... -*-'9 Safety Section, A.A.R.--Steam Railroad Section, N.S.C...................................... 459 Textile Section............................................................................................................. 485 Transit Section......................................................................... 495 Vehicle Fleet Section...................... 513 Wood Products Section............................................................................................. 529 I n d e x .............................................................................................................................. 537 National Safety Council Incorporated HONORARY MEMBERS A ssociation- or I ron a\ i> Stew. E lectrical RuIIERT \V. CaMI'UIXL A rthur W ii.i.iams E ngineers OFFICERS (1935-1936) Dr. C. M. W atson-, President. D. D. Fennell. Vice-President for Public Relations. Du. H art E. Eishf.r, Vice-President for Health. J ohn 11. Gibson, Vice-President for Community Safety Councils. Ilo.N. H auoi.ii G. I Ioitman, Vice-President for Public Safety. A i.rf.rt S. R kgui.a, Vice-President for Engineering. A. V. Rohukiii.r, Vice-President for Industrial Safely. R. T. SoI.knstkn, Vice-President for Membership. A i.iiert W. W hitney, Vice-President for Education. \V. E. Worth, Vice-President for Finance and Treasurer. \V. II. Camf.ro.n. Secretary and Mauactin.it Director. EXECUTIVE COMMITTEE (1935-1936) A. I.. A rmstrong, Chemical Section. C. JI. A uf.i., Past President. J. f. IIanasii, Past President. C. \V. IIercqcist, Past President. H akoi.d S. IJuTTKNiiF.iM, The American City Magazine. W. II. Camtuon, National Safety Council. Robert W. Campbell, Past President. Roman' I. Gatlin, Aetna Casualty S: Surely Company. I.i:\vts A. Di.Ci.ois. Past President. C. W. Dumbest, Food Section. Makui' s A. Dow, Past President. D. D. Fennell, Consulting Engineer. Donai.ii A. ITnkiuinkr, Toledo Safety Council. D k. II.\ier E. lMSttF.it, Chicago Rapid Trandt Company. E. W. Eiski:. Jit., Marine Section. R. II. Fortp in , Lehigh Valiev Safety Council. J ohn H. Giiison, Western Electric Company. E. E. Grant, Paper & Pulp Section. H arry Guiliikrt, The Pullman Company. Ilo.N. I I aroi.ii G. Hoffman, Governor of New Jersey. Edwin A. K ayskr, St. Louis Safety Council. Walter G. King, Past President. Officers and Directors W illiam C. K noei.k, Street & Highway Traffic Section. C. F. L arson, Association of American Railways. J ohn K. Long, Past President. Titos. II. MacDoNaui, U. S. Department of Agriculture. F. J. Meiikkn, Portland Cement Association. I. \V. M illard, Industrial Gloves Corporation. Arthur T. Mutter, Past President. Lew R. P almer, Past President. C. E. P etti hone, Past President. J A. P urrv. Wood Products Section. Albert S. R egula, Industrial Relations Counselors, Inc. I. t. Col. I I kxrv A. R eningek, Past President. A. V. Roiiwedkr, Duluth, Missahe & Northern Railway Co. George E. Sanford, General Electric Company. Robert I- Schmitt, Louisville Safety Council. Gen. J ohn II. S herborne, Massachusetts Safety Council. Charles P>. Scott, Past President. C. W. S mith, Standard Oil Company (Ind.). W alter D ent S mith, Delaware Safety Council. R. '1'. Soi.e.nste.n, Elliott Service Company. J ames M. Strike, St. Joseph Safety Council. C. I'. T oi.man. Past President. Dr. C. II. W atson, American Telephone X' Telegraph Co. A. W. W hitney", National Bureau of Casualty & Surety Underwriters. C. T. W inecar, Automotive & Machine Shop Section. W. E. W orth, International Harvester Company. A rthur II. Young, Past President. I i DIRECTORS (1935-1936) J. W. Alt, Mining Section. i N elson R. A nderson, Seattle Traffic it Safety Council. F rederick Archer, Child Education Section. A. L. A rmstrong, Chemical Section. J. I. P.anash, Consulting Engineer. Ernest W. Beck, United States Ruhher Products, Inc. C. W. Bf.rgquist, Western Electric Company. P ercy- D'. IIetterly, Worcester Safely Council. D avid S. Beyer, Liberty Mutual Insurance Co. Cuitoru M. Bishop, Brooklyn Safety Council. E. F. Blank, Jones & Laughlin Steel Corp. C. F. Borkenhagen, Kenosha Safety Council. S. D. Boyd, York County Safety Council. W. A. Brown, Transit Section. S. W. Burciiiel, Automobile Club of Rhode Island. H arold S. B utteniieim, The American City Magazine. P reston D. Cali.um, Baltimore Safety Council. W. II. Cameron, National Safety Council. National Safety Council Incorporated HONORARY MEMBERS A ssociation' o r I kon- and S tkki. E u -.ctrh'ai. E . \ gini:kks Ruiihrt W. Cami'ukli. A rthur W ii.uams OFFICERS (1935-1936) Dr. C. M. W atson, President. D. D. Fknni-.u .. Vice-President for Public Relations. Dr. H art F.. Fisiif.r. Vice-President for Ilcnltli. J ohn II. Gibson, Vice-President for Community Safety Councils. H on. H aroi.d G. Hoffman, Vice-President lor Public Safety. Ai.bf.ht S. Ru.i' i.a, \ `ice-President for Engineering. A. V. Koiiutmi;. \"iee-I're>ident for Industrial Safety. K. T. Soi.v.nsyfn, Vice-President for Membership. A i.rkkt W. W iutniiv, Vice-President for Education. \V. K. Worth, Vice-Presiilent for Finance and Treasurer. W. II. Camf.ron. Secretary and Managing Director. . E X E C U T IV E COMMITTEE (1935-1936) A. I,, A rmstrong, Chemical Section. C. IT Auf.i., Past President. J. I. JIa n a s ii. Past President. C. W. IIkrcquist, Past President. H aroi.d S. Lum.NMF.iM, Tbe American City Magazine. W. If. Camfron, National Safety Council. Koiiirt W. Camit.kli., Past President. Koinarr I. C.vrux, Aetna Casually S: Surety Company. Lewis A. D kL i.ois, Past President. C. W. Dkmfksy, Food Section. Marcus A. Dow, Past President. D. D. Fkxxkli., Consulting Engineer. D onai.d A. F inkiikinkr. Toledo Safety Council. Dr. H art E. F isiif.r, Chicago Rapid Transit Company. E. W. F iskk. Jr., Marine Section. K. B. Foutpix, Lehigh Valley Safety Council. ' John 1!. Giiison, Western Electric Company. E. E. Grant, Paper & Pulp Section. H arry G uii.rkrt, The Pullman Company. I I on. I I aroi.d G. H u ff m a n . Governor of New Jersey. E dwin A. K ayskr, St. Louis Safety Council. W alu:r G. King, Past President. Officers and Directors W illiam C. K noeek, Street & Highway Traffic Section. C. K. I.arson', Association of American Railways. J ohn E. Long, Past President. Titos. If. MacDoxai.i), U. S. Department of Agriculture. E. J. Menken, Portland Cement Association. I. \V. Mtu.ARD, Industrial Gloves Corporation. Arthur T. Morey, Past President. I.fay U. P almer, Past President. C. E. P ettiroxe, Past President. J A. P urdy, Wood Products Section. Albert S. Rec.ula, Industrial Relations Counselors, Inc. I. t. Col. I I kxry A. R eningek, Past President. A. V. Romwedkr, Duluth. Missuin' & Northern Railway Co. George E. Sanford, General Electric Company. Rorf.rt 1.. Schmitt, Louisville Safety Council. Gen. John II. S heriiurnf., Massachusetts Safety Council. Charles P. Scott, Past President. C. W. S mith, Standard Oil Company (Ind.). W alter Dent S mith, Delaware Safety Council. R. T. Soi.ENSTE.v, Elliott Service Company. J ames M. Strike, St. Joseph Safety Council. C. I'. Tot.man. Past President. Dr. C. If. W atson, American Telephone & Telegraph Co. A. W. W hitney, National Bureau of Casualty & Surety Underwriter C. T. W inegar, Automotive & Machine Shop Section. W. E. Worth, International Harvester Company. Arthur II. Young, Past President. ' I i DIRECTORS (1935-1936) J. W. Ai.t, Mining Section. i Nelson R. A nderson, Seattle Traffic & Safety Council. Eredeiuuk Archer, Child Education Section. A. L. Armstrong, Chemical Section. J. 1. Banash, Consulting Engineer. Ernest W. Beck, Uniied States Ruhher Products, Inc. C. W. Bergquist, Western Electric Company. P ercy D. Betteri.y, Worcester Safely Council. David S. Beyer, Liberty Mutual Insurance Co. Clifford M. Bishop, Brooklyn Safely Council. E. E. Blank, Jones & Laughlin Steel Corp. C. F. Borkf.nhagf.n, Kenosha Safety Council. S. D. Boyd, York County Safety Council. W. A. Brown, Transit Section. S. W. B urchiei., Automobile Club of Rhode Island. H arold S. B uttex h eim, The American City Magazine. P reston D. Cali.um, Baltimore Safety Counril. W. II. Cameron, National Safety Council. T'ivcnty-fourlh Annual Saf et y Congress-- National S af et y Council Carni'.y, Chicago Safety Council, i i;r I. C u i .in, Aetna Casualty & Surety Company. . Cody, Evanston Safety Council, if. Cullman, Cement Section. Hf.khf.rt Corson, Safety Dept., Nashville Chamber of Commerce. \K E mkry Cox, Berkeley Traflic Safety Commission. Cullinf.y, Hetlilehem Steel Company. \Y. Dark, Metals Section. i.i.iam G. Deaner. Rochester Safety Council. n s A. DkBlois, Consulting Engineer. E. Df.ckkr, Mason City Safety Council. \Y. Dkmpesy, Food Section. M. Dif.tz. Rubber Section. Mrs 15. Douglas, The Philadelphia Gas Works Co. . I.runs I. Dum.i.x. Metropolitan Life Insurance Co. I). F enxf.li., Consulting Engineer. XAt.n A. FixKr.rtxi n, Toledo Safety Connril. . H art E. Fisher. Chicago Rapid Transit Co. W. F iske, J r., Marine Section. ms. F itzgerald, Western Pennsylvania Safety Council. >\Y.\ui) B. Fonda, Burroughs. Wellcome & Co. (U. S. A.), Irtc. 1!. Fokiuix, Lehigh Valley Safety Council. Fostfr, J r., Quarry Section, ux 15. Gitisox, Western Electric Company. y M. Godwin, Public Utilities Section. F. Grant, Paper & Pulp Section. uiry Guii.pf.ut, The Pullman Company'. MAit IIai.f, The Atchison, Topcko & Santa Fe Ry. Co. ajor Rolling IT. I I axdy, Richmond Safety Council. . T. H arrington, U. S. I'ureau of Mines. . C. H aven, Vehicle Fleet Section. . W. I I eiss, Textiie Section. . T. I I m.i.muth, Chicago, North Shore & Milwaukee R. R. Co. iiAiu.r.s E. H im., New York Central Lines. ox. I I auoi.I) G. H offman, Governor of New Jersey. ;. \unr. J. Homung, Albany Safety Council. nwiN A. K aysf.u, St. Louis Safety Council. iiomas P. K earns, Industrial Commission of Obio. . T. K i.li.fr, Detroit Industrial Safely Council. 'A V. Kki'NEU, Pennsylvania Salt Mig. Co. Vii.i.iam C. K nofi.k, Street & Highway Traflic Section. '. 1.. I.aF o u n t a in e , Great Nortbern Railway Co. . F. Larson, Missouri Pacific Railroad Company. mon Lazarus, Safely Council of Columbus (O.) Chamber of Commerce. K. Long, The Delaware & Hudson Railroad Corp. Y. R. Loyd, Safety Div. Birmingham Chamhcr of Commerce, nos. H. MacDonald, U. S. Department of Agriculture. .. T. McArthur, Teona Safety Council. J. McCann, Meat Packing, Tanning & Leather Industries Section. Officers and Directors M iller McCuntock, Harvard University. '1'. II. McK'ennf.y, Carncgic-Illinois Steel Corp. A. U. McW horter, Safely Div., Metupliis Chamber of Commerce. II. T. Martin, Fisk Rubber Company F. W. Matson, Minnesota Safety Council. J ames K. Mays, Elizabeth Safety Council. E. J. Meiiren, Portland Cement Association. I. \V. Mi u .ard, Industrial Gloves Corporation. J ames K. Miller, Grand Rapids Safety Council. Leslie W. M iller, Superior Safety Council. H arold L. M iner, E, I. du Pont de Nemours & Co. Lawrence M. Moore, Eastbay Safety Council. R. Ik Mokley, Industrial Accident Prevention Assns. Choree C. A. Oi'P, The Detroit Edison Company. George Oit en h ei.mer, Kansas City Safety Council. Lew R. P almer, Equitable Life Assurance Society. D avid A. P atton, Newark Safety Council. C harles \V. 1'kndock, Safety Div., Milwaukee Assn, of Commerce. C. E. P f.ttieone, American Mutual Liability Insurance Co. Gen. George Ik P ili.srurv, United States Engineer Oflico. A rthur P ottertc:, Hudson County Safely Council. W. D. P rice, Employees' Publication Section. J. A. I 'urdy, Wood Products Section. Aerert S. Rkguea, Industrial Relations Counselors, Inc. Lr. Col. H enry A. Rkninger, Lehigh Portland Cement Co. Makings R iter, Paterson Safety Council. R. 1!. Roarer, Petroleum Section. A. V. Ron wirier, Duluth, Missnbe & Northern Uy. Co. George E. S anford, General Electric Company. H enry G. Sciiaefner, Eric Safety Council. Rouert L. Schmitt, Louisville Safety Council. Karl G. S chokiteer, Railway Safety Council. I I aruv A. Schultz, United States Steel Corp. M arl S. S iiartzer, Utica Safety Council. R ay H. S heets, Madison County Safely Council. Gen. J ohn II. S iif.rrurne, Massachusetts Safety Council. Dr. L. A. S iioudy, Bethlehem Steel Company. E rnest L. S imonus, New Haven Safety Council. J udge Lf.e E. Skefx, Cleveland Safety Council. C. W. Smith, Standard Oil Company (Tud.). E dwin C. S mith, Blaekstone Valley Safety Council. W alter D ent Smith, Delaware Safety Council. W. A. S now, Construction Section R. T. Solensten, Elliott Service Company. , E. C. String, I.ansdale, Pcnna. George R. Stephens, Safety Bureau, Buffalo Chamber ol Commerce. J ames M. Stkikf., St. Joseph Safety Council. A rthur M. T ode, Consulting Marine Engineer. H arold M. T oomiis. Refrigeration Section. \r T he Katie the first, Industria the sessi Section ; All! The sm: it cover request. S T'vcnty-fourth Animal Safety Congress-- National Safety Council W. W. T rench, Schenectady Safety Council. W. D. T ukhkvili.e, Sail Antonio Safely Council. E. J. W au,man. Power Press Section. Dr. C. II. W atson-, American Telephone & Telegraph Co. H arry M. W f.bber, Illinois Bell Telephone Co. Albert C. W hite, J r., Springfield Safety Council. S. E. W hiting, Liberty Mutual Insurance Company. A. W. W hitney, National Bureau of Casualty X: Surely Underwriters. T. A. W illson, Accident Prevention Equipment Manufacturers' Section. W. H. W ixaxs, Union Carbide X.- Carbon Corp. C. T. W inegar, Automotive X: Machine Shop Section. H arry W ise, Sr., Chattanooga Safety Council. J. M- Woltz, 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. iicil to tile group to .) took it I a year maintain tcrature, 'ins. -Iieets of wived a . to save ng lucky depart i days dditional Icularly ; trolley reduction ice of a a coal ers, but solely rhaps I I be re.iployee -upaigu tst give tisplays .mittee- 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. II. Watson, ncwlv-clcctcd 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 General Manager, Association of Casualty and Surety Executives New York, N. Y. Since the prevention of diseases is. to some decree, a community problem, the state ought to do its part toward the prevention of occupational diseases, along with ail others. The. public health authorities should study the causes of such dis eases, their prevalence, virulence and the means tor 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 scrious drawbacks to he efficient. They are apt to he indexible and quickly become "out of date"; and they arc too apt to he perverted for the establishment of fictitious bases tor wasteful and demoralizing damage-suit 'litigation. Scientific bureaus of occupational hygiene, under direction of public health authorities, arc the best public instrumentality. Efficient bureaus of that character are now to he found in several states; hut. generally, such public health organizations arc inadequately manned and 'equipped. Therefore the primary need in occupational disease legislation is for measures to improve our public health services. Emphasis should he placed on'prevention, not merely because "an ounce of pre vention is worth a pound of cure." but because public measures for the assurance of 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 self-protection. Expert opinion now calls strongly tor the entire elimination of employers' liability for "damages" for occupational injuries--l>y disease as well as 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 he so liberalized as to he prosslv 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 sclf-providcncc or for "social insurance"--for "sickness insurance" to heln out during brief finesses, and for "invalidity." "old age" and "widows' and orphans' " insurance where illnesses or infirmities result in long or permanent disability or untimely dcnlth. The cost of these insurances against the common misfortunes of life cannot rightly or expediently be imposed wholly upon industry, but tteeds to be distributes! somewhat in proportion 1IS Tsvenly-fourlh Annual Saf et y Congress-- National Saf et y Council to responsibility. And benefits, at a Inch scale ot maximum earnings, as in workmen's com pensation. simply raiinot be provided for all such workmen's misfortunes. In invalidity. old-nee and life insurance, at least, the benefits must be graded, 11101c or |cc;. in proportion to the individual workmen's contributions to the requisite reserves; ;,nd the rich! 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, b'rom its beginnings. the workmen's compensation law lias covered all injuries to health resulting from occupational accidents, k'urtlier it lias now. in this cuuntrv 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 Latin 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 arc that industry shall be held responsible and liable to compensate for the losses from those injuries only which are caused by "trade risks ", resulting from employment and which the employer can control ; and that the liability for such risks shall be suffi ciently well defined as to he 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, lint 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, flcnerallv the causal relation between the employment and the accident and between the accident and the resulting injury can be traced with reasonable certainty, flcncrnlly the imploycr is automaticallv identified. And there is a clcnr-rut event from the date of which time-limits on notices, claims, etc., ran he measured. Til 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 he 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, lint merely of the existence of the disease, but also of its causes ami consequences. A further dilfirulty is that, where the disease is of slow contraction, it may he contracted bv 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 highelv 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 diffirultv incidental to the provision of new insurance for coiupi le.atioii for such diseases of slow contraction as silicosis. Under siieli comlitions, 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 phvsirul impairments already incurred though the liabililv therefor is not yet matured. In insurance parlance, these aie 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 Vnrk. aggregate many millions of dollars. '| Ins r ust is additional to losses from current risks: and bow to meet it and bow to fix. reasonable rh.nre.es for insuring it is a complex financial problem. Occupational Diseases 119 The situation, then, in my opinion, is this: The principle of compensation, re gardless of fault, may well he extended to cover those disabling diseases that are characteristic of and peculiar to and have their origin in the occupation nr process in which a person is engaged. This would exclude the diseases of ordinary life, and would he 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_acci-_ dental injuries, and these distinctions should be constantly emphasized. The problem" 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 diagnosahlc, of quick contraction and non-progressive. Piif it is difficult in I respect to such progressive diseases of slow contraction as silicosis and aslstosis-- / now generally regarded as being truly "occupational." Fortunately, however, there J arc 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 he made "compensable" should he distinctly specified--by listing in a "schedule" or otherwise. They should include all those diseases, hut only those, to h found in the state, which, according to prevailing medical opinion, can he traced. . in individual eases, to origins in "trade-risks"--f. c.. risks, not of ordinary life, hut created by special practices or processes in industrial occupations. 2. There should he a special regime for expert adjudication of medical questions in occupational .disease eases. 3. There should he definite periods of exposure required ns a condition to the right to compensation for various occupational diseases; the time within which, in order to he compensable, disability or death must follow exposure should be limited; and eases resulting from exposures prior to the effective date of the compensation coverage, or in industries wholly outside the particular state, should he excluded. 4. Prompt notice either of the first manifestation of the disease or of disablement --the time of such event to he determined as a medical question--should he strictly required; and every presumption should be against the validity of a claim not made as promptly ns practicable. I 5. In ease an occupational disease: merely aggravates, prolongs or accelerates disability or death due primarily or prnximatcly to a non-nreupalional disease or infirmity or, above all. to old age, the compensation should he reduced to he 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. Put all such liabilities, whether dirccllv. for compensation or for con tribution to the compensation payable by others, should he subject to brief time limitations. 7. In incurable diseases, especially silicosis, the obligatory medical benefits should he specially limited in time and kind. 8. In silicosis and other diseases of slow contraction, there should he special provisions for limited compensation to workmen laid off before actual disablement, with the alternative, under some conditions, of waiver of compensation hv such work-* men for aggravations resulting from being allowed to continue in the hazardous occupation. 9. A law newly imposing liability to cnmpcnsale for silicosis ami other diseases of slow contraction should leave a substantial inlrisal for preparation between the date of its enactment and that when it shall take effect; the compensation for such diseases should he specially reduced and limited below wlial would otherwise he appropriate until the "aecnicd liabilities'' are worked olf. 10. Compensation for occupational diseases should be insurable separately from compensation for accidents ; and. in the initial stage, at least, of a regime of rum- prnsalinn for such diseases as silicosis, the rating practices now imposed upon insur ance carriers need to be radically modified. , 7rente-fourth . l i nn ui l Sa j ety ( oui/rcss-- National Safely Council Tlu; aho>e program is sound and would la; highly conducive to occupational -asc prevention. lint I am not so confident that it would he safe. The pressure is in-T for "liberality" in compensation laws. Merely a few amour; a large numher i.rnhahle slight diversions from what I suggest would convert compensalion for iputional diseases into indefinite health, old-ape .and life insurance for workmen in v industries. 'I he cost might ruin the industries, and, at least, would he so uirulahle as to make the risks "uninsuruhlc." except on the unlimited assessment n, with all its financial perils and uncertainties. In reput'd to prevention, there arc still some practices to he decided upon in f itiiur a regime of .compensalion for occupational diseases about which there ,ins much doubt. hor example; Such a regime will practically compel employers, living employment, to discriminate against all the ailing or aping--against all pt tlie most healthy and robust. 'I hat seems to he desirable in occupations when occupational disease hazards are great. Tmt is it desirable otherwise? Again, an ideal common to those of us who emphasize prevention is to rcipiirc prompt removal from exposure of workmen manifesting the first symptoms of an iputional disease. But for the elderly or skilled workman the loss of his trade-job . he 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- ulm have sincerely at heart the welfare of workers could he delegated the au- \ itv to devise a solution, sonic progress might he made. But when political l Uganda is injected into the situation there is little chance for an adjustment ! uietory to all concerned. The greatest need today is the divorcement of nceupn- ' al disease legislation from politics or political considerations. Some Practical Considerations in Dust Control By J. J. B L O O M F IE L D r-jitary Engineer, United States Public Health Service, Washington, D. C. The prevention of occupational diseases due to the inhalation of industrial dust -imarily ail engineering problem. Until recently, however, little attention had devoted to the control of dust, accounting for the paucity of fundamental data '0 subject. The consequences of the neglect to furnish adequate protection from hazards arc now being felt, and the cost is becoming a serious drain oil industry, now well established that exposure to certain kinds of dust, such as those con ic considerable amounts of quartz, has increased the morbidity anil muvlality from respiratory diseases; while metallic dusts, such as lead and ils compounds, been associated with general systemic poisoning of workers. It is obvious, lore, that any serious attempt to control die dust hazard should, in lime, result nly in llie improvement of the health of workers, hut also he of definite economic il to industry. Ihe benefits of a preventive program in the field of accidents are well known, lev is fast realizing the need of a similar preventive program with rcsprrt to ational diseases. Evaluation of the Dust Hazard Ilie first step in the evaluation of the dust hazard is the determination of the `.ational exposure to the dust in question. A typical example of such a study sene to clarify the methodology involved. able 1 shows the various occupations in a granite quarry and the numher of ers employed in each occupation. Drillers arc the only persons using pneu- tools, known to, produce considerable quantities of dust. In other words, 38 i nt of the quarry personnel arc shown to he exposed to a potentially dangerous 'uzanj. 'I he occupational analysis at once indicates that the dust investigation Occupational Diseases 121 Table 1--Occupational Classification of Granite Quarriers Occupation Number in Each Occupation I b illers: Lcyncr ........................ 17 l'lug and jack hammer 37 Other <|iiarry employees: Superintendent ................................................................ 1 Foremen ........................................................................... 7 Compressor engineer .................................................. 1 Hoisting engineers ..................................................... 12 I.ocomotivc engineer .................................................. 1 Locomotive fireman .................................................... 1 Steam-shovel man ......... I Crant" operator ........................................................... 1 Derrick men .............................................................. 24 Muckers ...................................................................... 24 Blacksmiths ................................................................ Tool boys .................................................................... 2 Water boys ................................................................ 1 Machinists .................................................................. 3 Air-line repairers ....................................................... 1 Pipe fitters .................................................................. 2 Total....................................................................... 142 Table 2--Occupational Dust Exposure of Granite Quarriers Occupation Lcyncr drillers .................................................................. Plug and jack-hammer drillers (quarry-hole)............. Plug drillers fyard).................................... .'.................. All other workers.............................................................. Number in each occu pation 17 37 88 Dust counts in millions of particles per cubic foot of air. Weighted Average 144.4 112.1 36.9 S.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 arc responsible for the dust. For example, experience has taught us that the various activities, comprising the processes of most dusty occupations aie 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 Lcyncr drilling. (In this ease 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 _>2 7 v-fourth .-himini Safety Coni/ress-- National Safety Council Table 3--Summary of Dust Exposure of Leyner Drillers in a Granite Quarry \. tivily ..achin'.; ........................ wing off holes........... Aver-a.ee ritlsf tWpf'Mirc in milli'iiis of piii lii K"' i*>r niliir loot of air ( a ) . . . ........... ............. ............. ............. 21.1-1 PS SO 6.0 1.085.0 \ Tumber .nf Ilnurs Spcul in .rin h nrlivilv fi.i 4 1 7 K 'A Total.......................... S I'arlich.'. hours in mi 11ir>1)5; per ruliic I.... (a X 1.) 53/. 0. 16.0 1.5 271..5 1,155.2 particle-hours in millions per cubic foot = I-l-i.-t million particles per cubic foot 8 hours M hazard. I lls evident that the practice of hbiwiii:-; off holes by means of inscrtin;; ora; icssed air line into each hole is attended with a great amount of dust; and null this activity lasts hut 15 minutes of the 8-hottr working clay, it is responsible r 25 per cent of the total dust exposure. It is evident that 2.5 per rent of the l.evncr tiller's dust exposure may lie at once eliminated by prohibiting this practice. And :-;ly. such an analysis indicates the necessity for devoting all one's efforts to the -u". nl of dust during the drilling process, since this activity accounts for 74 tier rent : the total dust exposure, although a l.evncr driller spends but one-half of the :!:r:r.' day at his drill. ?.o iar wc have dealt with an industry in which the workers, as a rule, do not '-ange their occupation. Often workers have had several occupations, cither in the ate industry or in several different kinds of establishments. If the worker has been ::;! y<d in various occupations in the industry, it is a simple matter to determine P't'.l dust exposure in that industry. This is important from the viewpoint of rrcd.-.tinjr a worker's dust exposure and his clinical condition. A typical example is w:t in Table 4. Tacle 4--.Total Occupational Dust Exposure of an Anthracite Coal Worker Oenipnt ion Number of years in each occupation '.ite ' ickcr ................ ...................... 2 u !: " . . . .................. 9 : :le 'river ................. ' ; laborer ........... ...................... 3 ct:' foreman ......... ...................... 5 Dust concentra tion in millions of particles per cubic foot 380 71 71 480 480 7 Millions of particleyears pet cubic foot 700 M2 213 1,410 7 200 35 "Mai.................... ...................... 30 9.700 760 -bilious of particle -years per ruliic foot -- ---------------------- -326 millions of particles tier cubic foot 30 years ; I able J the worker's occupations arc arranged in the order of employment, ; i.. - .one U-mg his present occupation. It is obvious that had one considered this mu-'.on only, the dust exposure wotdd not have yielded a true stale of affairs, Occupational Diseases 12.3 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 lair estimate of a worker's dust exposure and lii.s proper designation. Such an analysis is justified by the fact that results obtained with this technic yield excellent correlations with the clinico-roentgenological studies conducted on anthracite coal miners." It is thus apparent that there is more to engineering dust surveys than the taking of dust samples-anil their analy sis. Owing |o the i.u l that the malting of dust studies is rapidly being adopted in industry, it has seemed necessary to emphasize the impor tant iactors in such investigations. Although the making oi dust counts, yYr sc, is not a difficult, proc edure, the: collection of dust samples in industry and their proper interpretation should he done: by a thoroughly trained investigator. The examples just given show the value of this technic in the subsequent steps to he taken in the control of the industrial dust hazard. General Dust Control Methods The selection of any method of dost suppression will depend primarily upon its effectiveness in reducing a given hazard and its adaptability. A large percentage of reduction in dust does not necessarily indicate that the method imcd is ellicicut, unless the reduction has actually been sufficient to bring the exposure Iidem the sale limit, and does not iuteriere with the industrial operations involved, hi general, there are four methods of dn-t control: (1) substitution of nuudtist-producing or harmless sub stances; (2) isolation of the dusty operation; tJ) welling the dn.-l at its source; (4.) local exhaust ventilation. 'J hese methods may he supplemented by personal respiratory protection. The first method has a limited application. One example is the use of a nonsilica parting compound for a silica compound in connection with the: linking of foundry molds. Table 5 shows that although the use o( parting coiiipounel, in thi particular study, only necessitated an exposure of 5-1 minutes of the 5-10 'minutes of a moldcr's work day (10 per cent), actually this activity accounted for approximately 5S per cent of the moldcr's total exposure. It is obvious that the employment of a parting compound, which is not as harmful as one compeiscd of free silica, will lessen the elust hazard in this instance to a considerable extent. Table 5--Dust Exposure of Molders Activity ------------'------------ ---- - -------- I 'sc of Parting Compound........... Jveinaining tasks in molding......... Pouring" ........................................ Dumping molds ("shakcoiut" ) ... Average Dust ' Exposure in Millions Time of Exposure in minutes of Particles per Cubic Toot (a) -------------------- --... -(b) . .. 54 638 412 4.4 $8 3.1 ir, 32.5 ParticleMinutes in Millions (a X b) ----- - 3.445 1.813 180 52(1 T o t a l ...................................... 540 5,958 5958 million particle-minutes ---------------------------------- = 11.0 million particles (per cu. ft.) 540 minutes 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.1 Table 6 shows the improvement effected by this type of substitution. Not only is the dust concentration reduced from an average of 969 to 155 million particles per cubic foot, but the potential exposure to quartz dint is diminished from -12-99 to 3 per cent. Ijl ' lumia! S a f ety C'oni/rcss-- National Safety Council pvduction in Concentration and Quartz Content of Dust in lMis With the Substitution of Steel for Sand Abrasive Average <lust concentration in millions <if particles lYrrrutage per cubic foot of Quartz ............................................................ %> ................................................. 155 -IJ-'i.S 5 p.i.l of lust control, isolating the dusty process, possesses many , innately is not widely used. The theory underlying isolation ,|n-1 sources to one locality or to a single closed space. In this l,,.i of employees arc exposed. At present, many foundries, dur- 11 x\ ot Iters who normally arc engaged in occupations with low | Inis, molders in a foundry may lie exposed to a dust conccn- ,, tides per cubic foot under normal occupational conditions, but 1moiis are carried on close hv. their exposure may he increased ' ,, I he same condition exists when annealing flasks containing ,| in malleahle iron foundries, exposing grinders and tumbling [1 1(|, close bv. ' , v iinple of isolation of a dusty process is the abrasive cleaning I, , iieloses a hazardous process and exposes only the blaster who 'l with a protective helmet. The room is also exhausted, which (ll i concentration. Processes which are isolated rc<|uirc go o d iiuplrs of isolation are the automatic turntable for abrasive | and hatch-mixing rooms found in some pottery establish* l i haps the oldest known, is the practice of welting the dust , I, ' an example is depicted in connection with the drilling and ' o.i.n ite coal mine operations* It is apparent that a tremendous i,,,ii effected by this method. However, as alrcadv pointed out. is attendant with a reduction of the dust to a safe limit. I . iieeessful. In the present instance, the workers engaged in , .1 to unsafe concentrations of a highly dangerous dust* and ,1 of controlling the dust in drilling operations hv dust traps , .b illing and loading operations involving an exposure to dusts ,,,i lining ln'eli amounts of free silica, as in the rase of coal or ,ii.in shown by the use of wet methods may he considered \Vet" and "Dry" Methods of Rock Drilling and Loading Mo. of Samples Average dust count in million; of particles per cubie fo "Dry" "Wet' , 23 5b,S 33 in b.3b 32 exhaust ventilation--is perhaps the most effective, and one ,..,11. We cannot discuss here the details of the tlieorv and ; -.vslems. except to point out there is a real need for more type conducted hv I bilia Valle with reference to the design w hich he has presented in Public Health llulletin 217. Tie, 111.agues* oil the rmilml of the silicosis hazard in the hard .Per example of a scientific approach to the dust elimination Occupational Diseases 125 Table 8--Summary of Results Contrasting tlie 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 filing charge . ........... 40 834 Loading coal or rock.. 32 Loading coal .. ...........4-26 Drilling........... ........... 33 636 291-113S* 568 Hauling coal in mines. 1.2 17 Preparation of cual... 24 . 3S0 ' Tlie lower result is ;issn iatel wit the is ha>c<l on the haiul lo.itlmi; o( 11\ coal. Unless at least 15 minutes elapsed alter firing a charge, miners found to be exposed to high dust concentrations, liy wetting tlie loaded material the dust count is reduced as shown. Mechanical loading decreases the dust ex posure as indicated. Wet drilling is effective in reducing the dust concentration. Further reduction would necessitate exhaust ventilation. Welting coal and empty cars reduces dust in haulngcways. Wet breakers reduce dust counts as shown. {atlim; of wet coal w hile tire higher average It is apparent that there are no set rules 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 lie 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 Controlling the dust hazard. Tlie follow ing two examples indicate the value of such investigations. Table 8 indicates the various control measures which were found in use in the anthracite coal mines investigated in the study referred to earlier. Although no single mine practiced ail 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 nierciirialism among workers in the hatters' fur cutting industry. Table 9 -hows the exposure to mercury dust and vapor of some 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 I!lowers ........................................ 4.6 .. Shippers .................... .................. 7.2 .. Cutlers ................................. 4.0 1.8 Sorters ........................................ .18 1.7 Polishers ......................................... .11 1.2 Drummers ................................... 2.5 0.6 Clippers ........................................ 1.5 0.7 Method of Control None practiced " " Local exhaust ventilation " Segregation " .:o J'went y - j out lit Annual Safety Lontjress-- A'atioual. Saf et y Council under controlled mil uncontrolled working conditions. It is apparent that where rmne measmc of control is practiced hy such methods as segregation or local exhaust ventilation, a material reduction in the exposure to mercury has hcen effected. It Is our belief that in the case of the Mowers' exposure, a reduction may he effected by mechanical enclosure and local exhaust ventilation, and that the shippers' exposure to mercury vapor may he lessened hy a general system of ventilation sufficient to chanyc the air in the store room frcqncntlv enough to briny the mercury coucentrairalion to a lower level. Unfortunately, in the present investigation, it has hcen 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, r.ecausc 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 nil 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 he detrimental to health. It should be pointed out that the L'. S. lhircnu of Mines is equipped to conduct approval tests ot respirators .used for protection against various dusts and fumes (Schedule 21). These tests arc conducted against the dust for which the device is to be used and arc rated, not on an efficiency basis, hut 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 ('anvil.' 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 P9sitivc 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 in-ide 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 cotientrntion in the sandblast room (outside the helmet) constant. The positive supply of Ci 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 hy the worker and not the volume of air supplied. Too much emphasis cannot he stressed on the necessity of maintaining in good order the personal nspiralorv derives for the protection of the worker against various toxic dusts. Maintenance of exhaust vciililntinn systems, and other types of protec tive equipment, should he a rule in industry rather than an exception. Too often the term "rood housekeeping" has I i n t e r p r e t e d as signifying only the periodic removal of diet rollii'ti'd on Hours, rafters, etc. Although such practice Conti ihulcs to the general slate of cbanUtuex <,f a workroom and should always he in force, the time lias surely come when serious ntleiiliun should he given to the installation and rigid naiiiti nance of all types of dost control devices. In every plant there should he some responsible individual charged with the periodic inspection of all workrooms as to sanitation, ventilation, and maintenance of all dust removal and other protective dev ices. Pit haps the best criterion of the effectiveness of these devices is the prtiofhc deti tminatioit of the die.1 conlrnl oi die air at the workers' hiealhing /one. inly hy conqa111 vigilance and an appromli to the prolilein as nullitied in this paper may one hope t.> make progress in the control of the dust hazard in industry. f til* ti the l,i ip |,|s of even a most extensive program of dust ronlrol are not I'timi di.itetv irali/rd. 'I hU is especially tine m dcatine. with lihrie.i.e piodnciug dusts in plants where some of the workmen have already inhaled sufficient quantities to Ocatj'olioiuil Diseases 12 7 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. Rrunda.ee. statistician of this oilier, that the minimum expectancy in savings to employer and employee from an indicated reduction of tbc accident rate and of the time lost on account of illness (or an eipiivalent reduction in mortality), demonstrated as attainable, is JJO.OOO per year per 1.1100 employees. And this estimate is for plants whose accident rate is considerably below the average, in which there arc no occupational health hazards. In plants where hazards arc known to exist the savings should be far in excess of Ibis conservative estimate. When one realizes that in this country there are approximately 15 millions of workers engaged in manu facturing, mechanical, and mineral industries, then it is evident that the magnitude of the problem lias not been overemphasized. References 1. BloomficM, T. J. ami Brecssen, \V. C .: Siilo-* among granite rjuatvie*. Public Health Reports, Voi. *19, No. 23, June 8, l'34. 2. Antltraco-Silicosis among hard coal miners, Public Health Bulletin No. 221, 1935. 3. Bloomfield, J. J., am) Grcetiburg, Lcouaid: Sand and metallic abr.iMvc bl.i<ting as an industrial health hazard. Jour. lini. Ilyg., voi. 15, tin. 4, July, 1933. 4. Dateli. Theodore, Drinker, 1'hilip. ami Choate. Sarah I*.: Control o f the silicosis hazard in the hard-rock industries. I. A. laboratory study oi l!;e tienigli oj du st control syste ms for w<c with pneumatic granite c ullin g tools. Jour. hid. Ilyg., voi. 12, no. 3. Marcii, 130. Jlatch, Theodore, Kelley, George S., and J-'cl.iu:!. J. \V. : Control oi the mIco-s hazard in the hard-rock industries. JI. An investigation of the Kclhj lust trap for live with pneumatic xock diill of the "Jack-hammer" type: Jour. lud. D yg.. v.d, 14. no. 2, IVInuary, P32. Hatch, Theodore, Wairen, Henry,, and Kelley. George S.: Contini of the >ilK" >i? hazard in the hnnj-tock iwhiMrics. IIJ. Devigli and pfiatnuj of a Just-riniti! syvtrm for live with pneumatic mck thills in open e sc avat i" . Jour. Jiul. D y g ., vnh 14, no. 7, September, 1932. ^ Silicosis and Silico-Tubcrculosis Medical Problems of an Important Industrial Disease By EDGAR MAYER, M.D. f New York City A bidden element of tbc cost of production is industrial disease.- Industry lias reached a stage beyond tbc concern only oi wages and bouts, bar more important is conservation of man power by preventive medicine and improved engineering. Disease preventive measures are not 1 cost, but, in the long run, a great economic saving. Iiidilencr. In the United States it lias been Computed that there are from 5(1(1.1)00 In a 1,000.000 people employed in occupations where a silicosis hazard exists. In N'cw York City there are about 05,000 such employees. In a r*presinlative group of granite workers in Massachusetts silicosis alone was present in about 15 per cent and silicosis complicated with tuberculosis in almost X per rent. Tuberculosis was the cause of death in over one-third of the granite wot her-. which is lour times the incidence for males oi JO years and over in ibis country. In foundry men studied in Massachusetts, silicosis was less frcipieut (about ') per cent) and less advanced in degree than in graniti- workers. The duration of expo-.ure in foundry wnrkns with pneunumoroninsis lias averaged many moie years than that rripiitrd to produce silicosis in an industry such as gold mining. The tnhi-mdnsis hazard in foundries is nearly as great as that reported for some of the other dusty trades, but tbc lienres are much loner than those of miners of gold, silver, copper and lead, among whom tbc mortality from tnbemdosis is X lo IX time-, the general esperi.mry. I leatli rates fur all non tuhrvoilimx infections have been rrpmlrd lii-lu i among workers in siliceous dusts than in the general population. It is suggested lh.il the woikrr in silica succumbs more often to arnie pulmonary infcelioiis railin' than surviving the chronic fibrosis. S T-.ccnty-fourlh A ni ma l S af el y Congress-- National Saf el y Council Silicosis is defined as a pathologic condition of the' limps due to llie inlialation .lira. whether free or eomhined in such a Mate as to he capable of setting up its acteristic pathogenic effects. Tlic principal faclors (licit determine the incidence Micosis arc (1) the percentage of free silica in the inhaled dust; (2) the conration of silica particles less than 10 miera in diameter in the atmosphere; (3) duration of exposure to the dust, and. (-1) the susceptibility of the individual ...sed as modified by ape, complicating infections, etc. The occupational disease altintr from such inhalation has been defined as "morbid results of occupational a its traceable to specific causes or labor conditions and followed by more or extended incapacity for work." Metabolism 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 info the blood as shown by the constant excretion of silica in urine. All vegetable foods contain silicon especially the bulls of grains, bay and ,w. The bnv silica content of the liver, spleen and kidneys indicates the little ntion 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 cfticicnt 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 ? 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 he a constant drainage of silica from the ; through the inhalation of extremely fine particles of silica in dusty atmospheres, -mall that they are not seen under the mirroscope. .Attempts to influence the absorption of silica from the lungs by administration alkali have been inconclusive. Kliminalion of silica by way of the sputum from cuts having deposits of silica in their lungs appears to be higher than those nig no ln.-tory of exposure to dust. Only small amounts of silica are in the 1 anu this level is little different in normals than in silicotics. 'alhalagy. This disease is essentially a fibrosis of the lungs developing espe'.'.y in such industries as hard-rock metal mining, granite cutting, metal grinding : sand-blasting. The pathological changes re believed to result from two causes, locking of the lung lymphatics by mononuclear cells laden with dnst in addition the action of colloidal silica, the exact nature of which is in doubt. The small icles under 10 miera are the only ones callable of penetrating the lung tissue. Although silica plays the dominant role in the production of silicosis, the ad rare of Cither dusts tends to modify the pathological changes in the lungs so ; 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 stos. produce a definite change in the lung, as well as other dusts such as :Mc. coal, etc. Such changes are represented by a fibrosis brought about because lively insoluble minute particles of minerals in sufficient concentration have brought by the activity of phagocytic cells into intimate contact with the v.onary 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 ire the supporting connective tissue of the adjacent blood vessels and to some nt also the walls of adjacent air spaces. However, when the great majority of inhaled particles arc composed of or contain silica, there develops, in addition, a 'lie and localized type of fibrosis called the silicotic nodule--an orderly whorlcd ugcnutU of cells and fibres, and with sharp definition from the adjacent pareu nia. Many dusts create a generalized fibrosis but only one, namely one combined silicon dioxide produces the special fibrosis of silicosis. .Seriate-, known as `e mica, which is a hydrated silicate of aluminum and potassium, has not produced nimal experiments the silicotic nodule, but instead generalized fibrosis resulted. Uusts must be differentiated into those which are chemieally active and those h arc 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 'nb on its -.olubility. This activity which is manifested in the areas where dust civs are carried along the lymph stream by phagocytes, causes lesions of two Occupational Diseases 129 types, "toxic" ami "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 tlusls arc insoluble in body fluids and cannot exert chemical action in the lung tbsiic, but it 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-antbracutics than in silicotic lungs. Other dusts may even protect, as in the case of certain clays, gypsum and aluminum oxide, fine pnctunonoconiosis may be only a laboratory disease, as the pulmonary fibrosis of workers in dusty trades probably results from the combined action of dust and infection, whether it he tuberculous or not. In silicosis it is not the mineral particles that are 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 nciiic 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 anlhracolic dust. ITirthcrmorc, unequivocal cases of silicosis, with or without tuberculosis, can no longer he doubted. Tuberculosis. Most apical tuberculosis is acquired before the aim of 23 and so silicosis at the age of .30 makes a previous tuberculosis more serious. Most workers with tuberculosis going into tbc mines before the age of 30 die of tuberculosis by the age of -15. The silicotic develops a sputum that contains tubercle bacilli late in life and tbc children who are contacts with tubercular silicotics develop very little clinical tuberculosis. It is impossible to say definitely that tuberculosis engrails itself upon the silicotic or vice versa, fur we see apical tuberculosis in silicosis that spreads downward, while other silicotics show only the tuberculosis in the lower lobes. It lias 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 arc 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 oi lung tissue. We must at times rely 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. I.ung fibrosis may be present without any silica. Silica may he present in lung tissue or the pulmonary lymph channels without associated fibrosis, l'incl.v divided siliceous particles from lung tissue may contain innocuous silicate which cannot lie dislingiii-hcd from harmful silica particles. Hydrated silica which is not doubly refractive cannot lie demonstrated with prisms. Therciore ill the pathological section the presence of siliceous fibrosis can he suspected hut cannot he specifically identified with the siliceous material that it may contain. Accordingly tin: imcromcmcraticm method of Irwin with hydrochloric arid 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 history. Quartz grinders working under conditions oi 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 (lie same industry, indeed in the same room, experience different degrees of exposure dependent upon perhaps the dust-filtering capacity oi the nose ami functional condition of the lung as deter mined bv constitutional characteristics and antecedent disease. Tlie size and col loidal structure of the particles of silica, as well as the dosage ami total amount of `lien, will influence the rate of development of the disease. Apparently particles that arc larger than 10 uiicra arc not pliagncyloscd in the lung. So a definite Safety Equipment Safety Equipment WEDNESDAY AFTERNOON SESSION October 16, 1935 m The session was called to order by Chairman, Irwin \ \ \ Millard, president. Industrial Gloves Corporation, Danville, III. Chairman-AIHard mentioned some oi the problems of providing adequate safety equipment tor industry. Respiratory Protective Devices (An interpretation of the U. S. Bureau of Mines, Schedule 21) By CARLTON E. BROWN. Chemist, and W ILLIAM 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 oi air deficient in oxygen. The devices in common use arc the mechanical tiller respirator (commonly re ferred to as respirator) for protection against the inhalation of dusts, smokes, fumes, and mists or what may he 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 does- 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 ami the impact and abrasion from the atmospheric particulate matter generated in sand blasting or abrasive blasting with steel shot. These devices are designed to fnrnish protection cither liv making the wearer's inspired air safe to breathe or he supplying the wearer with safe air from a supply which he carries or from outside the contaminated zone. The wearer of the fir.-t or air-pnrifying 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, oilers no protection against atmospheres deficient in oxygent 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 oi compressed'oxygen, liquid oxygen, liquid air, or from a chemical which yields oxygen upon decomposition. This air supply is ('art of the self-contained unit, all of which is carried by the wearer. In the other type a hose, attached to a l'acepiccc. is connected to a compressor or blower whose intake is located in safe air. Air is forced through the hose to the wearer. Note: Published by permission oi Director, l :. S. bureau of Mines. (N'ot subject to copy- Twenty-fourth minimal Sa fe ty Congress-- Nat ioual Saf et y Couneil here s some confusion in the use of the term "respirator,'' to designate devices ritection against the inhalation of atmospheric particulate matter. Such devices lie first and for a lone; time were the only respiratory protective devices, they iopicallv called respirators, and as long as they were the only devices of this here was no confusion. The development of other devices of industrial hygienic 'mice ami the development of devices for maintaining artificial respiration over rinds .and for enabling men trapped in submerged submarines to reach the sur'fely, all called respirators, was responsible for the confusion. The Bureau of suggests that the term "respirator'' he retained for all of these devices, hut 'pir.ulnry protective devices of industrial hygienic importance he called indiis<'pirators and that the different kinds of industrial respirators he assigned a .Inch will indicate their operating principle or field of use or both. Satisfacames in common use should he retained. .On this basis, the Bureau of Mines ts the following classification for respiratory protective devices of industrial ic importance: Industrial Respirators iplictl-Air Respirators 'clf-containcd type ']) Oxygen breathing apparatus'1 lose type Ml Hose mask '2> Air-line respirator1' .A Abrasive blasting respirator' Purifying Respirators hemical filter respirator1' 11 Acid gas or type A" chemical filter respirator 'I Organic vapor or type IT chemical filter respirator 1 Ammonia or type C' chemical filter respirator !,i Carhi.n monoxide or type D' chemical filter respirator Pchamcal filter respirator' I i Dust or type A' mechanical filter respirator ') Inline or type B' mechanical filler respirator A Mist or type C' mechanical filter respirator unieal and mechanical filter respirator* and Approving of Industrial Respirators by the U. S. Bureau of Mines its organization the U. S. Bureau of Mines has been interested in industrial | - as a means of protecting workers in the mineral industry against harmful : ic contaminants. To this end the Bureau has developed an approval system, c.s of which arc: (1) To encourage and aid manufacturers in the dcvclopI marketing; of safe and. suitable ei|uipment; and (2) to encourage the eon- use s uch eiptipinent. to a id h im in o b t a i n i n g it a nd to in struct h im in its r.-se purposes are accom plished by establishing a schedule o f the material and e.c lcipuictncnls that a safe and suitable device should m eet; by making ests fur conform an ce In such a sch ed u le; and by inform ing the public of the nines ran''d mine u-scuc lueadiiiiir ap p a iam s. times called paint-spray respirator "r .positive picssnvc respirator. ''inies raliett sand-ldast tietmet nr lio.al. itonly callril r as mask. is assigned In eanisiers o! clieinica) filler le -p i ia lm s . Sec It. S. llnrcau of Mines ):e<l. HJ), I'rneeilnrc tor Tes tin g (ins Masks for Permissibility, 17 pp., 19.15. nn.nly ealleil respirap.i'. Sometimes ir te n c d In as ilnst respirator or incrlianical . rspiiap.r. "rs assigned to mo liani.'al filler respirator fillers. Sec tl. S. Unreal! of Mines . I.e*l. 71, l'lorrihnc for Testing TillerTvpe llnsi. Inline, ami Mist Pcspitatnfs for '1v, It pp.,' 19.11. desires nmv iefeiir.1 to as T>|ic N nr All Sc iv ie c Gas Mask ami tlic rlieiniral , |.n .itor tall under this heading. Safety Hquiftncnt 135 advantages in the use of ileviccs bearing Bureau of Mines approval. If the device is fourni Iiy examination and test to meet the re<|uimiien1s of the schedule the Bureau of Mines gives the manufacturer a certificate of approval which he may display as evi dence of the finality of his product. The approved devices arc marked in a manner which dearly distinguishes them ami indicates the purpose for which they arc ap proved ami the limitations under which they may he used. As an aid to the con sumer, the IJureairof .Mines periodically issues a list of the devices which have met the rccpiirements. The submission of equipment is entirely voluntary on the part of the manufac turer. On making application for tests, the manuiaeturer 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 hy the desire cd the manufacturers to produce and market Rood equipment, the interest of the Pmreau of Mines in having safe equipment available commercially, and the demand of the consumer for such equipment. Approval schedules have heen issued for oxygen breadline apparatus.1 chemical filler respirators or pas masks,5 hose masks* and mechanical filter respirators.* The schedule covcrinji hose masks is being revised to include the other kinds of supplied* air respirators, namely, air-line and abrasive-blasting respirators. When this revision is completed, the bureau of Mines will have approval schedules for 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 th limina* lion of confusion in their selection and use. The general plait of the various schedules is similar. The requirements may he liviiled 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. I"'or example, tho respirator must he in a fully developed form ready for market and available for pur chase if approval is granted. Also, the manufacturer must he prepared to test and maintain control of the essential characteristics of his device hy a method which meets the approval of this Bureau. 12) Material, construction, anil performance requirements which the equipment must meet hy examination and test. | (3) Post-test requirements, or those with 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, anil 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 litem 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 Tc-ting Filler-Type Dust. Fume, and Mist Respirators for Permissibility, was the realization hy the Bureau of Mines and others that there was a definite need (or 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 either not available or practical, the inefficiency of existing mechanical tiller respirators, and 1 Bureau o{ Mines, Vmccdurc t*r KstaldUhing a 1,m *d S<*lM\tnt;iiuel (Kvgeu Iticatliiiig A pp ai aius ; Tecs, Char.icier of T es ts , and Condition I 'ndcr which Mine Kcsctie Breathing Apparatus will lc Tes te d: Schcd. MA, Janu ary 21, I'WO, I? pp. Bureau of Mines, I'roccdurc for Tenting (as Masks for J'crmisshlii v : S hcd. Ill), Mav 9. IW.\ 17 pp. s Bureau of Mines, Vrocednrc for T e s tin g H m e Masks for )'crun**ihilitv: Schcd. 19, April 29, Vt>7. 6 pp. Bureau ol Mines, 1'ioccdurc fur T e s tin g l*'iltrc*Type Dust, Tmtte, and Mist Kcspiratnis for Permissibility: Schcd. 21, A u g u s t 20, 1931, 14 p|i. I'^eenty-f mirth A ni ma l S a f et y Coiu/rcss-- National Sa fe ty Council -!s from ninmifnclnrers ;ind consumers that lliis bureau test ami ajij'rovc such C , -Jicdule -'1 follows tin- "fiu-ral plan o tlu: oIIkt bureau a]i)>rnva1 schedules for ini respirators: the pre-test and post-test requirements arc quite similar, and ncral principies of the test requirements arc the same. The primary purpose of . aper is to explain the reasons for the various test requirements. Prc-Test Requirements The pre-test requirements of Schedule 21 require that the manufacturer submit nation, drawin.es, and samples of. the device to he tested. The device must be . h'tcl.v developed and ready for release to the public, and the device when tested ho manufacturer or his agent must have passed tests of the nature described chcdnlc 21. The reasons for the third requirement are: (1) To assure the an that the manufacturer is prepared to control the filtering characteristics of -espiralor; (2) to eliminate any question of competition with private consulting vie# in developing respirators: (3) to iurnish evidence that the respirator really ady for release to public market: and (-1) to save the manufacturer's ami the i au's time. After the manufacturer has complied with all the above pre-test iicments he must submit a fee for the examination and test of his device. fee is turned into the miscellaneous unds o 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 quote protection. f2) be reasonably comfortable and physically convenient to .r. and (3) provide an acceptable service life. Adequate protection implies that the mechanical filter respirator when properly gamed and with must prevent the wearer from breathing enough particulate ter 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 are equal in importance to adequate i'Ction. lven though aware of the ultimate serious effect which will be produced r prolonged daily exposure, workmen are inclined to he diffident and unwilling it'll r much daily inconvenience and discomfort from the respirator. !.nriunhraner and discomfort also increase fatigue, cause distraction, ami in -:11 handicap the wearer's ability to take care of himself, thus increasing the diility of accident. Important specific items include the weight of the respirator, arriase on the face or herd, effect on vision, heating of the area of the shin r the facepiece, inability to expectorate, difficulty in talking, and resistance to thing. The importance of comfort and physical convenience cannot he over .o a P 'd. The service life involves elements of practicability in tip: wearing and maintenance die device, and indirectly the safety. This type of respirator is primarily not an rgenry device, hut a .part of the workman's equipment for doing his regular job iy. If the service life is short, the bother of changing of tiller elements will reflected in the workman's attitude toward good maintenance and use. All mechanical filter respirators are subjected to certain inspections and tests they must fulfill certain requirements. The general design and construction, lvularly as to facial fit, freedom (rom irritating facial contacts, weight, effect vision and the wearing of goggles, and ease of changing filter elements, and' lined. The materials are examined to determine if they are obviously suited the purpose for which they are designed. Rubber parts which come in contact h the skin must not contain any skin-irritating constituent. .Resistance to Air Blow Requirements The requirements for resistance to air How arc the same for all approved niclieal filter respirators. At no time during or after the filter efficacy testing period, 't th o 'resistance to air being drawn through the device at the rate of 85 liters Safety Equipment 137 (3 cubic feel) per minute exceed 50 millimeters (1.97 indies) of water column height or the resistance to air being blown through the device at the same rateof flow exceed 25 millimeters of water column height. An air flow of S5 liters per minute is approximately equivalent to the respiratory rale of a man doing heavy work. The amount of particulate matter pulled to the device during the filter cilicacy tests is roughly equivalent to the amount that would he pulled to the filter by a worker wearing the mechanical filter respirator in a moderately concentrated Mi.-pcnsion of the particulate matter <Uirit>n an 8-honr period. Thus resistance to air flow of an approved mechanical filler respirator should not become excessive when worn for ;m 8-hour period in most suspensions of atmospheric particulate matter en countered in industry. The manufacturer is rei:;---' to give instructions on cleaning o r changing the filter elements when the resist:::!.-- ah' iluw noticeably inennses. Direct Leakage and Man Test All mechanical filter respirators arc subjected to a direct leakage and man test to determine facial fit. whether there is any direct leakage of unfiltercd air. and to obtain information on the comfort of the device. Three of the mechanical filter respirators arc worn for .10 minutes by 3 men with different facial features in an atmosphere containing a heavy suspension of Intumiivuis-roal dust. At the end of the period the respirators are removed and that part of the face covered by llid 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 pari of the lace covered by the edges of the facepieces. The nasal passages and sputum of tlie 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, ni 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, and particle size: 1. Mechanically fiennalcd ilnsls resulting from the disintegration of a solid. Mich as the dust clouds produced in the various processes of mining, ((Harrying and tunneling and the grinding, crushing, and general processing of solid materials. This type of atmospheric particulate matter is referred to ns 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 are referred to as Type II mechanical filter respirators. 3. ,1lists as produced by spray-coating with paint ami vitreous enamels, chromic acid mist as produced in chromium plating, and other mists of materials whose liijuid 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 ns Type C mechanical filter respirators. The mechanically generated dusts anil 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 pa'ticie size of fumes is much smaller. The upper limit is in the lower microscopic age (about 0.5 micron), while the lower limit probably approaches molecular nensions. '1 lie particles of soon- fume", partictilaily zinc anil magnesium. readily a ami form laree llocklikc chMers. Tin- elfeet is least pronounced in the ease lead. Mist pai tieles are spherical ami prohaldy more uniform in particle size than sc of dusts and fumes. Suspensions of each of the types of industrially-gcueralcd atmospheric particle alter were selected for use in the hherine.-elVicacv tests. These suspensions were sen on the basis of their industrial hygienic significance .and their physical ..pci ties, such as particle-size distribution and tendency to aggregate. which have appreciable client on filtration. It was desired to test the mechanical filter pirators against the most common or widespread harmful suspensions of each e: the test suspensions to have physical properties, such as particle size and ..reyation tendency, which would render them as difficult to remove by filtration any other suspension of the same type. The. test suspensions selected arc: (a) lo r testing Type A mechanical Idler respirators or those designed to' "nisli protection against mechanically generated dusts a suspension generated from re fine (99-1- per cent through 325 standard mesh sieve) silica dust consisting of -7 per cent free silica (SiOs) is used. The suspension is generated in such a way at all particles larger than about 3 microns arc removed before tlie suspension ters tin- test chamber. The particle-size distribution of the test suspension must ! exceed a geometric mean of 0.6 micron and a standard geometric deviation of :0. | he particle-size determination is made hy collecting samples of the suspension the Owens jet dust counter and determining the particle size distribution by a vroprojectinu method developed by the Dureatt of Mines." (h) bor testing Type 15 mechanical filter respirators or those designed to rnisli protection against fumes, a lead oxide fume generated hy the comhustion of tural gas containing lead tetraethyl vapor is used. The particles of this fume are trcincly small and have about the least tendency to aggregate of any funic, hence cy are very difilcult to remove from the air hy mechanical filtration. A suspension magnesium oxide is also used to determine the effect of a fume, whose particles !il;. aggregate in large clusters, oil the resistance to air flow of the filter of flic vice. (c) For testing Type C mechanical filter respirators or those designed to rnisli protection against mists, three different suspensions are used. Chromic : i intst generated hy electrolyzing an aqueous solution of chromic acid, as is done industrial chromium plating: had paint mist generated hy spray-coating with bad :ill; and a water mist carrying silica dust generated by spraying a 2 per cent cons suspension of silica dust are used. The water-mist carrying silica dust is ! 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 actnitration of mechanically generated dust found in industry varies over such dc limits it was decided to test Type A mechanical filter respirators against two icenlrations: one to represent the more or less average dusty industrial condim, and the other to represent very dusty conditions. The complete mechanical filler, respirator is tested on a mechanical testing : aratus. The test suspension is pulled through the device at the rate of 32 liters .1.5 cubic feet) per minute, continuous flow. The volume of air pulled through mechanical filter respirator is 10 cubic meters in all cast's except in some > against particular hinds of suspensions as mechanically generated lead dusts I in the high-silica dust-concentration test and the magnesium oxide lest whose unary object is to determine the increase in resistance to air flow u( the fitter ih the amount of particulate matter retained. Ten cubic meters is approximately mvalenl to the volume of air breathed hy a worker in 8 hours. The samples of rfinil.'iic matter for concentration drtcriuiunliiuis are precipitated electrically in the air of the test suspension both before and after it has passed through mechanical filler respirator. The samples are collected in containers which lie weighed readily on an analytical balance. For reasons of convenience, spied, * I * t t' v i i , ( i i l it i * ' *m ;m<l invest I., a n , l Y a n i , \ \ * . |*. ( ' m u c u t r : i t i " i T he M irnijn..j.a tnr A l i m ^ i ' h r t i r l>n.|s, h*r I >rti i iiu n in i1 I ' i i i l i r l r S i/ r l * . S. I I u m m i i >i M i n e s K c | * n t ;i i k 1 accuracy the samples of silica dust are quantitated l>y weight ratlicr than by a uml. Samples of the other particulate matter are quantitated chemically. The requirements as to the amount of particulate matter that the mechanical filter respirators must remove from the air pulled through them is based on the best available information on the concentration of the paniculate matter that, is safe to breathe. These requirements are subject to ehan.ee with the accumulation of knowl edge on the pliysioloeica! effects of industrially pcncralcd atmospheric particulate matter. In other words, the filtering-efficacy requirement is that the air inhaled by the wearer of such a device must he safe to breathe, and not that the device have any particular percentage filtering efficiency. Mechanical filter respirators arc not approved for any substance more harmful than the particulate matter in the test suspension against which tlnv are tested. Thus Type A respirators are not approved for any substance more harmful than (rec silica (SiO;) 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 hv breathing dusts whose main harmful constituents arc metals or their compounds. However, two mechanical filler 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 ho 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 he provided with substantial and durable containers. Copies of the approval labels issued to the iii.iiiuiaetiircr by the Bureau of Mines must lie attached to these containers. The approval label gives the approval number, ishows to whom the approval is issued, stales what the device is and is not approved for, and cautions the wearer to follow the manufacturer's instructions for the use am] care of the device. 'fhe following is a sample of the required instructions furnished by the manu facturer. These instructions arc 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 fetter 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 headslrap with the (.tlicr hand. Dace the facepiece against the face and hold it in place while pulling the hcadstrap over the head and below the cars. Then adjust the facepiece until a firm snug fit is obtained. The headslrap may he 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 theheads!raps ami position of the respirator oil the face a- cardboard disc is enclosed. To use this disc unscrew the filter hag. place the disc against the felt washer in the metal coimection on the felt hag, assemble the-respirator, and put it on. The wearer should not he 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 cm the face inside the line of fit of the fan-piece after wearing the respirator in a dusty atmosphere can also he used to tell whether a proper fit was obtained. I. The recommended procedure for cleaning the tiller hag is lx insert loosely the nozzle of a high-pressure air lmse into the hag opening and to blow several 1-10 Turnly-Jourlh Annua! Saf et y Congress-- National Safely Council TA BLE 1. DETAILS OF F IL T E R IN G EFFICACY TESTS AND LIST K iud of :m eh.iiurat n i l r i i> j-c I C-J'U ilof Jmlu>tially ycnciatvd atm o -p h en e pallidi* late nvalU'i' a g a i n s t \ybic h tlic d e v i c e is designed to furnish piotcction Test suspensions ii`eri JypeA Mechanically pcneiated dusts icMiltini; p iim tpally horn |he ilistiiiloKration of a solid, mu'Ii ;is tlic d u d clones p roduced in mining:. qn.'m y in ^ ani) t uijuciik. a n d the iinhi'-tual operations of jriiiulmt;, ctusltinK* ami processing of minerals Air*suspended ptouml Hint, which cvmsisis of 99-|- p e r c e n t five silica (SiO;-). O v e r 9'.* p e r c e n t of th e d u s t p a r s e s th i o u ( ; h 32.5* mesh standard sieve Jvpcll , I,` p e t. hm ics of cations metals (usually their <hcmical compounds, as oxides or carbon- ales.) such as k*ai, mevcuiy (exiept rner* cure vapor), manganese, copper, chromium, iron, cadmium, zinc, magnesium. ahimi- num, antimony, aml aiscnic resulting from sublimation or romlcnsalion of their vapor, nr limn chemical icactn'iis between their u j i -t ami irn.-es M i ' i s as produced hy spray-coating with paint ami vtitcous enamel-., cinmnic acid in*S'l as puwlmed in chtomimn plating. **'* other m is ts of materials \vhoc liquid vc* h id e does not produce hanniul prases or tapers (a) head oxide fume produred hy the tie* composition ami conilniMioii of lead tetraethyl f|,> Magnesium oxide fume, ftc>hlv pro* ditred hy Imiuitu; m.iguc'-ium ribbon fa) Chromic acid mist pmduccd hv ricctio* Iv/iug an mjneous solution grains of ibio mic .iciil per liter) of chromic acid uallv n-d load M echanically generated d u -ts uho-<- m a m h a i m i n i c o n s ) i m e n i is lead, s u c h ;o> lead d n M s g e n e r a t e d in m.u ii il iu tin in: s t o r a g e b a tic ! ic-; i ii.itucling : piltey m a k in g ; nthher coinpoiimlitn: ; sandpaf>riimt and chip p i n g p a i u i r d s u r f a c e s ; p a i u tm a k iu K ; p>e* I anni.: lill a - t r a i m f e i s ; au<l m i n i n g , m i ll i n g am i processing lead ores (h) bead paint mist produced hy spraying a paint having the following composi- lion: white lead Ipasic having appmxi- m a t e l y 91 p e r c e n t w h i t e lead a n d ** p e i c e n t li ns e ed oil by w e i g h t ) , 1(X) g r a i n s : li n se e d oil, 50 c u b i c u n t u n e * l e r s : a n d M r a m - d j s | i l l e d tu r ' p e n t in e . 2a cubic centimeters (c) Mist produced hy spa>imr a 2 p n ee n t a'jueous su sp e n sio n of m o u n d Hint, air* fl o a te d (99-f- peic-ni .il u o ii j 'h sfaml* ad m esh Mere). T h e e n u m d Hint con- i s t s of 99-). p r ic e n t h e r ` i|j<a (SiO.d, M is tin e used in m a k in g n*gntjvr plates ol lead M o r a r e b a t l cue-.. ( `o n i a i n s 7 * p en - cu t li th a r j r c , i ' b O ; 25 p e r c e n t t e d le ad . I 'h . O , ; a n d .1 p e r c e n t l a m p b l a c k * One m i l l i g r a m 0.0IM gtain. ' l i n e c u b i c m e t e r A5.A1S cu b i c fret. * b a l e ol s a m p l i n g 32 li te rs M,M cu bi c feet) p e r m i n u t e . * O n e m i l l i g r a m o( lid*, silica dip-t c o n t a i n s a p i > t o \i i u a te lv Atti) cirri bv the i m p i n g c r m e th o d ns described by the. U. S. l'tiblic `m inili pci c u b i c m e t e r of th is d u s t is a p p i v * s im a td y ci jirivnlcnt <iil-ic foot. * S c p rev io u s listini; of com pany for rom plcte address. million p ailid cs Health Service. t o K.5 m i ll i o n s of as drlei* Hence, 1 pm tides Safety Equipment OF APPROVED MECHANICAL FILTER-TYPE RESPIRATORS Otmeentration of test su'l-cji*-Dn. miDigi '"is1 per cubic m eter1' of air - lO*1 if.) 5 2* IS J; 5 of lead Volum e of test suspension p u lid through the device, cubic meters* Maximum amount of particulate m atter p e r m itid t*> p ass iluough the device M illigram s M d igram s f'Cf u|''c, m eter ol air N;mP` and manufacturer ical liltei-l\|< e ic>pir.it<i to date, September 2.88 -1 mg. for any I of I.0d 3 devices. or an average of 3 mg. for each of the 3 devices M .S.A. Com! Respirator \r. 2101, i-Med tr Mine pliauces Co. W illson flag Respirator Approval S o . 2102, issue son I'roducts, Inc. 9.98 12 mg. for any I Ur* WdUun Hag Respirator of 3 devices, or Apprvrd No. 2in(, ismif, ,*m average of Id 'or J'rdmts. Inc.* mg. for each of (he 3 I'uhnosan .M I5 l'om h*T Respirator. Appuyal N'u mied to l 'uhu*>au S a fe ly 1 Corp. H ievcr Ue<|*tatpr. App 210?, jvucd ! S tand.u K t|uipm em Co. 9.98 1.5 0.15 Wills Hag R esp ira to r N* p rn v a l N*. 2It/*. i<*>nc<! t rro d u c is , Inc.* jut 25 5 <>f * iiunuic acid .tiO-MM) of lead n --i 9.98 1 M .S.A. Com Respirator. i 01 No. 2101, tw te d ' to Min A ppliances C.* 9.98 1.5 0.15 M .S.A. Cumin Respirator proved for lead containing ? H :,* ol .ihi a dust 15 5 of lead 9.98 5 2.88 0.1.1 0.5* M.S.A. fm nfo Re-piiator. No. 2K>1, issued to Mine Safi pliante* Co.* 0.15 M .S.A . Com Respirator era! filters for le.nl dn*t. A Xi>, 2R17. i*.?.ncd to Mine Sab pliances Co.* W illson Hag Respirator NV Approval No. 2R1S, issued ti son P ro d u ct* , Inc.*