Document 71vVb9dZeaynVMQewEO18VE3o

FILE NAME: National Safety Council (NSC) DATE: 1930 Sept-Oct DOC#: NSC053 DOCUMENT DESCRIPTION: Transactions of the NSC - 19th Annual Safety Congress - Vol 1 I 93 TRANSACTIONS OF THE N ational Safety C ou n cil NINETEENTH AN N U AL SAFETY CONGRESS VOLUME I Pittsburgh September --October 3, 1930 William Penn and Fort Pitt Hotels Copyright, JQjf, Mattonai Safety Council N ational Safety Council 20 N orth Wacker Drive, Chicago HONORARY MEMBERS A ssociation ok I ron and S teel E lectric R obert W. Campbell OFFICERS (1930-1931) E ngineers jV C. W, Bergquist, President. i . J. I, B anash, Vice-President for Finance. ' C. L. Close, Vice-President for Industrial Safety. E dward D ana, Vice-President for Public Safety. ^ G. P, H ellmuth, Vice-President for Business Administration. J. /?.. L ong, Vice-President for Territorial Councils. George C. A. O pp, Vice-President for Membership. . G. E. S anford, Vice-President for Engineering. A. W. W hitney, Vice-President for Education. Dr. C.-E. A. W inslow, Vice-President for Health. H arvey E lleud, Treasurer. W. H. Cameron, Managing Director. EXECUTIVE COMMITTEE (1930-1931) H. 0 , A llison, Western Pennsylvania Safety Council. C. B. A uel, Past President. j. Ban a sh , Consulting Engineer. C. R. Beardsley, Brooklyn Safety Council. E. W. Beck, United States Rubber Company. L. G. B entley, Richmond Safety Council. C. W. Bergquist, Western Electric Co. W. H. Cameron, National Safety Council. R. W. Campbell, Past President. C. L. Close, United States Steel Corporation. W ill Cooper, Food Section. J. A. Culuney, Bethlehem Steel Corporation. E d vard D ana, Boston Elevated Railway, Lewis A. Df.Blois, Past President. M /rcus A. Dow, Past President. H arvey E llerd, Armour & Company. H oward B. Fonda, Accident Prevention Equipment Mfrs. Fi. P. F owler, Tower Hill School. J oseph X. Galvin, Chicago Safety Council. D. T. H arrington, United States Bureau of Mines. G, P. H ellm uth, Chicago, North Shore & Milwaukee R, R. H. G. H ensel, Metals Section. C, E. H ill, New York Central Lines. .J. Brook J ackson, General Motors Corporation. W alter G. K ing. Past P resident. Section. Co. 4 Nineteenth Annual Safety Congress Frank J. Lana han, Fort Pitt Malleable Iron Company. J. E. Long, The Delaware & Hudson Railroad Corporation. Burton W. M arsh, Traffic Engineer. A rthur T. Morey, Past President. H omer E. N iesz, Past President. G eorge C A. O pp. The Detroit Edison Company. Lew R. P almer, Past President. C. E. Pextibone, Past President. C. E. Redfern, Providence Safety Council. H enry A. Renincer, Past President. G. E. Sanford, General Electric Company. C. B. Scott, Past President. Glenn H. S haw , Electric Railway Section. J ohn S. S haw , Chemical Section. E dward H. S ykes, Mine Safety Appliances Company. R. F. T halner, Flint Safety Council. C. P. Tolman, Past President. A. J. V an Brunt, Newark Safety Council. J. E. W alters, Power Press Section. George H. W arfel, Steam Railroad Section. A. W. W hitney, National Bureau of Casualty .& Surety Underwriter D r. C.-E. A. W inslow, Yale Medical School. A rthur H. Y oung, Past President DIRECTORS (1930-1931) M artin A ckerman, Dayton Safety Council. H. O. Allison, Western Pennsylvania Safety Council. W illiam F. Ardern, Safety Division, Milwaukee Ass'n of Commerce. J. I. Bana sh, Consulting Engineer. H o w a r d F. Baxter, Laundry and Dry Cleaners Section. C. R. Beardsley, Brooklyn Safety Council. E. S. Beaumont, Public Utilities Section. E. W. Beck, United States Rubber Company. L. G. Bentley, Richmond Safety Council. A. M. Bequette, Chattanooga Safety Council. G. W. Bergquist, Western Electric Company. D av;d S. Beyf.r, Liberty Mutual Insurance Company. E. F. Blank, Jones & Laughlin Steel Corporation. W. R. Boyd, Jr., American Petroleum Institute. D. L. Boyle, Central Pennsylvania Safety Council. W illiam Brennan, Paper & Pulp Section. R obert M. Bruce, Rochester Safety Council. W. H. Cameron, National Safety Council. R. I. Catlin, Aetna Life Insurance';Co. T. P. C hapm an, St. Louis Safety Council. H arry J. Clark, Safety Division, Syracuse Chamber of Commerce. C. L. Close, United States Steel Corporation. H ubert L. Clover, Packers & Tanners Section. W ill Cooper, Food Section. J. E. Culliney, Bethlehem Steel Corporation. E dward D ana, Boston Elevated Railway. F. A. D avidson, Chesebro Whitman Company. Lewis A. DeBlois, Consulting Engineer, j J ay E. D ecker, Mason City Safety Council. National S a fety Council R. K. D onovan, Petroleum Section. J ames B. Douglas, The Philadelphia Gas Works Company. Dr. Louis I. D ublin, Metropolitan Life Insurance Company. Frederic W. E aston, Blackstone Valley Safety Council. H arvey E llerd, Armour & Company. H. B. F lowers, New Orleans Public Service, Inc. H oward B. F onda, Accident Prevention Equipment Manufacturers' R. B. F ortuin, Cement Section. R ichard R. F oster, New Orleans Safety Council. B. P. F owler, Delaware Safety Council. H. L. F rachek, Automotive Section. T ho. W. F riedrich, San Antonio Safety Council. A. L. F rost, New Haven Safety Council. J oseph X. Galvin, Chicago Safety Council. S am Ganz, Kansas City Safety Council. E rnest P. Goodrich, Consulting Engineer. W. H. Greenwalt, Woodworking & Lumber Mfg. Section. Dr. T. Y. Greet, Etowah County Safety Council. I saiah H ale, The Atchison, Topeka & Santa Fc Railway Co. D. T. H arrington, United States Bureau of Mines. G. T. H ellmuth, Chicago, North Shore & Milwaukee R. R. Co. H. G. H ensel, Metals Section. Chas. E. H ill, New York Central Lines. T. A. H orrocks, Delivery, Taxicab & Bus Section. R ush H osler, Mining Section. W alter R. H ough, Baltimore Safety Council. E. E. H unker, Safety Bureau, Duluth Chamber of Commerce. J ohn S. H unter, Marine Section. H arry D. I mmel, Pennsylvania Department of Labor & Industry. J. Brook J ackson, General Motors Corporation. J ohn P rice J ackson, New York Edison Company. J. H. J en k in s, Dallas Safety Council. Dana E. J okes, Manufacturers Association of Erie. J ohn D. K arel, Grand Rapids Safety Council. Ira V. Keener, Pennsylvania. Salt Manufacturing Company. V. H. K upferer, Employees' Publication Section. Frank J. L a na han, Fort Pitt Malleable Iron Company. E, R, L awler, Rubber Section. E. L. LEPKOt, Chillicothe Safety Council. R. M. L ittle, New York Department of Education. W m. Loeb, Safety Div., Memphis Chamber of Commerce. J. E. Long, The Delaware & Hudson Railroad Corporation. Burton W. Marsh, Traffic Engineer. H. T. M artin, Fisk Rubber Company. P axton M endelssohn, Detroit. W m . E. Metzger, Detroit Athletic Club. P h ilip M. Morgan, Worcester Safety Council. R. B. Morley, Industrial Accident Prevention Associations. Frank A. Morrison, Detroit Industrial Safety Council. Dr. T. F. M urphy, Statistics Section. C. E. McBride, Fort Wayne Safety Council. M iller M cClintock, Harvard University. J. P. McG rath, Atlanta Safety Council. T. H. McKenney, Illinois Steel Company. Section. 6 Nineteenth Annual Safety Congress i-'RKn NiCHoLi,, Madison County Safety Council, H omer E. Niesz, Commonwealth Edison Company. J ohn- A. O artel, Carnegie Steel Company. E. J. O 'B rien, Louisville Safety Council. George C. A. O pp, The Detroit Edison Company. L. R. P almer, Equitable Life Assurance Society. C. E. P ettibone, American Mutual Liability Insurance Company. E. E. P lace, Textile Section. R amsey P robasco, Eastbay Safety Council. !'. H. Ransom, Oregon & Columbia Basin Division, X. S. C. C. E. R edfern, Providence Safety Council. H enry A. R enincer, Lehigh Portland Cement Company. J. W. R iddle, Employees' Benefit Association Section. Dm A. D. R isteen, The Travelers Insurance Company. J. K. R obinson, Lehigh Valley Safety Council. G. E. Sanford, Genera! Electric Company. C harles L. Sawyer, Toledo Safety Council. Otto S chenk, Wheeling Safety Council. Gh a s. B. Scott, Bureau of Safety. Glenn H. S haw , Electric Railw ay Section. J ohn S. S haw , Chemical Section. J ohn H. S herburne, Massachusetts Safety Council. Dr. L. A. S houdy, Bethlehem Steel Corporation. J ohn D. S huart, Springfield Safety Council. Lee E. Skeel, Cleveland Safety Council. H. J. S poerer, Evanston Safety Council. W alter J. Spriggs, Safety Div., The St. Paul Association. E. S. Spring, Lehigh Valley Transit Company. J. K. Stafford, Decatur Safety Council. George R. Stephens, The Safety Bureau, Buffalo Chamber of Commerce. E thelbert Stewart, U. S. Bureau of Labor Statistics. Lucius S. Storks, United Railways & Electric Company. A lfred H. S wayne, Genera! Motors Corporation. Edward H. Sykes, Mine Safety Appliances Company. T. R. T ennant, Hammond Safety Council. R. F. T halner, ASSE-Engineering Section aim Flint Safety Council. Arthur M. T ode, The Texas Company. A ustin H. U pdvke, Hudson County Safety Council. A. J. Van Brunt, Newark Safety Council. W illiam F. Veech, Rahway Safety Council. P rof. A ugust Vollmer, Street & Highway Traffic Section. V incent W akefield, Refrigeration Section. J. E. W alters, Power Press Section. Georce H. W arfel, Steam Railroad Section. H arry M. W ebber, Illinois Bell Telephone Company. S. E. W hiting, Liberty Mutual Insurance Company. A. W. W hitney, National Bureau of Casualty & Surety Underwriters. George W idua, Construction Section. W. H, Winans, Union Carbide & Carbon Corporation. D r. C.-E. A. W inslow, Yale Medical School. F. B. W inslow, Birmingham Safety Council. J, M. Woltz, Youngstown Sheet & .Tube Company. A. L. W orthen, Quarry Section. H arry E. Yockey, Indianapolis Safety Council. Clayton P. Yoder. F.rie Safety Council. n outer >e con- systems i, a s to should assible, depend :n. In as and j: open ce the ned a ployce ;d and design point ve no g the y for sc vr f< J , --- ..................................................... f f lf f l Chemical Sectum 477 Incustrial Dust; Its Estimation and Mitigation. By J. J. BLOOMFIELD Assistant Sanitary Engineer, United States Public Health Service, New Haven, Conn. The subject of the health of workers in dusty trades has received considerable attention from students of industrial hygiene, and although much work has been done in the study of the dust hazard we find that many phases of th;' problem are still being investigated with great interest. The importance of the dust problem cannot be overestimated, since it is well known that the workmen employed in the dusty trades comprise the largest group exposed to any one industrial hazard. . F u r thermore it has also been well established that exposure to certain kinds of dust has increased the mortality rate from respiratory diseases. Since it has been recognized that there is a marked difference in the action of certain dusts on the human system, attempts have been made, to classify dusts in accordance with the harmful effects exercised by them. The most recent classifica tion is that suggested by Pancoast and Pendergrass, who state that, (1), while all dusts if inhaled in excessive quantities may be harmful, only a few. may be classed as dangerous. The dangerous dusts were divided by them into (a) poisonous dusts such as iead, etc.; (b) those causing irritation in the respiratory tract, resulting in certain diseases such as asthma and bronchitis; and (c) those which tend to produce pulmonary fibrosis and thereby may predispose to tuberculosis and pneumonia. As will be discussed more fully later, the Public Health Service, in its investigations of the dust problem, has attempted a classification based upon the chemical and mineralogical composition of dusts, which allows one to associate more accurately the pathological results with the exact nature of the dust under consideration. Effects of Industrial Dusts on Health Prior to discussing the present day methods employed in the estimation and sup pression of industrial dusts, it seems well to present briefly the most recent evidence concerning the effects of the inhalation of industrial dusts upon the health of workers. This evidence is the result of six intensive investigations conducted, by the United States Public Health Service, each dealing with a different type of dust. The first two of these studies have already been completely analyzed and reported in two bulletins issued by the Public Health Service (2) (3). Much of the material which follows has been drawn from these two publications. A list of these dusts follows: 1. Calcium Dust (Portland Cement Plant). 2. Silica Dust (Granite Industry). 3. Metallic and Other Dusts (Silverware polishing). 4. Carbon Dusts (Anthracite and bituminous coal mining). 5. Vegetable Dust (Cotton cloth manufacturing). fi. Municipal Dust (Street sweeping). In the past our knowledge of the effect of industrial hazards on the health of workers has been gained cither from the study of occupational mortality statistics or from the physical examination of sample groups of employees in an industry. In the investigations conducted by the Public Health Service an attempt has been made to utilize both of the above procedures and in addition large groups of workers were observed for a considerable period of time, in order to learn something of the character and severity of the sickness they experienced and to correlate such illness with the occupational environment. In order to permit as detailed a comparison as possible between the different dust studies, the same methods of conducting these investigations were utilized. Briefly 478 Nineteenth Annual Safety Congress t h e s e m e t h o d s of study may be divided into six tarts, ns follows; (1), examination to determine the general physical condition of the workers under observation; (2) special physical examination to determine the prevalence of specific diseases of the respiratory system and the lung pathology resulting from exposure to the particular dust hazard; (3) record of the nature and severity of the disabling illnesses; (4) analysis and detailed study of the occupational environment; (5) occupational mor tality statistics relating to the specific dust; and lastly (6) autopsies. In brief, Jhc chief value of each of these studies lies in the fact that it represents careful and de tailed observations on a fairly large group of persons whose working environment was accurately determined, especially with reference to the nature and quantity'of the dust exposure. Qw*'*--ko Granite workers Ha-rd Jlock Gold-mining Cement industry r.'aJ iron emd Steel industry enervl sick b en e fit data A lt Retjura tiry Respiratory ite/t>t ni< !':</urr 6 fifen Respiratory As previously mentioned two of these studies, cement and granite, have already l>cen reported upon in full, and although the complete data for the other four studies are as yet not available, sufficient analysis of the morbidity records of all the studies is at hand and is presented in_ Table 1 which follows. This table presents a comparison of sickness for two working days or longer from respiratory conditions in six dusty trades, the annual rates being based on 100 years of observation. An examination of this table shows that in the anthracite industry and in the cement plant there is a high rate of illness from grip and certain other minor respiratory affections. In the bituminous coal industry, bronchial diseases and pneumonia are excessive; in the cotton industry grip and diseases of the nasal fossae are predominant; whereas in the granite industry, tuberculosis and pleurisy arc excessive. The dusty occupations in silver polishing show no excess from any cause. In order to show the significance of some of these rates another comparison is presented in the accompanying illustration (Figure 6). This figure shows a com- Chemical Section 4 79 T A B fcS I Sickness1 from Respiratory Conditions in Siuc Dusty Trades DiaKnoBti A nnual !Ratc ixir 100 Years of Observation. <u S .e . U 8 U c ** J u,!H K E <5 2 V p: U o Number of c ucs I c 8 u 1 V G S U ea * jp 4>*Gm rc*S Pot AiUima Bronchitis Pneumonia Tuberculosis Suflpcctcd Tuberculosis Diseases of the nasal fossae Influenza arid grip Pharyngitis & tonsiUtis Pleurisy Other respiratory diseases Total respiratory diseases. Years of Observation 0.2 0.4 0.9 0.4 0.3 5.0 9.0 14.4 2.0 2.1 0.5 0.4 0.2 1.0 0.2 0.1 3.7 0.1 0.7 ) 0.1 0.8 __ ) 4.9 8.7 8.4 26.0 7.4 4.3 20.6 18.1 1,2 18.6 6.6 0.7 7.5 5.7 4.7 2.9 0.7 1.1 0.3 0.9 0.2 0.2 0.4 0.1 1.7 1.4 0.4 3 4 4 38 100 73 2 50 1 6 1 1 >6 66 94 58 157 202 9 57 64 IS 2 10 1 19 73 71 16 15 52 1 *. ) . . )` 208 53 6 149 47 23 23 5 12 3 73 16.5 42.7 45.1 22.9 51.2 17.9 223 325 503 113 410 126 1346 763 1116 494 801 .715 * Lasting two consecutive working days or longer. 5 Males only, to agree with the other studies. parison of the frequency of absence due to sickness among- granite workers with that in certain other industrial groups. It is to be seen that the rate for all causes (eight days and longer in the dusty trades is much higher than in the general ex perience represented by the sick benefit data, but it is not unique. (This general sick )>cnefit data is based on information reported by many industrial concerns to the Public Health Service). For respiratory conditions, however, the rate for the granite industry is higher than any of the other groups compared. When allowance is made for the incidence of sickness due to tuberculosis, the gold mining experience (where dust of a similar nature is involved) and the cement experience are somewhat higher, all three dusty trades being marked above tjic usual experience. For non-respiratory sickness, except ill-defined, the granite industry shows nothing significant. Later it will be shown that some of these variations in the severity and nature of the respira tory diseases may be attributed to the nature and quantity of dust exposure. Suffice it to say for the present, these results established a real difference in the nature of respiratory diseases occurring among workers exposed to different kinds of dust. Estimation of Dust From the evidence just presented concerning the injurious effects produced by the inhalation of certain dusts it is quite evident that a knowledge of the dust content of the atmosphere is a matter of considerable importance. Such evidence is needed not only for the sake of determining the extent of the hazard involved in various industrial processes but is also useful in measuring the efficiency of certain protective devices which may be used for the suppression of the dust hazard. The numerous investigations of the dust problem in industry have conclusively shown that in studies of this sort a knowledge of the nature, particle-size and con centration of the dust under consideration is of the utmost importance. Concerning the nature of dusts there is ample evidence at hand that those dusts containing free silica in the form of quartz arc dangerous, since they produce silicosis which usually terminates in tul>erculo.sis. For this reason in all our dust studies chemical and petrographic analyses were conducted on the various dusts encountered. Table 2 480 Nineteenth Annual Safety Congress presents the results obtained on analyzing dusts in five industries. Examination ot this table shows the wide variation in the amount of quartz found and also shows that this amount of quartz bears no relationship to the total amount of silica in thedust as disclosed by chemical analysis. TABLE 2 Chemical and Petrographic Analysis of the Dust in each Study Granite; Average Silver polishing: Hollow-handle-making room Wet pumice (2 averaged) Brass foundry Cement: Pack house Crusher house, raw mill, stone Soft Coal: Coal dust Rock dust Hard Coal : Coal Dust Rock dust house Total Silica Per cent 70.0 22.2 70.5 73.3 21.2 16.8 high (?) high Quartz ( free silica) Per cent 35.2 1.7 less than 0.5 19.0 less than 1.0 6.5 12 54,0 1.5 31.0 It is evident that from the standpoint of the amount of quartz our analyses indicate that the rock drilling occupations in the coal mining industry and certain occupations in the granite cutting industry may be considered as dangerous. In fact, reference to Table 1, previously discussed, shows that in the granite cutting industry there was a high rate of illness from tuberculosis. Since only a few rock drillers were studied we were not able to establish a definite dust hazard among them. Since the South African (4) and other investigators have conclusively demon strated that only particles under 10 microns in longest diameter are found in the lungs on autopsy, particular attention-has been given to express the magnitude of exposure in terms of size of pr.rticles. Concerning the lower size limit of the potentially dangerous particles Mavrogoruato (S) and other investigators believe that the smaller ultra-microscopical particles are not dangerous and that the minimum size of particles which are likely to be retained by the lungs is about O.S microns. For this reason we have used methods which revealed the number of dust particles of a diameter between and 10 microns. With reference to the quantity of dust exposure it has been agreed by students of this problem that the panicle count is the best index of the extent of the at mospheric pollution. For this reason our dust determinations are always expressed in numbers of particles per unit quantity of air, usually in millions per cubic foot of air. Many methods have been devised and employed for the sampling and estimatipn of atmospheric dust. These methods have been discussed in an excellent review of this subject by Dr. Greenburg (6) and for this reason need not be considered at this time. Prior to undertaking the series of exhaustive dust studies the Public Health Service, in cooperation with other interested agencies in this country, carried out comparative tests at the U. S. Bureau of Mines laboratories in Pittsburgh, Penn sylvania, of various instruments for determining atmospheric dusts (7).. As a result of these studies the Impinger apparatus was developed and found to contain alt the requirements of the ideal instrument for dust studies of this sort, namely, simplicity Chemical Section 481 of operation and accuracy in both high and low dust concentrations. This instrument was utilized in all our dust studies, being supplemented at times by the Konimeter of the South Africans (S) and the Jet Dust Counter of Owens (8).. At the present time these three instruments are the ones finding greatest use in dust studies of a public health nature. It is of interest to note at this point that each of these instru ments depends on the principle of impingement at a high velocity for its dust sampling efficiency. The Kotze kenimeter is a small instrument capable of sampling' the dust in 9 or 10 cubic centimeters of air. Essentially it consists of a circular brass chamber into which fits a glass plate cemented into a toothed frame of brass. Firmly attached to the brass chamber is a cylinder in which moves a spring-actuated piston, so ar ranged that on release of the piston spring, air is drawn out of the chamber. The only means of ingress of air to the chamber is through the impinging orifice, and the air enters here, striking the previously vaselined glass plate and leaving its dust thereon. After taking one spot the glass plate is revolved by means of a pinion gear and the instrument is ready for the next sample. The technique involved in analyzing konimeter samples has been described in detail by the inventor of this instrument (9) and needs no further discussion at this time. This instrument is small, portable and very convenient for use. With it twenty-nine samples may be taken on one slide, and once taken, may be very rapidly analyzed. It is highly efficient for sampling dust in ordinary work places where the atmosphere is not too highly polluted. The objections to its use are that it takes an instantaneous sample of only 9 or 10 cubic centimeters of air, that a weight analysis is no. available and" that it yields low results when used in very dusty atmospheres. The konimeter may be used for studies of atmospheres of low or medium dust content where the desider atum is to quickly establish the conditions of the atmosphere. For plant engineers it is to he highly recommended. The Owens Jet Dust Counter depends for its action on the following principle: When air which contains dust passes through a narrow orifice towards a glass sur face which faces the jet a short distance away, the dust will adhere to the glass and can be examined microscopically, In the instrument this result is brought about by causing a very fine ribbon-shaped jet of air to strike a microscope cover glass placed about Imrn. from a slot-shaped opening forming the jet. The air before entering the slot passes through a dampening chamber, and the velocity in the jet is such that a fall of pressure results, thus bringing about a condensation of moisture. The air is then deflected and the dust, being unable to turn the corner, strikes the cover glass, the velocity of the air falls oil, the pressure and temperature rise, causing the water to be evaporated and the dust is left behind. The dust sample is examined microscopically in a manner very similar to the technique employed for the konimeter samples. This instrument is also not adapted for studying dusts of a high concentration, such as arc encountered in many of our industries today. It has been found to be very useful in studying the pollution of the atmospheres of our large cities and is especially valuable in obtaining samples for the determination of particle size of dusts. The Impinger apparatus, which has already been described in numerous publica tions of the Public Health Service (2), (6), (7), also operates on the principle of impingement, but in this instrument air is impinged at a 'high velocity on a wetted surface and then bubbled through distilled water of a known dust content. After sampling, the dust-laden water is examined at the laboratory in a manner described in the papers just mentioned. Wc have found this instrument to l>e highly efficient, capable of sampling large volumes of air (one cubic foot per minute), and one having low control errors. It is recommended for use in all intensive dust studies, no matter how high or low the dust concentrations may be. Wc have also found it useful in other investigations, such as the lead hazard in storage battery plants and in study ing the amount of chromic acid present in chromipm plating establishments, 482 Nineteenth Annual Safety Congress In Table 3 which follows, there is presented a summary of the average dust con tent of the air in certain dusty trades. This table shows that with the exception of soft and hard coal the highest dust exposure was in the granite cutting industry. Owing to the higher percentage of free silica as quartz, however, granite cutting is certainly first cm the list so far as the magnitude of exposure and dangcrousncss to health arc concerned. TABLE 3 Average Dust Counts in Certain Dusty Trades Industry Cement Granite Cutting: Cutters Hand pneumatic too! operatives' Others3 Attendant labor Anthracite Coal Mining: Miners and miners' helpers Attendant labor Bituminous Coal Mining: Coal cutters and coal loaders Attendant labor Silverware Manufacturing : Rooms where dust is created Dusty processes Non-dusty processes Other rooms Municipal Dust (Street Clcancr-O: Congested district Residential district Cotton Industry : Carding room Weaving and spinning room Dust Count Million particles per cu. ft. of air. 26.0 59.2 35.9 17.0 231.5 31.1 112.3 3. 5.2 1.7 0.8 8.6 4.5 il> I n c l u d i n g 58 p e r c e n t of all wo rker* . ( 2) Carvers and le tte rrrs included with operatives and sand blast operatives). other cutters ("surface machine operatives, lathe As a result of all these dust studies in this country, as well as studies of a some what similar nature in South Africa ami Australia, it has been possible to suggest tentative standards for the upper limit of dustiness to be regarded as allowable in certain industries. The South African investigators (9). using the Kotzc konimeter for dust sampling and dealing with a dust found to contain free silica as quartz in excess of 85 per cent, set a tentative standard of 300 particles per cubic, centimeter of air (i. e,, 8.5 million particles per cubic foot) as the upper limit of dustiness to lie regarded as allowable. On the other hand, the Australian investigators dealing with a sandstone dust in the Sydney mines, found that the quartz content of this dust was from 86 to 95 per cent, and advocated a standard of dustiness not to exceed 200 particles per cubic centimeter as determined by the Owens jet dust sampler. These investigators also found that the Owens dust counts correlated very well with the weight of the dust determined hy the Impingor apparatus, the instrument used in all our studies. Our investigation in certain plants of the granite cutting industry discussed alxivc Chemical Section 483 has shown the dust to contain from 31 to 38 per cent of free silica in the form of quartz. At the outset, then, we might expect to arrive at a less severe dust standard than advocated by the South Africans and Australians. Of particular importance in our study was the fact that it was possible to divide the workers into four groups, depending upon the average, exposure in terms of the amount of dust hi the air. In Group A, -which included hand-pneumatic tool operators and in which the ex posure averaged about SO million particles per cubic foot of air, it was found that 70-- tea cS - "AC-K so O **r t, 2.0 <0 Ort Gr+nit* worker: l 10 A iHfetbs ' Fffr c p DoTht I* . umths of stm4 % working up Hunt I Vermont Ay0-59 practically 100 per cent developed an established silicosis within 10 years from the time of beginning employment. Also, in this group the highest rate was found for cases diagnosed on physical examination as having active tuberculosis. (See Figure 2). Furthermore, a definite relation was established between length of sendee in the industry and the prevalence of tuberculosis. All of the statistical data obtained indicated definitely that hand-pneumatic tool operators in these plants suffered from an occupational hazard. In Group R were included those workers other titan hand-pneumatic tool opera tors who were also exposed to more than the average plant: dustiness. Taking the group as a whole, the average dust concentration was nearly 45 million particles per cubic foot of air. This group showed the same reflection of a dust hazard as Group A. ~~....' v ^ ... f r1 V\U/ 484 Nineteenth Annual Safety Congress In G rou p C , con sistin g o tW sv occupations*! groups exp osed to the a v e ra g e p la n t dustiness (about 20 million particles per cubic foot of air), silicosis developed much more slowly than in the groups just discussed and there appeared to be very little excess in the rate for tuberculosis, with no tendency for an increase according to length of service. Analysis of occupational mortality over a period of 25 years, however, indicated that some of the occupations in this group may have been exposed to a real dust hazard. Group D was made up of those occupations in which the dustiness was less than that of the average plant atmosphere. The average exposure for the group was less than 10 million particles per cubic foot of air. Although a certain amount of silicosis was found even in this group, there was no indication of serious results, even when the workers had been employed for many years. From the results of this study it was found practicable to suggest a tentative standard for the upper limit of allowable dustiness between 10 and 20 million particles per cubic foot of air for workers exposed to dust resulting from gTanitc cutting. The same limit would presumably be applicable in the ease of other dusts with the same physical characteristics, particularly with a quartz content of about 35 per cent. Dust Supervision In the foregoing' pages of this paper sufficient evidence has been presented to indi cate the close relation existing ixttween the morbidity and mortality rates from various respiratory diseases and the exposure to certain dusts in industry. In the study of the dust hazard in the granite cutting industry we have been able to definitely prove that there is a direct relation between the magnitude of the dust exposure and sick ness and death resulting from tuberculosis. It is quite evident, as a result of all our studies, that the remedy of the dust evil lies in the effective removal or suppression of the dust to a concentration considered safe. There are several methods at present in use in combatting the dust hazard, the application of any one particular method depending largely on the industrial process creating dust. The protection of workers against certain dusts may be at times accomplished bv the mechanical enclosure of the dust creating processes. An excetlcnt'rillustration of this type of protection is afforded by the modern sandblast barrel used in the cleaning of small objects. Sometimes it is possible to protect workers by the substitution of wet for dry processes. In one instance in our granite study an operator using a diamond point pneumatic tool worked the stone w et; the resulting dust amounted to 21.8 million particles per cubic foot. The same operator was then requested to work the stone dry; as a result, the amount of dust reached the high figure of 45.2 million particles per cubic foot. In the weaving of asbestos cloth it has been possible to re duce the amount of dust in the air by wet weaving to one-fourth of the amount present when the process is conducted by dry methods. However, wet methods are not always to be relied upon for the complete suppression of dust. For example, in a study of the dust hazard in the wet and dry grinding shops of an ax factory, Winslow and Grcenburg (11) have shown that protection afforded by wet grinding, as compared with dry grinding using an exhaust system, is, in most instances, illu sory. The same result.was found in our granite study in determining the exposure of tool grinders in that industry. -In certain extreme cases such as in the sandblasting of large castings in sandblast rooms, the only practical safeguard to the worker is to provide him with a helmet of the positive air pressure type. In most dusty processes, however, the most effec tive means of dust elimination, are by the use of properly designed local exhaust ven tilation systems. In certain rock drilling operations in mines a dust trap is now in use which effectively removes dust created by pneumatic rock drills. Such a trap has been designed by Captain Hay of Ixmdon (12), and the practical tests conducted with his device have demonstrated its ability to remove fine dust created by pneu- Chemical Section 485 niatic drills. Quite recently workers at the Harvard School of Public Health (13) have reported the results of their laboratory study of the design of dust control systems for use with pneumatic granite cutting tools. Tlrcse workers, using our tentative standard of allowable dustiness in the granite cutting industry, namely, 10 million particles of dust per cubic foot of air. have designed hoods and determined air flows to be used in keeping the dust created by pneumatic tools below this pro posed standard. A similar investigation, hut somewhat briefer in scope, was made by the writer in studying the efficiency of dust removal devices now actually in use in modern granite cutting plants. The results of this study were repor'ed in the Public Health Reports (14) and Figure 5, summarizes the results of this study. This figure shows the relation between the dust concentration in the air at the worker's breathing level when using various pneumatic tools and the air velocity at the local exhaust ducts. From this figure it is apparent that a velocity of 1,500 linear feet per minute is neceyary to keep the dust concentration at the worker's breathing level below 10 million particles per cubic foot of air, the amount found in our study as not associated with any disabling illness. The Massachusetts State Board of Health some years ago laid down the principle that in fixing standards of industrial hygiene it was reasonable to require that condi tions should be maintained in arty industry' approximately equal to those already found in the best plants of that industry in actual operation. With such a rule in mind, Winslow, Greenburg and Angermyer (15), in studying the efficiency of exliaust systems in polishing shops, also found that an air flow of 1,500 linear feet per minute was the minimum exhaust velocity to he maintained at exhaust ducts used with polish ing and grinding processes. In the absence of clinical and morbidity data, this is a pretty good rule to follow. 486 Nineteenth Annual Safety Congress At the present time many state* haft industrial codes which specify the amount of suction and type of exhaust hoods to be maintained in connection with dust re moval systems. All of these codes arc general in nature and arc not based on definite knowledge of the harmfulncss of the particular dust under consideration. It is necessary to maintain certain suction heads and air velocities in dust removal sys tems, but what one really wants to ascertain is whether the dust has actually been removed. For this reason the only standard that can be satisfactory and one which should be incorporated in.our State Industrial Codes, is the one based on the number of particles of dust which hat been found by careful investigation to be an amount which can be inhaled with impunity. The Public Health Service, in undertaking its series of dust studies, has had such an object in mind, and as a result of these investi gations we arc in a position to present data in connection with threshold doses of dusts, as illustrated by the results just given for the granite cutting industry. It is only through such studies, which take into consideration all the factors of occupa tional environment and their relationship to the physical condition and sickness of workers, that we may hope to make progress in coping with the industrial dust problem. Reference (1 ) . Pancoast, H. K., and Pendergrass, E. P .: A revievr of our present knowledge o f Pacumonocoixiosc* based upon Roentgenologic studies with note on the pathology of th e con dition. Amcr. Journal of Roentgenology and Radium T herapy, 14, No. 5, 381-423. ( 2 ) . U . S. P ublic H e a lth S ervice B u lletin N o. 176. ( 3 ) . U . S. P ublic H ealth S ervice B ulletin N o. 187. (4 ) . Final Report of the M incra' P hthisii Prevention Committee, U nion of South Africa, Johannesburg, Jan. 10, 1919, p. 17, P retoria. (5 ) . M avrogordato, A. The V alue of the Konim eter. Publication* of South A frican Medical Rcacarch. No. 17. (6 ) . Greenburg, Leonard. Studies on the Industrial D ust Problem. Public Health Reports, R eprint No. 1004. ( 7 ) , U . S. P ublic H e a lth R u l'e tm N o. 144. ( 8 ) . Owens, J. S , J e t D ust C o unting A p p a ra tu s J o u rn a l In d u stria l H ygiene, p. S22, ApriL, 1923. (9 ) . General Report of the M iners' Phthisis Prevention Committee, U nion of South Africa, Jo h a n n esb u rg , M arch 15. 1916, A ppendix N o. 8, P re to ria . (1 0 ) . E xtract from the R eport of the D irector-G eneral of Public H ealth, New Strath Wale*, 1927, Section I-E , S erial N o. 12, p. 98. (1 1 ) . W inslow , C--E. A-, and G reenburg, L eonard: A S tudy of the D ust H asard in th e W et and Dry Grinding Shops of an Ax Factory. Public Health Reports, October 8, 1920. (12) . H ay, P. S .: Modified Design of H ac D ust T rap. Journal of Industrial Hygiene, Janu ary, 1930. (13) . H atch, T ., D rinker, P ., and Choate, S. P .: Control of the Silicosis H axard in th e H ard Rock In d u stries, P a rt I. Jo u r. In d u strial H ygiene, M arch, 1930. (1 4 ) . Bloomfield, J. J .: A S tudy of the Efficiency' o f Ehist Removal System s in G ranite C utting P lants. Public H ealth Reports, O cc 18, 1929. (1 5 ) . W inslow, C.-E. A., G reenburg, L ., and A ngerm ycr, H. C .: S tandards for M easuring the Efficiency of E xhaust System s in Polishing Shop*. Public H ealth R eports, M arch 7 ,3 9 1 9 . C hairman W hittemore: I think this is a very interesting subject and wc would like to hear any comments you may have at this time. J ohn S. S iiaw (Hercules Powder Co., Wilmington, D el.): I would like to stak, in arriving at the tolerance of ten million particles of dust per cubic foot how do you determine that this is the safe limit to which the worker may endure dust? .Also how is dust eliminated from the bronchi and lung tissue. Is it thrown off through the expectorant as a result of the raising of the mucus from the bronchi? ' Mr. Bloomfield : These people in group "D" exposed to ten million particles, per cubic foot of air were not disabled, even after working thirty or forty years in the industry. I wonder if we couldn't hear from Dr. Greenburg on this particular matter. D r. L eonard Greenburg (U. S. Public Health Service) : I think Mr. Bloomfield's contribution is an interesting one and it causes me to go hack ten or twelve years ago. Really the first study we did before I came with the Service was in cooperation with the Bureau of Mines in regard to work being carried on in hard rock mine*. W c got some interesting results, and we compared them with the South African findings. Chemical Section 48/ Even today it constitutes the best literature on the subject, outside of what we have received from the Public Health Service, and the accomplishments of a half doxen who have given the matter study have been a real contribution to the medical aspect and public health aspect of this whole problem. To you, as chemists, perhaps some of these things may be uninteresting but nevertheless in the chemical industry for grinding sand for the making of scouring soap and carborundum and allied fields of that type, the problem is an exceedingly important one. One very interesting thing to me about this whole afternoon's discussion is the new aspect of our handling these problems. Some years ago we were happy if we could get a few fundamental facts to talk about, and today you see a new status quo, and the studies are being put on a careful quantitative basis. I think perhaps that leads ns to believe that we will have a very warm outlook for the future. Wc know more about the handling of dust problems, and we know more about the handling of ventilating problems, than we ever knew before. If we keep up this quantitative type of work, and instead of generalizing so much, perhaps, keeping up this type of work as described by Mr. Gumacr this afternoon, and also the type of work as described by Mr. Bloomfield, we will be able to handle these subjects in a more satisfactory manner than ever before. ADJOURNMENT