Document BQ8Z1d5wZQV0M1zOavzOZ5Yw

FILE NAME: National Safety Council (NSC) DATE: 1983 May DOC#: NSC214 DOCUMENT DESCRIPTION: NSC - National Safety News - What Does the Worker Breathe? W liat Hoes Ilie W o rk e r B reathe? By J. jf. BLOOMFIELD* > ^ rH * A audy of the dust content of the workroom atmospheres in attempting to evaluate its hafuuuhitss. t various dusty industries I t has been our experience that to determine the exact mineralgica! com - position of a dust one should resort to ' * 7 Til E properties of a given dust which determine its capacity to produce pulmonary pathology are, the na ture of the dust, that is, its chemical and mineralogical composition, its par ticle size, and finally the quantity of the dust dispersed in the atmosphere. One of the outstanding results of the last 20 years of research in the field of dust Inhalation is the demonstration of the fact that, in general, the degree of period of time titan he will when the dust concentration of the atmosphere is relatively low, and since the rale of pro duction of the fibrosis is partially de pendent upon the rate in which the dust is inhaled, this latter item plays an im portant role in predicting the relative danger of different environments. Hence the need for evaluation of the quantity of dust in the industrial atmosphere is obvious, a combined chemical and petrographic analysis, By no other method have we found it possible to determine the amount of quartz present in a given sample. In certain instances, such as a mixture of quartz and pure potash feldspar, it is possible to determine iIn: amount of quartz present merely by chemical analysis. However, most dusts which come into question are mixtures of quartz and < * 5 - J -*** " health hazards associated with the in silicates. The average granite is made v halation of any dust, all other factors remaining constant, is dependent upon the mineralogical composition of the dust. For example, it is now well estab lished that the inhalation of certain types of dust, such as granite dust, will in time produce fibrosis of the lungs, at times associated with tuberculosis. :t In other cases exposure to dust may I result in the production of much less } fibrosis without notable tendency toward l subsequent tuberculosis; this is true of cement dust. And finally, there are * certain types of dust, as typified by f marble dust, which in the quantities and ; lengths of exposure so far observed pro' duce little lung fibrosis. In general it i has been found that those dusts which I' are high in quartz content are the ones ~ which produce a disabling fibrosis of the INattire of Dust Research on industrial dust inhalation has indicated that so far as their fibrosis producing qualities are concerned, dusts may be divided into three groups: 1. Those composed completely of combined silica (silicates) such as pure asbestos. 2. Those containing free silica in the crystal line form known as quartz. (Granite con tains approximately 35 per cent of quartz.) . 3. Dust containing free silica in a noncrystalline form, such as diatomaceous earth. In general, it has been found that the harmfulness of a quartz-containing dust is in direct proportion to its quartz content. For this reason it is of the utmost importance to ascertain the exact mineralogical composition of a dust in up chiefly, of three minerals in about the following percentage proportions: feldspar 60, quartz 30, and mica 15. Chemical analysis shows that this aver age granite contains 70 per cent o silica. Of this 70 per cent, 3;) per cen is pres ent as quartz (free silica), and the other 40 per cent is present as combined silica, in chemical combination with other min erals that make up granite. It is possi ble to determine these proportions only with the aid of a petrographic micro scope. In practice, samples of dust settled out of the atmosphere at the breathing level of the worker serve admirably tot* berth chemical anil mineralogical deter mination, Table 1 presents the quart/, content of dusts obtained in various in dustries which we have studied. i lungs most readily. f- So far as the sir* of the dust particle is concerned, it is apparent: that in order for any given dust to produce injury to l the lungs,"'it must gain access to the parenchyma of the lung, the site where TABLE I Percentage of Quartz Present in Various Industrial Dusts * the harmful effects of the dust take place. It is known that not all of the 1 particles of inhaled dust gain access or are retained by the human lung. In this connection it is of importance to have : regard to the size of the dust particles present in the industrial atmosphere. With reference to the quantity of dust , present in the air of a workroom it is A apparent that when the dust concentra- Kind of Dust Percentage of Quartz Rock drilling dust (bituminous coal m in e ) ......................................................,54.0 Granite cutting d u s t ..........................................................................................3.5.2 Rock drilling dust (anthracite coal m in e ) .......................................................... 31.0 Brass foundry d u s t ........................................................................................... t'i.O Dust from raw mills in cement plant ................................................................. 6.5 Slate mill dust (Vermont red slate) ...................................................................... 10 Silverware polishing d u s t.................................................................................. 1.7 Anthracite coal d u s t ................................................................................................ 1.5 Bituminous coal d u s t .............................................................................................. 1.2 Cement dust .............................................................................................................. 1.0 L lion is high the exposed person will p inhale a greater quantity in a given V Sanitary Engineer, United States Public Health Service, Washington, 0. C. Slate mill dust (Vermont greens la t e ) ..................................................................... trace Talc mill dust ............................................................................................................. none Marble cutting d u s t ........................................................................................ none It ' Ado 34 TABLE It .Average Dust Counts in Certain Dusty Trades Industry and Pecupatloh Dust exposure in millions of particles per cubic foot 'talc Alining &s;.dMining; Jack-hammer .drillers . . . . . . . . . , .i . . . . . . . . . . . . . . . . . . . . ,lii() PaH aas ................... - . " . . . . " , ,:S ; 2. - SO Mui !>:'r51.............. . i .......... ...,............. 45 Cnn'liensjen andeyllndermen r , . 2 r . - a . 14 Slate Finishing M ills:1 2.2 -i ; Hoof m en ............ ............ V-. ...... .1,598 ; Loaders . , . .............. i .......... .... . F, /, j ik'd'. ... .1,276 Di:-c crusher operators . . . . . . . . . 2. . . . . . . . . 312 , Qnatxv Grinding Plant: ` Mill operators ^ .: 173 PaCorers .................. ........................ . 83 Packers .............. Granite Quarrying and Finishing:. ...........................- : S3 1-eviuT drillers ........................ i - .. . 144 Jack-hammer driHers . . . . . . . . . . , . Hand pnetmmtic tool finishers . . . .......... . 112 59. Machine pneumatic tool finishers . . 36 Plug driHers ............................... Attendant labor (indoors) ... . . . . . . . 37 . 17 Anthracite Coat Mining: Miners and helpers . . ; ......... . . .. . . . 232 Attendant: la b o r.................. ............. . 31 tiittimimms Coal Mining: Goal cutters and loaders....... . 112 ' Attendant labor ................ 'Marble Gutters . ....... . . . G, , 4 . 33 Colton Cloth Maihiiuduring 9 Weavers and simmers . ,.:. .. s: Silver ware Manufacturing: . Dnr.tr trades . . . . . . . . . . . . . G . ; ' ' '5 Ncc.-dustv trades............ ., 2 -- .... Average ; per cent of quartzIn dust None None None None None 3 3. 3 3 1 '. 99 9999 99, : 35 35 "35 : 1 35 35 35 35 . 1.5 1.5 1,5 1.2 1.2 1.2 None. None None 1.7 1.7 1.7 it is evident from this table that, rock drilling occupations in the coal mining industry and certain occupations in the granite cutting industry and in brass foundries would be in the hazardous class as judged by . the proportions of qtiutta in the atmospheric dust. , .1.1. has been demonstrated Hurt partides of dust of a size greater than .10 to 1.2 mien ms in longest dimension are very seldom found; hi the lungs.: This absence of larger particles F partly due to dm fact that the numbers of such p an ic! greater than ten tmctouH in sice present, in industrial -air is. as com pared with the lower sizes, comparative ly .small; furthermore, these larger par ticles do not penetrate to the terminal portions of the respiratory tract. Hence we need only concern ourselves with those duel particles that are less than ten nucrom in longest, dimension. In order to ascertain whether or not. an industrial dust is capable of gaining access to (lie lungs, it t$ necessary to know something'of the size of the pav- tidcs in the dust under consideration. In practice the samples for particle size studies may be obtained by the use of the Owens jet dust counter. The ad vantage of this instrument over other devices is that the Owens apparatus pro jects the atmospheric dust in unaltered condition directly bn a m icro sco p e cover-slip. This cover-slip may then be properly mounted and examined by any one of several methods. Quantity of Dust In another method a fnierophotograph of the dust is made at a high magnificanon; the particles revealed on an en larged print or screen m ay'be measured by means of a millimeter scale. No matter which method one uses for par ticle-size measurements the results may be treated in the customary manner. '.Hie particles may be grouped in classes according to size, from which a percent age distribution curve is easily obtained. As pointed out earlier, a knowledge of the quantity of .dust dispersed in the atmosphere is very important, since wHo any given dust the- r a te .of -pmcItfctuMbyii;i of the injury will be dependent uponl! F \ total quantity From the practical hygienic vm point, the particle count is at i the best quantitative index of tin* dem of atmospheric pollution. The decta^-i! j as to the size range of the particles which2;r | should be included in the dust; conn1 i a question requiring .careful considaW irijljj tion. : Obviously the size of the smaikA; '| visible particle Will:defend on the magy:yj nification and type of illumination u .i c in the microscope, the; refractive prop- i:;;2 i erties of the dust and to some exl**' oh the visual'acui >y of the observer. We must bear in mind that our chid interest in this prcblem is in the hum.: trial hygienic aspect. Primarily we am interested in differ mtiating between lL` dust content in flic ordinary normal it mospheres, not yet known to be bnrtdri, and certain industrial dusts whii h a ' known to be associated with lung hum age. This difference'' is .sharply marked 22 so far as the d u s t' particles between ,22; approximately one-half and ten miron: in diameter are concerned; but the vis ference between such uormal and all normal air is masked and lost when we include in our determination the pm tides of ultra-microscopic size whiih ;m present in vast numbers in all an. So far as the it|>per limit of panulr size is concerned it has been demon strated by the South African Simla1' Chat particles greater than ten micro'! in longest dimension are, as a Nile, m negligible importance. The data ton- cerning the lower size limit of potential ly hazardous dust is not so condioNi1. Moir of South Africa, who ex.tmiwil microscopically 120 dust particles oh tained from two specimens of silked' lung, found that only 13 per cent of the particles were less than 0.5 microns ami about 36 per cent of the. particles wee less than one micron in diameter. The majority of the pirticles, 60 per tint, were between one and three microns in size. 'The median size of the Ins' v.-.n, found to be 1.2 microns in diamn.r .Drinker, in comparing the size frequen. cy of tlie particles measured by Mui1 with the particles measured by him d the dust found in the sputum of men employed in ore mills, found a cluse correspondence. These findings hacf also been colrroberated by Mavrogor data. * In connection with the lower limit d particle size of dust of pathological sig nificance the following pertinent <|hm tion arises: Aside from the evidrwe (Please turn to page 52) ' NEWS : Uhi*. Worker Breathe? (Continued from page 34) blow cm the road struck by rm d. the six-wheel type is only one hub 11 Of the rear axle of the four-wheel rlA carrying the same load. J'eerw| direct or indirect oJ. the non-retention of minute particles of dust by the lungs, what evidence is there that ap preciable p m nags of ordinary indus trial dusts ever fragment, into those minute sizes less than 0.5 microns in diameter? ; : 1 : y, ; ?...; .. The best answer to this question would be. data of actual measurement of such dust. Unfortunately we, have but scant published'data on the particle size frequency of dusts in llie air of in dustrial establishments, In 1*129 Fetale! made sortie particle size measurements in connection-' with th dust study of hard rock drilling in New York Uilv. He reported the findings on three sam ples, which showed the dut which :was ' less than 1 micron in size to vary from 1 to 1.5 per certi. Most of th e,dust, in these hard rock drilling operations was between 2 and 5 microns in size. Bad- bam, in studying the dust hazard among sandstone workers its Sydney, Australia, measured some 16,000 particles of drtst in. the air of work places and. found that 67 per cent of these particles were about 1 micron in size. In a particle size study of 25 samples of eleven different kinds of aerial indus trial dusts made by the filar micrometer method at a magnification of 1,000 diameters, the speaker found that prac tically all of the dust was less than 5 microns in size. Only 2 percen t of the paritele?, were less than 0.5 microns, 21 per cent were less than 1 micron, and the majority of the dust, 71 per cent, was found to be between t and 3 microns in. diameter. From all of the evidence therefore, and .in the absence of conclusive proof to the contrary', It is apparent that we need only be concerned with those dust, particles between one-half and 5 microns' in size, and from a practical standpoint the lower limit of particle size to be mira teri may well be taken at about one minori. Many methods have been de vised acri used for the purpose of deter mining the quantity of dust in air, Suffice it to say that for the purpose of dust sampling in either high or low dust cotrcennations, the Greenburg - Smith impinger apparatus now finds universal favor. This .instrument has been Used by the United States Public Health Service in all of lis dust: studies during fee past nine years and is also being need by other workers in this field in this century and abroad. During the past nine years the writer has made numerous investigations of dust, hazard in many industrial estab lishments throughout the country. In 7'able II, a. summary is presented of the average dust content of the air in a few of these dusty industries. This table clearly shows that the highest dust ex posure was in the talc mines, slate finish ing mills, quartz grinding plant, coni mining and granite cutting industries. Owing to the high percentage of quartz present in the dust of the quart2 grind ing and granite cutting plants, as com pared with the dust in the other indus tries listed in Table II, quartz grinding and granite cutting are revealed to be the most hazardous of the occupations we have studied. > The Driver and His Truck (Continued from page 25) ding or slipping is practically a danger of the past, The question naturally arose, "Why. would a six-wheel truck pull easier or coast, farther than a four-wheel truck?" Consideration of the following facts, gives a simple explanation. On a four-wheel truck at least 90 per cent of the payload and body is carried over the rear axle. A paved road seem ingly level will, upon examination, prove to be a series of little waves of varying heights. As you follow a passenger car or truck along one of your best paved city roads notice the rear end of the vehicle bobbing up and down. This means that the load must be lifted ver tically every time it passe? over a little bump in the road. Remember that if it takes but 30 pounds to pull a ton along a road, it takes 2,000 pounds to lift it in a vertical direction. This con stant lifting of the load is accomplished by power developed by the engine. In a properly designed six-wheel vehicle the two axles are pivoted at a central joint. If one of the axles passes over a four-inch bump in the road, the pivot point, and th load are moved upward not more than one-half this dis tance. Due to flexible spring mounting, the lift of the load will probably be considerably less than one-half. In other words, the load rides along practically On a level while the axles bob up and down over slight variations in the road surface. Government statistics show that the shocks will, of course, increase the 1.1 of the chassis and body, at the sa time greatly reducing the fatigue of ft drivers. The drivers tell us -that ti can drive longer distances with Ms fatigue than cm any four-wheel vehkt As it has been indicated that lb truck rides-easier and' pulls .easier/;would be natural 'to expect a eorrespont; ing gasoline economy. In phllkijt! four-ton or 'rafter load on six-wii!M trucks,'operators average from Id In I miles per gallon under actual opruii-n conditions. The possibility of safe and eeonomku operation of motor vehicle;; is dmili!>:; largely a t tie; time of purchase. Wlassume that every fleet operator wii take proper care of his equipment if satisfactory results are to be obtafefe I t is impossible, however, to obtain - u isfact.ory operation from a truck ' does not fil tie operator's req u ttam i1 R a ilro a d S afety M en M ets in St L o u is / T 'H E Safety Section, American ife1' i way Association, held a very v" cessful Regional Safety (Jonferetu f 11 St. Louis, at tie Stallur Hotel, on M " 1 22. A program of outstanding value < presented in two sessions. 1 During the day tdiaries E. Hill, CM < Safety Agent, New York Central `in; Chairman of the Safety Section, Amen can Railway .Association, called athu tion to some striking facts in railm ft1 safety. Accidental deaths on railt*.-. he said, amount to only five per ceM w the annual accidental death .toll, and i *' one per cent of the serious injuries o' kinds happen on the steam raihn>l There has been only one year since f -u : work was organized on the raih-.-1 when accidents did not decrease. In 1913 there Were 3,715 deaths to ir I road employees,1in 1932 there were crib 557. In 1915 there were 171,ui' injuries to employees, but in 193? onw 17,400. Thus casualties to empkque have been reduced 85 per cent in 15 years; and passenger fatalities in *' same time have been reduced 92 n . cent. "However," aid Mr, H ill,'"there -u> still thousands of deaths and injur a happening to employees and other'. on the railroads each year and the ratio .>4 still have 1 very1 serious problem cos- fronting them ,- The safety movemwi still needs more aggressive leadership, :N A T T O M a f.' c a iwrao- 'ratefe?