Document 7MNd6ppm60eXE6k90GapYwgEE

'[Engineering Control of 'OCCUPATIONAL-DISEASE HAZARD By WARREN A. COOK CONNECTICUT STATE DEPARTMENT OF HEALTH ;TT IS the purpose of chis piper ro outline a practical procedure I which the engineer can employ in his own plant to assist in the control of occupaciooaMiseasc hazards, Thcsolucion of the occupational-disease problem is by no means a one-man job; it requires the active cooperation of all concerned, the engineer iplaying a large part ia its successful solution. He is more than an important cog in the wheel; he is a vical center in the I mechanism for control of industrial healch hazards. The mechanism to be set in motion for provision and main renance of healthful working environment is, within limits, imuch the same whether the cnginecc is associated with a large manufacturing organization or wich a small unic. j. The first step for the engineer to cake is to ascertain just what ^'hazardous materials, processes, and conditions exist in his plant. We all know generally that a variety of organic solvents are Used in spray lacquers and thinners, that grinding wheels are )nade up of various types of abrasives. But such generalized information is not sufficient. Ic is essential thac the engineer know specifically every potentially hazardous material used in his plant. tin presents a list of hazardous occupations Jnd the injurious materials and conditions which may lie associated with then). The potentially hazardous materials to which workers were exposed in a group of plants in a typical industrial area arc listed in the report1 of a survey recently conducted by the United States Public Health Service. This reporr includes the number and percentage of workers exposed. It may also assise in compiling the list of such materials used at your plant. The permanent record of che potentially hazardous materials and che operations wich which they ate associated may well be compiled in the form of the pbcenrial-heakh-hazard chare pre pared by our bureau, in which the injurious materials arc listed along che abscissas and the industrial classifications along the ordinaces of cross-section paper. In the chart which you make up for your plane, the individual departments and operations will be substituted for the industrial classifications. The in formation given by this chart may be made more complete by inserting, instead of the X used in our charr, che number of workers exposed togerher with a symbol co indicate che relative severity of the hazard. | UST THE MATERIALS THAT ARE HAZARDOUS LEARN WHAT PROPERTIES OP HAZARDOUS MATERIALS AFFECT HE ALTH I. This chen is the first item of the practical procedure to follow; Having made a complece pecmanenc record of che materials ; Go through the plant, department by department, and list the used, including their constituents, and of the department and 'materials used in or given off by cich operation. You may be occupations where they occur, be sure that you arc informed 'of the opinioa chae you know all these items as parr of your on the properties of these materials which affect health. You intimate knowledge of the plant. But it has been our experience should know relatively how much of the material is required when making plant surveys thac there arc usually a number of co cause injury and, generally, how the maccrial affects the gaps in the engineer's knowledge of these materials. body. You should be sure that your information is reliable Do you know, for example, whecher the thinner used in and chat it is in accordance with up-to-date knowledge and .your plant contains benzol as a constituent, whether gasoline opinion. Research on this subject is continually being con ' fot nonfucl purposes is free from lead, whether sandstone grinding wheels arc employed, and what abrasives are used ; on made-up wheels or disk- grinders? A complete survey of plane conditions will disclose such information and provide information oa che porcncially hazardous materials with which ' you have to contend. t Since new materials are constantly being introduced, have a ducted and our knowledge of the injurious action of these materials extended. Occasionally, erroneous impressions of the hazards presented by various materials gain credence and must be corrected, Some years ago che cextbooks stated that pneumoconiosis was caused by sharp-edged dusc particles such as those of grantee and aluminum oxide. It has since been shown that the 'mnding arrangement with the purchasing department to keep Jyou informed of any such materials ordered. If it is decided co substitute methanol for denatured alcohol, it may nor be neces, sary co make any mechanical changes in a process and you may not be notified of the substitution. But you should know chat jj this more hazardous solvenc has been introduced, as additional *- control measures may be required. One of che succsc mcchods of keeping your permanent record up to date is co have che purchasing department transmic this information to you. Of assistance in compiling the list of injurious materials iiused in the plant is che bulletin, "Occupation Hazirds and Diagnostic Signs," prepared by Dublin and Vane.' This bulle- 1 U. S. Bureau of Labor Statistics Bulletin Mo. 582, 1933Cootributcd by the Safety Commiccec and presented ac a session on Occupational Diseases ac the Annual Meeting, Mew Yorfc, N. Y., Dec. 3-6, 1935, of Tub Americin Society or Mechanical Engineers. sharpness or hardness of che dusr particles is not the criterion of their pneumoconiosis-producing properties and that workers exposed co sufficient concentrations of quartz dust co cause pneumoconiosis do not develop this coldition when exposed to similar concentrations of equally hard and sharp-edged aluminum-oxide dust. Many engineers have a goud conception of the types of dust which are most injurious, but erroneous impressions come to light when industrial health hazards arc discussed. For example, we often find that the engineer fails to recognize thac carbon tetrachloride is injurious on its own accounc but has che misconception chat only its products of hvdrolysis when used in extinguishing fires are hazardous; and again that toluol is nonmjurious since it was recommended 1 "The Potential Problems of Industrial Hygiene in a Typical Indus trial Area in the United Sraces," by Bloomfield, Scott, and Sayers, Public Health Bulletin Mo. 216, December, 193-4. 105 106 Mechanical Engineering is a substitute for the m.-re toxic benz-d The facts .1:; that hazard '"ci-md safe limits. Only bv knowing the hazards and .ill the uru.inic solvents .ire toxic, though to vamns degrees determining that the exposure to them is within safe limits .an so although you cannor expect to know die whole suhiecr of you be assured that your plant will nut be visiced by any such industrial toxicology, it is miport.iiic chat you be reliably in iamencable occurrence. formed on the miunous properties of the materials used in your Not onlv do determinations of these atmospheric contami plant Such information can be obtained from some of the nants show where control measures must be instituted but, in recent general references on the subreer. or, even better, from other instances, they may permit appreciable saving by showing such sources as ynuc plant physician, federal and scare bureaus that control measures involving expensive exhaust equipment of industrial hygiene or occupational diseases, insurance engi may not in every case be necessary. Illustrative of such a situa neering departments, universities, and private consultants. tion is the potential hazard from the lead melting put. DETERMINE WlltCU POTENTIALLY HAZARDOUS MATERIALS, PROC ESSES. AND CONDITIONS ARE ACTUALLY CAUSING INJURY TO HEALTH OP THOSB EXPOSED For years there has been a tendency to recommend exhausc ventilation over melting pots containing lead and its various low-melting alloys in slush casting and linorvpe-nuchine operation. To determine just hoiv necessary it is to nave hoods The third step in the procedure of controlling occupational- over the melting pots of type-setting machines, lir analyses disease hazards is co decide which of the potentially hazardous were made in connection with an investigation of health materials, processes, and conditions are actually exusing in hazards resulting from the use of these machines.1 The results jury to the health of chose exposed These potentially hazard of these analyses showed that the daily exposure where there ous conditions will fall into three categories. Those obviously were no exhaust hoods was less than 0 2 mg Studies made by requiring control measures, rhosc which may be considered our bureau where no local exhaust was applied to the linotype negligible, and chose which require determination of the machines have also shown lead concentrations of (his same exposure to show whether or not the potential hazard may order, welt below rhe amount which causes poisoning, fa actually be atfccting health. studies conducted in lead-casting departments of four plants The use of determinations of atmospheric contaminants has during the past year, we found the exposure of the casters to been emphasized in the Connecticut Bureau of Occupational vary from 0.1 to 0.5 mg of lead per 10 cu m of air. The amount Diseases as an exceedingly satisfactory basis on which co of lead collected in samples taken directly over the melting proceed. Engineers arc trained to worlc from facts; the results pots varied from less thanO.l mg to less than 0.4 mg per lOcu tn. of determinations of injurious materials in the air arc the Since it has been well established that except for prolonged fundamental facts in occupational-disease control. exposures the limit of safety under most industrial conditions The following experience shows ivliar can happen when in is an atmospheric concentration of lead dust or fumes of less formation is lacking concerning the exposure of workers co than 1.5 mg per 10 cu m of air, che foregoing determinations in potentially hazardous conditions. Eighty men were con dicate chac there are more important control measures than the nected with a department in which two machines involved the provision of exhaust ventilation for lead melting pots kept at use of one of the newer organic solvents that had been shown moderate temperatures. to be only moderately toxic. Eleven of these men were di Of incercst in chis regard is a table of rhe calculated maximum rectly engaged in the operation of the machines. The process lead-vapor content of air over surfaces of lead kept at various had been in use for some time when an alteration was made temperatures from 250 C to 1500 C which was published in chc which increased the concenrrarion of the vapor and duration foregoing paper.1 A portion of this table is reproduced^in of exposure of the workers. Even wiclt the increased concentra Table 1. * tion of the vapor, die odor was not unplcasanc nor, as far as we know, did it cause the workers to complain. TABLE 1 CALCULATED MAXIMUM LEAD-VAPOR. CONTENT Within a fortnight, one of these 11 workers, a normally healthy young man,"29 years of age. went home after the extra long Sunday shift oT II hours feeling ill. He died six days lacer, the cause of his death being attributed to influenza and <Jilaced heart. No cause-and-cfTcct relation was linked at that time between his occupation and his death. Oruthe Sunday following, a second man working ar these machines was taken ill. and on chc next day a third. Cases 2 and 3 were still ill OF AIR OVER SURFACES OF LEAD KEPT AT VARIOUS TEMPERATURES ------- Temperaturef' CooccocnQoo of lead, mg per 10 cu m 300 572 0.00006 350 <562 0.0016 400 752 0.02 430 ?42 0.2 500 932 2.0 when two more workers were transferred from workroom co hospital; and within U days from die death of the first victim, live workers had succumbed co fatal poisoning. The point of this illustration is nor that the organic solvent was extremely poisonous nor due ic should necessarily be re placed bv some less miurious material. There is no question bur what the process, employing the very same solvent that caused the deaths, could have been conducted in such a manner as to cause no iniury to health The poinc is thac the engi neer in charge of the operation did noc recognize his responsi bility to ascertain definitely wherher chc exposure to che solvent vapor was within safe limits Had vapor determinations been made at die time the process was changed, the hazard could have been Controlled before die iniury co health occurred. Materials of equal or cheater toxicity are being used in many From this table it will be noted chac the temperature must exceed 9tX) F before injurious concentrations of lead vapor are given olF from the melting pot. A warning should be given, however, chat as the temperature exceeds this value the amounr of lead vapor evolved from the surface of the molten lead in creases rapidly; when che temperature doubles from 500 C to 1000 C the equilibrium concentration of the lead vapor above the surface of the molten lead increases 50,000 times. Since things are noc always what they seem, even when con sidering such a prosaic enriry as occupational-disease hazards, che engineer should have information on the amounc of the in jurious substance to which the worker is exposed wherever there is a possibility of doubt. Determinations of atmospheric contaminants bring co light hazardous conditions before oceu- pilots cod.iv If anv change is made in an operation or :n the 1 "Hygiene in Seizma'chincnriiimen," by Vajc and Weber, Schriftea materia! used, ascertain that such change .iocs not increase the -lus deni Gesamcgebiec der Gewerbchygicne. no. -14, 1935. Fkbr.ua.rv, -1936 l diseases develop. In lormcr years :he only criterion of helmet when lie le.i.-s over .n :he . .u-se >i -a .rl i'-e -.e_- Sxhe healthfulness of the industrial environment was whether !-ja:y of the dust is so great during sa.iJi'la::i'g ti-^t :: .till jo^not dearly demonscrahle in)ury to health occurred. And find its way into che helmet if there arc openings of appreciable lly it was necessary for several cases of occupational size even against the scream of air escaping from ic. : to develop before the working conditions were accepted Hiving ascertained that the heimec fits properiv and is so ; the aetiological factor. adjusted chat the dusc docs noc have access to its interior, turn pDdluc the methods available today to keep one step ahead your attention co the air supplied in the positive-pressure line. ' the occupational-disease specter. Determine whether the How muclidusrdocs ic contain? Is the intake of the compressor Rrorhing conditions are safe or hazardous on the basis of the so located chat die air is dean? Even when an air washer is fcbocentracioQ of che hazardous materia) presenc. If the worker supplied we have occasionally found this to be ineffective a Eb exposed to more than the threshold dose, then act at once to dust has been allowed to accumulate in it or if die water : the condition. It is not necessary for che engineer co has evaporated or the glass cracked. And is a sufficient volume ay, fearing that he may be overestimating chc severity of of air supplied? Does che valve on the airsupplv line permit Jthe hazard and so letting his concern in for unessential and the sandblaster to reduce the volume of air below chat necessarv ^productive expenditures; he can stand behind his recom- to make die helmet as effective as its manufacturer designed k fraeodations when they arc based on facts which show che to be? Possibly die air line contains some oil from che Com to be excessive. It has been our experience due the pressor and die blaster may shut off the air to avoid the dis Jengtncer armed with such facts has received support from chc comfort ac che expense of subjecting himself to a severe health PiManagement such as had previously been accorded him only on hazard. Provide che man wich a clean air supply and be sure Eprojccrs which offered an assured production profic. he is getcing the proper volume of ic. V Ifaivcr EKODiKERlS'Q PRIHCIPC.es TO KEEP WORKER S BXPOSURS wrrsiH SAFE LIMITS Having checked these items, make a dusc determination of the blaster's exposure while conducting operations in the usual manner. A determination of the frcc-silica contcnc of die jtThis leads to the fourth step in the procedure for che control dust wilt assist in die interpretation of the result. But a good ief oocnparionil-disease hazards: The application of engineer helmec will keep che exposure well below five million particles ing principles to keeping the worker's exposure co pocencialLy per cubic foot of air which is considered good performance hazardous conditions within safe limits. As stated by Clark whatever the free-silica content. j*d Drinker in their new book,4 ''Prevention of industrial After the actual sandblasting has been completed, arc there disease is largely an engineering problem,as its basis is a separa other dusty operations which the blaster may include as a tion of the toxic or irritating substance from contact with che part of his duties? An approved filter-type respirator should be jwodker.'' worn while performing incidental jobs involving moderately SlThis separation of the harmful material and che worker may excessive dusc exposures. application of the most ingenious engineering skill or Perhaps one of these jobs is emptying the dusc collector cwo [merely of simple engineering principles, but in cither case or three times a day. In one case we made dust determinations jtfcere should be a generous porcion of chat most valuable qual- of the blaster's average exposure while transferring the dust , the ability to be practical. General methods of occupa- from the hopper of the collector into barrels and found it to be jriottxl-disease control measures can he divided into a number 32-4 million particles per cubic foot of air I Even this repre groups, such as provision of enclosures, exhaust ventilation sented an improvement over a former condition since a canvas vboth local and general), changes in process (dry to wet, for cover had been provided which extended chc canvas discharge 'example), substitution of more toxic by less toxic materials, cube so that ic fitted over che top of chc barrel. Ac the plant ! 'and wearing of special protective equipment. where chis determination was made, the blaster was exposed Without going into examples of each of these general meth for ten minutes twice a day to this high dust concentration. ods, consider from an industrial-hygiene point of view some Ic is essential noc only to keep die average exposure within isunplc operation, such as sandblasting. Assume chat this safe limits, but also to avoid exposures to greatly excessive operation is conducted in a modern, specially designed room, concentrations foreven brief periods. The importance of avoid 'that the sandblaster is equipped with a positive-pressure helmet, ing such exposures is not limited co dusts but also applies to 'that a steel abrasive is used, and chat a cloth-filter cypc of dust many ocher injurious materials found in industry, especially 'collector is provided. It may perhaps be felt that the condi- where che brief exposures arc repeated day after day. ,atioo can be dismissed as completely satisfactory, There are several methods for removing che dusc from the hi,. But is the sandlbaster adequately protected? Let us see jusf collector without subjecting the worker co large amounts * what should be taken into consideration to assure that an of it and some effective method should be utilized. In problems | affirmative answer can truly be given. of this cypc the engineers of the equipment manufacturers are jv The dust to which the sandblaster may be exposed comes of much assistance. ( from two sources, that in chc sandblast room and that in the A survey of che sandblast operation should include exposure g air line to his helmet. If there is an appreciable amount of of ocher workers in ics vicinity. Is the sandlbast room itself .J molding sand on the castings being cleaned, chc dusc in che tight? Where is the dust collector discharged? There lus been Stoom will coneain free silica, though che percentage will be much discussion concerning chc discharge of cloch-fikcr dusc j considerably lower than if a sand abrasive were being used. collectors back into workrooms where free silica is one of the J The positive-pressure lielmer may look good on paper, but constituents of che dust.- The final answer to this question de -| "examine ic on the man co-make sure it permics no easy access pends upon the ability of the engineers of the equipment manu 2 foe the dust. Wich some types of helmets there is a strap or facturers to provide a collector which will clean chc air suffi I elastic which pennies a tight fit around the neck. Does che ciently and with such certainty when all operating factors are ?i sandblaster so adjusc chis that the dust cannoc eneer che bre.ich- considered chat the worker is noc exposed to an injurious at ! ing space? Or perhaps there is an opening at die front of che mosphere. * "Industrial Medicine,** by Clarke and Drinker, National Medical The difficulties of dusc suppression, the limitations of Just Book Co., New York, N. Y , W35. collection, and certain ocher factors cause che preponderance of 3d 4i l 1-)S M i.C i t A N iCA t Ils'G! V EE RI N'O opinion it the present rime to lavor tile Jisch.irc: it a point outside the plant m air from collectors handling a dust of hiuh silio content However, in .1 particular plane under certain cir cumstances. tt m.iv Iv: especially desirable to return the air from the collector to the w sricroom. If this is done, then by all means ascertain bv Just determination that those empioved in the workroom are not exposed to excessive dust conceiitrarions, and further, institute a ritt-d routine of maintenance and check dust determinations M assure a ourself that the dust exposure is being kept within safe limits two weeks, iirr-Ttiii-itv -,v.ts taken to ^..ile^t :(ii i-arther omtnerer samples .ic these dust collet tors and average conce.ecr.itians of 2 3 million particles and ! 5 million particles per cubic foot of atr were found. The engineer who maintained these dust collectors in such excellent condition deserves much credit, winch the engineers who originally designed the equip ment would gladly accord him. Other pieces of equipment than dust collectors also requite adequate attention to maintenance to assure thac a health hazard once controlled will continue to be controlled. ISSTITCTE ROUTISTS OP M MNTEWASfCB aN'd chcck-op The engineering control of any occupational-disease hazard cannot be attended to once and for all and then forgotten. Eternal vigilance, in the form of maintenance and check de terminations of the atmospheric contaminants, is essential to the complete solution of the problem. This is che fifth step in the engineering control of occupacional-disease hazards. Maintenance is of such paramount importance in occupationaldisease control that it should be made the subject of an entire paper. The following is an example of what can be done when such a piece of equipment as a dust collector is properly main tained under the direct supervision of the plant engineer. Dust collectors were connected to two sandblast-table rooms using sand abrasive. The collectors had been in continued use for six vears. During this time they were thoroughly inspected and cleaned every month. Konimeter dust samples were taken at che discharge of the two collectors. These showed counts of 1 1 and 0 7 milliun particles per cubic foot of ait for one of them, and, for che other, 3 l and 2,8 million particles, A week later the second dust collector was checked with an impinger and i concentration of 2.35 million particles was found in the exhausted air. This collector had been cleaned and inspected about three and one-half weeks previously. Another impinger simple was taken within a iew days after its next regular cleaning and the concentration at the discharge was found to be onlv 0.87 million particles per cubic foot of air. After another COXCl.CSIONS A procedure has been outlined for the engineer to utilize in his plant as his part in the control of occuparianat-dtscasc hazards. CO He should make a permanent list of the materials used in his plant and keep the list up to date. (2) He should be informed concerning the injurious proper ties of the hazardous materials used. (}) He should determine which of the potentially hazardous conditions are actually causing injury to health and should be controlled, (4) He should engineer the control measures, preferably checking che completeness of control by determinations of the injurious materials in the air breathed by the worker. (5) He should institute routines of maintenance and check up determinations. The manner in which this procedure could be followed was outlined in connection with the simple operation of sand blasting. This same procedure can be utilized for the control of health hazards of similarly simple operations or of the most complex operations' where a variety of hazardous materials are involved. Every available aid should be made use of in coping with the occupational-disease problem.to_ the_end thac the hazardous condition may be controlled before it manifests itself in the form of cases of occupational disease. / A it /*U P Xf*44 S*t It# Crmf*9