Document gbz5Qg6wev28aZ6wR5kKX1Qe9

AMERICAN INDUSTRIAL HYGIENE ASSOCIATION QUARTERLY Volume (0 DECEMBER, 1949 Number 4 Control of Environmental Industrial Hazards i .. ALLEN D. BRANDT Bethlehem Steol Company Bethlehem, Pennsylvania - he health hazards in industry which, labor and management, the engineering con Tif uncontrolled, may cause occupational trol of industrial atmospheric sanitation illnesses and discomfort, are many andwill be discussed in detail. No further ref varied. The more common ones may be erence will be made to the other health - divided conveniently into seven groups as hazards, not because they are unimportant, follows: (1) Atmospheric contaminants but because of time limitations. (dusts, fumes, mists, gases, vapors and smokes); (2) Heat, cold, high humidity and Engineering Control of Atmospheric rapid temperature changes; (S) Radiant Contaminants energy other than heat; (4) Faulty illum 'T'HE objective in controlling dusts, fumes, I ination ; (5) Noise; (6) Unsanitary con mists, smokes, gases and vapors is to ditions; (7) Fatigue. prevent the amount in the air breathed by ` All of these factors are capable of con- the workers from exceeding safe limits j troi by sound engineering to such degree commonly called muximal allowable con I as to render them innocuous to the indus centrations. They are not truly maximal ' trial worker. It follows then that engineer allowable concentrations, but are the ing is the first line of defense in the con amounts which all but the unusually suscep trol of ill health and discomfort of indus tible workers can endure day in and day trial workers. out without producing significant elTccts on Fortunately for the engineering profes their well-being. These concentrations vary sion, the human being is a miraculous or from mntorial to material, some being rela , ganism and can stand considerable mis tively harmful and others being almost in treatment without showing illness or even nocuous. Knowledge of the safe limits of > discomfort, For this reason, noise, radiant the materials in question and how the energy, atmospheric contaminants, fatigue, amounts in the air can be measured is etc., need not be completely eliminated, they important to the engineer in addition to need merely to be controlled within certain ways and means of reducing the concen limits. These limits have been fairly well trations. defined for most of the factors included in Engineering measures for preventing the the foregoing list, and serve as bench marks inhalation of excessively contaminated air for the engineers. have been discussed by many authors, and , Of the groups listed in the first pnrn- there are about as many different classifi graph, the atmospheric contaminant group cations of these methods as there are papers I is the most important one. Because of its on the subject. - The principles expounded, however, are always essentially the same. J importance and the keen interest taken by m rc**,nt*il *1 th, Srrand Cult Cflut ItecfonxI Confar* They may be divided conveniently into throe main groups ns follows, depending upon the nr on Industrial ttntlh. Houston. Texas. October 6. a,a avenue of approach: EMO 02961 Page 82 INDUSTRIAL HYGIENE QUARTERLY firccmhfr, 1. Eliminating the sources of contamina tion or reducing the amount: (at Design, alteration, and maintenance of buildings and equipment; (bt Substitution of less toxic materials; tc) Process or operation changes; (d) Housekeeping. 2. Prevention of contaminant dispersion: (a) Segregation of hazardous processes; (b) Enclosing the hazardous processes; (c) Wet methods; (di laical exhaust veiltilation; (e) Equipment maintenance; (f) Worker education; (g) Housekeeping. 3. Protecting the worker: (a) Equipment alteration; (bt General ventilation; (c) Respirators; <d Worker education. The control pf an atmospheric health hnznrd is rarely accomplished by a single measure; it usually involves the use of a combination of methods. Eliminating the Source of Contamination Qbviously, the. most successful approach to the problem of industrial atmos pheric sanitation lies in the deeign or altera tion of plant and equipment so that the ' control features are engineered into the structure and machinery. Factories con structed without due consideration to keep ing the air clean, and existing plants, pre clude the most efficient use of engineeringcontrol knowledge. Much control equipment, installed on "unprepared"- machinery even if carefully planned, is makeshift at best and has all the features of the proverbial "sore thumb." Probably the most important single ave nue to better atmospheric sanitation lies in the education of manufacturers of indus trial equipment aud machinery so that at least the basic elements of control equip ment are included as an integral pari of each machine which is known to produce or disperse dusts, fumes, smokes, mists, gases, or vapors. Some action in this con nection is in progress, but the surface is only being scratched. Some new plants are being laid out with the atmospheric-sani tation problem in mind. Also a few indus tries which are undertaking industrial hy giene on a long-term basis are slowly me chanizing and modernizing their existing plants to increase production, eliminate arduous labor, and reduce atmospheric pol lution. Fully as important as the original design of any piece of equipment is its maintenance. Deterioration, wear, corro sion, abrasion, aud shock result in iuellicienl operation unless maintenance is good. In the smaller industry, maintenance is too frequently left to the user of the equip ment. This is not a satisfactory procedure. All maintenance work should be made the responsibility of one man or one depart ment. A very effective method of control is tin- MihslilitlioH of noulo.rir for toxic ittnlcrialit. The application of this method is very lim ited in scope because of the basic require ments on which materials are usually select ed. It should, however, always receive due consideration since it is both effective and usunlly inexpensive. Yet, for this very rea son, the engineer or chemist must guard against overdoing substitution. It is gen erally agreed that any material, he it ever so harmful, can lie handled sufely if pro perly engineered.' This feeling has been verified in practice by the experience of the atomic-bomb plants and the military explosives manufacturing aud loading plants. As substitution of less-toxic materials frequently runs counter to quality control in production it must be recommended with caution, particularly since oilier methods are available for the adequate control of haz ards. Exnmplcs of successful substitution of less-toxic materials are the replacement of steel grit for sand in abrasive blasting; artificial abrasive grinding and polishing wheels for sandstone wheels; nonsilira part ing compounds for siliceous compounds in foundries; petroleum naphtha or toluol for benzol in the lacquer, ink. and rubber cement industries; Stoddard solvent for carbon tetrachloride, in dry cleaning (spe cial equipment is usually required to comply with lire regulationsl; quartz-free or lowquarlz minerals for smut under mine loco motives; and relatively insoluble lead com pounds for lead oxide in paints and ceramic glazes. A change in the-process can sometimes be used to elimitiitle or control a health hazard. Kuril change frequently involves major changes in other parts of the pro duction line, and this control measure is therefore very limited in scope. Examptes are controlling the temperature and speed of chemical reactions so that the rate of mist, gas, or vapor production is decreased; welding, crimping, riveting, or otherwise : ill EM002962 1 NS' /y December. 101,0 ml shock result in inefHnless maintenance is good, dustry, niiiintciinnce is too o the user of the equip t a satisfactory procedure, work should be made the one man or one depart* c method of control is tlie nioxic for toxic materials. f this method is very limause of the basic require-mterinls arc usually select* wever, always receive due ce it is both effective and ve. Yet, for this very rea* r or chemist must guard g substitution. It is genit any material, be it ever be handled safely if pro1. This feeling has been ice "by the experience of plants and the military tufacturing and loading n of less-toxic materials counter to quality control must be recommended with irly since other methods are adequate control of hazof successful substitution erinls are the replacement sand in abrasive blasting;, e grinding and polishing lone wheels; nonsilica part* for siliceous compounds in leum naphtha or toluol for lacquer, ink, and rubber es; Stoddard solvent for ride, in dry cleaning (spe* usually required to comply ions; quartz-free or lowfqr sand under mine loco* Intively insoluble lead com* oxide in paints and ceramic the process can sometimes linate or control a health -hunge frequently involves in other parts of the pro* <d this control measure is limited in scope. Examples the temperature and speed .ctions so that the rate of or production is decreased; ng, riveting, or otherwise Vou 10, No. 4 INDUSTRIAL HYGIENE QUARTERLY I'ttjie XX joining to eliminate soldering operations; and changing from manual batch charging to machine and hopper charging. More can be done by pood housekeeping to eliminate sources of contamination, par ticularly dusts and fumes, than is commonly realized. In dusty industries or workrooms where dust is continuously settling on nil surfaces which approach the horizontal, and collecting on vertical surfaces, good house keeping in the form of vacuum cleaning, wet washing, and sometimes brushing pre vents the material from being redispersed into the air. The amount of dustiness which is con tributed to the air of dusty industries by the continual redisseminatiou of the settled material is sometimes more than 50' r of the total dust concentration. Yet this dust can be prevented from getting into the air very readily by constant cleaning. Painting the walls a light color, improving the illumina tion, and oiling or wetting the floors are effective in promoting good housekeeping. While good housekeeping alone is seldom sufficient to control existing hazards, ex perience has shown that the housekeeping in most plants is a good index of the in dustrial hygiene program. Prevention of Contaminant Dispersion jyfANY industries have operations which L produce considerable atmospheric con tamination but which require the immedi ate attention of only a relatively small num ber of workers. If located indiscriminately throughout the plant or if conducted at certain times, such operations may expose many other workers to a needless amount of atmospheric contamination. By segre gating or isolating these operations, only those few workers engaged there will be exposed to the hazard, and they may be protected by means of respirators. Also the segregation or bunching of hazardous opera tions aids materially in the effective ap plication of local exhaust ventilation or other control measures. The usefulness of this measure is so ob vious that examples are senreely needed. Blasting in mines at the end of the shift so that the gases and dusts will have settled or dissipated by the time the workers re turn, sweeping and cleaning at night when other workers are not on the job, shaking out foundry castings at night when most workers are off the job, and locating the plating or degreasing tanks in separate rooms arc common examples. Unclosing an operation might be con sidered an extreme form of isolation. The contaminant or contaminated air is pre vented from reaching the breathing zone of any workers except in rare instances when one or two men may be exposed within the enclosure. It is superior to segregation or isolation since it acts nearer the source of contnminalion. in one instance the simple expedient of attaching a loose cover for the containers being filled to the end of a canvas discharge chute from a gyratory screen reduced the dust concentration in the screen room by well over 5(1'.;. in another in stance a toxic and highly explosive material was transferred from 50 pound to five pound containers in a complete enclosure. The large cans were mounted on a frame in the top of n home-made enclosing device, and after closing the door the contents were dropped into a hopper by rotating the handle. Measured quantities were then dropped into srnidl cans through n dusttight corrugated hose. Two slide gates served to close and open the top and bottom of the measuring device. Hence by closing the lower gate and opening the upper one the material from the hopper filled the sec tion between the slides which served as the measuring device. By closing the upper slide and opening the lower one the meas ured quantity of material was charged into the small container. This arrangement re duced the atmospheric concentration of the toxic material from a harmful level to al most nothing. Process enclosure has been found par ticularly successful at abrasive-blasting operations, such ns barrel and cabinet types of equipment which operate on the batch basis. The equipment is closed tight dur ing the cleaning operation and is open only for charging and discharging after the abrasive blasting has been discontinued. This method of control does not find wide application except in conjunction with local exhaust ventilation which will be discussed later. Wetting dust with water or other liquids is probably the oldest method of control. It was practiced in the pottery industry in Great Britain as early as 1713. Wet drill ing and water sprays have been widely em- E HO 02 963 Page si fMOUSTSJAL HYlfi QUARTERLY December, 1049 ployed in mining operations in recent years. the area of contnminnnt escape of such The use of water sprays in quarrying direction and magnitude as to carry the operations also has been reported recently. highly contaminated air into the exhaust Substantial reductions in the -dust concen hood which is located as close as possible tration have been reported as wet-grinding to, or around, the source of contamination. operations, and as wet-drilling operations The more nearly the hood encloses the in mining, but even then-the atmospheric source of contamination, or the closer it can concentrations were still greatly in excess be located to the source of contamination, of the maximal allowable concentration. the smaller will be the required exhaust The effectiveness of wet methods for dust rate to capture the contaminant effectively, control depends upon two factors--wetting liood shape an<Hocation are of the utmost the dust, and proper disposal -of the wetted importance and deserve considerable study .dust. "Some dusts are hard to wet and un and head-scratching on the part of the de less wetted will not be captured. Even if signer. In addition to the hood, a local ex the dust is wetted satisfactorily, It Is neces haust system includes piping or ductwork, sary to collect and dispose of the wetted an exhauster (usually a centrifugal fan), material before the liquid evaporates and and usually a collector. The contaminated the dust is again redispersed by air cur air is moved through the piping to the rents, walking, or blasting. In certain collector and the filtered air is then dis mines, for example, the dust from the wet charged to the outside of the exhauster^ drilling operations settles out'as the water The design of the hood and piping, and (lows away, and collects also as water drop the selection of collectors and exhausters are lets on the walls from where It is readily complete studies in themselves and will not redispersed. Even though wetting of the be covered here. dust must be recommended with discretion, Examples of the satisfactory use of local it has been found an effective dust control exhaust systems are numerous. Some are aid in rock drilling, blasting, crushing, welding; granite surfacing; pickling and screening, materials transfer, foundry plating innks; wood working equipment; shakeout, core knockout, and abrasive blast grinders; buffers and polishers; and spray ing, and the addition of moisture to molding painting booths. sand decreases greatly any amount of dust Like all other types of equipment, that produced while making molds. ' are employed to control health hazards they Local exhaust ventilation is probably the require constant checking and maintenance. most important single method of preventing It should be included with other equipment industrial atmospheric pollution. Yet the in the cleaning and maintenance schedule. principles involved and the bases for ad Dust collectors, fans and in many instances equate design are so poorly understood that ductwork require periodic denning to ob a large percentage of the installations made tain satisfactory operation. Bent hoods in recent years are unsatisfactory or in and lenky or damaged ductwork and en efficient. The design of good local exhaust closures should be repaired promptly. Blast systems is a specialty requiring knowledge gates and dampers, if used, should be not normally possessed by any engineering locked in position, but even then they need group including ventilating engineers, un constant watching to see that the setting is less they have received special training in ' not altered by the workers and that the bal this held. This is neither the time nor the ance of the system'is not thereby disturbed. place, however, to discuss the details of Only too frequently management invests this most important subject; they have been substantial capital In jrood control equipment covered adequately elsewhere.Suffice it and then, either through complacency or to mention briefly the method of operation lack of understanding proceeds to forget all and to cite a few examples of operations about it until faced with a case or epidemic at which local exhaust systems are used. cf occupational illnesses. The answer, and . Local exhaust systems function by re the only way to protect their investment, moving the contaminant or grossly con is periodic checking and maintenance just . taminated air as close as practicable to as is done with production equipment. the point where it is released or generated. Very few if any measures or installations This is done by producing nlr currents in for the control of atmospheric pollution are EM002964 Page 88 INDUSTRIAL HYGIENE QUARTERLY Decvmhrr, l !)',!> sponsibility it is to select them end super vise their use and care. Each and everyone assigned this responsibility should study some of the literature on this subject.1*0'?-* Examples of places where respirators may be used satisfactorily are spray painting; abrasive blasting; cutting metal conted with lead paints by means of oxyacetylene torches; welding; handling dusty materials; clean-out operations; shaking out operations in foundries; and housekeeping or other cleaning and sweeping. The education of the worker for his pro tection is fully as important as to prevent the creation of unnecessary dust, fumes, mist, gases, or vapors. He must be told which contaminants are harmful and sold on the iden of avoiding the higher con centrations. Careful and continuous educa tion is necessary to get workers in the habit of standing upwind of all operations which produce or release considerable material, such as spray painting, welding, cleanout .and other maintenance operations, and handling bulk materials; also to keep his face os far from the point of operation as possible, or out of the line of throw or movement of the contaminant. Examples of Results Obtained TN conclusion, I should like to cite one A or two examples of the results achieved in decreasing occupational diseases through engineering. After all, "the proof of the pudding is in the eating." In the gold mines of South Africa, dust concentrations averaged about 150 mg/m* before a program of control was'begun and the reported incidence of miners phthisis was about 30%. About seven years after the dust control program was started the atmospheric dust level had been reduced to about 5 mg/m*. The incidence of miners phthisis began falling about nine years after the dust control program was started and reached a level of about 2% approxi mately seven years after the dust level had been reduced to 6 mg/m*. In this instance, the incidence of illness had been reduced from about 30% to 2% by reducing the atmospheric dust content from 160 mg/m* to 6 mg/m*.* An effective industrial hygiene program was launched in the government-owned ex plosives manufacturing and loading plants inte in 1042--about one year after I'earl Harbor. The atmospheric concentrations of TNT were on the ascent at that time and continued to increase until about April, 1943 when they began to decline, the decline continuing until the close of the war. Peri odic medical reports from these plants show that the incidence of lost-time cases be cause of TNT poisoning, of mild TNT poi soning cases, and of medical transfer from TNT exposure paralleled the atmospheric dust and fume levels very closely. The fig ures in this instance are somewhat as fol lows. The peak concentration of TNT was about 2.7 mg/m* in April 1943 nnd the peak incidence, of lost-time, mild, and medical transfer cases was about 21, 640, and 450, respectively, in terms of cases per thousand man years of exposed employees. The peaks of the cases occurred about July, 1943. By the end of 1944 the average atmospheric TNT concentration had been reduced to about 1.0 mg/m* and the corresponding in cidence of TNT cases was 1, 80, and 85. Engineering measures alone, of course, were not responsible for this entire reduction. The personal hygiene program, and the periodic medical examinations contributed substantially. References 1. IIranuTi AfXKN I).: "Industrial Health Knicinecrinir. John Witty nnd Son*. Inc,, New York. 1947. 2. AMiRN, John 1..: Dnlgn of lndiittinl Kxhmmt Syntem*. Imluntrlal Trews, New York, 1039. 3. UntNKf.R. P,, nnd Hatch, T. T.: InrfuMtrlnl Dust. McGraw-Hill Hook Company, New York, 1030. 4. HkmkoN, W. C. !.: Air Dilution In Industrial Ventilation. Itratinp and IVnfiiafiiin, 3*2:39 (Novrto>HT) 1040: 37:42 (December) 1940; 39:40 (February) 1041; and 39:71 (March! 1941. 6. Heating. Ventilating, and Air CWrillhmliitf Guide, 20th Kdltlon. American Society of HcaUnit amt Ven- tliatinr Engineer*. New York. 1043. 6. The live and Care of Umptrator*, Preventive En gineering Seritw, llullctin 2, Tart 2, Indn*trlnt Hygiene Foundation of America, lnc,, Tittahurgh, 103K. 7. SCII9RNK, H. H., and Tkaarie. S. J.: Selection, the, and Maintenance of Itcajdratory Protective Device*. In formation Circular, 723d.(April) 1943, U.S. Itgrcau of Mine*. Waahington, D.C., 1941. 9. Protecting Plant Manater, Practical Point* on In dustrial Sanitation and Hygiene. Dc|<atlment of loiter, Dlvlainn of Iahor Standnrd* Special lluiletln 3, Govern ment Printing Ofllee. Washington, D.O.. 1941. 9. MAVROfmKtiATo, A.: Contribution* to the Study of Miner*' Phthlaf*. PubL 8. African tnmt. Med. Ufa., Jo* hanneaburg, 1920. . tO. MrCoNNRi.u W. J,, et ah Occupational DUmtc* In Government-Owned Ordnance Eicpjolve Ttantx. Orrupu. Cfonal Medicine, t:SBl (June) 19(0. EM002965 :rly December, 104$ -onteminant escape of such magnitude as to carry the inated air into the exhaust located as close as possible the source of contamination. <rly the hood encloses the mutation, or the closer it can he source of contamination, til be the required exhaust the contaminant effectively. .1 location are of the utmost ! deserve considerable study hing on the part of the detion to the hood, a local ex* tcludes piping or ductwork, usually a centrifugal fan), -ollector. The contaminated hrough the piping to tho he Altered air is then dis- outside of the exhauster, the hood and piping, and ollectora and exhausters are ; in themselves and will not the satisfactory use of local ; are numerous. Some are e surfacing; pickling- and wood working equipment; ' a and polishers; and spray * types of equipment,- that control health hazards they cheeking and maintenance. uded with other equipment and maintenance schedule, ans and in many instances e periodic cleaning to ob* v operation. Bent hoods imaged ductwork and en* e repaired promptly. Blast ten, if used, should be i, but even then they need g to see that the setting is s workers and that the bal* n is not thereby disturbed, ntly management invests ` <1 in good control equipment through complacency or -ding proceeds to forget all ed with a case or epidemic Inesses. The answer, and protect their investment, ng and maintenance just reduction equipment. * measures or installations atmospheric pollution are VoL. 10, No. 4 INDUSTRIAL HYGIENE QUARTERLY Page S.l foolproof. Much depends on the attitude of the worker. A cooperative, interested, and well-trained worker can accomplish much with any control equipment, whereas the indifferent, lackadaisical, untrained worker produces the maximal amount of atmospheric contamination with any con trol device. The solution lies in the education of the irvrker. This is an unending task and be comes very discouraging if labor turnover is high. Nevertheless it is the key to the really successful operation of atmospheric sanitation equipment. As a rule the labor turnover will be much less if the working conditions are good. Therefore, proper edu cation of the worker is the Arst step .in a chain of events which lead to a satisfactory educational program. To be successful the education of the worker must begin the day he is employed. If he is permitted to begin his work without proper instruction in the performance of his tasks he will form faulty habits of operation which require much effort to undo. On the other hand the educational'program must not cease as soon as the worker has been trained in the cor rect procedure of doing his job. It must be continued throughout his period of employ ment to keep him on his toes and to pre vent him from falling into a faulty routine. Examples of what can be accomplished in atmospheric sanitation by worker education are unnecessary--they are quite obvious. Any operation (whether it be provided with control equipment or not) which produces or releases an atmospheric contaminant can be done, and should be done, in a manner which results in the escape of as little ma terial as possible into the workroom air. Good housekeeping will serve to prevent the dispersion of atmospheric contaminants. However, it is considerably more important in eliminating sources of contamination as was discussed previously in that connection. Protecting the Worker jMTOST INDUSTRIAL machinery or equipment which produces or releases harmful contaminants can be engineered either in the originat design or by alteration of existing installations to decrease the worker's exposure. In many instances, however, the reduction of exposure is not sufficient to eliminate the hazard, and other control measures are needed. Yet there are some operations where the principle may he ap plied to render the worker's exposure harm less. Examples are the use of mirrors and/ or extensions on operating handles to per mit the worker to stand clear of the escap ing contaminant; arranging all hot pro cesses so that the operator stands beside rather than nbnve the process; and locating a fan dingonnlly to the rear and to the side of the worker to blow the relatively clean workroom air through his breathing zone and to carry the highly concentrated con taminant from the operation lie is doing away from him, or locating the terminal of a supply duct between the operator and the source of contamination to blow the contaminated air away. General ventilation is second in impor tance only to local exhaust ventilation. It is particularly well adapted to certain con taminants and to certain sources of con tamination but is unsatisfactory for others. Unlike local exhaust ventilation, it does not prevent, the contaminant from escaping in to the general workroom air, it merely di lutes the contaminated air of a given room or building with sufficient clean air to keep the concentration of contaminant in the room air from building up to a harmful level. Like local exhaust ventilation, gen eral ventilation is misused a great deal by people who do not understand the funda mental principles of- contaminant control. Major sources of contamination, especially if near to workers, cannot be controlled effectively by general ventilation; the dilu tion rate required to effect a safe concen tration in the workers' breathing zones is so great as to be prohibitive. Minor and scattered sources of relatively harmless con taminants, on the other hand, nm.v be con trolled effectively and economically by gen eral ventilation. The subject of atmospheric sanitation through general ventilation is a very large and complex one. For further information on it, the reader is referred to treatises on the subject of which there are many.1-*-"' Respiratory protective devices have a dis tinct place in the Acid of occupational dis ease control. That they are a last line of defense can hardly be denied. Neverthe less, where they should be used, how they should be selected, and how they should be used and maintained is not understood ad equately by some of the people whose re- Ey002966