Document ELdyJww6L0nOZg1kyGx9gBK0

AMERICAN INDUSTRIAL HYGIENE ASSOCIATION QUARTERLY Control of Environmental Industrial Hazards ALLEN D. BRANDT Bethlehem Steel 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 rapid temperature changes; (3) Radiant energy other than heat; (4) Faulty illum Engineering Control of Atmospheric Contaminants jt 'J'HE OBJECTIVE in controlling dusts, fumes, 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 trol by sound engineering to such degree commonly called maximal allowable con 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 effects on Fortunately for the engineering profes their well-being. These concentrations vary sion, the human being is a miraculous or- from material to material, some being rela tively harmful and others being almost in nocuous. Knowledge of the safe limits of the materials in question and how the amounts in the air can be measured is important to the engineer in addition to ways and means of reducing the concen trations. Engineering measures for preventing the inhalation of excessively contaminated air for t>io engineers. have been discussed by many authors, and Of the groups listed in the first para graph, the atmospheric contaminant group is the most important one. Because of its importance and the keen interest taken by there are about as many different classifi cations of these methods as there are papers on the subject. The principles expounded, however, are always essentially the same. They may be divided conveniently into three Presented at the Second Gulf Cqast Regional Confer ence on Industrial Health, Houston, Texas, October 6, 1949. main groups as follows, depending upon the avenue of approach: ' 4. Page 82 INDUSTRIAL HYGIENE QUARTERLY Vol. 10, No. 4 1. Eliminating the sources of contamina tion or reducing the amount: (a) Design, alteration, and maintenance of buildings and equipment; (b) Substitution of less toxic materials; (c) Process or operation changes; (d) Housekeeping. 2. Prevention of contaminant dispersion: (a) Segregation of hazardous processes; (b) Enclosing the hazardous processes; (c) Wet methods; (d) Local exhaust ven tilation; (e) Equipment maintenance; (f) Worker education; (g) Housekeeping. 3. Protecting the worker: (a) Equipment alteration; (b) General ventilation; (c) Respirators; (d) Worker education. The control of an atmospheric health hazard 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 design 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 and machinery so that at least the basic elements of control equip ment are included as an integral part 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, and shock result in ineffi cient 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 the substitution of nontoxic for toxic materials. 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 usually inexpensive. Yet, for this very rea son, the engineer or chemist must guard against overdoing substitution. It is gen erally agreed that any material, be it ever so harmful, can be handled safely if pro perly engineered. This feeling has been verified in practice by the experience of the atomic-bomb plants and the military explosives manufacturing and loading, plants. As substitution of less-toxic materials frequently runs counter to quality control' in production it must be recommended with caution, particularly since other methods are available for the adequate control of haz ards. Examples 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; nonsilica part? ing compounds for siliceous compounds in\ foundries; petroleum naphtha or toluol forbenzol 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 fire regulations); quartz-free or lowquartz minerals for sand under mine loco motives; and relatively insoluble lead com?' pounds for lead oxide in paints and ceramic glazes. A change in the process can sometime? be used to eliminate or control a health hazard. Such change frequently invohes major changes in other parts of the pro duction line, and this control measure is therefore very limited in scope. Examples 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^ joining to eliminat and changing from m to machine and ho] More can be don< to eliminate sources ticularly dusts and f realized. In dusty i: where dust is conti surfaces which appr m collecting on vertica keeping in the fori wet washing, and sc vents the material : into the air. The amount of d tributed to the air the continual redissc material is sometime total dust concentrai be prevented from g readily by constant walls a light color, i tion, and oiling or effective in promoti While good housekc sufficient to control ,'perience has shown in most plants is a dustrial hygiene prc Prevention of Conta MANY industbies produce conside tamination but whic ate attention of only her of workers. If 1 throughout the plai certain times, such many other workers of atmospheric coni gating or isolating those few workers exposed to the haz; protected by means c segregation or bunch tions aids materiall m- plication of local c other control measur The usefulness of vious that examples Blasting in mines a so that the gases anc or dissipated by the turn, sweeping and < other workers are n out foundry casting V?1 ' . r 9j Y December, 1949 d shock result in ineffiless maintenance is good, ustry, maintenance is too the user of the equipa satisfactory procedure, rork should be made the one man or one depart- method of control is the atoxic for toxic materials. ' this method is very limuse of the basic requireaterials are usually selectvever, always receive due e it is both effective and e. Yet, for this very rea- or chemist must guard substitution. It is gen ; any material, be it ever oe handled safely if pro- This feeling has been ce by the experience of plants and the military facturing and loading 1 of less-toxic materials :ounter to quality control lust be recommended with rly since other methods are adequate control of hazof successful substitution rials are the replacement sand in abrasive blasting; 2 grinding and polishing one wheels; nonsilica partar siliceous compounds in sum naphtha or toluol for acquer, ink, and rubber s; Stoddard solvent for ide, in dry cleaning (speusually required to comply ons); quartz-free or low:or sand under mine locoitively insoluble lead comxide in paints and ceramic he process can sometimes nate or control a health iange frequently involves i other parts of the pro ; this control measure is nited in scope. Examples le temperature and speed tions so that the rate of r production is decreased; g, riveting, or otherwise VOL. 10, No. 4 INDUSTRIAL HYGIENE QUARTERLY Page S3 f 9 joining to eliminate soldering operations; and changing from manual batch charging to machine and hopper charging. workers are off the job, and locating the plating or degreasing tanks in separate rooms are common examples. If! More can be done by good housekeeping to eliminate sources of contamination, par ticularly dusts and fumes, than is commonly ' fisf realized. In dusty industries or workrooms where dust is continuously settling on all P 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 Enclosing 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 contamination. 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 tributed to the air of dusty industries by the continual redissemination of the settled material is sometimes more than 50% of the reduced the dust concentration in the screen room by well over 50%. In another in stance a toxic and highly explosive material total dust concentration. Yet this dust can was transferred from 50 pound to five pound be prevented from getting into the air very containers in a complete enclosure. The readily by constant cleaning. Painting the large cans were mounted on a frame in the walls a light color, improving the illumina top of a home-made enclosing device, and tion, and oiling or wetting the floors are after closing the door the contents were effective in promoting good housekeeping. dropped into a hopper by rotating the While good housekeeping alone is seldom handle. Measured quantities were then sufficient to control existing hazards, ex dropped into small cans through a dust- perience has shown that the housekeeping tight corrugated hose. Two slide gates in most plants is a good index of the in served to close andjapen the top and bottom dustrial hygiene program. of the measuring device. Hence by closing Prevention of Contaminant Dispersion . A/fANY industries have operations which ' 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 i of atmospheric contamination. Bv searer gating or isolating these operations, only those few workers engaged therewill he exposed to the hazard, and they may be protected by means of respirators. Also the , segregation or bunching of hazardous onerations aids materially in the effective ap plication of local exhaust ventilation or other control measures. : The usefulness of this measure is so ob1 vious that examples are scarcely needed. Blasting in mines at the end of the shift 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 as 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. so that the gases and dusts will have settled Wetting dust with water or other liquids 1 : or dissipated by the time the workers re is probably the oldest method of control. turn, sweeping and cleaning at night when It was practiced in the pottery industry in other workers are not on the job, shaking Great Britain as early as 1713. Wet drill out foundry castings at night when most ing and water sprays have been widely em- Page 84 INDUSTRIAL HYGIENE QUARTERLY December, 19$ ployed in mining operations in recent years. The use of water sprays in quarrying operations also has been reported recently. Substantial reductions in the dust concen tration have been reported as wet-grinding the area of contaminant escape of such direction and magnitude as to carry the highly contaminated air into the exhaust hood which is located as close as possible 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 Hood shape and location 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-i 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 flows away, and collects also as water drop the selection of collectors and exhausters ar# lets on the walls from where it is readily complete studies in themselves and will nof, redispersed. Even though wetting of the be covered here. dust must be recommended with discretion, Examples of the satisfactory use of loca it has been found an effective dust control exhaust systems are numerous. Some ar aid in rock drilling, blasting, crushing, 'welding; granite surfacing; pickling and' screening, materials transfer, foundry plating tanks; wood working equipment;- shakeout, core knockout, and abrasive blast grinders; buffers and polishers; and spray1 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 yentiln.tinn jg prnhghlv 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 instance equate design are so poorly understood that ductwork require periodic cleaning to ob-'. a large percentage of the installations made tain satisfactory operation. Bent. hoods' in recent years are unsatisfactory or in and leaky 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 nfeed 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 field. 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 good control equipment covered adequately elsewhere.1'2'3 Suffice it and then, either through complacency of 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. of 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 installatior This is done by producing air currents in for the control of atmospheric pollution arfe- December, 1949 4 t . Vol. 10, No. 4 INDUSTRIAL HYGIENE QUARTERLY Page 85 iminant escape of such jnitude as to carry the ed air into the exhaust ited as close as possible source of contamination, the hood encloses the ation, or the closer it can source of contamination, De the required exhaust 5 contaminant effectively, ication are of the utmost (serve considerable study ig on the part of the de n to the hood, a local exides piping or ductwork, lally a centrifugal fan), ector. The contaminated ough the piping to the filtered air is then disutside of the exhauster, e hood and piping, and lectors and exhausters are n themselves and will not i satisfactory use of local are numerous. Some are surfacing; pickling and ood working equipment; and polishers; and spray types of equipment, that mtrol health hazards they kecking and maintenance. ded with other equipment nd maintenance schedule, .ns and in many instances periodic cleaning to oboperation. Bent hoods naged ductwork and enrepaired promptly. Blast ers, if used, should be , but even then they need : to see that the setting is workers and that the bal l is not thereby disturbed, ltly management invests I in good control equipment through complacency or ling proceeds to forget all id with a case or epidemic Inesses. The answer, and protect their investment, ng and maintenance just 'oduction equipment. measures or installations atmospheric pollution are iuoipruoL. much aepenas on the attitude of the worker. A eoonerative. interested. and well-trained worker can accomplish much with any control equipment, whereas tne lnauterent, lackadaisical, untrained worker produces the maximal amount of atmospheric contamination with any con- The solution lies in the education of the worker. 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 first 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 atfflflsftfleihc contaminants. However, it is considerably IH5TO important* in eliminating sources ol contamination as was discussed previously in that connection" Protecting the Worker A/TOST industrial machinery or equipment which produces or releases harmful contaminants can be engineered either in the original design or by alteration of ex isting 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 be 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 above the process; and locating a fan diagonally 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 he 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, may 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.1'4'5 Respiratory protective devices have a dis tinct place in the field 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 1 Page 86 INDUSTRIAL HYGIENE QUARTERLY December, 19W sponsibility it is to select them and super vise their use and care. Each and everyone assigned this responsibility should study some of the literature on this subject.1'6'7'8 Examples of places where respirators may be used satisfactorily are spray painting; abrasive blasting; cutting metal coated 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 idea 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 as far from the point of operation as possible, or out of the line of throw or movement of the contaminant. . Examples of Results^ Obtained JN conclusion, I should like to cite one x 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/m3 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/m3. 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 5 mg/m3. In this instance, the incidence of illness had been reduced from about 30% to 2% by reducing the atmospheric dust content from 150 mg/m3 to 5 mg/m3.9 An effective industrial hygiene program was launched in the government-owned ex plosives manufacturing and loading plants late in 1942--about one year after Pearl 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/m3 in April 1943 and 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/m3 and the corresponding in cidence of TNT cases was 1, 80, and 85.10 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. Brandt, Allen D.: "Industrial Health Engineering. John Wiley and Sons, Inc., New York, 1947. 2. Alden, John L.: Design of Industrial Exhaust Systems. Industrial Press, New York, 1939. 3. Drinker, F., and Hatch, T. F.: Industrial Dust. McGraw-Hill Book Company, New York, 1936. 4. Hemeon, W. C. LAir Dilution in Industrial Ventilation. Heating and Ventilating, 37:39 (November) 1940; 37:42 (December) 1940; 38:40 (February) 1941; and 38:71 (March) 1941. 5. Heating, Ventilating, and Air Conditioning Guide, 26th Edition. American Society of Heating and Ven tilating Engineers, New York, 1948. 6. The Use and Care of Respirators, Preventive En gineering Series, Bulletin 2, Part 2, Industrial Hygiene Foundation of America, Inc., Pittsburgh, 1938. 7. Schrenk, H. H., and Pearce, S. J.: Selection, Use, and Maintenance of Respiratory Protective Devices. In formation Circular, 7236 (April) 1943, U.S. Bureau of Mines, Washington, D.C., 1941. 8. Protecting Plant Manager, Practical Points on In dustrial Sanitation and Hygiene. Department of Labor, Division of Labor Standards Special Bulletin 3, Govern ment Printing Office, Washington, D.C., 1941. 9. Mavrogordato, A.: Contributions to the Study of Miners' Phthisis. Publ. S. Airican Inst. Med. Res., Jo hannesburg, 1926. 10. McConnell, W. J., et al: Occupational Diseases in Government-Owned Ordnance Explosive Plants. Occupa- tional Medicine, 1:551 (June) 1946. Ventilation Engineer, Division of Industrial Health, State Department of Health, Lansing, Michigan You have heard lectures and discussions that the concentrations of the atmospheric mostly on the general principles and contaminants are toxic rather than a seri theories involved in the control of air cono-us nuisance, we have found that most in tanainants. In my discussion, I am going to dustries will consider a practical approach stress the other side--the practical applica in eliminating the air pollution problem tion of these principles and theories. A gov arising from their plant. One of the most ernment agency such as ours is in an ex successful methods we have of working out tremely favorable position to make this a satisfactory solution is to get both the type of presentation because we are direct citizens and the management of the indus ly involved with the pollution problem from try together. In this manner, management the time the initial complaint is received realizes the extent of the nuisance, and the to the time when a study is conducted to people of the community realize the prac evaluate the collection equipment installed. tical difficulties facing the management in Whether the contaminant be fly ash, eliminating it. alpha-napthoquinone, or odors from a near Investigations by the Michigan Depart by rendering plant or millpond, we are even ment of Health have turned up a wide va tually called in to investigate. These inves riety of contaminants (Fig. 1), and some tigations can be initiated by the irate house are very difficult to control. In some in- wife who is disturbed by sulphide odors, or the plant manager who maintains that dust from a nearby abrasive reclaiming plant is A TMOSPHERtC CONTAMINANT ASpfJOe^ 0--1--0M9--00 ' NUMBER OF PLANTS INVOLVED* o t t s a 5 e re 9 c x e <*s * e ruining the bearings in ,his expensive ma chinery. Baking wm (point) odors Bromine Buffing dost Actual legal authority on these problems rests squarely with local governmental Co/aum oxide Catvn tydroxide Cement dust units. In the Michigan Department of Health, we can act in an advisory capacity Cotton dust DDT dust Ftyosh only. Many of the air pollution cases we are asked to investigate come from local Foundry dust Fluorides Gmretdust governments who do not have the techni cians and the equipment to work on the Hydrogen Sutfide iron dust iron oxide cases or because the local officials are re luctant to act, fearing that the company will suspend operation in their town. They Lendoxide andfumes Mkpondodors MonocNorbenrene Naphthalenes Oxde of ntrvgen would rather have the state take the brunt of this burden. In all cases, we make every Pant trust Phosphde fertilizer dusts PhthoUc antydride effort to be of assistance to the local autho rities, to the people of the community, and Ptahng ptont odors Rendering pkmt odors Rockwool dust to the industry involved. The year-to-year increase in the number Rubber (burnt) odor Rubbish burning Sktca dust of requests received for service on air pol Smoke Sohents lution problems, from six in 1940 to nearly Sulphur dioxide a hundred in 1949, indicates the prominence of air pollution in our everyday life. Many of the plants at fault are probably not of sufficient size to afford to spend a great Sulphuric acid Vohnc (iso) odd Welding furies Wood dust Zinc oxide Miscellaneous deal of money on contaminant control. De spite the fact that we are not backed by a *$ome plants responsible for sarerat conkaminards. specific statute and are rarely able to show Fig. I. VOL. 11, NO. 1 INDUSTRIAL HYGIENE QUARTERLY Page 65 stances, a satisfactory method of collection is still to be found, and we welcome any suggestions you may have. There is, of course, no perfect method of collection for any contaminant. When faced with the problem of collec-> tion, there are four things to be considered: first, the selection of the method or collector which is suitable for the job; second, the initial cost of the equipment and installa tion--and whether this cost is justifiable considering the extent of the nuisance; third, the maintenance on the equipment (a big item with many collectors), and whether it is within an acceptable range or requires frequent expensive replacements and high maintenance costs; and fourth, whether dis posal of the collected material is difficult or costly. The following case histories demon strate that these considerations are ex tremely important factors in every air pol lution problem. j i"C**ase No. I A ir pollution problems involving odors are often extremely difficult to cope with. One of the biggest problems is the elimina tion of odors. Our sense of smell is often an excellent method of chemical analysis; its delicacy is often greater than any chem ical analysis we can run in the laboratory. There are many materials which we can smell long before the concentrations are high enough to enable us to run a chemical determination. Since odors may be due to these minute concentrations of gases and particulate matter, they are extremely hard and often almost impossible to eliminate from the air. . Inasmuch as rendering operations are practically a necessity in all good-sized communities, this case will serve to sum marize some of the difficulties we have had with them in several of the cities of the state. The complaints concerned obnoxious stenches which permeated the residential areas near the rendering plant. Upon inves tigation it was observed that the operating techniques in most of the departments were unsatisfactory, and that a good deal of the odor could be eliminated by improved sani tation and work methods. Several recom mendations concerning housekeeping and sanitation procedures were made, including the following: 1. That the sanitation and housekeeping be well planned to include all operations, and that one or two individuals be delegat ed the responsibility of carrying out the program. 2. That an ample supply of steam and hot water be provided for cleaning and rinsing purposes. 3. That the building receive a thorough initial cleaning, and that certain structural changes be made, such as re-surfacing floors with an impervious material. 4. That a central wash station be pro vided for all containers and a storage space provided for all clean containers. 5. That materials coming into the plant which were not to be used immediately be stored in properly enclosed containers. 6. That a driveway be constructed of im pervious material which could be flushed off. In addition, local exhaust ventilation for certain operations was recommended. Shortly after our study of the operations, a group of citizens and the city filed a suit asking that an injunction be issued to re strain the company from polluting the at mosphere with offensive odors. In court, the company stated that in an effort to abate the stenches and smells emanating from the plant, they were acting upon our recom mendations. In addition to our recommen dations, they had installed two modern cookers; a modernized, used cooker; a new septic tank; a condenser water tank; an ad ditional sewer, and an ozone generator. They had enclosed the elevator shaft with steel, entirely segregating it; purchased an additional boiler, and agreed to construct a new driveway. The driveway was to be of concrete or other comparable material, and was to be made non-absorbent. The court found that the nuisance did exist and had existed for a long time, and stated that the plaintiffs were entitled to the relief sought by them. The company was ordered to wholly abate the nuisance within 30 days; with additional time, if necessary, to com plete the installation of the new boiler. The complaints of the residents, the legal action taken and the efforts made by the company to eliminate the odors have helped a great deal to minimize the amount of atmospheric pollution taking place. Since the completion of the previously mentioned work, there have been no fur ther complaints to the court. It is our opin ion that the ozone generators mask the Page 66 INDUSTRIAL HYGIENE QUARTERLY March, 1950 Fi*. 2. odors for the plant employees but do not affect the odors emanating from the plant. It is obvious that effective sanitation and housekeeping programs have to be main tained if the odors from rendering plants are to be minimized. Case No. 2 tf- "NJOW let us consider a plant producing ' phthalic anhydride. I have selected this plant because it is a good illustration of practically all the four considerations in selecting a collector which I have outlined. The plant is large and centrally located in a residential district. The neighborhood is contaminated by a strong pungent odor as well as small quantities of particulate matter. The problem of collecting the an noying stack effluents which are given off by 14 stacks is difficult, and is further ham pered by the pyroligenous acids which are produced and can result in explosions and fires. Correspondence with manufacturers of phthalic anhydride and with industrial hygiene units in this country indicates that the same difficulties of collection exist everywhere. In an attempt to solve these problems, a committee was formed of members of the chemical engineering department of a near by university, outside engineering consult ants, representatives of the company, and several of our engineers. The first attempt to control the contaminant was with the use of steam jets in the tall stacks with the thought that the addition of steam might result in satisfactory collection. It was found that the steam did not help and, in fact, increased the nuisance to the neigh borhood. Following this, a standard com mercial wet collector was tried and also found unsatisfactory. While this was being done, the proper ties of the material were studied and it was^und that the contaminant had a tend ency to seed and adhere to the ductwork or any other material it contacted. An experi mental, box-like duct (Fig. 2) was built. The thought was that a large portion of the material going through the tortuous passage would seed sufficiently and adhere Vol. 11, No. 1 INDUSTRIAL HYGIENE QUARTERLY Page 67 to the baffles, thereby minimizing the amount of objectionable material given off. Although large amounts of the material were collected, the odor did not seem to be lessened appreciably. Following this failure at collection, an attempt was made to con dense the vapors on a water-cooled, stain less steel wall. However, it was found that the material would not adhere to the wet surface, nor was enough vapor condensed to solve the problem. A good many things were tried with this box, such as using orifices to increase the velocity in order to impinge the material on a plate. As shown by Figs. 3, 4 and 5, this method removed much of the material but, as previously brought out, did not decrease the odor. Following months of work on these col lectors, a special high pressure fog unit was installed and appeared to work unusu ally well. However, much water was re quired and it was found that the water com ing from the firlt section of the collector had a pH of slightly over two and the cost of neutralizing this to allow for disposal was prohibitive. By this time, sufficient work had been carried on in experimental laboratories to lead us to believe that the strong odor was caused by a by-product, alpha-naphthoqui none, and that concentrations as low as 1 ppm would be objectionable. Some time after this fog unit was dis mantled, the company was approached by two men who had developed a catalyst for burning organic matter from stack effluents. They had had very good success with this catalyst in eliminating odors from wire bak ing ovens and, judging from previous in stallations, the system would be reasonably inexpensive to install. Fig. 6 shows the type of system that had been used on the gases from the baking oven. The company de cided to try an experimental unit, and a system which might possibly work was de signed. Experiments in the laboratory with the catalyst showed that a high temperature would be required. Subsequent work with the unit proved that 400 C was the mini mum temperature at which the catalyst would operate. Previous trials had proved that the ducts would clog unless arrange ments were made to keep them open, and so a counter-flow system was designed to keep the ducts warm with the thought that the heat from the catalyst would hold the ma terial in the vapor state. An experimental unit was installed, using a gas flame to increase the air temperature sufficiently for operation of the catalyst. It was found that a good deal of work was Y Page 68 INDUSTRIAL HYGIENE QUARTERLY March, 1950 necessary to achieve an even temperature and even distribution of air through these catalysts. When this was accomplished and all of the leaks were finally stopped (this was very difficult because of the high ex perimental temperatures), the system oper ated quite satisfactorily. At the present time, work is going for ward on the design of a unit which can be installed to control the contaminant from each of the 14 stacks. Fig. 7 gives an idea of the size and complexity of the piece of apparatus to eliminate odors from this plant in comparison to the very simple catalytic arrangement used in another plant with a different material. Regarding this air pollution problem, I should like to emphasize the desire on the part of the offending company to find a solu tion of the problem which will be economi cal and satisfactory to the residents of the community. Practically all reasonable ap proaches were tried. One method appeared to be satisfactory, but this produced a water pollution problem almost as great as the air pollution problem. I should also like to bring out here that one of our greatest difficulties results from the fact that it is almost impossible to use a system developed for one operation on another operation in a different plant with out many major and often expensive changes. Case No. 3 A common atmospheric contaminant is fly ash. Practically every city and village is confronted with this problem. I have se lected one fly ash problem from our files be cause it brings out a point that may be of interest. *s The plant is situated in a community of 9000 people and employs about 120 workers. When the plant was built for war purposes the citizens were elated because it gave a big industrial boost to the community. Now there are some citizens who wonder whether their elation was not somewhat prematurei Throughout the war, the plant worked on a round-the-clock basis with no complaints from the people of the community, but after it was taken over by a private company, the local city officials began receiving com plaints. The principal complaint was due to fly ash. The people of the community were of the opinion that there had been a col lector used when the plant was operated for the government and also that the power house was operated more efficiently and gave off no fly ash. In making our investigation, we found several reasons for the complaints. One was that the plant had been built along the water's edge to take advantage of dock fa cilities and, unfortunately, the major part of the city was on a bluff overlooking the plant. Most of the houses of the community are actually higher than the top of the stack of the plant. Like many war plants, this one was designed for a specific oper ation which utilized the flue gases for a car bonization process. The flue gases required scrubbing which, while consuming a great deal of power, was justified by the fact that the gases would be re-used. In peace time operations, the carbonization process could not be used and the company could not economically justify the use of such a scrubber. Contrary to the belief of. some citizens, the power plant is being operated more efficiently now than ever before. .Fly ash collectors are in use, but, like all collec tors, they are not 100% effective, and some escaping fly ash settles on the residences nearby. At the present time, an addition to the stack is being planned and will undoubted ly be built when weather permits. It will be interesting to see whether the addition of this extra height will eliminate the com plaints, or will simply deposit the fly ash on residences a little farther out. It appears to us that proper installation of electro static precipitation might be more justifi able than a gamble on high stacks for dilu tion purposes. Case No. 4 'The collection of air contaminants in the manufacture of calcium carbide is al most as important a problem as the manu facture of carbide itself. In our investiga tions into the manufacture of carbide by one large concern, we found that this was a universal problem among the carbide manufacturers. While much work has been done and many engineering organizations have attempted to solve this problem, we believe that contaminant control will not be satisfactory with present collecting devices unless manufacturing procedures are im proved. VOL. 11, No. 1 INDUSTRIAL HYGIENE QUARTERLY Page 69 Calcium carbide is manufactured in the electric furnace by fusing a mixture of lime and coke. The yield from this reaction varies a great deal depending upon the quality of the coal and lime used. The gases and much of the particulate residue from the reac tion are removed from the electric furnace by exhaust fans. The particulate matter taken off from this reaction can run over 100 tons per day. Now if the efficiency of a collector installed to remove this particu late matter from the air runs as high as 96%--and this figure would be high for any collector--it would leave four tons of this material to be thrown into the open air and over the community. If you disperse this four tons of residue into the atmosphere, you can understand that it would do a fair ly good job in covering the community in 24 hours. This is the actual problem in con-' trolling air pollution created by a carbide plant. While this air pollution is not a health hazard but a nuisance, it reaches extremely annoying proportions. It is par ticularly damaging to the painted surfaces of houses and, in some instances, it ruins the finish on automobiles, furniture, etc. ^ In our work with this particular plant, we collected air samples throughout the plant and in the surrounding neighborhood. The results of the study are shown in Fig. 8. The management, in attempting to alle viate this air pollution, had installed Cott rell precipitators in the stack. The reasonsfor selecting electrostatic precipitation as a means of collection were: first, experience has shown that electrostatic precipitation, in most cases, works satisfactorily on par ticulate matter, and, second, the company owned a share of the water rights and pro duced its own power in that community. On our investigation, we found that there were several limiting factors in attaining complete success in the collection of the ma terial. We discovered that the dust-laden flue gases were cooled and moistened by a bank of water sprays before entering the precipi tator units. The efficiency of the precipita tor varied considerably, owing to the fluc tuation in temperature and humidity of the flue gases. Another factor controlling the success of these precipitators was the com pany's limited water rights. While what power they produced was cheap, production required the greater portion and the re- iEIKB Ait tce.tlaa Zhut Count Curt tft. C(0B)2. ftC*M), NUMOB Tartlelvt Ife/IOM? Hf/loO In ~ fmr CuMc feet of ilr ef wlr of Air 5>nI St root So. 1 0.126 5.5 0.74 1).% St root So. 2 0.415 7.4 l.U U.O Pttot An.lrooo 1- --Sottlod ftnt In Want that frog Mait Stack bolow Cato^li Wat or too* on Ignition (crtsn) Total oUlea e. - e*(o02 To ToS 0.8? 24.lft 1.7ft 67.1ft 7.2ft Wator Loot on ICnltlon (carton) Total olllea C.m C(0H). TO ! ToS l.lft M.lft 1.9ft 49.6ft 7.T< location Cottrell Sot So. I inli So. 7 Tot*) Weight Dry Dnn% Omlno nor CuMc root of ai. Average 0.093 0.102 0.055 0.107 0.029 0.161 0.122 0.0956 tatod velrao 150,000 CM 0.0956 1W.OOO x 60 n 24 2.950 pound dual nor day fros lot 7.000 fc, i- Sotoj So data far Sot So. 2 tot rooolto ohoold to e-sm.ratlo to Cottroll Sot So. 1 Fig. 8. Carbide Chemical Manufacture mainder was insufficient for constant suc cessful precipitator operation. We recommended that the company in stall automatic current and voltage controls; that local exhaust ventilation at the fur naces be improved, and that other collectors be installed between each furnace and the precipitator. But every recommendation re quiring an increase in the amount of power used, whether for wet collection or addition al electrical precipitation, brought the re ply that the power consumption could not be increased at the time and that all available power was necessary to produce an amount of carbide to justify the existence of the _glant. In addition to the various aspects of the problem just mentioned, the fact that the company is the largest single plant in the area, employing about 500 people makes its existence necessary if economic stability is to be maintained in the city. While it might be possible for the residents to take legal action against the company, in view of the important place the industry occupies in jthe community it is doubtful if such action is wise. The situation I have just outlined is not unusual. Every collector installation has its limiting factors, and you can determine from the account I have given that these can be extremely perplexing. Page 70 INDUSTRIAL HYGIENE QUARTERLY March, 1950 Fig. 9. Case No. 5 J7R0M inquiries we have received from all over the country, the control of air con taminants from chemical fertilizer plants is of interest to many engineers and com munities. For that reason, I have selected a chemical fertilizer plant in which I be lieve we have been quite successful. The usual air contaminant from the phosphate fertilizer plant is due to the dust and vapors given off during the mixing of sulfuric acid with calcium phosphate, resulting in exces sive pollution of the atmosphere with phos phate, fluoride and sulphate dust and silicic acid. The equipment used by the company for controlling the materials given off during the mixing consisted of a wooden paddle type blower which sucked the gases and solid materials from the mixing process up a tall wooden scrubbing tower. Several hap hazardly-placed water sprays were used in an attempt to effect water scrubbing and collections of the materials given off. As a result of our investigation, the com pany, in attempting to determine what equipment would be suitable for complete collection of the contaminants, had highpressure fog spray equipment installed and requested that we conduct test runs for de termining its effectiveness. The installation was very effective and the results of our tests are shown in Figs. 9 and 10. Visual observance of the stack during operation of the process with the high-pressure fog spray collection equipment both on and off indicated satisfactory collection as shown. After a period of use during which the fog spray equipment was satisfactory, the Fig. 10. company gradually cut down on the water pressure used and finally reached the point where it was considered wise to discontinue the use of a high-pressure pump and install in its place an ordinary pump- capable of delivering pressure up to 120 pounds per square inch. No further complaints about the mixing process have been received. How ever, we recently received complaints con cerning a dusty material which was coiltaminating the neighborhood, and upon in vestigation we found that a great deal of dust was being liberated by the natural draft ventilators during the mixing of a high nitrate composition fertilizer. It was suggested to the company that bag type collectors be used for collecting this dust. No follow-up investigation has been made, and no additional information is available. It appeared from our work on this plant that the fog spray method of collection is very well adapted for fertilizer plants of this type, providing, of course, the effluent can be satisfactorily disposed of. Another fertilizer plant which has been constructed since, with fog filters installed, has proved satisfactory. Case No. 6 'T'he next case is that of a manufacturer of asphaltic base sound-deadening coat ings. The contaminant involved is once again odors. The plant is located in a city of approximately 2400, and employs about 85 people. Neighborhood residents com plained of the foul-smelling stack effluent given off during the processing of flux oils. The process, known in the trade as "blow ing asphalt," consists of blowing air Vol. 11, No. 1 INDUSTRIAL HYGIENE QUARTERLY Page 71 through molten asphaltic flux oil which is maintained at a temperature of about 500F. During the process, certain volatile com pounds are formed and the lighter por tions of the flux oil itself may be distilled off, owing to the elevated temperature. Requests for information concerning con trol of the "blowing" process were answered by two large oil companies who supply the company in question with their flux oils. One suggested the use of an electrostatic precipitator or "routing the vapors through a furnace where all hydrocarbon particles are burned, giving off a normal stack gas." The other suggested condensing the vapors into a liquid or washing them with water "by which means the greater part of the more volatile portions are knocked down in the form of a liquid." A third inquiry to the author of an article on petroleum base protective coatings brought the reply that he knew of no completely successful method of controlling the stack effluent but thought that it could be successfully collected if passed through "at least two stages of water spray." The company did not believe that it could consider the costly electrostatic precipitator installation and, because of the highly in flammable nature of the process, ruled out furnace burning of the stack gases. At our suggestion it was decided to try a high- pressure water spray process, and a near by manufacturer provided the company with a pilot model so that test runs could be made. Although it could easily be seen from the draining water effluent that much oily type material was being collected, the fog spray process did not completely eliminate the foul-smelling white smoky material which went through the collector and out of the stacks. Fig. H is a data sheet cover ing our fog spray test findings. Although additional test runs with a larger capacity water spray unit might have proved more effective, no further work has been carried out. The problem of collecting the contami nant remains unsolved, but the company plans to continue the search for a suitable collection apparatus and has informed the city council that it will shut down the blow ing operations whenever the prevailing winds result in contamination of the neigh borhood. tyXUBK A. hi hr*} ClltMtlN *f tfnM fM flu Ml llnllfflMN* 1. . tea fc. 1 to mhIm n, fall air flaw ftw >t. * 12 MftlH m. pat. taa air flaw hik. 1 30 MtilN M. e*4Mi air flaw 7*9 Callaotar Oallaator Alrflaw Mrflavi tea n mi VatMr tala* Oatlat talat Oatlat 155-h. (U. ?.r Tank Tawp. flaw lata M. Ucfc) (?> Qal./Mla. Imp. (T) (oft) (fl) 1 km 530 a.o 050 *30 700 1*2 2 050 5*0 10.0 050 90 *05 at 3 *3* 5*0 21.0 -- . - *05 at t. Gallaatlaa tfrielaulaa Iwi Ba. 1 It 2A 1A 9 folat lightly Mid lightly acid lightly Mid lightly Mid lightly eld lightly Mid Mill _ MtfBl aaatral antral lightly Mid ii*tiy Mid hiad * (Oraaa par ctt. ft.) 0.09 1.M l.lfl 0.90 O.Oh 1.99 Oatlat (naa tar n. ft.) _ 0.17 0.17 0.13 0.20 0.20 Fig. II. Asphaltic Bass Coatings Xffletaaar af . Callaatlaa <*> ___ n M AO 5$ 7 Case No. 7 YWE WERE requested by a city health de partment to investigate numerous com plaints concerning hydrogen sulphide odors. Stack samples collected during the mixing of sulphur with hot purified lard oil indi cated high concentrations of hydrogen sul phide. The gases emanating from the mixing process were passed through beds of lime stone and water in an attempt to collect the hydrogen sulphide. Our study indicated that the collection procedure was ineffective. Knowing of no process which would success fully eliminate the hydrogen sulphide, the company had installed a high-pressure fog spray collection unit so that test runs could be made. The results of our study on this unit are shown in Fig. 12. Ordinary water was used as the spray medium, and the col lection of the hydrogen sulphide was un successful. In an effort to decrease the amount of hy drogen sulphide given off, the company de creased the reaction temperature and in creased the reaction time. No follow-up study has been conducted since this modi fication of the manufacturing process, but we plan to evaluate the new procedure as soon as possible. At the time of the test runs using the fog spray collector, it was suggested that an al kali solution in place of plain water also be Page 72 INDUSTRIAL HYGIENE QUARTERLY March, 1950 mm sap A. Jo* epray lnetalletlon for collecting nixing trade affluent ceeet 1. H28 ecneentmtlone (Inlet end Outlet) Staple Wo. 1 2 3 HjS Co&centratLona (ailllcnaa par cubic feet) Inlet Outlet 166 140 *90 415 800 775 Collection efficiency () 24.6 15.3 3.1 2, Air qeTenent date Duct iieseter (laehee) THiet *r*n (equare feet) Air vateelty (feet rer nitrate) Air wuiimt (cubic feet per nitrate) Inlet 6 0.196 2865 562 Outlet 7 0.267 2110 ' Vettt Collecting aedlmt water Fig. 12. Oil and Grease Company used for testing purposes, but such a run was not made. Case No. 8 ^OMPLAINTS were received from citizens living near a chemical company engaged in the manufacture of pharmaceuticals. During part of the processing, atmospheric pollution with bromine took place and caused disturbance throughout the neigh borhood. The complaint was investigated and it was learned that the pollution dis turbance resulted during the warm weather months only. In order to eliminate the annoyance, the company agreed to compound the materials involving the use of bromine during the winter months. No further com plaints have been received. Case No. 9 ^OMPLAINTS were received from the people ' residing near a small chemical plant en gaged in the manufacture of iso-valeric acid. It was learned that the company was considering a new location but its capital was limited. Unable to relocate because of lack of funds, the company was forced to abandon the contract for the manufacture of iso-valeric acid. Conclusion WfE believe these case histories may serve to bring out the importance of the four considerations previously men tioned; namely, the selection of a suitable method or collector, cost of the equipment and installation, maintenance of the equip ment, and disposal of the collected material. They also show that there is no cut-anddried method of controlling the contam inants involved in the term air pollution. At the present time it is our belief that, in many cases similar to the phthalic plant mentioned, even the plant operators do not know what their problem is. We hear a good deal about smoke and fly ash elimina tion, possibly because we know more about how to eliminate them than most of the other contaminants found. Obviously, the lack of knowledge is the biggest handicap in the control of odors.