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Industrial Dusts WEDNESDAY MORNING SESSION October 13, 1937 The meeting was railed to order by Chair man A. .S. Regula, Executive Secretary, In dustrial Relations Counselors, Inc., New York City, and Vice-President for Engineer ing, National Safety Council, who intro duced (lie speakers. What Industrial Dusts Are Harmful? Why? By SENIOR SURGEON R. R. SAYERS Chief, Division of Industrial Hygiene, U. S. Public Health Service While dusts exist everywhere in the at mosphere, it has been recognized for cen turies that workers in certain dusty occupations are less healthy than those not to exposed. The number of persons ex posed in dusty occupations comprises one of the largest industrial groups. The occu pational diseases of workers in dusty at mospheres have been found to be due to entrance of dust into the system by inhala tion, by ingestion, by direct absorption through the skin, by irritation of the skin, or by a combination of the foregoing. The suspensions of particulate matter in air have been broadly termed dusts, fumes, id smokes. Such a classification is neces sarily arbitrary, since the line of demarca tion between them is not very sharp, and the chief differentiation is based on the size si the particles. Investigations by the Pub lic Health Service in dusty industries' re scaled that about 70 per cent of the dust particles examined were between 1 and 3 microns in size, only about 20 per cent were bs than 1 micron, and the median siz.e was j IJ microns. Industrial dusts are mainly less than 10 microns in size. However, fibrous dusts in the air, such as asbestos, have been found to contain particles as large as 200<0 mircons in the greatest diameter. While, generally speaking, according to Collis, dusts are more injurious as their diemieal composition differs from that of the human body, or from the elements of thich the body is normally composed,' it is difficult to establish a comprehensive definition for toxic dusts. Sollmann,' after analysis of various definitions for poison, felt that it is very difficult to give a definition which will not be ambiguous in some cases, but believed that the following covers most of the points which must be considered in classing a substance as such "A poison is any substance which, act ing directly through its inherent chemic properties, and by its ordinary action, is capable of destroying life, or of seriously endangering health, when it is applied to the body, externally, or in moderate doses (to SO Gm.) internally." Some dusts are known to be poisonous, while others, in the concentrations usually encountered, are comparatively harmless. However, it may be stated that breathing dust in high concentration is not desirable. According to Fairhatl, the damage arising from the inhalation of toxic dust may be either local or remote, and depends upon whether the material is a protoplasmic poi son, whether it is caustic in reaction, or whether it is absorbed into the blood stream and carried to other centers which are in turn affected,4 It is now well established that exposure to certain kinds of dusts, such as those con taining considerable quantities of free silica, has increased the morbidity and mortality rate from respiratory diseases; while me tallic dusts, such as lead and its compounds. 85 86 Twenty-sixth National Safely Congress Industrial Dusls 87 have been associated with general systemic pulmonary tuberculosis. The second type poisoning.' Dusts may be swallowed with of reaction is caused by toxic dusts like lead, saliva, water, or food, and direct poisoning cadmium, and radium. A third type of mal has been traced to absorption by this ady follows the inhalation of finely divided method; other dusts may act as irritants and metallic fume particles such as zinc oxide, produce affections of the skin, irritate mu and is known as metal fume fever. The cous membranes of nose, eyes and throat, fourth reaction, allergic in rliarsclcr, is often causing inflammatory diseases of caused by breathing organic dusts such as these organs.' pollen and certain types of pulverized wood Some inorganic dusts are able to pene trate the deep lung tissues and are sufficiently insoluble to be retained there. Some of these may Ire active in the human and flour. In all four cases the sole cause of the disability may be dust inhalation, but the reactions from toxic dusts result from swallowing as well as from inhalation.'' tissues, causing definite and permanent in For various reasons it is difficult to set jury, while others arc inert and may be tip an absolute classification for dusts. retained for years, apparently without seri Opinion is rapidly changing regarding so- ous damage; some are gradually absorbed called inert or harmless dusts and further without causing pathological changes.' investigation may prove some of them to be ATI inhaled particles are soluble, at least to a small extent. If harmless, cell activity is stimulated so that phagocytes remove the dust. If the solute is toxic, the viability of the phagocyte is affected and an ineffective accumulation results. At the same time, further solute may diffuse into neighboring tissues, setting up an irritation and subse quent fibrosis. The nature as well as the injurious. Some dusts may have both a toxic and an irritant action; while on the other hand, the poisoning resulting from ex posure to a dust may be the combined effect of more than one mode of entrance into the body. However, the following classification of dusts, according to physical character istics and physiological effect, is used for convenience. solubility of the solute is an important fac tor, but of two substances of approximately equal toxicity, the more soluble form causes the greater damage. However, sub stances of such low solubility as silica may ultimately produce extensive injury.' Kettle has stated that harmful dusts, if inhaled into the lungs, may activate a latent tuberculous infection; they may exaggerate an active tuberculous lesion or a coincident infection. If sufficient quantities of a harm less dust are inhaled, some of it remains in the lungs and causes a mild degree of fibro sis merely through mechanical irritation, but such fibrosis is never sufficient to inter fere with the function of the lung.' Some writers state that while the influ ence of nonpoisonous dusts on health is a debatable subject, abnormally high death rates from bronchitis and pneumonia are sometimes attributed to chronic exposure to nontoxic dusts. Large amounts of dust are occasionally found in supposedly normal I. Organic Dusts Organic dusts arc those which contain carbon, and were originally supposed tn come from organized substances derived from animal or plant life. Living dusts come under this classification, and are thought to be of the same order of size as industrial dusts, with which they arc fre quently associated. IJactcria are usually be tween 0.5 and 3 microns, except in a few cases, such as the anthrax bacillus, which ranges from I to 1.25 micron in breadth and 4.5 to 10 microns in length and 10 or 1? microns in diameter. However, it is possi ble that the larger and heavier varieties, like the larger ami heavier dust particles, settle due to gravity, and do not remain suspended in the air. Many thousands of organic, substances, carbon-containing, are made synthetically by chemical processta, such as dyestuffs explosives, etc. lungs, at autopsy.* According to Drinker, there arc four dif ferent types of reaction produced in man by the inhalation of dust. The first and most I. NONLIVING ORGANIC DUSTS. As the name implies, these are comprised of nonviable particles, which may or may not be inherently toxic or irritant, hut which nevertheless produce untoward effects in the human organism. "Allergic" dusts, or those to which only certain persons are or mi? become hypersensitive, with resulting asthma, rhinitis, or other disturbances, are included in this classification. a. Toxic and/or Irritant. Toxic or irritant dusts are all organic dusts which produce untoward symptoms, either systemic or local. Those producing local symptoms are usually described as irritant; those produc ing general or systemic symptoms are termed toxic. A dust may he both toxic and irritant. In reported cases of Injury or cleath fol lowing inhalation of dust from organic com pounds, among the chief offenders arc paranitraniline, the dinitrobenzenes, chtorodinitrobenzenes, trinitrophenol, and nitronaplithalene. Eye damage due to inflamma tion of the cornea has occurred among workers exposed to methyl violet dust. The dust from paraphenylene diamine derivatives is particularly irritating and dangerous, causing not only a severe form of derma titis where the dust comes in contact with the skin, but also producing acute inflamma tion of the mucous membrane of the respiratory passages.' Toxic dusts may be Itenerated during the handling of powdered dyes and in preliminary dyeing operations, particularly the hydro-extractor process, where particles are disseminated in all di rections," Coal tar and indigo dyes are substances most frequently used. Cases of amblyopia have been reported from exposure to inhalation of tobacco dost,'1 It lias been found that inhaled to bacco dust exerts a nicotine action on the organism fifteen times greater than that produced by the same quantity of smoked tobacco with an equal nicotine content." dust, or powder forni of the preparation, ex erting a direct irritating effect on the skin." Dermatitis due to other vegetable dusts such as vanilla, powdered arnica, pyrethrum, etc., have been reported.1* Dental lesions, of occupational origin, have been reported among workers in sugar. The gingivitis caused by sugar dust is clas sified as purely mechanical, with laterdeveloping caries. Digestive disorders, respiratory conditions, and cutaneous con ditions (especially of the face) were also found." Dork workers, transporters of grain, workers in grain and flour mills, etc. are exposed to dusts during their work. Dusts from cereals may contain many impurities, which may cause an irritating action on the respiratory passages, as well as inflamma tion of the skin. Digestive disturbances, dental defects, diminution in hearing, and conjunctivitis have been observed among millers, and have been attributed to the dusts to which such workers are exposed." b. Allergic. Many apparently innocuous substances may produce reactions in per sons of peculiar personal susceptibility. The term "allergy" is used to describe this con dition of hypersensitivencss or susceptibility, and allergic phenomena most frequently manifest themselves in skin reactions. How ever, they may cause acute reactions else where in the body. When the respiratory tract is involved we have such well known diseases as hay fever or asthma. These diseases may develop as a result of hyper sensitiveness to such substances as pollens from plants, horsehair, rabbit's fur, furs, feathers, etc. Severe dermatitis is experienced by many workers handling powder containing T.N.T., which is used in making high explosives. Picric acid, which is also used for this pur pose, requires drying, and in this latter state has been found to produce a dermatitis. Ficric acid is also the oldest synthetic or- ffor instance, furriers, workers in clothing industries who are exposed to wool dust, etc., may suffer from hay fever or asthma.'* It is unnecessary for the offending dust to reach the depths of the lungs--giant pollens for example are reported to produce their effect after being caught in the upper res tnnic dyestuff." Dermatitis occurs among handlers of silk with varying frequency. Sails determined that a rash occurring among workers in a silk factory was due to dust from silk cocoons imported from | Africa." Persons engaged in the manufacture of quinine and quinine preparations suffer from dtin phenomena, which occur for the most tart on exposed parts of the hotly, and may be caused by ingestion or by quinine piratory passages. Should such an offending substance be finely ground it could reach the alveoli and as a result probably all . physiologic reactions would be accelerated." In a survey of a plant where resin is mixed, ground, and molded, it was found that 80 per cent of the occupational derma titis there was due to hypersensitivity to hexamethylenetetramine and formaldehyde contained in the dust to which the workers were exposed." During the first processes 88 Trvcnty-sixth National Safety Congress of cotton spinning:, cotton-strippers are ex posed to dust arising from cotton husks and d4bris, which produces a typical form of asthma,1 Ordinary wood dust has been of interest due to its purely mechanical action, but still greater care is required in handling certain kinds, especially woods coming from abroad, because of the essential oils impreg nating them, which when freed in the dust may affect the health of the workers con cerned. Some of the woods capable of causing skin lesions are Brazil wood, satinwood, feakwood, cumaru or tonka wood, black ebony wood, West Indian mahogany, Japanese fagayasan, coccoloba, chestnutwood, oliyewood, California sequoia, etc. All per sons who handle these woods are not in jured, only those particularly susceptible to the substances they rontain becoming affected." trichum dermatodes), which is scattered when the bark is stripped off. This powder is irritating to the skin and mucous mem branes. Mycelia and spores of moulds are commonly found to cause rashes: for in stance, the black powder coming from macerated sugarcane stalks. Among basketmakers, the mycelium and spores, in the form of a white mould (hyphomycete) from the rhattan canes used, get shaken out when the canes are split, hammered, and cut, causing painful fissures to develop on the skin where they alight.1* A form of asthma or spasmodic cough, suffered by cotton weavers and known as aspergillosis, has been considered due to in halation of spores of a mildew which some times occurs on the threads." In a study of silicosis among miners, made by the Public Health Service, a number of cases of typical miliary calcification were en countered. Unstained smears of those cases 2. LIVING ORGANIC DUSTS. These examined were positive for fungus, two contain particles capable of exhibiting the types of Aspergillus fungi being identified. phenomena of life* (especially the property All of the subjects but one were farmers, of reproduction or multiplication), such as teamsters, feedmill workers, or residents of bacteria and fungi. They are usually found small agricultural towns where grain is in low concentration* and are associated marketed. Farmers are exposed to fungi in with nonliving dusts in the air. threshing wheat, baling hay, or handling a. Bacteria. One of the most important among these is the anthrax bacillus, which is contained in the dust from skins, furs, wool, and animal hair, horns, hoofs, bones, etc. This disease may occur in two forms: cutaneous (in which the organism affects the skin), and pulmonary (when it is inhaled, as in the form of anthrax known as wool- sorters' disease)." Cases of tetanus, reported in connection with jute manufacture, were traced to the various smalt grains." Some other fungus diseases such as actino mycosis and blastomycosis are associated with occupational exposure to dust. The former occurs among workers handling straw, bay, grass, vegetable debris contami nated with mould, etc. Actinomycosis is likely to affect people engaged in commercial handling, storing, and cleansing of grain (grain distilleries. Hour mills, grain crush ing, breweries, and malting houses, etc.)." raw material, the bacillus having been found in the factory dust,* Diphtheria, tubercu II. Inorganic Dusts losis, smallpox, typhoid, or other bacillus- Inorganic compounds are of mineral produced diseases, may result from exposure origin, not requiring a living organism to to infected dusts. produce them." A number of dusts not Bacterial sensitization can be the cause of any of the allergic diseases, namely, asthma, perennial, hay fever. Urticaria, angioneurotic 'edema, eczema, or migraine headaches.* b.1 Fungi. Dusts containing the mycelia and spores of parasitic fungi give rise to annoyance and discomfort. "Maltster's" itch from the dust alone lias been reported. In Provetice, reeds used for ceilings are stacked while still wet and undergo fermentation; they become covered with a white powder (a dry fungus of the Mucor family; Sporo- usually classed as toxic may, under some conditions, produce untoward effects on the human organism. Classified under inorganic are toxic and/or irritant, fibrosis-produc ing, and nonfibrosis-producing dusts. a. Toxic and/or Irritant. Toxic dusts are those which are inherently toxic when in haled, ingested, or otherwise absorbed. Among those which produce systemic poi soning, some of which are also irritant, are the dusts from heavy metals and their salts, such as lead, mercury, arsenic, cadmium, Industrial Dusts 89 zinc, etc. Irritant dusts are injurious by reason of their strong irritative or corro sive properties. As a rule, inhaled irritant substances im mediately cause a reaction in the upper respiratory tract of such severity that they are prevented from reaching the lungs, al though they may cause lung damage by extension of inflammation if the mucous membrane is corroded.' Lime, calcium oxide, and the di-chromates are examples of irri tant dusts. An inorganic dust may possess both toxic and irritant properties, and the poisoning produced may be the combined effect of more than one mode of entrance into the body. Of the directly poisonous dusts, the most widely prevalent are those of certain lead compounds, particularly the oxide, carbon ate and the chromate. The dust is readily absorbed by the mucous membrane; some dust passes into the stomach and is dissolved by the gastric juice.* According to Fairhall, perforated nasal septum is a common occurrence among workers with bi-chromate dusts.* Tn a study made by the U. S. Public Health Service it was found that continuous daily exposure to concentrations of chromic acid mist greater than 1 milligram in 10 cubic meters is likely to cause definite injury to the nasal tissues." It is believed that a similar concentration of the dust would be equally toxic. In the case of poisoning from some heavy metals, exposure may be to both dust and vapor. For instance, investigations have shown the safe limit of total exposure to lead oxide dust and fumes to he less than 1-5 mg. per 10 cubic meters of air, except for prolonged exposure.* In exposure to mercury dust and vapor, it was shown that the incidence of chronic mercurialism in creases rapidly with increasing mercury concentration, after such concentration ex ceeds 2.0 mg. per 10 cubic meters." Alkalis and metallic oxides are common causes of dermatoses. Lye, potash and lime are known to cause irritation to plas terers, cement-makers, bricklayers, masons, stonecutters, modellers, and metal platers." Ulceration and perforation of the nasal sep tum occur among workers exposed to the dust of soda ash; systemic poisoning also occurs from inhalation of calcium cyanimide dust." Cases of dermatitis, scleroderma and can cer arc reported to have been caused by exposure to dust of arsenic compounds. Certain aluminum salts are skin irritants and aluminum dusts may contribute to the infection of skin and mucous membranes, through mechanical action." b, Fibrosis-Producing Dusts. The most important of these are the inorganic, slightly soluble dusts which cause fibrous changes in the lung tissues, some of which are seri ous, and some of which cause little or no disability.' So far as is known, no inorganic substances other than silicon derivatives cause more than a very moderate degree of fibrosis of the lung, Moreover, there seems to he no evidence that any other constituent of ordinary dusts can influence so unfavora bly a pulmonary infection.* Although other dusts, when inhaled in sufficient concentrations over a long period of time, have been shown capable of pro ducing a pulmonary fibrosis, nevertheless, the pneumoconiosis characterized by nodu lar fibrosis has to date been shown clini cally and experimentally to be associated only with the inhalation of dusts containing free silica. Since this dust, to exert its harmful action, must enter the finer divisions of the lung, the particle size of the atmospheric dust may hear a definite relationship to the in jurious effect produced. The silica must be present in the air in particles small enough to enter the finer air spaces and of such dimensions that the phagocytic cells may engulf them. The greater majority of par ticles found upon microscopic examination of the lung fall within the limits of from I to 3 microns." Examples of siliceous dusts are granite, quartz, sand, pumice, slate, etc. In a recent study among anthracite miners, the correlations between exposure to dust (which contained silica) and the evidence of constitutional changes left little doubt as to the etiological significance of the dust in the air breathed. Like correlations were found between the silica exposure and the extent of pulmonary changes,* When the inhaled dust consists of silica combined with bases, silicates, some degree of change in the pulmonary tissue may result. In this respect asbestos dust seems to be unique among silicates in the prevalence and se verity of the disease it causes.* The chipf distinction between silicosis and conditions due to simple reactions caused by other dusts is the active proliferative 90 Tsi'cntv-sixth National Safety Congress reaction in the tissues which results in progressive nodulation. Silicosis, when once established, strongly predisposes the lungs to infection, especially with the tubercle barillas. Chronic interstitial pneumonia, Dust may be entrapped at its source by suction devices and thus removed and col lected. Familiar examples art exhaust hoods in grinding operations, and the devices used in rock drilling. chronic bronchitis, and emphysema are fre Generally speaking, the exhaust ventila quent complications of advanced degrees of tion method, where applicable, is to be pre silicosis. The relation of the acute respiratory in fections to the reaction due to dusts other than free silica has never been established, though a heightened incidence lias often been shown statistically in workers in dusty trades. It is fairly certain that a dust dam aged lung, whatever the cause, fares much worse if an acute infection does supervene upon it,' In a study conducted by the U. S. Public Health Service among marble finishers in ferred in controlling a dust hazard. Water may be used to entrap dust and prevent its dispersal, and under certain circumstances it may be of advantage to combine the use of water and the use o! suction. Sometimes a dusty process can be completely enclosed in a sealed room or compartment. It must be remembered, however, that any mechani cal device of this kind offers adequate pro tection only if it is properly designed, installed, and maintained. A great deal of attention has been given Vermont, it was found that marble dust when inhaled in the concentrations found in the examined plants produced a mild, bi lateral, linear fibrosis in some cases, but no serious lung changes were noted and there was no disability due to the dust, even after years of exposure." c. Nonfibrosis-Producing Dusts. These the subject of individual protection from dust, and there are many types of respira tory protective devices now available. These are generally of two types: those which provide fresh air from an uncontaminated source and those which rely upon a filtering medium for removing dust from the air breathed. Where the use of such a device is indicated, only one of the types approved are inert, that is, they do not cause fibrous by the U. S. Bureau of Mines should lie tissue to be produced, but may become used. As a rule, it may be said that masks, encapsulated or tie free in the tissues; or respirators, or other such protective device they are absorbed without production of should be used only where exposure to the fibrous tissue. Included among them are dust is intermittent and hrief, or where alundum, coal, corundum, emery, limestone, some unusual condition makes a more ade magnesite, marble, plaster of parts (gyp quate dust control impracticable." sum), and polisher's rouge. Where bacteria or other tiving dusts in Dust Control the air are associated with a process, steri lization methods such as increased tempera Engineering and medical control are the ture, ultraviolet radiation, and chemicals two most important factors in comliating like chtorine'or other bactericidal substances, the industrial dust hazard, and arc to a large may be of use. Pasteurization temperature extent complementary. (about 140' F.) will kill most organisms Engineering Control. As Lanza" has stated in a recent paper, "It is a basic principle in dealing with a dust hazard that the dust should lie attacked at its point of origin and thus prevented from being dis seminated into the atmosphere." After the dust has been spread throughout the air it is difficult to deal with it, and reliance must be placed on individual protection, which is never wholly satisfactory. except those bearing spores. Steam disin fection is used for Itorsehair, and proves to be practicable if the temperature does not exceed 230* F. Wool fibres, however, lose their elasticity by steam disinfection, and the "Duckering" process now used in Eng land includes soaking of the wool in a form aldehyde solution, and drying in a current of air at a temperature of 160* F." There are few occupations in which there would be a sufficient concentration of dead bac Lanza further cites various methods used teria to cause untoward effects in man. in controlling dust. These will lie reviewed but briefly, since a paper dealing with the subject of dust control in detail, will follow on this program. In the case of dusts producing external irritation, auxiliary protective measures may include the use of protective clothing. /udnstrkil Ousts 91 gloves, goggles and aprons; as well as pro tective salves, ointments, or other com pounds to delay or diminish the irritant action. General rules for hygiene and good housekeeping should also be observed. Medical Control. Equally important, and closely interrelated with (he engineering phase, is medical control of occupational hazards. In addition to directing the proper placement of new workers, and guarding the health of all employees, medical control is a check on the efficacy of the engineering control methods already instituted, or a measure of the need for new protective de vices. of disease." Since some occupational dis eases tend to clear up and recur, records of previous occupations should be included in the physical examinations. The frequency of examinations should be determined by the medical director, unless otherwise speci fied by law. Those exposed to known occu pational disease hazards may have weekly or monthly examinations." "It should always be kept in mind that the basic principle of physical examinations in industry is to keep men on the job and not allow the physical examination to be merely a weeding out process."" It has been stated that "Industry has found that the best way to treat industrial injuries and illness is to prevent them,"* and medical control, through precmploymetit and periodic physical examinations, is one of the most important factors in such prevention. The preemployment examination is made to determine the employee's physical and References Bloomfield, J. J. and DallaValle, ]. M. "The Determination and Control o( Industrial Dust." 1/ S. Public Health Bulletin No. 217, April, 1925. * Collie, Edgar L, "Industrial Pneumoconioses, wilh special reference to Dust Phthisis/' Mitroy Lectures, 1915. H. M.S.O., London, 1 Solimann, Torald, "A Manual of Pharma cology/' W. B, Saunders St Co,, Philadelphia, 1932. * Fairhall, Lawrence T. , "Toxic Dusts and Fumes," Journal of Industrial Hygiene and Toxi cology, November, t936. mental fitness for work. It serves to dis close the presence of any contagious dis I Bloomfield, J, J, "The Sampling and Analysis of Industrial Dusts/' American Public Health Asso ciation, Yearbook, 1935-36. ease. reveaH any minor physical defects which might later become serious, or whether Ihe examinee's condition precludes his em ployment in certain ot in all types of work. * Gibbs, W. E. "Dust Haxsrd in Industry/' Ernest Benn. Ltd. London, J925. , T Air Hygiene Foundation of America, Inc, "Sili cosis and Allied Disorders/' Medicsl Series, Bulle tin No. I. Pittsburgh, Pa. April 15,1936. * Kettle, E, H, 4lThe Action of Harmful Dusts." It should be remembered that such preem ployment examinations are not to be made ior the purpose of eliminating an employee, but rather for allocating him to the type of work for which he is physically suited. A worker should be given employment unless totally unfit, or unless his disability, even Hough slight, would cause him to lie a haz- I1n9s3t4,. of Mining and Metallurgy, London, June 15. * "Dusts. Fumes, and Smokes." Occupation and H19e3a0l.th, Scries, International Labour Office, Geneva, " Drinker, Philip, "Causation of Pneumoconi osis." Journal of Industrial Hygiene and Toxi cology, October, 1936. II "Dyeing," Occupation and Health Series, International Labour Office, Geneva, 1930. " Legge, Sir Thomas. "Industrial Maladies." Oxford University Press, London, 1934. ud to himself or his associates. Further more, the practice of preemptoyment w Burstein, A. "Nicotine Action from Inhaled Tobacco Dust." Journal of Industrial Hygiene, De cember, 1927, (laminations should be extended to include (wcutives and officials of industrial organi- M White, R. Prosser, "The Permatetgoses, or Occupational Affections of the Skin." H, K. Lewis & Co. Ltd., London, 1934. ations. 'The purpose of periodic physical (laminations is to secure and maintain physical fitness and thereby lengthen work spans.''" Reexamination of employees some times results in the discovery of defects and disabilities which were not observed at the it Schwartz, Louis. "Skin Hazards in American OIncdtoubsetrr,y.1"93U4,. S. Public Health Bulletin No. 215. ' Downing, J. G, "industrial Dermatoses: Treat ment and t.egal Aspects: Review of Reeent Litera ture." Journal of Industrial Hygiene and Toxicology, July, 19,15. ii "Occupational Lesions in Workers in Sugar." Belgium Letter, Journal of American Medical Asso ciation, Scjit. 10, 1927. Aljat. Journal of Industrial Hygiene, February, 1925. time, of employment. In such cases, an ocfflpational adjustment should he made to provide continued employment, but remove tht risk of permanent injury. Reexamination of employees is required '* "Flour Mills. Occupation and Health Series, International Labour Office, Geneva, 1930. 'Mayers, May R. "Susceptibility to Dermatitis." vTohte. 1In6,dnuos.tr2ia. l Bulletin, Albany, N. Y. Fch. 1937, " Drinker, Philip, and Hatch, Theodore. "Indus Ntreiawl YDourskt,."193M6,cGraw-Hill Book Company, Inc., law in certain occupations in which the " Schwartz, Louis, "Skin Hazards in American handling of poisonous or otherwise deleteri- Industry. Part II." U. S. Public Health Bulletin Na 229,, Sept. 1936. ws substances may result in the contraction "Poisonous Woods." Occupation and Health Series, International Labour Office, Geneva, 1930, 1 92 Tiventy-sixth National Safety Congress Hope* E. W,. Hanna* W., *n<l Stallybmi, C. 0t "IiidtMtml Medicine end Hygiene." BiiiJicre, TliwBUrollwennd, CGo*x* TLvond"Tonh*e19D2l3a.cnoidu of Bacterial Allerfjr/' Southern Medical Journal, Vol. 27, No, 10. S*irte1n9,3*R.* R_ end Merewether, F. V. "Miliary Ltinr Oiteue Due to Unknown Cause. U. S. Public Httith Reports,. Dec. 5, 1930. M MActtnomycoeia.*1 Occupation and Health Series* International Labour Office, Genera* 1930. Holland, J. W. 'Textbook ot Medical Chemistry and Toxicology," W. B. Saunders Company, Phila delpBhlioao* m19fi2e0l.d, J. J. and Blum, Wm. "Health Haz ard* in Chromium Platini." U. S. Public Health Serrlce Reprint No, 1245, Washington, 1930. Russell, Jones, Bloomfield* Britten and Thomp son. "Lead Poisoning in a Storage Battery Plant." U. S. Public Health Bulletin No. 205, June* 1933. Neal. Jotiea. Bloomfield. DallaValle and Ed* ward*. "A Study of Chrome Mercurialism in the Hatters Fur Cutting Industry," U, S. Public Health Bulletin No, 234* May, 1937. 11 Sayera, R R. and Jones, R, R. "Silicosis and Similar Dust Diseases/* National Silicosis Con ference, Washington, D. C., April 14, 1936. * Sayers, Bloomfield* DallaValle* Jonea, preeaaen* Brtmdage and Britten, "Anthraco-Silicosi* among Hard Coal Miners." U. S. Public Ilealth Bulletin No".M2i2d1d* lDeetocnem* bEe.r* L1.955^.'Industrial Pulmonary Dis ease due to the Inhalation of Dust." The Lancet, July 4 and 11* 1936; M Dreesaen, Waldemar C. "Effect of Inhaled Marble Dust as Observed in Vermont Marble Finishers," U. S, Public Health Service Reprint No. L1a63m0a. * A. J. "Control and Prevention of Sili* costs," Symposium on Silicosis. California Tuber culosis Association, Ran Francisco* 1937, Newqmat* M. N. "Medical Service in Industry and Workmen's Compensation Laws." American College of Surgeons, Chicago, 1934. _ ""Medical CaTe of Industrial Worker*," Na tional Industrial Conference Board, Inc. New York, 1926. The Engineer's Part in Eliminating Dust Hazards By ARTHUR S. JOHNSON Assistant to Manager, Engineering Department, American Mutual Liability Insurance Co.. Boston, Maas. When one realizes that control of the dust hazard depends upon the combined contribu tions of the physician and the engineer, he ap preciates that the solution requires scientific treatment By scientific treatment I mean the technical analysis of the hazard to discover the causes which contribute to injury or ill health, and the development of control meth pensive methods for making the air clean are , still in the realm of dreams. Much work must be done to know more about silicosis and i more how to make atmospheres safe inexfenlively. As an accident prevention job, dust control lies almost entirely within the admin- J istrative responsibility. The control measures ' are capital expenditures of considerable size ods which obey physical law and physiology, A plant with a dust hazard is sick, it needs and which will be directed at causes that an expert diagnosis and scientific treatment, admit of most immediate and economical which may include expensive major opera treatment. tions. Home remedies are seldom much good, That goes for handling the dust hazard in and supervision and employee safety con a given plant It goes double for acquiring sciousness alone cannot accomplish anything. knowledge to the end that the whole problem There may be observed in countless shops may reach ultimate solution. Right now our installations for exhausting dust which are knowledge of the problem is in big chunks, derisively called "tin knocker" jobs in which loosely put together and largely empirical. the horsepower dissipated is out of all pro There are estimates only to judge the mag nitude of the dust health problem, and it is so closely associated with other health problems that a clean-cut estimate of it alone is im possible. We do know that it is great in the aggregate, and for the individual plant it may be very bothersome and expensive. What actually makes quartz dust cause silicosis is not known. It does, so the air breathed by workmen must not contain harm ful quantities of respirable quartz dust. Inex portion to the air-borne dust moved. Tonnage efficiency of material moved may be the proper yardstick for pneumatic conveyors but if the material to be moved is air, contaminated with nearly weightless particles of dust, the entire health hazard can lie in the half of one per cent of material not moved. I do not mean that unless a dust supression job was engineered it can be no good. There arc many good installations that were never figured at all hut grew like Topsy. The rr- I liditsirial Dusts 93 suiting freedom from dustiness was so satis factory that efficiency held little interest to the owner. This is exceptional, however, and I offer the opinion that dust suppression jobs should be engineered. A dust-suppression installation is a safety device, designed and operated to provide pro tection against possible disease and provide a sense of security which must be absolute. Its safety is not rushing air and rattling chips but a minimal residual dustiness. There is no more pathetic defeat for a dust control job than to find faith in its effectiveness so low that workers must wear respirators to find (he reasonable safety that was expected from the hoods, ducts and fans. I want to go so far in my opinion as to state that the engineer should not attempt to define the quality of health hazard in a given plant or industry, nor should he establish threshold limits of safe or permissible dusti ness. This may be debatable, but I shall con tend that the engineer who writes the speci fications of hazard and dust tolerance is really an industrial hygienist, and is using a very much broader knowledge than engineering alone. fn the first case the quality of the health hazard is an opinion arrived at after studying all the environmental conditions including the genera! sanitation, occupational analysis and Diagnosis and Control a scientific analysis of the dust exposures. In the exploration of dust exposures, the Let us examine some of the features by which we recognize this dust hazard problem, tawing out the socio-legal aspects. In order to develop more fully the engi neer's place in this dust control program, it stems desirable to separate as sharply as we cw the diagnostic considerations from those which deal with control. In (he first com partment wc can place all the analytical com ponents which describe the hazard and its exposure, tiie probability of its producing ill health and all the rest of the medical and industrial hygiene' facts which- make out a cue against the existing dust. In the second compartment place the knowledge of physics and engineering necessary to plan the dust control program and so design it that when installed its performance follows prediction that the probability of industrial disease is reduced to insignificance. nature of dusty operations must be viewed from physical, chemical and mechanical aspects, the determinations of dustiness must be not only counted and classified by particu late sizes, hut chemically and mineralogically analyzed. The plant layout must be studied with respect to dust production and distribu tion, and the housekeeping and existing dust control equipment evaluated. The presence of specific hazards, such as toxic gases, abnor mal temperature and humidity conditions, etc., must be explored for their complicating effect upon the whole picture. This is distinctly an industrial hygiene job, and some of the most critical data requires only medical viewpoint. This is absolute in the case of tuberculosis study and the qualifying of men for employ ment. So far, not one atom of engineering to suppress dust is involved. It is entirely anal ysis of hazard. The diagnosis must be that The Industrial Hygienist the dustiness is hazardous to health or that it Our first feature of interest would naturally be (he specific and relative toxicity of silica, tilica-bearing and other dusts which make up fte dust health hazard. Much might be said to advantage about the quality and quantity of hazard in many dusts. The acquiring of firs knowledge has been, and must remain a nedical problem. It involves gross and micro scopic pathology and x-rays, and experimental atimals. Engineers do not talk that language. Mintrial hygienists do; they are a happy combination, half doctor and half engineer. Many of them arc quite capable of handling <x dust health hazard in all its phases of is safe. If it is hazardous, ft must be brought down to a specified residue. If it isn't, leave it alone. On the second point, if the hygienists can not specify threshold limits graduated upward for relatively less hazardous dusts, let the engineer not worry about it. The diagnosis is dust which is harmful and too much of it. The remedy is control of the dust. The engineer designs controls which will produce the lowest practical residual dusti ness. He should not attempt to write his own specifications of threshold limits or permis sible dustiness. This may be an important goal in the study of dust health hazards. bwtigation and control. For the purpose of Safe Limits iris discussion I throw their interest in with fce doctors. At the present time the medical men and hygienists believe that quartz dust is safe 94 Twenty-sixth National Safety Congress Industrial Dusts 95 Mow five million particles. They seem will ing to graduate upward to 20 million for medium silica ami SO million for low silica percentages. Five million particles is virtually system, boss at the hoods, loss at the bends, trical phenomena which bear upon dust be- ! and loss in the ducts must not be guessed at. havior. Pipe design must take into account the gage Those are all principles of physics which of the metal and reinforcing to withstand explain the behavior of dust and upon which pressures and erosion. tions must be known and used. Performance cannot be left to guess work. Supplying suffi cient air to be exhausted is part of the prob lem. The same may be said of beating. dust free, and is very difficult and expensive engineering practice must be based- They The selection of a fan and its motive power IJo l give the problem too severe a build to achieve and maintain. The declaration of must be understood and be taken into account. is a matter of calculation, not guess work. up ? I think not. Remember these two things : safety of the installations must remain in the hands of the medical and hygiene groups in whose 1lands now lies the responsibility for determining the hazard. We now enter the chapter of our discussion intended to demonstrate that dust control is Dust control is not a matter only of general Power consumption in the system is calcula ventilation; the engineer must study the pro ble, fans follow certain laws, so the engineer duction as well as the dispersion. The problem must know the behavior of axial flow, pro should be analyzed to determine the applica peller type, radial flow, paddle wheel and bility of segregation, enclosure, welling, local other fan performance. exhaust and general ventilation. More physics and engineering calculation 1. You arc dealing with hazardous mate rial so small in size and so little of it by weight that it is as invisible as the air that hears it. 2. Physical laws involved in the behavior an engineering job, that it must he given Ill some instances, substitution of itoil-haz- goes into the air-cleaning apparatus. The of dust and air do not permit inexpensive scentific treatment, not guess work, applying ardous material, or non-dust-producing oper selection of gravitation, inertial or filtration methods of control. 1 am acquainted with engineering methods which are based upon a ations may have specific application, and they method depends upon what the dust is, the budgets set up for this purpose which amount knowledge of physical law, the behavior of should be explored first. This implies plant calculation for any methods requires knowl to more than a quarter of a million dollars, dust, the performance of air-moving machin engineering. I am convinced that many bad edge of discharge througn stacks, the deter and I know of many where 60 to 80 thousand ery, etc. installations are bad because plant engineering mination of sizes of settling chambers; the dollars is involved. was not used. In the designing of exhaust behavior of cyclones. The use or non-use of Prerequisite Knowledge I-ct me recite briefly, a few of the things which, in my opinion, the engineer should systems installed to capture the dust at the i filter, and if so, what type, how it should points of generation, the physical behavior of perform, how big it should be. wbat kind of air moving toward hoods and in ducts most resistance and bow much each kind offers, to be known, and that knowledge used, Each |ay nothing of their proper location with The need for this much engineering is rec ognized by men who know. Already much has been done toward getting the knowledge into handbook shape. Perhaps the best job know to do this job correctly. He must know system must consist of collection hoods, pip relation to cleaning, accessibility, etc., arc all of this sort to date is "Fundamentals Relating how to make a survey. Surveys depend upon ing, air-cleaning plant and a Source of suction. Jitems for accurate engineering determination. to the Design and Operation of Exhaust sampling, and sampling is not a catch-ascatch-can proposition. It involves the place, Before selecting a hood for a job the engineer must know dust dispersion by dynamic pro Apparatus to check the behavior of installa Systems" developed under American Stand ards Association procedure. the time, the frequency, the amount in a sam jection as well as dust dispersion hy air cur ple, and the number of samples so that maxi rents, and design the hood accordingly. mum, minimum and average data mean some thing, so that credibility can be given them. Knowledge Needed For the type of sample involved lie must know how to weigh or count respirable dust, as distinguished from large masses of nonrespirable dust which complicate the picture. The aero-dynamic characteristics of suction! hoods appear to be little known because little thought was given to them in designing The Doctor's Part in Controlling Dust Hazards By A. D. LAZENBY, M.D., F.A.C.S. He must know how to observe the sources of dust floods as distinguished from conditions of normal dustiness. He must know the sources of dust and the principles involved in the dispersion of dust. He must determine how much dust enters the problem because it is part of the material, and what dust is created in the process by the fracturiugof the material. Any less survey cannot tell the engineer thousands of hoods which can be fouud^every- wherc in industry. All the possibility for Chief Surgeon, Maryland Casualty Co., Baltimore, Maryland entrapping dust and much of the efficiency of Con_s_id_e_r_a_b_l_e__confusion has existed in the recognize the disease when it is fully de the system lies in this factor. Air velocity, static suction, and rate of air flow are all as (o just w])at js t))e phySic;an's func. jn the prevenljon of dust d;seas,, and veloped. related, and they must be known. It is essen- B( what js the engjneer>s jt ;s very ob. It is not necessarily the physician's func tial to use high vefocity of air in certain typ iou5 upon even casua] t|loug[u that the tion to analyze dust. That is a task for the of exhaust systems to entrap dust projected ro sciences must work hand in hand in at high velocities as in the case of a granite ,;r efforts to solve the problem, surfacing machine, and low velocities mast it The p, ,idim ,, , ,; ,, . . used in others, as m the case of cleat m Bt bc M engineer wha du ts chemist and the petrographer. It is not the physician's function to count the particles of dust in a given industrial atmosphere. That, in reality, is the function of the engineer. It what his task of dust control is. To visualize asbestos fibre of dust to prevent wastm, r dangerous and what aTe not He mult is not the physician's function to devise that task intelligently lie should know the ventilating equipment for the removal of physics of Brownian motion, laws of resist material. w how those dusts enter the body and dust, nor even to be more than an adviser ance to the motion of particles moving in air, ' both when the air is in turbulence and for Quantity of air and its velocity must manner in which they do their harm. He determined, then the piping should he d (st be trained in the examination of per- as to the means that must be adopted to render the atmosphere safe. stream-line motion. He should know terminal velocities, movements due to centrifugal mo tion; flocculation and the effects of air motion and the effects of humidification on it. He must know all about the difficulties of wetting and what is known about overcoming these difficulties. He should know the several elec signed to take into account the behavior t M w)10 are to be employed to work in air-flow through pipes at low and high vefoo st, and to discover those who are already ties. Where the problem is complicated b gased, or are peculiarly susceptible to the large sized particles which go along witl 5t disease. He must be able to detect the the fine dust, how these behave must be take g signs of disease in workers who are into account. Pressure losses are very tmpM tos1 to dust, and must be prepared to taut elements in the design of an exhauS The physician nevertheless must correlate with his medical knowledge and with his studies of the industrial worker the findings of the engineer. A diagnosis of silicosis, for example, requires not merely characteristic occupational history and characteristic physi- 96 Twcutv-sixth National Safety Contjrcss Industrial Dusts 97 cat findings, but the knowledge as well that the patient has been exposed to hazardous dusts in dangerous concentrations. Ati dusts -when inhaled in excessive quantities may be considered as harmful, but only a few can be regarded as dangerous. From the standpoint of their dangerous properties, they may he divided into three We have no real knowledge as to true figures, but as a simple rule, we can .adopt for practical purposes the thought that the human body can withstand successfully a concentration of dust containing 100 per cent silica dioxide in a particulate size less than 10 microns, in a concentration not in excess of 5,000,000 particles per cubic foot. If we decrease the percentage of silica dioxide general groups. present in the dust, we can correspondingly 1. Those which are dangerous because of their poisonous action, such as lead, arsenic, mercury, and similar substances. 2. Those which cause only irritation in the respiratory tract, resulting in such condi tions as bronchitis or local inflammation; such substances as vegetable fibre, cork dust, flour, starch, and other relatively innocuous organic or inorganic materials. 3. Those which tend to produce fibrosis of the lungs, thereby predisposing to respira tory infections, especially tuberculosis, such dusts as asbestos, silica dioxide or mag nesium silicate. I shall confine my remarks chiefly to dusts occurring in the fatter category. It has been generally believed that the increase the concentration with comparative safety. We must, of course, take into ac count the portion of the worker's time spent in the dusty atmosphere. To arrive at a rough conception of a safe atmosphere, we multiply the percentage of free silica in a given dust by the total num ber of particles per cubic foot. If the result is under 5,000,000 the condition may be con sidered relatively safe. If the result is over 5,000,000 the condition must be regarded as unsafe. Bear in mind too that silicosis is essentially a disease of great chronicity. Except in a few exceptional instances it will require from seven to thirty years for a worker to develop advanced silicosis. It is evident too that coincident dusts may either retard the ' ; harmful effects of dusts inhaled into the development of silicosis or hasten it. Recent lungs depended more upon their physical research seems to indicate that the admix structure than upon their chemical. It was ture of aluminum dust to a silicious dust ' believed, for example, that silica dioxide, or will greatly inhibit the reaction of the latter; quartz, was particularly harmful because of whereas a silicious dust combined with some its crystalline structure, and the hardness alkaline coincident dusts may hasten the de and sharpness of its particles. This concep tion is now known to be faulty. The dusts which cause their damage by mechanical in terference with function are the dusts which are relatively innocuous, whose symptoms are transitory, and which subside upon re moval from exposure to the dust. velopment of silicosis. Much research is now under way in prob lems such as this. We have never learned how to cure silicosis, but we are learning rapidly how to prevent it. Our knowledge in thii respect seems to be limited to tbe removal of dust from the breathing zone of the worker. ; ' ` , I . Chemical Effect Is Harmful Later discoveries may show us how to | The disease of particular interest to us today, silicosis, owes its harmful effects very largely to a harmful chemical reaction oc curring between silica dioxide and the body tissues. It so happens that silica dioxide is decidedly a tissue irritant to the body, re gardless of the part of the body it invades, 1 it causes local irritation, local destruction of tissue, and the replacement of that tissue by scars. Thus, given a dust containing silica diox ide in sufficient concentration, in sires small enough to permit its entrance to the ultimate , air spaces in the lungs, we have a situation which offers danger to the worker. modify existing dusts with contaminant ; dusts that will render silica dioxide innocn- ous. Owing to its very great chronicity, it ii only the rare case who actually develops, disabling silicosis during his industrial life* time. It is realized, of course, that excep tional instances take place, but the coincident ravages of age usually keep pace with tti efeels of dust, so that much nt the dil ability usually attributed to silicosis is ofteg; in fact, actually attributable to other dit-j eases or incapacities which advancing yean bring in their wake. To me the great peril of silicosis, the peril not only to the Industrie worker himself, hut his family, co-workers and t/ie public generally, is the accompany ing susceptibility to tuberculosis. Complicated by Tuberculosis Silicosis per se does not kill. Tuberculosis as a complicating factor of silicosis rarely recovers despite treatment, and the indi vidual so afflicted is not only totally dis abled himself, but a definite menace to all with whom he comes in contact, particularly the fellow worker who may have silicosis. So perhaps the most important places in which the services of the physician in a dusty trade are necessary are--first, along lines of discovering and barring from exposure to a silicious dust those persons who may al ready have arrested tuberculosis; and sec ondly, discovering those persons already ex posed to dust, possib'y already silicotic, in whom tuberculous infections may have de veloped. It is well recognized that no individual should be exposed to dust containing silica dioxide until he has undergone a thorough physical examination, including carefully made and interpreted x-ray films of his chest. It is likewise obvious to anyone fa miliar with silicosis that no person who is exposed to silicious dust should be denied the privilege of frequent physical examina tions and x-rays of tbe chest, not entirely to discover the existence of possible silicosis, but to discover a coincident tuberculosis if such exists. silica dioxide is very likely to excite into activity a turbcrculous lesion which may be quiescent or arrested, and once such a lesion is reactivated, the chances of recovery are remote, The second problem which confronts the physician at the pre-employment physical ex amination is whether a given individual is, (jy reason of secondary physical defects, more susceptible to the development of sili cosis than a normal. Is lie suffering from diseases of the nose or upper respiratory tract, such as chronic sinusitis, disease of the lungs or air passages, or obstructions which produce mouth breathing? We must remember that silica dioxide is not dangerous until it reaches the lungs, and that the normal individual retains in the nose and the upper air passages a large quantity of the dust inhaled from the atmos phere. In instances where this nasal reten tion is disturbed, exposure to silica dioxide dust may be dangerous to that individual, where it would not be to another. It is believed that certain diseases of the heart and circulation, of the kidneys, possi bly syphilis, chronic coincident diseases of the lungs, all may render a man more sus ceptible to silicosis than normal. The physi cian at his pre-employment examination must follow certain established criteria in this respect, and bar from exposure to dangerous dusts those persons who through existing disease may be more ready prey to silicosis or tuberculosis. A man so diseased should, in protection to himself and to all with whom he comes in contact, be removed from industry. Let me emphasize the uselessness of a physical examination, unless it be accompanied by properly taken x-ray films, except in cases of gross tuberculosis. It is the function of the physician, there fore, to conduct in a thorough and an intelli gent manner the pre-employment examina tion of all persons who are to be engaged in a dusty trade, The purpose of this ex amination should be threefold. First, to discover and bar from employment in dust, any person who is suffering from tuber culosis in an active, a quiescent or an ar rested state. A possible exception might be made in individuals suffering from a so called healed primary complex, or a healed childhood in fection. It is well known that exposure to Re-Examination Needed After the applicant for employment has successfully passed his physical examination and is engaged in a dusty trade, the duty of the physician is not yet ended. This work man must be periodically re-examined, first to discover the early appearances of pul monary fibrosis, but what is even more im- ' portant, to detect the early evidences of complicating tuberculous infection. A man should not be dismissed from em ployment in a dusty trade merely because he lias evidences of non-disabling silicosis. Workers in dusty trades, especially stone cutters, moulders, pottery workers, and similar craftsmen, are usually highly skilled, and it seems unfortunate from a social and economic point of view to deny them em ployment so long as they are physically able to carry on, especially since the actual dis abling qualities of silicosis are in doubt. fin 98 Twenty-sixth National Safety Congress They should he denied employment in a dusty trade if that condition is found at pre-employment examination, but they should not be barred from continuing an employment in which they are already en gaged. Of course, in such instances you, as engineers, must realize that you have failed, because if you had kept the brealhing zone of the worker free from dangerous dusts, silicosis would not be present on physical examination. In this work of preventing dust diseases in industry, it should be evident that the closest and most intelligent cooperation between the physician and the engineer is necessary. The physician must, through his knowledge and research, tell the engineer what dusts, or, for that matter, what other substances used in industry are harmful. He must tel! the engineer how such dusts or other materials enter the body, how they leave the body and what they do in their passages through or their residence in the body. Must Make Analyses The engineer must in turn tell the physi cian of the harmful dusts and other sub stances surrounding his workers. He must make chemical and petrographic analyses of the dusts, and other indicated analyses of the atmosphere in the workshop. He must make dust counts and check his counts at regular intervals, conferring with the physician in an effort to discover whether, in the light of their joint knowledge, working conditions are dangerous. He must develop and install carefully designed ventilating equipment. He must arrange for modification of chemical and other industrial processes, where such modification is possible, and must bend his efforts toward removing from the danger zone of the worker the offending suhstance, whatever it may be. Too many engineers construe this function loosely. They pass on to the physician as iits responsibility certain functions which es sentially are theirs; such functions as dust analyses, dust counts, and similar technical duties. All too often it is considered ade quate merely to install a fan. Ventilating devices in dusty work rooms must be constructed only after careful en gineering study has given a knowledge of the physical properties of the air and of substances polluting it. It is possible to calculate to a very fine point the volume of air that must be removed from a given spot to remove the dust originating at that place, and the engineer must approach his task from just as scientific an angle as the physi cian approaches his. There is no room In industry for hap hazard methods on the part of either the physician or the engineer. \'NM!iXT Industrial Fumes, Gases and Vapors THURSDAY MORNING SESSION October 14, 1937 The meeting was called to order liy Vuyta of Wisconsin, Madison, who presided ami Wrabetz, Chairman, Industrial Commission introduced the speakers. Injurious Effects of Metal Fumes and How to Prevent Them By ROY R. JONES, M.D. Division of Labor Standards, XJ. S. Department of Labor, Washington, D. C. The inhalation of metal fumes is a com mon cause of illness among certain occupa tional groups. Two very different systemic reactions may result from breathing air containing particulate metal or metal cornsounds; (a) metal fume fever, an acute, transitory, non-fatal disease causing slight or temporary disability; (b) systemic metal poisoning, mild, severe, or even fatal in its effect. The same occupational exposure may produce both reactions, metal fume fever developing following the worker's early ex posure, chronic systemic poisoning develop ing later as a result of prolonged exposure. We may consider metal fumes as solid particles generated by condensation from metal in a gaseous state. Condensation is usually accompanied by oxidation. There are two chief physical character istics of metal fumes which bear a direct relationship to the case with which they may be absorbed: (a) The solid particles are mtch finer than atmospheric dust, probably averaging less than .5 micron in diameter; lb) they tend to flocculate and settle out of the air as dust. The finer the solid particles upended in the air, the longer the time required for them to settle out. Many of the coarser dust particles in the air are 'rapped in the upper respiratory tract and by the ciliated cells lining the trachea ami bronchi, while the finer particles may he tarried to the terminal air spaces of the tangs. Here they arc taken up hr the phago cytic cells and are eliminated chiefly by way of the hlood and lymph. Sayers and his associates1 found that only about 15 per cent of inhaled particulate matter, such as lead dust from automobile exhaust gas, was retained in the lungs, the remainder passing out with the exhaled air. Drinker and his associates* and Brown* made quantitative measurements of fumes retained in the [tings. They found a direct relation ship between the percentage of fumes re tained and the size of the particle and the density of the fumes breathed. They also showed that slow deep breathing increased the reaction resulting from inhaling zinc fumes, Such breathing should increase the percentage of particulate matter retained. Hazardous Processes For convenience we may place the more common occupational environments which are likely to afford a harmful exposure to inclnl fumes in three large groups; 1. Smelting of ores and refining of metals. 2. Employment at processes handling mol ten metal such as molding, cutting, and welding operations. .1. Salvage and cleaning operations, includ ing the burning of metals or metal covered objects, especially by means of acetylene torch or electric arc. In the first class, the ores or metals proc essed provide the source for the generation 99