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Ninth Annual Convention ,Greater Kew York Safety Council April IS, 20 and 21 1338 Occupst:-.cr.a 1 Jiaoase Nco 1 Session ieo<. 22 Paper No.- b4 INDUHTRXAL LEAD POISONING Prc Ho A. Ksho Ecttsring Laboratory of Physiology University of Cincinnati C ir..cnnat i, Ohio The Occurrence of head Poisoning in Industry The available statistics Indicate that there has been a progressive decline in the incidence of fatal lead poisoning in the United States during the past eight een cr twenty years. Considering tne obvious inadequacies in those statistics one may doubt that they represent tho facts reliably, but cannot escape the conclusion that the more har.ard.cua types cf occupational load exposure have been brought, under sem degree of control. The data provided by state compensation agencies also points to a fairly general brand toward reduction in the incidence? of 'non-fatal lead poisoning ever the period cf years and in the areas for which information is recorded.-. Thu:-; in Ohio the number of compensated oases cf plumbirm in 1928 was 130, while in 1936 such cases totaled 112 The decrease in the number and rate of oases of lead poisoning has not been so great or so con siatent from year to year as has bean the decline in fatal cases, and indeed an.actual diminution in such cases has probably not occurred in all parte of the United States o ISxpericnea has demonstrated that v/hsa tho atten tion of industrial management has been directed toward hazardous lead exposure by the increased cost of excessive labor turnover, occupational health insurance., sickness and disability benefits, or civil suits, or through the efforts of informed hygien ists, something ia done to improve operating conditions# Otherwise an attitude of la is sea fail's ia likely to exist. Thus, .in hygiena cally backward regions of the country, industrial plants can be found in which seriously disabling and fatal cases of load poisoning occur, not as the unforeseen consequence of uoms unusual or tempor ary change in plant conditions, but as the result of normal but grossly hazardous plant operations. Moreover, plant managers with no experience in the handling of load compounds may undertake the manufacture or processing of load-bearing materials, only to make use of unsafe methods long abandoned by more experienced end wiser man agement. Many other factors have exerted their influence to offset partially the advances rrwde toward tho progressive elimination of industrial plumedsn, among which the most troublesome, perhaps, ia the continual change in technical and manufacturing procedures whereby new opportunities for lead exposure are introduced into the indus try q In any case, we may.not take excessive- pride in tho improvement that has bean achieved in recent years, but rather .should wa feel disappointment and chagrin that the available means of controlling dangerous lead exposure have bean inadequately and incompletely applied. It will be of some interest to visualize the occupational distribution of fatal oases reported in the United States registration area, and of non-fetal cases compensated in Ohio, for tho year 1935, as shown in Table I, The data on Ohio do not cover all the industries and occupations that give rise to lead Poisoning since some of those are not represented in Ohio; nor do the numbers of eases as listed indicate tho true status of occupations with respect to their relative hazards# Howover, some of the oommon sources of occupational plumbism are illustrated. Comparison of tho numbers of oases in tho two columns shows that industries with a relatively high occurrence of non-fatal poisoning may have a low or negligible frequency cf fatalities# These data, when considered in relation to the approxima co nrmoere of persons employed in the several occupations, further suggest that safety measures hazardous types of ?.<;.-ad exposure without: r-sdvn ing the exposure to safe luvei*. V'hethsr true or not vhis thesis is of academia importance only, for the fact re mains chat th-s present incidence of load poisoning is still unnecessarily high and can Ice reduced greatly through the use of suitable method3 of control This la not to say that There are not difficult problems to be met in certain industries Some dusty lord oc t .pound3 are manufaotu.red and handled by methods which can bo rendered safe only cy the exercise qf continual vigilance and the application of unusual engineering skill* V-hat is needed in some instances ir the willingness era th part of 'vunuif ccurers to abandon certain pro css sea in fairer of ethers which can as con trolled cars satisfactorily, sven though, the product may be inferior in some rasoecta to that obtained by other methods* .Purely for the purpose of an example, and not to single out one manufacturing method for criticism, the bid butch process is employed for the manufacture cf a type of white lead which is regarded in some circles as superior to that obtained by other methods' of manufacture I may be in error.- but I do not believe that the advantageous qualities of the product justify the cost of the measures required tc safeguard the various operative stops cf this process* That such qualities justify the tolerance of unsafe conditions in plants which use this uroesss esnnot be a coopted - In general, however, it is not necessary to make .sweeping changes in manufacturing methods . There are, in fact, few types of occupational lead exposure that offer serious or unsurniountable obstacles to mod am engineering methods of attack* '"'hat is really required is an understanding of the means of detecting dangerous lead exposure. Satisfactory nsthod3 are available for this purposa - methods which not only will demonstrate the existence and the general magnitude of the hazard but also will identify the operations and conditions which ara responsible* for it* Tiie Measurement of Load Exposure The measurement of lead exposure in anticipation of its affects cannot be accomplished effectively by purely clinical meanse Nor can it be dona satisfactor ily through the study of any of the non-specific physiological reactions of the body to lead absorption. The so-called "lead line" of the gums or of the anal tissues is not specific for load, nor is it related, in rapidity of apoearance or in extent, to known quantities or concentrations of absorbed load* The increase In reticulocytes, or in diffuse or punctata basophilia of ths erythrocyte3 is substan tially con.-3tar.t in its occurrence as a response to seme dsgroe cf imroaas iu ivix absorption, but it is not the result of lend absorption alone, nor ic fcjie responce sufficiently uniform in quantity to give a reliable due to the magnitude of the lead absorption of an individual or group of individuals From th point of view of prophylaxix, the blood changes share with the "lead line** the virtue of bsing non-specific signs of lead absorption rather than of intoxication, end they are clinically useful in the detection of lead exposure, but they are not sound criteria for estimating the magnitude of lead exposure* Their use as such is but a makeshift, to be relied upon only when adequate methods for measuring the magnitude of the sxposurs are not available. Poisoning from the ingestion of lead compounds is of infrequent occurrence in industry,partly because of the general excellence cf wash room and lunch evos facilities in industrial plants and the resultant promotion of orderly and cleanly habits among the workmen., but chiefly because of the preponderant opportunities for intoaicafcion fro::* the inhalation cf particulate lead compounds which contemnsts the- atracnphere of workrooms, In other words, the ingestion of load compounds in ths course of th day's work can be and is largely prevented through the uxerciso uf ordinary cure, while the prevention of lead inhalation is attended hy much greeter ff 0022943 difficulties. Zn certain indns' ries cc reful supervision is needed to maintain the degree ox personal cieaniinasx `hat i.s required for the avcddonce of lead ip castion, and where this is the case such Eupsr-r. sion should be provided, for seriously die- abling lead poisoning can occur from load ingestion alone, as ia cl scons touted adequately by its ccourrsnoe irt the gov oral population, especially among children. An cverft'heisjing proportion cf o of industrial lead poisoning, however., is due to inhaled lead. It follows, b-i&rsforu, that determinations of the lead content of thy atmosphere of Yorkrooms yields faarly comprehensive informsticn as to the rcagni- tuti g of tho occupational load ha sards j.rt such rooms, Yatiofactory xaethods for stirratirg the atmospheric ?.cad a orient he vs been devised and amployod extensively in a variety of industries, not only in hygienic surveys but also in the routine periodic testing cf plant conditions, especially ia relation to changes inequipment and operauin* methods,* The development cf these methods, than' practical applica tion to the study of plant processes, end the correlation of date obtained by their use with the results of clinical studies on workmen, hsva provided a prsctiosl moans for the appraisal of industrial lead hasards. ns experionoe has b&sn gained it has bacons inoraasingly apparent that it is feasible to express the magnitude of the load ha sard? of a plant and of its individual operations in terms of the load uon~ tent of properly selected air aemplas, and to anticioats with reasonable accuracy the procable results of exposure, especially with respect to the severity of tho intoxication which is likely to ba associated with a given ms cni trade of exposure reoond method which is available for measuring the load anrards of an occupation, is baaed on th fact that load is eliminated from the body cf exposed persons at a rate which is determined by the magnitude and duration of the exposure, and in a manner which tends to identify the portal of entry Thus the periodic study of the alimentary and urinary excretory response of representative workman to the lead exposure associated with their occupations within an industrial plant giver, e eross-section&l picture of plant conditions which iu not afforded by v.ny other means. The method has the additions.! groat advantage, from the view-paint of the mediozi -tun, that it provides useful and often indispensable information for the diagnosis of obscure and unusual oases of illness among workmen* I.bngercus lead absorption sumotiroos occurs as tbs result of apparently insignificant changes in tsoimioal pro cedures. An occasional workman nay ba seriously poisoned in an occupation or plant th* c appears to ba safe. Such cases are commonly attributed to unusual susceptibil ity 5 Actually one Visually finds that such pereons have absorbed voxre quanfci tias of lead as the result of some unusual and unrecognised type.of exposure, Workmen in the lead trades also develop illnesses unrelated to lead exposur . Abdominal pain in the load worker is not always lead colic, Tho prompt analysis cf n pom pie of blood and urine siay servo to rule out lead intoxication- and permit the recognition and treat ment. of another type csf illness. These, as well as numerous on her practical consider ations fully justify the use of this general method of maintaining a check on the .loud exposure associated with tho operation of -an industrial plant. Obviously it, like air ssi.rpling, must be carried out as an adjunct to clinical supervision It may also be employed to advantage in combination with air analyses., using tho latter to obtain prompt results in situations in which for various reasons it is difficult or incon venient to obtain the necessary cooperation of the workmen, Discussions of mothcd.3 can be found in Industrial Dust, (Hygienic Significance, Ilea aursnent .and Control), by Drinker and Hatch., !vlc~Graw~Hill Book Co lieu York, 193 6, on U,, u,. Public tisaith Bulletin No.217, 1935, by Bloomfield and Dalle,vails, and in the Sixth Annual Year Book of the American Publio naalth Association, 1S35-36, in a. Sup plement to the American Journal of Bublio wealth 1936, n<3s ho,i,3D--83. H 0022944 Ths Recognition oC Hazardous Lead Ex-.joawra ' ` 'hen hazardous load exposure sxists it gives rise to caass of lead poison ing, the number and severity of which -rary in general with the severity of the expo sure > 'Vorkrasn ss&y be removed from more hazardous jobs either periodically cr when incipient pIambiera manifests itself, ani<i by being transferred to work involving less or no exposure, some unpredictable proportion cf them may be spared bha mors serious oonssousnoe cf their exposure, i'nl'ortunately it is often impossible to detect in cipient plumbism in time to obvia te its effects > In my xperisno the most reliable, indication of impending a out 3 ir.tcxics tion is found in th eubjactivo symptoms of a workman whan described under conditions that neither minimis or magnify thorn. Here, however, ova is dealing with actual intoxication and often i:i o stage which may giv3 no clue to its ultimate severity, Moreover workmen often conceal their symptoms to retain their employment, or they magnify them from, anxiety or intont to deceive. Doubtless for this reason undue reliance has been put upon certain laboratory pro cedures., especially microscopic blood changes, to 'provide warning of impending intox ication. Some industrial physicians have even resorted to n periodic deleading therapy in the case of heavily exposed workmen, with ths idea of avoiding oxoossave accumulation cflead in their tissues, and thereby maintaining them in their occupa tions for longer periods of time. I hasten to condemn this latter procedure un reservedly as based snor on faith and the spirit of adventure than on sound hygienic principle and practice, and as inspired by a greater seal to servo industrial man agement than to protect endangered workmen. In the long run oil such efforts to forestall the worst effects of admittedly unsafe working conditions are doomed to but incomplete success and, therefore, to failure, for cases of poisoning will occur if there is sufficient exposure, and sometimes without warning. Moreover the doc tor is not serving his primery function in industry through such efforts* Obviously ns should treat those who suffer from lead poisoning or any other occupational injury, tut lot us not delude ourselves or him in the belief that ho is making ar.y important contribution to industrial hygiene by so doing Hie most important role in relation to the industrial intoxications is to develop and to employ his skill for their recognition and thereby to demonstrate the need for their control. His careful clinical study of a plant population should serve to detect the existenoe, the loca tion and the nature of ths occupational factors which injure ths health of the work men. This involves a considerable knowledge of the plant conditions and the processes and a familiarity with changes in plant operations-. It also requires thorough inves tigation of all types of illness, and adequate study of detailed and well ordered medical records on ths plant personnel. Y.ith specific reference to lead hazards suah as regime of medio cl supervision as is envisaged above- involves a oonti;aid search for signs 'of.abnormal lead absorption. Such signs ore likely to be quite obvious whore ths methods for the control of exposure are ineffectual or haphazard but even under these conditions the more hazardous operations can be located by evidence that is apt to be so convincing as to justify remedial measures. An the magnitude of isad exposure in a plant is progressively diminished correspondingly more precise methods for detecting the effects of abnormal lead absorption come to be required, but the adequacy of any type of hygienic control which provides anything less than complete elimination of occupational lead exposure must rest upon the clinical data obtained on the exposed persons. The detection of hazardous lead exposure therefore is the one primary and indispensable contribution of the physician toward che control of industrial lead poisoning. .Safe Limits of Lend Exposure Compa mtivsiy recent studies of human lead absorption and excretion under normal environmental conditions and at various levels of experimental and occupational lead exposure have crovided a sound .physiological basis for the opinion advanced K f ' 0022945 > by industrial hygienists, that s-orrua degree of load absorption can bo born without injury by human beings. It is new quite clear that man and ether animals ingest snail quantities of lead daily with their food and drink, and that they establish an equilibrium with their environment by means cf which they maintain relatively constant con centre ti oris of lead in their tissues and excreta, and a balance between lead intaka and output. In experimental observations an human subjects, as yet un published, we have seen that within certain limits, which as yet have not been fully explored, an increased level of load intake results in s temperary increase in the load content of the tissues, with a progressiva rise in excretion until c "balanoa between intake and output is reached at a level higher then normals Under such conditions progressive accumulation of lead does not occur in the tissues. Yfe have obtained evidence, which has been detailed elsewhere, thet at some incompletely defined level of lead intake the excretory processes fail to keep pace v/ith lead absorption, and accumulation of laad occurs<> It seems probable that load intoxi cation occurs only &s the result', of the absorption cf quantities of lead with which the bedy is unable no cope for some reason s\ich as the foregoing. Conversely, it set ms reasonable to suppose that so long as lead absorption and excretion are main tained in balance, lead intoxication will not occur, regardless of the length of tine the exposure to lead is continued. Whether or not this is true over the entire range of balance^lead intake and output, has not been ascertained at oresent, but it can be accepted as fact that up to e certain level of intake and output, v.*e are deal ing with a set of normal or physiological processes which are no more associntod with toxic manifestations than are a variety of metabolic reactions of other mineral constituents cf the human bodyo This faot enables us to recognize that the poison ous properties hitherto attributed to lead and its compounds, are not necessarilyassociated with its more presence in the tissues but rather with the occurrence of definite quantities or conoantrations of the element therein. That is to say, lead j .3 a dangerous constituent of the human body only when it occurs in toxic concentra tions in the tissues. It is a dangerous factor in human environment only when it occurs in such form or in such quantity as to gain access to the body in toxic concentretione The primary problem of industrial hygiene, in relation to lead impounds, therefore, is to determine the lowest injurious concentration of lead in human tissues. For obvious reasons hygienic engineers have put their chief efforts into the study of plant conditions, employing the available and sorsatimss iradoaust* infor mation as to the general state of health of workmen as clue to the significance of lead exposure. By suoh means they have established criteria which if generally fulfilled in the lead industries would serve to eliminate a large proportion of presently occurring cases of lead poisoning. >'*ith the additional information which can now bs- supplied by the physician through maintained study of the physiological response of lead tvorkera to the lead exposure of their occupations, more precise criteria' for the recognition of potentially dangerous exposure con be set up. There in little room for doubt that by such combined efforts of the physician and the engineer, hazardous lead exposure can be brought under ccmplecc control, so that the many useful lead-bearing commodities of present and future industry can bs pro duced without the payment of the present unjustified toll of illness and death among workmen. KH 0022946 . t abu: Occupational Distribution of Cases of Flumbism in the Year 1935* Painters Paint Workers Foundry V/orkers Storage Battery Factory Yorkers Sanita ry-wa re Fnaraelers Lead '"'orkars Printers, Eleotro-Typers and Lithographers Potters Automobile Factory "'orkars Miners Rubber Factory Yorkers Farmers Miscellaneous Non-Ceoupatioral (mostly children) Total Fatal Cases in the United States 36 6 10 4 5 1 8 23 34 130 Compensated Cases in Ohio 36 13 23 102 ^Adopted from the data of Frederick L. Hoffman as reported in Hi S, Department of labor Serial Ho. R, 669, U. S Government Printing Office, "'ashington, D. C,, 1938. KZ 0022947