Document XybZ4jxGzmnpEj6N7Ld62bLR

Ninth Annual Convonticu Greater Kew York Safety Gonceti April IS, 20 and 2.1, 1338 0ccupatj.cr.u3. Llmese He o Y Soscion No. 22 Papar lo* 84 INDUSTRIAL LEAD POISONING pTe R o A Kahoe Esttsring Laboratory of Physiology University of Cincinnati Cir..cnnat i, Ohio 1ha Occurrence of Lead Poisoning in Incaatry The available statistics indicate that there has bean a progressive decline In the incidence of fatal, lead poisoning in the United States during the past eight een cr twenty years. Considermg tne obvious inadequacies in those statistics one may doubt that they represent the facts reliably, but cannot escape the conclusion that the more har.ard.cus types of occupational load exposure have been brought under scan degree of control. The lata provided by state compensation agencies also points to a fairly general trend toward reduction in the incidence? of non-fatal lead poisoning ever the period cf years and in 'the areas for which information is recorded Thus in Ohio the number of compensated oases of plumbirm in 1928 was 130, '.'/hilo in 1936 such cases totaled 112 The decrease in the number and rat of Gasee of lead poisoning has not been so great or so consistent from year to year as has been the decline in fatal cases, and indeed an.actual diminution in such oasoa has probably not occurred in all parts of the United States Experience has demonstrated that v/hen the 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 is done to improve operating conditions Otherwise an attitude of laissez fail's is likely to exist* Thus, in hygienically backward regions cf the country, industrial plants can be found in which seriously disabling and fatal cases of load poisoning occur, not as the unforeseen consequence of some 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 lead compounds may undertake the manufacture or processing of lead-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 medo toward the progressive elimination of industrial pluiabisn, among which the most troublesome, perhaps, is the continual change in technical and manufacturing procedures whereby new opportunities for load exposure aro introduced into the indus try In any case, we may.not take excessive- pride in the improvement that has been achieved' in recent years, but rather should we feel disappointment and chagrin that the available means of controlling dangerous lead exposure have beer inadequately and incompletely applied. It will be of soma interest to visualize the occupational distribution of fatal oases reported in the United States registration area, and of non-fatal casos compensated in Ohio, for the 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 these are not reprssented in Ohio; nor do the numbers of canes as listed Indicate the true status of occupations with respect to their relative hazardsc How ever, some of the oommon sources of occupational plumbism are illustrated Comparison of the numbers of oases in the two columns shows that industries with a relatively high occurrence of non-fatal poisoning may have a low or negligible frequency of fatalities* These data, when considered in relation to the approxima co nrmoere of persons employed in tha several occupations, further suggest that sc,f3by measures carried out in certain industries have tended to eliminate the mora dramatically hazardous Types of load exposure without radiit ing the siroosuro to a safs lavI-. V'hothsr trua or not unis then is is of academic importance only, for the fact re gains chat th-s pres ant ircoidonca of load poisoning is still unnecessarily high and oan C3 reduced greatly through the use of .suitable methods of control This ia not to say that There are not difficult problems to ha met in aorta in industries Some lusty laid oct.pound a are ma nufa otu red and handled by methods which can bo rendered safe only cy the exercise qf continual vigilance and the application of unusual engineer in:; skill* V.hat is needed in some instances is the willingness on th part of Knuffccurers to abandon certain procsssss in fairer of ethers which can be con trolled mors satisfactorily., even though, the product may be inferior in some rassecta to chat obtained by other methods. Purely for the purpose of an example, and not to single out on 3 manufacturing method for criticism, the bid butch process is employed for the manufacture cf a typo of white lead which is regarded in seme circles as superior to that obtained by other methods of manufactures I may be in error, but I do not believe that the advantageous qualities of th product justify the cost of the measures required to safeguard the various operative stops cf this p.recess. That such qualities justify the tolerance of unsafe) conditions in plants which use this nroesss cannot be acoopted * In general, hoever, it is not necessary to make swooping changes in manufacturing methods There are, in fact, few types of occupations! lead exposure that offer serious or unaumiountable obstacles to modern engineering methods of attack.- '"'hat is really required is an understanding cf the means of detecting dangerous lead exposure Satisfactory nsthod3 era available for this purposa - methods which not only will demonstrate the existence and the general magnitude cf the hazard but also will identify the operations and conditions which are responsible for it. The Measurement o^Load Exposure The measurement of load exposure in anticipation of its effects cannot bo 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 gut?i3 or of the anal tiacu&s is not specific for load, nor is it related, ir. rapidity of apoearanco or in extent-, to known quantities or concentrations of absorbed load.. The increase in reticulocytes, or in diffuse or punctata basophilia of ihs rrythrosytea is ouhutsntdaily constant in its occurrence as a reeperso to acme degree of increase in ..--ad absorption, but it is not tin result of land absorption lono, nor ic the responce sufficiently uniform in quantity to give a reliable d u e to the magnitude of the lead absorption of an individual or group of individuals. Krcia th point of view of prophylaxix, the blood changes share with the "lead lias** the virtue of being nor.-spacific; signs of lead absorption rather than of intoxication, and 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 rolled upon only when adequate methods for measuring the magnitude of th ex posure are not available. hoisoning from the ingestion of lead compounds ic of infrequent ocourreaos in industry, partly because of the general excellence cf wash room, ami lunch room facilities in Industrial plant and the resultant promotion of orderly and cleanly habits among the workman., but chiefly because of the preponderant opportuniti for intexioation from the inhalation cf particulate lead compounds which contaminate :he atmosphere of workrooms > In other words, the ingestion of lota compounds in the course of the day's work can bo and is largely prevented through the exercise of ordinary c.are, while the prevention of lead inhalation is attendee. % much grse.tsr difficulties Zn certain indus* riea c.ireful irurex'vision is needed to maintain the degree of personal cieanlines 3 -hat is required far the ftvcidance a? lead inpast:;,on, and wbere this is the cone such super*r. sion should be provided., for seriously dis abling lead poiseeing can occur from lend ingestion alone, ns is demonstrated adequately by its occurrence in the gey era! population, especially among children* An overwhelming proportion cf c?;r.?s o 1 industrial lead poisoning, hewever, is duo to inhaled lead. It follows, fc-i&rsforw, that &terminations of t-ho lead content of the atmosphere of .rorkrooms yields fa roly oorrprehensire information as to the magni tude of the cccunational load hazards in such room., ikjtxsfactory xnathods for stirrEtirg the otrrospheric lead content have been devised and employed extensively in a variety of industries, not only in hygienic surveys but also in the routine periodic testing of plant conditions, especially in relation to changes inequo-paent and operav.ing methodc,* The dovelopmwnt cf these methods, thair practical applica tion to the study of plant processes, end the correlation cf data obtained, by their use with tko results of clinical studies on workmen, have provided a practical moans for the appraisal of industrial lead hasards As exporicnco has been gained it has become increasingly apparent that it is feasible to express the magnitude of the load ha sards of a plant and of its individual operations in terms of the load uontent of properly' selected air samples, and to anticipato with rsasonable accuracy the procable results of exposure, ospecially with respect to ths severity of the intoxication which i likely to be associated with & giver, magnitude of exposure; A. osoond method which is ava:ilablo for measuring tbs load .insards of an occupation, is based on the fact that load is eliminated fro m the body of exposed persons at a rate which is determined b y t h e magnitude arc 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 ropreeer.tativa workman to the lead exposure associated with their occupations within an industrial plant giver, e oross-aectioa&l picture of plant conditions which is not afforded by any other means. The method has the additional great advsrings, from the vior'~point oC the medio 2 1 men that it provides useful and often indispensable information f o r the diagnosis of obscure arid unusual oases of illness among workmen* Itngorcus lead absorption some times occurs as tbs result of apparently insignificant changes in tcomical pro cedures. An occasional workman nay be seriously poisoned in an cocupatic-u or plant tha c aopears to be safe Such oases are commonly attributed to unusual ausaaptibil\tv: Actually on e usually finds that such pereons have aboorbod uoxie quantities o f lead as the result, of sene unusual and unrecognised type, of exposure, Workmen in the lead tirades also develop illnesses unrelated to lead exposur , Abdominal pain in the lead worker is not always lead colic- The prompt analysis of n rcnplo of bloo and -urine may servo no rule out lead intoxication and p e r m it the recognition and trea ment. of another type of illness. These, as well as mtmarous other practical coneidor ations fully justify the use of this general method of maintaining a check or, the loa exposure associated with the operation of -an industrial plant. Obviously it, like ai saixpling* must be carried out as an adjunct to clinical supervision* It may elec be emolcyad to advantage in combination with air analyses, using the latter to obtain prompt results in situations in which for various reasons it 2.3 difficult or incon venient to obtain the necessary cooperation of the workman. Discussions of mothcd.3 can be found, in Industrial Dust, (Hygienic Significance, lie.aaurcnent and Control), by Drinker and Hatch, Me-Grew-Hi 1.1 Book Co Slew York, IDotb on Hr 3-, Public il.vai.th Bulletin No.217, 1935, by Bloomfield end DaHe.-rails, and in the Sixth Annual Year Beck of the American Fublio Health Association, 19o5-3d, in -a Sup plement to the American Journal of kublio uealtn 1936, .G; 1.0,3,33-83;. HE 0022944 - 1- The ftecognifcicn oC Hazardous Lead Bx-.ioaura ' ` 'hen hazardous load sxpcsu.ro sxista it givss rise to oases of Iced poisonTM Inc. the number ana severity of which vary in general with, th severity of the expo sure > Workmen may be removed froit mono hazardous job either r/sriodioally cr "shea incipient pIambiera manifests its-slf, and by being transferred to work involving loss or no exposure., uomo unpredictable proportion of them may be spared the mors serious consscusnoe cf their exposure Cnfor tunatoly it ie ofton impossible to detect in cipient: plumbiam 'in time to obviate it3 effects, In my xporisnes the most reliable, indication of impending acuta iricxicstion is found in ths Eubjsctiv symptoms of a v-'arkmsn when described under conditions that neither minimis or magnify thorn Here* however, 0119 is dealing with actual intoxication and often i:i a stage whioh may give no olu to its ultimate severity, 'foreover woriemsn often conoeal their symptoms to retain their employment, or they magnify them from, anxiety or intent to deceive. Doubtlass for this reason undue reliance has been put upon certain laboratory pro cedures, especially micros.copie blood change;:;, 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 the idea of avoiding oxoossiv fioinnrvl tion of* lead in their tissues, and thereby maintaining then in their occupa tions for longer periods of time. I hasten to condemn this latter procedure un reserved ly as based more on faith and the spirit of adventure than on sound hygienic principle and practice, and aa inspired by a greater zeal to servo industrial man agement than to protect endangered workmen. In the long run oil ouch efforts to forestsII the worst offsets of admittedly unsafe working conditions ara doomed to but incomplete success and, therefor, to failure, for cases of poisoning will occur if there is sufficient exposure, and sometimes without warning. Moreover the lector is not serving his primary function in industry through such efforts. Obviously ns should treat these who suffer from lead poisoning or any other occupational injury, but 1st us not delude ourselves or him in the fcaiief that ha is -making any important contribution to industrial hygiene by so doing. His moat important role in relation to the industrial intoxications is to develop and to employ nis skill for their recognition and thereby to demonstrate the need for their control. His careful clinical study of a plant population should servo to detect the existenoe, the loca tion and the nature of ths occupational factor.1? which injure the health cf the work men. This involves a considerable knowledge of the plant conditions and the processe and 3 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 the plant personnel Y.ith specific reference to lead hazards such as regime of .medical supervision as is envisaged above involves a opntinued search fo signs of.abnorma1 lead absorption. Such signs are likely to bo 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 ba so convincing as to justify rsmedia1 measures. An the magnitude of land exposure in a plant is progressively diminished oorrsspondingly mor precis 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 loss 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 the control of i n d u s tr i a l 1osci p o 13 o n i n g > .Safe Limits of Lead exposure ' Comparatively recent studios of human load absorption and excretion under normal environmental conditions and at various .levels of xpcri.nental and occupationa lead exposure have crovidad a sound physiological basis for the opinion advanced K f - 0022945 > -O'-- by industrial hygienists, that ecrne degree of lead absorption can bo borne vdthout injury by human beings, It is new quite clear that man and c~her animals ingest snail quantities of lead daily with their food and drink, and thf-t they establish an equilibrium with their environment by means cf which the;/ maintain relatively constant con centre ti oris of lead in their tissues ar.d excreta, and a balance between leed intake and output. In experimental observations on human subjects, as yet un published v;e have seen that within certain limits which as yet have not been fully explored, an increased level of load intake results in a temporary increase in the lead content of the tissues, with a progressive rise in excretion until e balance between intake and output is retoad at a level higher then normal, Under such conditions progressive accumulation of lead does not occur in the tissues, ?fe have obtained evidence, which has been detailed elsewhere, that at some incompletely defined level of lead intake the excretory processes fail to keep pace with load absorption, arid accumulation of lead occurs. It seems probadla that load intoxi cation occurs only as the result of the absorption cf quantities cf lead with 'which the body is unable no cope for some reason sitoh as the foregoing. Conversely, it sacras 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 b&lancet lead intake and output, has not been ascertained at present, but it can be accepted as fact that up to s certain level- of intake and output we are deal ing with a set of normal or physiological processes which are no more associotod with toxic anifostat ions than are a variety of metsboiic reactions of other mineral constituents cf the human body. This faot enables us to recop,nixe that the poison ous properties hitherto attributed to lead and its compounds, are not necessarily associated with its mere presence in the tissues but rather with the occurrence of definite quantities or concentrations of the element therein.. That in to say, lead i3 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 fora or in such quantity as to gain access to the body in toxic concentrations The primary problem of industrial hygiene, in relation bo lead compounds, 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 end sen atildes inadequate infor mation as to the genere1 state of health of workman as a clue to the significance of load exposureo By such moans 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 be- supplied by the physician through maintained study of the physiological response of lead workera to the lead exposure of their occupations, more preciso criteria' for the recognition of potentially dangerous exposure can 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 cempiece control, so that the many useful lead-bearing commodities of present and future industry can be pro duced without the payment of the present unjustified tali of illness and death among workmen KB 0022946 ' A Occupational Distribution of Cases of Plumbism in the Year 1935* Adapted from the data of Frederick L. Hoffman as reported in H. Department of labor Serial Ho. R, 669, U. S. Government Printing Office, "'ashington, D. C 1938. H e 0022347