Document EvRVDpJnNYZRJZm23OJY0Mk2g

METHODS FOR THE PREVENTION OF LEAD POISONING IN INDUSTRY By Robert A. Kehoe, M.D. From the Kettering Laboratory in the Department of Preventive Medicine and Industrial Health, College of Medicine, University of Cincinnati, Cincinnati, Ohio Introduction The poisonous properties of lead and many of its common inorganic compounds have been known with varying degrees of understanding and misunder standing for centuries. This situation persists, for the growth of new knowledge has been associated with a tremendous lag in its dissemination, and with a still greater delay in it3 application in clinical medicine and industrial hygiene. Since almost everyone has heard or read something about lead poisoning, it is assumed by many people, and especially by physicians, generally, that they know a great deal about it. The facts are that laymen, as a group, know virtually nothing about it that is of value to them, and on the outside of industry that comparatively few physiclans/have had any contact with persons who were suffering from lead poisoning, or any experience that would qualify them to diagnose or treat this ailment, much less to make a valid appraisal of the conditions under which the disease occurs. It is not surprising, therefore, that many cases of lead poisoning, especially those which occur among very young children, or among adults who have no obvious exposure to lead, should go unrecognized. Still less surprising, and actually of common occurrence, is the opposite situation - that of cases of other types of illness, especially those of somewhat obscure character, being diagnosed as lead poisoning, merely because the patient who presents himself to a physician is found or said to be "working with lead," or is employed in a shop or industrial plant in which lead is used. It is cause for much more surprise and indeed for great concern, that in a country in which technical knowledge and skill have reached a very high point - in which research and development in industry have become magic words and deeds in our productive, competitive economy - we should find so great a lag and such striking ineptitude in the application of the available technical knowledge in providing conditions in which the uniquely useful physical and chemical properties of metallic lead and its compounds can be utilized to the full, without exacting an unduly high toll in sickness and disability from the men and women who work with these materials. Much of a congratulatory nature medicine and has been said, in many places, of the progress that has been made in industrial/ hygiene in the United States. Some of this is valid, especially that which has been limited to the contributions to our knowledge which have been made in the past forty years through research in laboratories of industrial toxicology and hygiene, and through surveys and persistent medical and hygienic supervision and investigation in various industrial plants. Out of these have come the basic information and the practical methods whereby familiar types of industrial intoxication have been brought under satisfactory control in some industrial establishments in some areas of the country. There are, for example, industries in which large quantities of lead and its compounds are being used in potentially dangerous operations, in which no cases of lead poisoning, even of the mildest type, have occurred for many years, and in which the risk of lead poisoning is under complete control. In contrast to this are industrial plants, usually but not always,small in which occupational exposure to lead, in operations that are well-known to be dangerous, occurs practically without control, and in utter disregard of any principles and practices of industrial hygiene. It is equally true that, as KE 0008974 -3- the utility of lead and its compounds in modern technology have talien these materials into a large number of highly varied types of industry, many of those who are responsible for production, in their preoccupation with the technology of production, have had no thought for hygienic technology, lacking experienced or trained familiarity with these matters, themselves, and having nc/ technical or medical representatives of industrial hygiene in their organizations. Thus it transpires that the incidence of lead poisoning in American Industry is high, and while most of the cases of poisoning are comparatively mild, we still see, from time to time, cases that compare in severity and in their capacity for producing permanent disability, with those which occurred in the darkest periods of industrial history. In bringing these dreary facts home to this audience, I must also emphasize the fact that the manufacture of electrical storage batteries is responsible for a large number of cases of lead poisoning in the United States - probably a larger number than any other one industry and that to my personal knowledge there have been cases, within the present year, of a type that occur only as the consequence of massive, essentially uncontrolled exposure to lead in the form of dust and fume. These things are occurring in this industry at a time when there is ample information with respect to both the methods of control and the criteria of human safety, whereby lead poisoning can be eliminated completely from among the occupational diseases. It is my purpose to bring to you the evidence in proof of the latter statement, and to discuss with you the basic reasons for the failure, in present-day America, to apply well established methods of industrial hygiene to the protection of the health of workmen and the preservation of KE 0008975 4 their ability to earn a living for themselves and their families. Hygienic Standards for the Appraisal of Exposure to Lead Let us first consider the results of certain precise observations that have been made over long periods of time in various lead-using industries in this country, whereby occupational conditions which are dangerous can be differentiated from those which are safe. Ini obtaining such results one cannot have ed fail to perceive the major features of the industrial operations and of the conditions under which they are carried out, which have rendered them dangerous on the one hand^and safe on the other. These conditions will be dealt with at greater length, separately. It is impossible in the time available for the discussion of this subject even to mention the principal investigations from which our present knowledge of the behavior of lead in the human body has been derived. Suffice it to say that on the bases of such physiologic facts, the determination of the rate of the excretion of lead in the urine and the measurement of the con centration of lead in the blood provide definitive means for establishing, indirectly, the approximate level of the absorption of lead into the body, under appropriate conditions, and for estimating the severity and the hygienic significance of an occupational exposure to lead. By carrying out analytical surveys of workmen at suitable intervals over a sufficient period of time, one can demonstrate the fluctuations and the general trends in their current rate of absorbing lead, and thus establish the quality of the conditions under which these men work, with respect to the relative severity of their exposure to lead. By maintaining an adequate medical supervision of such workmen, in concurrence with the analytical regimen, one can also determine, in an entirely Hi 0008976 5 factual manner, whether the analytical findings both in individuals and also in the group, and hence the individual or collective occupational exposure to lead, is associated with the occurrence of lead poisoning. By means of systematic observations of this type, carried out over periods of years in a wide variety of lead-using industries, it has been possible to develop criteria by which dangerous occupational conditions can certainly be dis tinguished from those which are safe. Moreover, varying degrees of hazard can clearly be portrayed, in terms of the physiological and clinical responses of workmen to the conditions under which they work. There are tremendous advantages in having information at hand which demonstrates the extent of the absorption of lead by individuals in a group, and by the group as the composite representation of a specific industrial plant. For one thing, it is no longer necessary to speculate as to the extent and the significance of the exposure of the workmen to lead. This is revealed as clearly and as meaningfully, by analytical means, as are the dimensions of an article in production, by instrumental measurements. As for another gain in reasonable certainty, in contrast with the general fuzziness of former lay and medical opinion, the factor of individual susceptibility to the absorption of lead, which has been one of the potent obstacles to sound environmental control of lead exposure, has been reduced to a level of practical insignificance. One need not concern or delude himself with the idea that this, that or the other Get of conditions is not dangerous, or that this specific compound or mixture of compounds in the form and manner in which it is being handled, is not absorbable. The fact of absorption cannot be missed, provided established methods of investigation are employed with sufficient K 0008977 -8 - skill and care, and if the analytical results are interpreted on the basis of sound physiologic facts and principles. Hie latter reservation calls for a word of caution. The development of methods of analysis which cannot be employed successfully in ordinary clinical diagnostic laboratories or in the usual quality control laboratories of industry, has placed this analytical service in the hands of highly competent chemists in specially designed laboratories. So far, so good, in insuring the validity of the analytical results. The problem of obtaining satisfactory samples of blood, and especially of urine, however, is up to the physician, as is also the responsibility for interpreting the results anct acting upon them. By no stretching of his function can the chemist or industrial hygiene engineer properly assume these responsibilities. The handling and supervision of men who are threatened by disease is a medical function, both by tradition and law, and since the satisfactory placement or displacement of workmen often arises out of these analytical results, such results should be dealt with as the confidential data of medical records. When they are made available to, and discussed with, non-medical personnel, especially workmen, through other than confidential medical consultations with individual workmen, they create situations which are often fraught with grave difficulties, including misunderstanding, apprehension, gossip, and labor-management controversies. (It is fairly obvious that medical matters are often involved in collective bargaining, but it is equally evident that this is not the desirable method of arriving at sound medical policies in industry.) It may be noted, with some surprise or concern, that the discussion of standards of safety has not included, thus far, reference to the tolerable limit (or limits) of the concentration of lead and its compounds in tho U 000807S -7 atmosphere of industrial establishments. It might have been supposed, for reasons of convenience and economy, as well as historical sequence, that such a standard (or standards) of safety would have been considered herein in advance of any other. It is not through accident or prejudice, however, that this matter has been relegated to a secondary position in its relation to human safety with respect to the absorption of lead. The fact is that the measure ment of the concentration of lead in the atmosphere affords many practical advantages in connection with the operation of a plant in which lead is being used, and specifically in the appraisal of the efficacy of the measures for controlling the lead content of the atmosphere. At best, however, one is dealing here with "rules of thumb," in relation to degrees of hazard. The latter vary with the physical and chemical characteristics of the particles dispersed in the air, and, therefore, unless these characteristics (i.e. the nature of the specific compound (or compounds) in the atmosphere, and the distribution of the particles as to size, shape and mass) are ascertained and are interpreted in terms of their potential absorbability, they provide little more than an educated guess as to the severity of the overall hazard sustained by men who work in the tested areas of the plant. The mention of "tested areas" should bring to the mind of the experienced industrial hygiene engineer the problems presented by the many operations which are carried out in many different areas of an industrial plant, and by the manifold variations in the volume of these operations from day to day, month to month, or year to year. The adequacy of the sampling program, as to methods and the satisfactory coverage of such variables as changes in the overall or localized volume of production, deterioration of production and control equipment, and many others, is always open to question and is subject to budgetary, as well as technical; obstacles. KE 0008979 3 The significance of the concentration of lead in the air in the vicinity of workmen, even if it is so determined as to relate only to respirable lead, is still an Incomplete expression of the occupational exposure to lead, for this is not the only source of significant exposure. Unless care is taken to limit the introduction of lead into the digestive tract, through the promotion of habits of cleanliness on the part of the men, and through provision of comfortable and attractive wash-room, "change-house" and lunch-room facilities1, the lead that is swallowed daily continues as a source of absorption throughout the 24 hours of the day and over the week-end (since the alimentary tract is not emptied of its residual contents at the termination of the day's work). It is true, of course, that the absorption of lead from the alimentary tract is slow and incomplete under the most favorable conditions, but it is also true that lead poisoning may result solely from such absorption, if the quantity ingested is sufficient. Since it is fairly easy, under suitable conditions, for the workman to avoid the ingestion of lead in the course of his work, it is obvious that this contribution to that which he inhales from the air, under much less easily avoidable circumstances, should be kept at the absolute minimum. In this connection it is a fact of con siderable importance that the large particles of lead-bearing materials (those in excess of 2 to 10 microns in diameter, or of even larger dimensions) which may remain airborne, in the immediate vicinity of a workman's nostrils, long enough to be inhaled, are deposited for the most part in the nasal and tracheo bronchial passages, and that large numbers of them reach the nasopharynx and are swallowed. Thus it happens that the alimentary tract may contain from a few to many milligrams of lead every day, which are derived from the dust laden atmosphere of a plant. Therefore, the use of an air-sampling device K 0008980 9- which excludes the larger particles - even those which fall out of the air rapidly - may fail to reveal the time significance of the exposure of workmen to airborne lead. For all of the foregoing reasons, and for others as well, the sampling and analysis of the air, as the sole or principal means of measuring occupational lead hazards, may fall partially or utterly to reveal the true state of the industrial environment, and it can never (or hardly ever) be expected to disclose the probable or actual hazard of the workmen, especially that of the group of workmen (such for example, as the maintenance and house cleaning personnel) whose work does not fit into the usual patterns of production operations. Other criteria have been and are being used to maintain a check upon the status of workmen in the lead trades. These range from some form of periodic physical examination to the use of procedures of the clinical laboratory (either as supplements to physical examinations or as the sole measures of medical examination), from which conclusions are drawn as to the likelihood of the onset of lead intoxication in a specific workman or among certain occupational groups of workmen. The strictly clinical examinations are intended to pick out the individuals in a group of men who are threatened by lead intoxication, or, more realistically, to discover incipient intoxication before it has reached a serious or disabling stage. Certain laboratory tests, among which the commonest, the microscopic examination of the blood for "stippling" of the erythrocytes (these tests are often extended to include other changes in the formed elements in the blood, such as reduction in the numbers and in the hemoglobin content of the erythrocytes) and, more recently, the examination of the urine for the presence of abnormal quantities of KH 0008981 10 porphyrins, are being employed as means of appraising the state of health of the workmen, or in reverse, the extent of the hazard of lead absorption to which they are being subjected. Without entering upon an ill-timed discussion, here, of the relative value of these criteria for diagnostic purposes or for revealing certain non disabling effects of the absorption of abnormal quantities of lead, it is sufficient for present purposes, to say that none of'them, singly or in combination with any or all of the others, is satisfactory. In order to put this fact in perspective in the present state of preventive medicine, I trust that I may, without impropriety, take a firm professional position. I would not be willing to accept the responsibility for the safety of a group of workmen in an industry in which there is an actual hazard of lead poisoning, if I had to rely solely upon any one or any combination of these clinical procedures. In the light of present knowledge, these are not adequate as procedures of preventive medicine in the lead-using industries. In an earlier period of occupational medical practice, they were the best moans available; they are now but makeshifts. Their only justification is that they are easier and less costly in their performance. Let me hasten to say that, in lead-using industries in which time and experience have demonstrated that the exposure of workmen to lead in current, stable operations is being so controlled as to be without hazard, it will not be necessary to resort to precise measurement of the rate of the absorption of lead. Sven in such industries, however, some of which are now known to exist, any important change in the type or method of the operations must be reexamined for its effects upon the absorption of lead by the relevant group (or groups) of workmen, if the health of the latter is to be adequately protected. Moreover, the equipment of the operations, as HE 0008982 - 11 well as that of industrial hygiene (ventilation, filtration, electrostatic precipitation) undergoes deterioration and oust bo tested and maintained at a higher level of efficiency, if satisfactory environmental conditions are to persist. .Methods for the Control of Exposure to Lead in Industry The principle that develops from the general consideration of the preceding discussion, is that the principal functions of the physician in the lead-using industries are those of recognizing the existence of the danger of lead poisoning therein, when it exists, and of estimating the extent and the significance of this danger, and of providing suitable specifications for its elimination. It is clear then, that the actual prevention of occupational lead poisoning, in all but secondary natters, resides in the control of the inherent opportunities for exposure to lead which derive from the industrial operations. The responsibility for such control lies in technical, not medical, hands, and is,fundamentally, a function of management. This function, however, in our day, may properly be delegated to the industrial hygiene engineer, provided the efforts of the latter are implemented adequately by management, either directly or through the medical department. It is not wise nor realistic to assign such responsibility to a physician, nor is the physician true to his humane role in society, if he accepts such responsibility There is no drug nor medicine - no chelating agent, no food nor drink, such as milk or lemonade - whereby men who are absorbing dangerous quantities of lead may now be shielded from the harmful effects of such absorption. The time raay come when medical research will have brought forth medication that will serve this purpose, but this has not been accomplished, and until such a time. KE" 0008983 12 - the responsibility for the occurrence of occupational load poisoning rests heavily upon the management of the lead-using industries. There are certain measures which can be employed usefully and effectively for short periods of time, or in unusual situations or emergencies, whereby the medical guidance of the management in the disposition of workmen can be used for the protection Of the latter in obviously dangerous situations. Such conditions should not be tolerated longer than is required to arrive at a sound conclusion as to the nature of the existing situation and the proper means of dealing with it over the long pull. The specific methodology of environmental control in lead-using industries need not and should not be spelled out in this discussion. Suffice it here to say that technical experience and expertness are involved in the location and design of an industrial plant, its operations and its equipment, to meet the requirements of production, along with those of industrial hygiene and public health. (The mere mention of appropriate methods for the disposal of airborne and waterborne wastes is sufficient, for present purposes, to justify considerations of public health.) Obviously, it is much more difficult to achieve satisfactory results in the conversion of an old plant to a new or revised use. This is a matter which should be considered c-xpertly in the hygienic appraisal of an industrial project of this type. It is not an uncommon experience to find that a new plant has been designed to achieve certain advantages in production, in disregard of the requirements of industrial hygiene. Almost equally disconcerting is the outcome of the attempt to utilize an available or conveniently acquired building (or group of buildings), only to find, too late, that the cost of remodeling, without achieving a satisfactory result, was greater than that of constructing a new, properly designed and safe XE 0008984 - 13 - plant. Before concluding these brief comments on the methods of environmental control in the lead trades of the present and future, at least one other general principle should be enunciated, this time from the point of view of the physician in industry, whose duty, among others, is to cultivate among work men the utmost in knowledgeable compliance with the requirements in personal performance. These requirements must be reasonable in their demands upon both the understanding and the behavior of the workmen. One cannot make light of the hazards of the day's work, and at the same time put the responsibility for meticulous care in the avoidance of hazard upon the uninstructed workman. The intelligent and effective use of a dust respirator is indeed a matter which requires both understanding and meticulous care. Moreover, if the require ment of the use of the dust respirator is to be more than a gesture of piety, against the overwhelming probability that it will not be used effectively by untrained, and unsupervised workmen, the respirator will have to be selected, inspected, cleansed and fitted to the workman by an appropriately trained representative of the management, and its proper use will have to be assured by an effective system of supervision. As the preceding comments suggest, there are situations which require the use of personal respiratory protective equipment from time to time and there are a few jobs which, it seems, cannot be carried out with safety without continuous use of such equipment. This is rare, fortunately, and each instance must be accepted as a real challenge to the ingenuity of the designers of processes and equipment, since it is the persistent, nagging evidence of a departure from sound principles of both Industrial engineering and environmental hygiene. It is a function of the process engineer to design the equipment of production to secure the maximum in efficiency and economy of production, consistent with the safety of those 0008985 14 who carry out the operations. The contribution of tho environmental (industrial) hygiene engineer, in this relationship is to secure the safety and the maximum of convenience and comfort of the workmen, to the end that they shall sustain no impairment of their capacity to work because of potential dangers of their occupation. The Basis for the Present Position of the Lead-Using Industries in Matters of Industrial Medicine and Hygiene In the preceding discussion it has been pointed out, with some emphasis, that there are now satisfactory criteria for the identification and appraisal of dangerous occupational conditions, with respect to occupational exposure to lead, and that there are methods for the complete elimination of the danger of lead poisoning from industry. The proof of the correctness of these statements has been furnished by those who have made effective use of the criteria for the differentiation of safe from dangerous conditions, and have employed methods of environmental control through which these criteria have been mot over periods of years. The bald fact which emerges from these statements is that despite the availability of adequate moans for the prevention of lead poisoning, the industrial users of lead and its compounds in this country now permit the occurrence of lead poisoning among their employees, while our society is willing to accept a certain toll of Illness, and a shortening of human life, while reaping the benefits of a large series of industrial products. The question with which all gentle and responsible people are con fronted at this juncture is - Why should these things be? Some partial answers to this question are worthy of consideration, not so much for the appeasement of our collective guilt, as for a clearer view of the way which lies ahead. First, what is true of the lead-using industries is true, in greater or - 15 lesser degree, of all of the hazardous trades in the United States. The evidence is not as clear, in many of these, as it is in those involved in the use of lead, as to the satisfactory means for controlling the hazard, but the practices of industrial medicine and hygiene are hardly ever on a par with the knowledge that is available, even in the most forward-looking and best informed industrial circles, while, in many others, performance lags far behind knowledge. There is probably no State in the United States in which there is not a very wide difference between those industries in which the practices are good and those in which they are less good or actually bad. If this is the case within certain outstandingly active States, in matters of industrial hygiene, there is an even greater divergence among the States, some of which occupy a primitive place in this setting, and make hardly a gesture toward occupational health. (It is for the latter reason that our soeiety as a whole cannot escape some share in the responsibility for the poor quality of industrial hygiene that is to bo or partially found in many areas of the country. If the government of the people is wholly/ unaware of its obligations, the people too are blind.) It is hardly to be expected, therefore, that the lead-using Industries should out-distance industry in general, in its hygienic performance, despite the fact that human experience in the handling of lead is old, even ancient, while that associated with many other materials is in its infancy. There is also, as has been said previously, a very great variation, among the lead-using industries, in their familiarity with the principles and applications of industrial medicine and hygiene, some have set fine examples in performance, others have resisted successfully every effort to win their adherence to good practices, while still others have engaged in the production (mostly of raw products) without even considering any need to protect their employees against lead poisoning. It is all too evident that the HE 0008987 - 13 principles of good medical and engineering practice in the American industrial community are extremely spotty in their dissemination and application, and that there cannot be said to be an effective professional representation of industrial medicine and hygiene within the industries of thi3 country. This is almost equally true, at present, of State, County and municipal health departments, despite the existence of notable exceptions to this generalization. Under these circumstances, it is not surprising that there is little by way ;of effective implementation of State legislation in matters of industrial hygiene in many areas of this increasingly industrialized country. A second feature, which goes far to explain the laxity of hygienic performance in many ieaa-using industries, is the insidious and often mild character of the intoxication induced by the absorption of moderate quantities of lead. Men who themselves have worked for many years in lead-using industries, and have supervised other workmen, remember the many men who, seemingly, have escaped illness, or have not been seriously disabled, and forget the smaller number of men who had severe cases of poisoning, as well as the larger number of men who were off work from time to time, but returned again and again to the job with which they were familiar. (It is usually in this latter group those who have suffered repeated attacks of lead intoxication of varying severity over a period of years, that our cases of severe and often permanent disablement - encephalopathy and palsy - are found. Despite their relative infrequency, these cases still occur.) The veterans in the industry, especially foremen and superintendents in the older types of plants and operations, will recount some of their earlier experiences, and insist, with truth, that present conditions are so much improve-a as to bear little resemblance to those of an Kf 0008988 1? earlier day. 'Die fact is that the penalties of compensation costs and the stress of personnel problems, including collective bargaining, have focused an increasing amount of attention upon the hygienic problems of the lead trades, and have resulted in greater and more widespread efforts toward environmental control. Many of these efforts have been poorly directed toward ill-defined goals, however, and have achieved varying degrees of improvement in the occupational conditions, without elimination of the haaard. What haa occurred, therefore, has been a fairly general reduction in the severity of the cases of lead poisoning, without a pronounced effect upon the incidence of the disease. Thus it is that cases of lead intoxication still occur ir* well-established Industrie-'. Moreover, as this metal and its compounds find their way steadily into new uses, an increasing number of workmen are being subjected to inadequately controlled occupational exposure, and the decreases in the incidence of lend poisoning, in some segments of industry, are counter acted by increases in others, A cursory examination of the foregoing statements would seem to face us with an old and frustrating dilemma on which many attempts to solve the lead problem in industry have bogged down - namely an unpredictable variability in human susceptibility to lead poisoning. This, however, is not the cues, for something new and decisive has been added to our knowledge in recent years, with the amassing of overwhelming evidence that, when the rate of the absorption of lead by men is kept within certain well-defined limits, no intoxication occurs. It is this fact which sets the standard of industrial medicine and hygiene which is to be achieved in the lead-using industries. It is also this fact which dispels much of the uncertainty which has plagued the physician in the lead trades for so long, as to what to expect of a certain set of KE 00^8089 13 occupational conditions. Certainly not all persons who are subjected to a dangerous degree of exposure to lead become ill at the same time or even ultimately, but all are in danger and may become ill at an utterly unpredictable time, and, as the severity of the exposure is found to increase from one occupation to another, the number and severity of cases of poisoning increase* These cases occur within a definite range of ordinary biological variability, fitting therefore into the usual patterns of biological phenomena. Even more importantly, for our professional peace of mind, at a sharply defined point in the progressive decrease in occupational exposure, cases of intoxication no longer occur, and the only evidence of the occupational absorption of lead that can be found is that of some elevation, above that of the ordinary normal individual in the general population, of the concentration of lead in the tissues and body fluids of the workmen. Summary The entire substance of the preceding discussion, apart from the presentation of the evidence on which it is based, may be represented briefly in the following summary. (1) The means by which dangerous occupational exposure to lead may now be differentiated from that which is harmless,are now available and have been put to the practical test of time and use. (2) Methods, derived essentially from engineering techniques, are also available whereby occupational exposure to lead can be brought and maintained within the limits of safety. These have proved their adequacy in use and are capable of general application. (3) The combined modern armamentarium of industrial medicine and hygiene can be so applied as to eliminate lead poisoning from American industry when KG 00089j O - 19 the determination to do so has become a general policy of industrial management. November 14, 1963 0008991