Document KJB9o7vmYnrd5xvVngQ00M9qQ

; THE LEAD CONTENT OF THE URINE AND BLOOD OF CERTAIN OCCUPATIONAL GROUPS WITHIN THE POPULATION OF CINCINNATI IN RELATION TO THE DISTRIBUTION OF PARTICULATE INORGANIC---L COMPOUNDS OF LEAD IN THE AMBIENT ATMOSPHERE INTRODUCTION In the initial draft of a report entitled, "Survey of Atmospheric Lead in Three Urban Communities," prepared for distribution by and within the Working Group on Atmospheric Lead Contamination, it was pointed out that the investigation of the effects of the general environmental exposure to lead of persons within the population of Cincinnati was to proceed along somewhat different lines than those carried out in either Philadelphia or Los Angeles. (It may be noted incidentally, that the subjects and the procedures of the surveys in the latter two cities were not strictly comparable to each other.) There were several reasons for this divergence in procedure in Cincinnati.: Of primary importance was the fact that many persons in ' Cincinnati and vicinity had been investigated/in thj.s manner previously, ' /' on several occasions, the latest of which was in tile winter of 1955-956. In the latter survey approximately 500 persons, engaged in various occupations, had been questioned and examined thoroughly in search of pertinent information, and their blood and urine, as well as their ' feces, had been sampled and subjected to analysis for lead. Very little more concerning the contribution made by atmospheric contamination to the absorption and excretion of lead, than had been learned in previous investigations of this type, was revealed by this investigation, and the conclusion appeared to be inescapable that if definitive evidence of the influence of air-borne lead upon the absorption of lead by the population of Cincinnati was to be obtained after so short an interval i 01 Dr N25005 2 of time, a different segment of the population would have to be investigated, or the investigative procedure would have to be refined. With respect to the specific technique of the investigation, the choice of the procedures of sampling and analyzing the urine and blood, as means of measuring the current and, hopefully, the more remote, experience of the individual human subject, with respect to his absorption of lead, had been based upon extensive evidence gained by prolonged and detailed investigation of the metabolism of lead in normal human subjects (1). There was no expectation that these general procedures could be replaced by other and better means of attack on the problem. There was some hope, however, that by a judicious selection of groups of persons in the population, and by the acquisition of certain items of supplementary information, it might be possible to * segregate certain individual sources of exposure to lead, and thus to /" ) recognize the relative importance of the atmospheric source. The problem of relating the rate of the urinary excretion of lead by any segment of the population, or the lead content of the blood of such a segment, to the lead in the ambient atmosphere, is complicated by several factors. The most important of these appears to be the intake of lead by the adult "with food and beverages. This usually averages 0.20 to 0.30 mg. per day per individual adult over considerable periods of time, but is sufficiently variable from one day to another (ranging from > 0 . 1 0 to ^2.00 mg. per day) to induce a considerable degree of variation in the lead output in the urine (with only slight to negligible variation in the concentration of lead in the blood, except during periods of sustained high intake in food and drink). 3 The next most important factor which tends to mask the specific influence of the air-borne lead to which individuals in the general population (exclusive of those employed in lead-using occupations) are exposed^ is the low concentration of lead in the ambient atmosphere. It is now clear that a fairly large proportion of the lead in the ambient atmosphere that reaches the alveolar surface of the lung is likely to be absorbed fairly promptly (25 to 40 per cent (2)). But the absolute quantity of lead so absorbed is minute and is less, under ordinary circumstances; from day to day, than that absorbed from the alimentary tract. Moreover, the lead content of the atmosphere in various areas of Cincinnati is variable, as shown both by the observations described in another part of this report and by those obtained earlier. Inasmuch as this variability has seasonal, diurnal and zonal features, the severity of the exposure of an individual to air-borne lead can be described for experimental purposes, during a specific period of the z1 ( year, only as the summation of the fractional periods spent from day to day at his place of work, at his home, on the way from one to the other, and at any other place frequented by him. During cold seasons of ^he year and under other conditions which involve the spending of much time indoors^ such factors as indoor ventilation and air conditioning; (especially filtration) can be expected to exert significant influences on the total daily or seasonal exposure. Many other factors, including out-of-the-city travel, have to be taken into account. The foregoing and other considerations rendered it desirable to seek out groups of subjects whose experience would seem to have yielded more than usually constant opportunities for respiratory exposure to the ) 4 principal sources of lead in the ambient atmosphere of Cincinnati. For obvious reasons, the most promising groups were those whose occupations require them to spend most of their working hours regularly in the streets and on the sidewalks of the city (in close relation to its motor traffic). In this category, and with some degree of intrinsic homogeneity as to social and economic status, fell city police generally (traffic officers in particular), postal employees, especially letter carriers on foot and in motor cars, city firemen (reasonably homogeneous but possibly subjected to unusual incidents of exposure to lead in their work), and certain peripatetic, technical employees of the City Health Department (housing inspectors, air pollution inspectors, and sanitary engineers). (Professional drivers of motor vehicles, especially in city traffic, such as taxicab drivers and the drivers of delivery trucks (powered by gasoline engines), were regarded as desirable subjects, / but were not readily available tjhroug^ any of the means that seemed feasible of general application, and, after the expenditure of con siderable time and effort in obtaining fourteen taxicab drivers as subjects, this group was abandoned. The results of these analyses are given in this report but are not taken to be representative of this occupational group.) For the purposes of this survey, it is not possible to establish an experimentally valid relationship between the specific environmental conditions to which either the groups, as entities, or the individuals of which the groups were composed, were subjected. That is to say that it is not possible, on the information recorded, to weigh with reasonable precision, the potential exposure to lead of a group or an individual in terms of the time spent per day in one or more of the several areas of -5 the City of Cincinnati. The search for significant evidence of atmospheric exposure to lead in the accumulated data had to be based, therefore, on the statistical examination of such variability as could be found within and between the several occupational groups, and on plausible interpretations of statistically significant findings. An additional point in the methods of the survey is worthy of mention at this point. It has been demonstrated conclusively in balance experiments carried out with human subjects, that, (under appropriate conditions, with respect to respiratory exposure to lead), the lead output in the feces, from day to day, over appreciable periods of time, is clearly indicative of the current intake of lead in the food and beverages ingested (3). It has also been shown that samples of feces, when collected on one occasion from each member of a fairly large group of normal adults, in such a manner as to approximate normal , daily evacuations of such individuals, contain quantities of lead which, > collectively, are representative of the daily intake of lead in food and beverages by the group. That is to say that the distribution of the frequencies of the quantities of lead found in the samples of feces of such a group, and the mean quantity of lead derived therefrom, correspond very closely in all respects to the results obtained in balance experiment's* carried out ever the period of many months during which the feces are collected as 24-hour samples. On the basis of these observations, it was thought that a reasonable estimate could be made of the intake of lead in the food of the subjects of the present survey, and that this factor could be so dealt with as to reveal, more clearly, any differences that might exist within or between the various groups of subjects in the severity of their exposure 6 to air-borne lead. Before undertaking to collect and analyze samples of the feces of these subjects, however, it seemed wise to reexamine the data gathered previously in the 1955-1956 survey from about 500 subjects, so as to assess the usefulness of this procedure in relation to the experimental objective. The criterion for this assessment, which appeared to be crucial, was that of the existence of a significant degree of correlation between the lead content of the feces of the subjects and the lead content of their urine. If such a correlationship should be found to exist in the former group of subjects, it could reasonably be expected to be found in the present survey. Unfortunately, no such correlationship was found, thus demonstrating either that the samples of feces, collected in the manner of the earlier survey, were unsatisfactory, i.e. were not truly representative of the facts with respect to the general level of the ingestion of lead in food and / beverages, or that the validity of the correlation between many samples ( of food and feces, while sustained for a fairly large group, does not7 extend to the individuals in the group, unless multiple observations on individuals are so made as to reduce the factor of individual variability from day to day. (There are, of course, other possible explanations of this lack of correlation.) In any case, there was no good reason to believe that satisfactory results could be obtained in this manner in the present survey, and this idea was abandoned. (It has been found entirely feasible to obtain samples of feces from a fairly large group of subjects in such a manner as to yield a close approximation of their 24-hour alimentary evacuations. This requires such careful indoctrination of each subject, however, and such close adherence to instructions on their part, as was not thought to be 7 possible under the conditions of this survey. It is also possible to obtain samples of urine of large volume, or multiple samples of small volume, so as to gain satisfactory information from each subject con cerning the general rate of his urinary excretion of lead, thereby dispensing with the relatively large factor of physiological variability in the urinary output of lead from time to time during the day. Such an investigative approach to a large group of subjects, would have extended this survey far beyond its intended scope.) Selection of Subjects Pursuant to the objectives indicated above, the groups and numbers of subjects under investigation in the present survey are indicated in Table 1. Table 1 , -G-r-o-u-p-s--a-n-d- yS-u-b-g-r-ou;-p-s--o-f--S-u-b-j-e-c-t-s Policemen / Policemen concerned primarily with traffic1' Numbers 123 37 Firemen 191 Post-office personnel .s 140 Health Department personnel Sanitary engineers Air pollution inspectors Housing inspectors .. 37 21 9 7 Taxicab drivers 14 Total number of subjects 505 Three of the groups, i.e. policemen, firemen and post-office personnel, are composed of practically all of the persons who were 8 available within the periods scheduled for the examinations. Some few were on leave or otherwise temporarily unavailable. The importance of this essentially full coverage of these groups lies in the fact that the effect upon the absorption of lead of any relevant but unusual feature of the life or experience of specific individuals within the group will have left its mark, within the sensitivity of the methods employed for the detection of such effects. (The selection of representative subjects or classes of subjects from a specific category of subjects is likely to be based upon assumptions, and despite the cautious exercise of judgment, grounded in experience, the incompleteness of the coverage becomes a source of concern.) The assurance as to complete portrayal of the relevant effects of the experience of these three groups does not extend to the selected groups of personnel in the Cincinnati Health Department, but the three * subgroups share with the other major groups the geographic coverage of the city. The drivers of taxicabs, on the other hand, are too few in number to be representative of this highly variable (in geographic, racial and social origin, and-in personal characteristics) category of citizens. For the purposes of this survey, they are merely other persons who have yielded additional items of data. No further reference will be made to them, other than to record the data, and to note that the latter fit into the general pattern of the larger body of data. . In order to call attention to other segments of the population of the Cincinnati community, and to include certain additional and seemingly pertinent vocational categories of subjects, it seems 9 advantageous to broaden this report by recording the results of certain observations made in the winter of 1955-1956 on 478 persons in Cincinnati and vicinity. The methods of questioning and examining these subjects differed radically, in their comprehensiveness, from those (to be described below) employed in this survey. The analytical data, however, augmented by those concerned with samples of feces (as referred to previously), were obtained by the same methods of analysis in the hands of the same members of the staff of the Laboratory, and are comparable, in every respect, to those obtained in this survey. The mere increase in the number of persons investigated, from approximately 500 to approximately 1000, is not in itself, of importance, but the locations and types of employment of the additional groups of subjects, in relation to the factor of the combustion products of automotive engines, provide a significant broadening of the scope of the investigation. in Table 2. The types and numbers of these subjects are listed /) Table 2 Groups of Subjects Numbers Gasoline service station attendants 130 Refinery handlers (tank truck) of gasoline 86 Garage mechanics 152 Car parking attendants 48 Drivers of motor vehicles 45 Cincinnati traffic officers 17 Total number of subjects 478 0151 9 10 Methods of Investigation Each subject was questioned by a member of the clinical team com posed of five physicians, assisted by a registered nurse and three clerical assistants, and the results were recorded in a uniform manner, employing the "Environmental, Occupational and Medical History" form of record authorized by the Study Group, a copy of which is reproduced for inclusion below. A specimen of urine, voided on one occasion directly into a glass container (a chemically clean bottle of approximately 130 ml. capacity, closed tightly by a latex rubber cap), was obtained under the super vision of the examiner, from each subject. Duplicate specimens of blood were also obtained by means of previously cleansed, rubbercapped and evacuated glass tubes and lead-free, metallic needles (the complete B and D Vacutainer equipment). Each specimen, in the container supplied for the purpose by the Kettering Laboratory, was labeled for' identification, and returned to the Laboratory for analysis by methods that have been described in the literature and in the preliminary report of the Study Group. The analytical data were ehtered into the record of the subject, punch cards were prepared therefrom, and by means of the latter,' various statistical arrangements and computations were made in search of relationships of environmental significance. Results All of the analytical data of the two surveys (that of 1955-1956, and that of 1963) have been assembled in Tables 3 and 4, according to the \ Table 3 Distribution of Persons in Various Vocational Groups According to the Concentration of Lead in Urine Lead in Urine Mg./L. Service Station Attendants Refinery Handlers of Gasoline Parking Attendants Garage Meehanics 0-0.009 1 1 1 ! 4 0.01 14 2 0.02 74 49 21 39 Stes 0.03 33 22 12 33 o 0.04 cn LO 0.05 ._1 0.06 13 5 3 9 4 7 30 2 21 1 16 0.07 4 0.08+ 1 3 Drivers of Cars 1956 1963 1 28 11 5 24 24 1 1 Police Traffic Officers 1956 1963 All Police 1963 Firemen PostOffice Emp. City Health Dept Emp. 22 9 6 47 49 12 5 13 29 71 52 18 7 21 36 19 6 3 8 30 19 9 1 2 12 91 17 2 13 1 36 Totals 130 86 48 152 45 14 17 37 116 185 130 37 Mean 0.027 0.028 0.028 0.040 0. 020 0.036 0.023 0.039 0.038 0.027 0.022 0 .022 S.D. +0.010 +0.013 +0.011 +0.020 +0. 011 +0.010 +0.011 +0.020 +0.018 +0.011 +0.009 +0 .007 Table 4 Distribution of Persons in Various Vocational Groups According To the Concentration of Lead in Blood - (Dithizone) Police Lead in Blood Mg./ 100 g. Service Station Attend ants 0-0.009 Refinery Handlers of Gasoline Park ing Attend ants Garage Meehan ics 41 Drivers of Cars 1956 1963 Traffic Officers 1956 1963 All Police 1963 0.01 1 2 1 3 12 0.02 m 0.03 ,42 71 30 46 1 8 17 4 7 23 78 26 43 19 9 9 9 27 _Jl 0.04 14 8 20 72 9 14 5 til t o 0.05 TO 0.06 2 25 14 / "- \ 11 Fire men Post Office Emp. City Health Dept. Emp. 18 22 123 90 44 24 62 1 1 10 24 2 * Totals 130 Mean 0.028 86 0.027 S.D. +0.007 +0,006 48 152 0.034 0,038 +0.006 +0,009 45 14 17 40 123 191 140 36 0.033 0 *031 0.031 0.030 0.025 0.025 0.023 0.021 +0.006 +0.006+0.006 +0.009 +0.007 +0.006 +0.007 +0.005 - 13 frequencies of occurrence of various ranges of the., concentration of lead in the urine and blood, respectively, so as to provide a convenient means of inspecting them in a uniform array, and noting the more obvious similarities and differences in the groups. The impressions gained by observing the differences in the distribution of the results, especially in the frequencies of occurrence of higher values in the data of certain groups, achieve more definitive focus as account is ta.ken of the mean values and their standard deviations. Bearing in mind that the concentration of lead in the urine of an individual, apart from such a regular and potent physiological variable as the quantity of water available in the body, at any specific time, for excretion in the urine, is dependent primarily (with some lag) upon the current rate of the absorption of lead from the alimentary and respiratory tracts, it is apparent that the degree of variability of the concentration of le-Sd in the specimens of the urine (Table 3) of nearly / 1^000 persons in these divergent walks of life is remarkably small, the /total range extending from 0.005 to 0.11 mg. per liter, When one realizes that there is virtually no physiological obstacle to the excretion of much higher concentrations of lead in the urine (than those recorded in Thble 3), under appropriate conditions of exposure and absorption Cu&lues in excess of 5 mg. per liter have been observed, while'values up to and in excess of 0.5 mg. per liter, in the course of occupational exposure to lead are not uncommon), it is clear that the quantities of lead absorbed by the individuals in these groups, from day to day, while highly variable within low limits, are of a uniformly small order of magnitude. There are significant differences in the groups, however, of which the outstanding example in the entire series is that of the garage 14 mechanics. Other groups, notably the police officers of this survey, as an entire group, and a fairly sizable sub-group of traffic officers (includ ing certain other police officers whose duties involve prolonged service on foot and in motor cars in traffic streams of varying density), are in the relatively high zone of the total spectrum of mean values. In considering the results of the analyses of the blood in Table 4, it should be pointed out that those represented in these tabulations were obtained by the use of the "dithizone" method of analysis. (The results obtained as a precaution against contamination or manipulative error, by the application, in parallel with the dithizone method, of the spectrographic method of analysis, were consistently confirmatory, in the sense that there was no instance of a deviation of the one from the other beyond the range of the known precision of the two methods. There were, therefore, no contaminated samples of blood and no unaccount- able errors in the analytical procedures. Since, however, the rj / variability of the results obtained by the parallel employment of the two methods is of lesser degree in the instance of the procedure involving dithizone, the results so obtained are preferable for statistical purposes.) In Table 4 aTMin Table 3, but in somewhat lesser degree, the groups are divergent, and again the outstanding example, on the high side, is that of the garage mechanics. A small group of men employed in several parking garages and parking lots (investigated in 1955-1956) is next in order on the high side, and a correspondingly small group of regular drivers of motor cars (also investigated in 1955-1956) come next and are almost paralleled (for whatever meaning the-fact may have) by the small and unsatisfactory group of taxicab drivers included in the 15 present survey. Next in descending order come the traffic officers (of the 1955-1956 survey) and, with insignificant difference, the larger group of policemen of which (in the present survey) they are a part. From here on down, from the mid-point in the sequence of mean values, come, in minutely staged differences of no apparent statistical or physiological significance, firemen, post-office personnel and the peripatetic technical personnel (inspectors of various kinds) of the City Health Department. It is obvious, despite the narrow range of the individual findings (0.01 to 0.06 mg. of lead per 100 grams of whole blood), and the small range of the mean concentration of lead in the blood of the several groups (0.021 to 0.038 mg. of lead per 100 grams of whole blood), that the differences between the groups reach statistical significance at several intervals* from the lowest to the highest, in view of the fact that the intrinsic variability r) within the group is of nearly the same low order of magnitude / throughout, as shown by the distribution of thq frequencies and by the mathematical expression of their variability in the standard deviations. The significance of these differences^in relation to ~ the primary environmental factor under examination - namely, air borne lead - is not so readily evident. As indicated previously, the situation is complicated by the quantities, and variability of the quantities, of lead ingested day by day with food and beverages. Many opportunities are afforded, daily, to individuals in our general population, to take in unusual quantities of lead. Cooking utensils, tableware, simple and not unusual incidents involving the handling of food (and other^objects introduced into the mouth) with unclean hands play their part in the environment in which lead is always present in S" J / 16 some form and quantity. An important feature that operates to limit the variety of human experience in these matters, and to promote a certain homogeneity of excitation and response, is the regular, daily, almost inescapable pattern in the highly organized life of the modern urban community. Common sources of food, water and other beverages, common avenues for the distribution of these products, and the common equip ment and routines of life in a large proportion of households, tend to limit the variety of experience. One may postulate, under these conditions, that such a variable as the atmospheric content of lead, if distributed in sufficiently distinctive orders of magnitude in welldefined areas of a city, would reveal its effects in a distinctly variable manner, through the responses of the residents of these areas. Accordingly, in order to determine the significance of one fact or.*which might contribute to the differentiation of the exposure to air-borne lead of individuals within the several groups, the subjects were classified according to the four general areas in which their home addresses were situated, as industrial, commercial, residential or rural (refer to the aerometric survey in Cincinnati). The results of the examination of the analytical data arranged in this manner are shown in Tables 5 and 6. The failure to find any valid or consistent relationship between these areas and the lead content of the urine and blood is evident. Another variable in the experience of the subjects - namely, their habits of smoking - in its hypothetical relationship to their absorption of lead, was examined in considerable detail because of its possible effect in masking or distorting the physiological response to the lead in the general (ambient) atmosphere. For reasons which have Table 5 The Mean Levels (and Their Standard Deviations) of the Concentration of Lead in the Urine of Four Vocational Groups of Subjects Distributed According to the Location of Their Home Addresses Within Certain Designated Areas of the Community Vocational Groups of Subjects Industrial Area Number Mean of .... Value Subjects Mg./L. S.D. Commercial Area Number Mean of Value Subjects Mg./L. S.D. Residential Area Number Mean of Value Subjects Mg./L. S.D. R Number of Subjects Policemen Firemen Post-Office Employees Health Department O Employees CJT ro All Groups 9 5 18 1 33 0.048 +0.19 0,027 +0.008 0.020 +0.005 0.020 0.028 12 0.037 +0.024 80 0.037 +0.017 10 21 0.026 +0.011 143 0.027 +0.011 16 14 0.020 +0.010 63 0.023 +0.009 15 6 0.020 +0.004 23 0.022 +0.008 3 53 0.026 309 0.028 44 / Table 6 The Mean Levels (and Their Standard Deviations) of the Concentration of Lead in the Blood of Four Vocational Groups of Subjects Distributed According to the Location of Their Home Addresses Within Certain Designated Areas of the Communi ty Vocational Groups of Subjects Industrial Area Number of Subjects Mean Value Mg./ 100 g . S.D. J' 1 Commercial Area Number of Subjects Mean -, S.D. Value Mg.y 100 g. Residential Area Number of Subjects Mean Value Mg./ 100 g S.D. Rur Number of Subjects Policemen 10 0.026 +0.007 12 0.029 +0.011 85 0.024 +0.006 10 Firemen oea Post-Office Employees o Cn Health fO Department CO Employees 5 0.026 +0.004 20 0.022 +0..005 1 0.025 22 0.026 +0.007 148 0.025 +0.006 16 14 0.026 +0.011 68 0.024 +0.007 17 6 0.021 +0.005 24 0.021 +0.005 3 All Groups 36 0.023 54 0.025 325 0.024 46 19 been set forth in the initial draft of a report of the Study Group entitled, "Survey of Atmospheric Lead in Three Urban Communities" dated January 15, 1963, it was not anticipated that this effect would be striking or even certainly discernible. On the other hand, the entire contribution made by the inhalation of lead to the absorption and excretion of lead by representative persons in the general population can hardly be detected readily, and the reduction of any part of it to discernible size might well be helpful in the appraisal of the other part (or parts) of it. The data that are available in sufficient numbers to be worthy of statistical examination are assembled in Table 7. (The division of all of the subjects or of certain of the groups of subjects into sub-groups, especially those concerned with varying degrees of intensity of cigarette smoking, resulted in such small numbers in certain categories as to be of highly dubious or obviously negligible representative significance.) It will be evident at a glance that the differences between the smokers and the non-smokers of cigarettes in the several groups of subjects, while very small and statistically insignificant, are, with one exception - that of the concentration of lead in the urine of policemen - in the right direction. That is, they tend to show, if anything, a trend toward the occurrence of larger quantities of lead in the urine and blood of smokers, as compared with non-smokers. This trend, not remarkably, in view of its essential uniformity within the group, is sustained when all of the groups are combined, and all of the smokers are compared with all of the non-smokers. Because of the larger number of subjects in the two categories, ^ the difference seems to have greater validity, but it is small indeed, 20 Table 7 The Mean Levels (and Their Standard Deviations) of the Concentration of Lead in the Urine and Blood of Four Vocational Groups of Subjects Distributed as Smokers and Non-Smokers,, and Accordine- to Certain Predilections of the Smokers, of Cigarettes Group of Subjects Sub-group Lead in Urine (Mg./L.) Lead in Blood (Mg. /100 g.) Number Mean Value Standard Number Mean Value Standari Deviation Deviati' Policemen Smokers Non-Smokers 104 8 0.038 0.039 +0.019 107 0.025 +0.013 11 0.023 +0.007 +0.006 Firemen Smokers 158 Non-Smokers 26 0.027 0.026 +0.012 163 0.025 +0.008 27 0.024 +0.006 +0.006 Post-Office Smokers 109 Employees Non-Smokers 19 0.023 0.019 +0.009 118 0.024 +0.007 20 0.022 +0.006 +0.010 Health Department Employees Smokers Non-Smokers 29 5 All Subjects 1963 Smokers 400 . Non-Smokers 58 0.023 0.018 +0.007 +0.004 30 0.022 5 0.016 1f / 0.028 +0.pi4 418 0.024 0.025 +0.010 63 0.022 +0.005 +0.002 +0.006 +0.007 All Smokers Inhale 282 Do Not Inhale 43 0.029 0.025 +0.012 294 0.024 +0.010 46 0.022 +0.006 +0.005 All Smokers Unfil teamed of Filtered Cigarettes 168 123 0.037 0.023 +0.017 +0.010 173 0.022 131 0.024 +0.0U5 +0.006 21 and cannot be taken very seriously, from the aspect of the one specific, but uncontrolled, variable. To the extent of the significance that may be attributed to this trend, it introduces a complicating factor into the interpretation of certain other statistical findings. It is important to recognize, however, that the differences between the vocational groups are influenced either slightly or not at all by the factor of smoking. Obviously, therefore, the factor which differentiates policemen from post-office employees, what ever it may be, is much more potent than the factor of smoking. It may be worthy of note, perhaps, (as much as is any other feature of these inconclusive findings) that the difference between smokers, with respect to whether or not they inhale, while minute, is favorable to the hypothesis that more lead is absorbed by those who inhale. Just what can be made, other than as the intervention of chance, of the contra;d-ictory findings yielded by the urine and blood of men who smoke unfi-ltered, as compared to filtered, cigarettes, is not apparent. A series of additional relationships between the levels of the concentration of lead in the urine and blood of the subjects in vocational and combined^groupings, and various features of their experience or environment, were investigated statistically. Included in these were such factors as the age of the subjects, the duration of their employment in their specific vocational categories, the source of their water supply, the type of heating and cooking devices in their homes or quarters, certain physical ailments (specifically, pulmonary, renal and hepatic diseases), and the frequency and severity of such suggestive effects of exposure to significant concentrations of carbon monoxide as headaches, dizziness and the feeling of undue tiredness, singly and in combination. Attempts to discover correlations 22 between these factors and the data indicative of variable levels of absorption of lead, were of no avail. Two charts portraying the product of the handling, in the computers, of the data with respect to the age of members of one of the groups, versus the concentration of lead in the urine, (Figure I), and the concentration of lead in the blood, (Figure II), will serve to illustrate the statistical procedure, as well as the lack of correlation that characterized this group of variables. This lack is so obvious in a mere glance at these two charts (as it was in all of the others) that there was no need to calculate correlation coefficients. Discussion The data as assembled systematically, for comparative purposes, in the preceding tables and figures, together with the explanations and discussions that have accompanied them, have conveyed the information obtained in this survey in a seemingly satisfactory manner. Some additional comments, however, may render this information more pertinent and responsive to the primary issues of the survey. It is all too apparent that the evidence which points to the influence of the"*lead content of the atmosphere in any part of Cincinnati upon the levels of the concentration of lead in the urine or blood of the subjects of this survey, as well as that of 1955-1956, is dubious at best. From the physiological viewpoint there can be no doubt that this factor exerts an effect upon the composite absorption and excretion of lead by the individuals in the population. But the best, and in fact the only, findings that contribute any actual weight of evidence to the detection of effects which vary with varying degrees / I I I ... .. - ... ... I I I l --- :---------- -- --- I I 0.0750 I i 1 I \I I .....- .... -- -- I L I __ EI A I _________ D 0.0500 I I I - .. .... N I ...... ....... - .. . .>__ I U I_ RI x. CTI I U-J N E I I I___ ....... 0.0250 - * _______ . . X X. I i . ... .. X X * < I I . . * X X* * . I ______ _ _ I I SCALE I I 1.0025 PER LINE I 21.00 27.00 33.00 NUMBER 0F PIECES OF DATA Figure J FIREMEN BY AGE _______________________________________ _______________________________________________ ,, __________________________ __________ _ _ __ ________________ '_______________ _________________________ i I I I I 1 I [ I I I I I I I I I 1 ----- 1_------------- 1------I -- r r r-- --I 39.00 65.00 51.00 SCALE AGE 0.60 PER SPACE SYMBOL TABLE 57.00 I I I I ---- 1:------- -- - I ------- -------1- 63-00 69.00 / Figure II FIREMEN BY AGE III I 0.0550 T l E A 0 0.0400 - 'I -- = N (J1 CM B . L 0 Q 0 0.0250 0 I T H I Z o SCALE r/ 0^015 PER LINE NUMBER OF PIECES OF DATA X *. * .* X*__ . X.___ * * *. X X X* X XX XX X XX * * X XX X .X X ___ - .. t_.X__ . , * . . -I- 21.00 27.00 -I- 33.00 -I39.00 SCALE AGE -I- 45.00 -c51.00 0.60 PER SPACE SYMBOL TABLE -I- 57.00 63.00 25 of severity of exposure to air-borne lead, lie in the somewhat greater extent of the current (and less recent) absorption of lead (as revealed by the level of the urinary excretion of lead and the lead content of the blood) by certain groups of subjects who would seem to have under gone somewhat more than the usual exposure to air-borne lead, namely, the:garage mechanics and car parking attendants of the 1955-1956 survey, and the policemen (including traffic officers), of the present survey. There is no doubt that many of the individuals in these groups have absorbed more lead than have corresponding numbers of persons in any of the other groups. Further, there is no doubt that there had been a significant gradation of the total exposure to and absorption of lead within the several groups of subjects, from the highest mean values recorded in Tables 3 and 4 to the lowest. The question at issue, of course, is whether these differences are due to differences in the exposure of the individuals within these gi?6ups t)o air-borne lead. It is tempting to conclude that this was the case", especially since this was the assumption on which certain of the groups of persons were selected. But the matter is not so simple in terms of valid evidence, primarily because the experimental design of the survey included no control '*f other environmental sources of lead, one of which, at least, must be regarded as no less than equivalent in magnitude and variability to that of lead in the air namely, the lead in the food and beverages of the individual and grouped subjects. There is no direct evidence in these data on which the actual order of magnitude of the absorption of air-borne lead by these subjects can be estimated. Moreover, as indicated above, there 26 is no valid direct or indirect evidence on which the differences between the various groups can certainly, or even probably, be ascribed to differences in their respiratory exposure to lead. The uncertainties with respect to the meaning of the variable results of the analytical findings from person to person and from group to group among the subjects, may indicate to some persons who are interested in the outcome of this investigation, that little or nothing of signi ficance has been contributed toward an understanding of the hygienic significance of lead in the ambient atmosphere. Such a view of the matter misses the main point of the findings, from the aspect of the potential halzard of air-borne lead to the public health. The fact is that the order of magnitude of the respiratory exposure to lead in Cincinnati is small - so small, in fact, that it cannot be dis * tinguished, with reasonable certainty, from other sources of the exposure to lead, on the part of/the general population, even by the refinements / of statistical analysis.* The importance of this fact is exceeded only by that of the further fact that the composite exposure of the general population of Cincinnati to lead, from all ordinary and general sources, is small, and that while such exposure is variable, from day to day, the limits of variability are such, and the frequencies of occurrence of the *The magnitude of the respiratory exposure and of the physiological response to it can be defined indirectly, but accurately, in well designed experiments in the laboratory, in which the several sources of exposure can be measured individually. It is possible also that a survey could now be designed in such manner as to yield valid information concerning the extent of the contribution made by individual sources to the composite exposure to lead of representative groups in the general population. Such a survey would be more elaborate and more costly than any that have been carried; out previously. 27 higher ranges of exposure are such, as to pose no hazard to the public health. Summary 1. Observations have been made this year (1963) on 505 persons in five different, active, vocational groups of males in the general population of Cincinnati, in search of evidence of the effects (upon the absorption and excretion of lead) of their exposure to lead in the ambient air of the city. The results of these observations have been combined or compared, so far as possible, with those obtained eight years earlier (in the winter of 1955-1956). 2. The specific groups of subjects (gasoline service station attendants, gasoline tank truck handlers and transporters of gasoline, automobile parking attendants, drivers of motor cars, and garage mechanics, in 1955-1956; and policemen, post-office employees (mostly > letter and mail carriers), firemen, technical personnel (peripatetic inspectors) of the Health Department of Cincinnati, and a small group of taxicab drivers, in 1963) were selected for investigation for the reason tht each group offered some prospect of including within its ranks a goodly number of persons the greater portion of whose work ing days were spent in proximate relationship to the motor traffic in the streets or within the confined spaces of repair or parking garages. 3. The subjects were also investigated from the aspect of the relative contribution which might be made to their respiratory absorption of lead through their use of tobacco (primarily in smoking cigarettes). 28 4. The subjects were questioned as to matters which appeared to be relevant in some degree to their past and present opportunities for the absorption of lead from any source, but with specific emphasis on respiratory sources. Other seemingly pertinent items of historical, occu pational or medical information were recorded. Specimens of urine and blood were obtained from each subject for analysis for lead. 5. The historical and analytical data were coded and assembled in a variety of strategic arrangements, combinations and juxtapositions for statistical comparisons and computations, and both the significant and insignificant relationships were examined and commented upon in the text of this report. 6. The essential conclusions derived from the combined data of the two surveys may be stated in much abbreviated form as follows: (a) Among the several vocational groups of subjects, garage ' j mechanics may definitely be singled out as having given evidence of / their subjection to greater exposure to and absorption of lead than have any of the other groups. Several other groups, namely the automobile parking attendants, the drivers of motor cars, and traffic policemen, have yielded suggestive but not consistent and definitive evidence of having*-absorbed somewhat more lead than the remaining vocational groups. Listed in the decreasing order of the mean levels of the concentration of lead in the urine and blood of the other groups are,interchangeably, service station attendants and refinery handlers of gasoline, firemen and postmen, and finally, a group of peripatetic inspectors in the City Health Department. 7. The mean levels of the concentration of lead in the urine nin c Sc*" ! 29 of the several groups range from 0.022 to 0.040 mg. per liter, while those in the blood range from 0.021 to 0.038 mg. per 100 grams. These ranges are small and well within the limits of the normal range as it has been defined in balance experiments conducted on normal, healthy individual subjects in this Laboratory (1), and the successive differences from the highest to the lowest are significant statistically at only two points between the extremes. From physiologic or hygienic view points these differences are of little significance, and from the aspect of the differentiation of the effects of the absorption of air borne lead, from that of ingested lead (which was not measured independently in these observations), they are too small to be informative. 8. The combined data derived from these surveys serve to demon strate that the composite exposure to lead and the absorption thereof, by the several groups of subjects investigated, is too small to be separated into its exponent parts by the methods that have been employed. 7 / References (1) Kehoe, Robert A.: The Harben Lectures, 1960 - The metabolism of lead in man in health and disease. Lecture I. The normal metabolism of lead. Journal of the Royal Institute of Public Health and Hygiene, 24:81-87, 1961. (2) Kehoe, Robert A.: The Harben Lectures, 1960 - The metabolism of lead in man in health and disease. Lecture II. The metabolism of lead under abnormal conditions. Journal of the Royal Institute of Public Health and Hygiene, 24:101-20, 129-43, 1961. 30 (3) Kehoe, Robert A. et al.: Experimental studies on the ingestion of lead compounds. Journal of Industrial Hygiene and Toxicology, 22:381-400, 1940. From the Kettering Laboratory in the Department of Preventive Medicine and Industrial Health in the College of Medicine of the University of Cincinnati, Cincinnati, Ohio. Clinical Work by: Harold R. Imbus, M.D. Sidney Lerner, M.D. Lee Miller, M.D. Lester W. Sanders, Sr., M.D. Leslie J. Schradin, M.D. Barbara Day Marilyn Franzen Louise McEnery, R.N. * Analytical Work by: Roland Burkey, B.S. - J. Cholak, Ch. E. / Statistical Work by: Theodor Sterling, Ph.D. Henry Weller, B.A. __ Charles Yarbrough Experimental Design and Report by: ... Robert A. Kehoe, M.D. Approved: DATE: August 30, 1963