Document pBXYpYk1gOYp3zj434oQ186aX

MEDICAL OBSERVATIONS ON LEAD ANTIKNOCK WORKERS Theodore R. Robinson, M . D . , I . M . D . Staff Physician Medical Department Ethyl Corporation Baton Rouge, Louisiana 0009797 Medical Observations on Workmen and Work Environment in the Organic Lead Antiknock Production Area of Baton Rouge M anufacturing, Ethyl Corporation This report presents certain medical observations concerning Ethyl Corporation's antiknock production. M ost-of the basic data for the report have been collected and recorded system atically and persistently over many years by the M edical Department of Ethyl's Baton Rouge M anufacturing f a c ility . Roy C . A. Bock, M . D . , d esig n ed and im ple mented the medical program involved. He also has provided the long term continuing supervision so vitally necessary for the program to serve the needs of the industry, including the provision and preserva tion of the data upon which this report is based. Without his strong,, support and assistance, the studies outlined below could not have been accom plished. The philosophical teachings and technical findings of Robert A. Kehoe, M . D . , have been significant influences upon the m edical program from the beginning. A number of other physicians have contributed in varying degree to the actual collection of the various types of medical data during this period of time. This collection of medical data is highly unusual in its scope, consistency of collection, and time span covered. The following observations and comments are limited to areas thought to be of relatively general interest. Only such detail as is thought to be essential for understanding is included. Extensive docu m entation, including much significant medical information of more strictly professional interest, is available. I . Lead Restrictions - Routine biological sampling of each worker in the lead anti knock production area of Ethyl's' Baton Rouge plant and formal, fixed medical criteria for medical recommendations regarding modification of work assignm ent to reduce occupational expo sure to lead (restrictions) have been available and applied c o n s is te n tly for the p a s t 21 .years ( i . e . , s in c e 1952). How ever, in 1972 Operators on restriction began to be assigned to work involving essentially no exposure to lead, rather than to reduced exposure to lea d . The duration of restrictions would be expected to be altered by th is. Such alterations should not be interpreted in the future as representing a change in pre-restriction exposure, of course. 0009790 It should be noted that, over this time span, only one employee at this plant has been classified as having missed time from work due to illn e s s cau sed by occupational absorp tion of lead. A review of this case shows that the worker involved had non-specific symptoms associated with a level of lead in urine thought compatible with the production of such symptoms. However, this same individual Jjas a long recorded history of similar symptoms, both prior^and subse quent to the work absence classified as due to lead intoxica tio n , when w7ork h isto ry and le v e ls of lead in urine were clearly not compatible with lead intoxication. Thus this case should be considered to be "possibly", rather than definitely, related to lead absorption. A. Graph 1 shows the rate of re s tric tio n a c tiv ity , expressed as the percentage of the "at risk" worker population entering re s tric tio n each y e ar from TEL Operations in 1952 - 1972. The rate of restriction for the l a s t 10 y ears can be se e n to be e s s e n t ia ll y double that of the previous 11-year period. Graphs 2, 3 and 4 show the relationships between air analyses, urinary lead values and number of restrictio n s for certain areas from 1952 - 1972. It should be noted that restrictions are not expressed as rates here--the size of the denominator ("at risk" population) for these work groups over the years could not be determined very readily. Restriction activity roughly parallels group urinary lead values once levels greater than about 0.09 mg. Pb/1. have been reached. Air analyses and group urinary lead levels show little correlation. A similar lack of correlation has been found in numerous attempts over the years to relate air analyses to urinary lead levels of individual w'orkers. .' B. Graph 5, covering the time period 1944 through 1971, shows the distribution of restrictions by the month in which they began. A degree of season variation is noted. The explanation for this pattern is not obvious. C . Graph 6 shows the pattern of the average duration of . restrictions for Operations and M aintenance personnel beginning in each of the years since consistent re s tric tio n c rite ria have been in u s e . As c an be s e e n , the average duration of restrictions has not shown a tendency to increase over the 20-21 year time period. HE 0009799 r-;\ p w iWp*r*`*- )- iijMQ sru o ^j^^Q QLbt sybi cn-zp/ -*.o$ --k-'Q3 A * G)b\ t? y Ssb\ hAXQ'M U/j? h ia -%%-<>. * j m uy M,i Pi ^ - ^ ii '-' '^ q s w s * 'w&^* K 000SS3  fr <Y ,,t t V) ' 0 "^r ^ ^t- cr 30 J So /bl -* sb - S 3- o ^ oypL Jrtv. D. . Table 1 shows the number of individuals who have had one, two or more restrictions during their career at Ethyl Corporation (through 1972). A comparison for each individual concerning "subsequent" restrictions (i.e., 1st to 2nd, 2nd to 3rd, 1st to 3rd, e tc.) over the time period during which consistent restriction (and restoral) criteria have been used indicates that "subsequent" restrictions are as likely to be shorter than any previ ous restriction as they are to be longer. This means that subsequent restrictions for an individual do not tend to be longer in duration. This in turn indicates that medical management has been adequate to prevent a cumulative "loading" effect on individuals such that their clearing up would be prolonged on subsequent exposures at restriction levels. E. Summary: Air an aly se s have shown no u sab le correlation with biological measurements of worker exposures under ; the conditions experienced at this plant for the past 10- ' 20 y e a r s . Working conditions and practices (including restriction procedures) have been adequate to prevent any cumulative "loading" effect (as measured by duration of restrictions) on the workers in the TEL a re a , both a s groups and as individuals, over the past 20-21 years, and have been successful in the prevention of overt illness attributable to the occupational absorption of (organic or inorganic) lead. I I . M ortality Experience of TEL W orkers A m ortality study h a s been done covering a ll TEL O perators and a control (comparison) group of all Sodium Operators and Hydrocarbon Operators and Hydrocarbon M aintenance men on the active rolls (wage roll) at Ethyl Corporation on December 21, 1947. The mortality status of ail of these men was determ ined as of D ecem ber 31, 19 67. There w ere 592 men in th e TEL group re p re se n tin g 1 1 ,4 6 5 m an -y e ars of e x p erien c e during the 20-year follow -up period. There were 660 men in the non-TEL group representing 12,716 m an-years of experience over th is sam e 2 0 -y e a r p e rio d . There w ere 51 d e a th s in the TEL group and 68 in the non-TEL group. The d istrib u tio n s of death by categories are given in Table 2. The unadjusted 20-year crude death rates were 4.4/1000 many e a rs for TEL workers and 5 .3 /1 0 0 0 m a n -y e a rs for non-TEL workers. Making appropriate adjustm ents to correct to the KE ''OOS-306 RESTRICTIONS 1944 - 1972 Number of Times Same Individual Restricted Operations M aintenance ONE TWO THREE FOUR FIVE MORE THAN FIVE TOTALS 129 21 9 3 2 164 89 14 5 - -- 88 Mixed Totals - 198 2 37 - 14 1' 4 - . -- 2 -- 3 255 TABLE 1 Kg' 0008307. C auses of Death in 20-Year Period for TEL and Non-TEL W orkers C ause of Death Infectious & parasitic Malignant neoplasms Vascular CNS (Stroke) Heart Respiratory Accidents Homicide & Suicide Other Percent of Total Deaths Number of Deaths Represented by this Category TEL Non-TEL TEL Non-TEL COMBINED - 1 - 1.5 0.8 8 11 15.7 1 6 .2 16.0 2 3 3.9 4.4 4.2 18 31 35.3 45.6 " '41.2 1 1 2.0 1.5 1.7 13 6 25.5 8 .8 16.0 3 4 5.9 5.9 . 5.9 6 11 1 1 .8 1 6 .2 14.3 TOTALS 51 68 100.1 100.1 592 TEL men, 660 Non-TEL men. Time period 1 2 /3 1 /4 7 - 1 2 / 3 1 /6 7 . 100.1 TABLE 2 KET 0009808 1950 distribution of U.S. white male population for these groups gave a 20~year d e ath ra te of 174/1000 men for TEL workers and 209/1000 men for non-TEL workers. This com pared with the published rates of 190/1000 men and 224/1000 men for 1950 U .S. white males in corresponding age brackets. Thus TEL workers showed an "advantage" of 8% and non-TEL workers showed an "advantage" of 7% over U .S . w hite m ales by this procedure. Using a slightly different (but also "standard") approach whereby 20-year U .S. white male death rates (in this c a se , r a te s a s of 1950) w ere applied to the TEL and non-TEL d i s tributions of ages to obtain an "expected" number of deaths for all causes and for certain specific disease categories, so that the "expected" deaths could be compared to those actually observed, the information shown in Table 3 was o b ta in e d . The o v e ra ll "advantage" ex p erien c ed by TEL workers w as 12% and by non-TEL workers w as 15% by this method. The observed death rate from cardiovascular d is e a s e (primarily h e art a tta c k s and strokes) w as about 17% l e s s for TEL workers than th at "ex p e c te d " on the b a s is of the general U .S . adult white male experience. The "d isa d vantage" of 14% o b served for TEL workers in the "neoplasm " (cancer) category actually represented but a single "excess" death. If rates for 1960 were used, the "expected" number becomes identical with the "observed" number. Use of 1960 rates does not result in any change in "all causes" or "cardiovascular" figures. D e ath s in the " a c c id e n ts " c ateg o ry for TEL workers were in excess of the general U.S. white male category, but such scattered reports as are available that concern themselves with males employed in industry show a rate only slightly l e s s than th a t of the TEL group. The non-TEL d e a th s in this category were somewhat less than that experienced in the general U.S. white male category and probably were significantly le s s than would be expected from published "employed in industry" figures. A third "standard" approach was used which was similar to the previous one but with the "expected" rates for the U.S. white males expressed as an annual (rather than 20-year) rate and coming from a somewhat different so u rce. Applying th ese r a te s to th e (differing) annual d istrib u tio n and a g e s for TEL and non-TEL for each year, and expressing the "observed" deaths as a percentage of the "expected" deaths for each year (so called "Standardized Mortality Ratio" or "SMR), the HS 0009809 KE 00098i0 Expected v s . O bserved 20-Year M ortality for TEL and Non-TEL W orkers and 1 9 5 0 / U .S ./ M a l e T-------- ----- Age at Start No. of Men TEL Non-TEL 1950 Table Rate 20-24 114 65 0.041 25-29 138 143 0.055 30-34 152 168 0.084 ! 35-39 124 145 0.129 40-44 38 81 0 .1 9 6 45-49 20 36 0 .2 8 4 50-54 55-59 4 15 0 .3 9 4 2 5 0.525 60-64 - 2 0.670 ALL CAUSES CARDIOVASCULAR TEL Non-TEL Deaths Deaths Exp. O b s. Exp. O b s. 1950 Table Rate 5 3 3 1 0.007 8 7 8 6 0.015 13 9 14 13 0.032 16 14 19 18 0.0 5 9 7 10 16 12 0 .1 0 0 6 6 10 11 0.155 2 1 6 3 .0.227 1 1 3 2 0.316 - - 1 2 0.419 TEL N on- TEL Deaths Deaths Exp. Obs. Exp. O b s. 10 22 54 00 21 58 7 6. 9 9 44 86 33 66 10 32 11 22 -- 12 TOTALS 592 660 Ratio Observed/Expected "Advantage" Observed by Ethyl Workers 58 51 80 68 0 879 ' 0. 850 +12.1% : +15 .0% Tine period 12/31/47 - 12/31/67 TABLE 3 24 20 0.833 T.\+ 1 6 . 7 % 36 36 1.000 Zero p a tte rn shown by Graph No. 7 w as o b tain ed . By th is method, the TEL and non-TEL w orkers showed an overall "advantage" of 32% and 34%, re s p e c tiv e ly , over the general U .S . white male population of similar age distributions. The SMR's for TEL and non-TEL workers appear to have been ra th e r c lo s e ly parallel over the 20-year time period covered by this study. Summary: A mortality study with a 20-year follow-up showed essen tially the same death rate s, both for specific causes and o v e ra ll, for TEL workers a s compared to non-TEL w o rk ers. The rates were less than in the general U.S. white male population for most causes and overall. No unusual patterns of causes of mortality were seen. H e alth Experience of Long-Term TEL W orkers A detailed analysis has been made of essentially all available m edical records on a ll th o se TEL O perators who w ere hired prior to January 1, 1948, and who had worked continuously as TEL O perators through D ecem ber 31, 1967. E s s e n tia lly all factors measured and/or recorded were utilized: age, height, weights, blood pressures, hemoglobin content of blood, urinary lead lev els, blood lead lev e ls, diagnoses (made or reported at time of periodic exam inations, during absences due to personal illness or off-plant injury, e tc .), number of absences, duration of absences and types of illnesses causing absences-- all were analyzed by diagnostic categories, by year of occurrence and by certain sub-groups (as persons with highest urinary lead levels, persons with lowest urinary lead levels, persons with restrictions, persons never restricted, etc.). ' A control (comparison) group, properly matched for age and length of service, was studied for the same factors as men tioned above. The control group came from workers in the Hydrocarbon Operations and Maintenance' and the Sodium Opera tions groups, with careful scrutiny of records to assure that no occupational exposure to lead had occurred for any of these individuals. Unfortunately, no actual values for urinary or blood lead were available for this group. - TEL M a in te n an c e w orkers w ere not u tiliz e d in th is stu d y b e c a u s e their exposure to lead occurs at irregular intervals, with conse quent difficulty in expressing their absorption of lead over a long period of time in any meaningful manner. Confining attention to TEL O perators w as thought appropriate to magnify or maximize any health effects that might arise from long term absorption of (organic t inorganic) lead. 0009811 fi<c~ The only c o n sisten tly recorded factor not utilized in this study was experience concerning occupational injuries. Due to the widely dissim ilar nature of the physical activities involved in the work of the different groups, a comparison of this type of information was considered to be not justified or useful. There were 153 men in each group. As of the end of the study period (December 31, 1967), the a verage age of the TEL workers w as 5 3 .2 y e a r s , of non-TEL w o rk e rs, 5 2 .5 y e a r s . As of this same date, the average lengths of service were 25.4 years for TEL men and 2 4 .6 y e ars for non-TEL men. The TEL men had averaged 0.089 mg. P b/l. of urine over the last 8-10 years of the study. Blood le a d s , collected m ostly on individuals with higher urinary lead v a lu e s , averaged 0 .0 4 3 mg. P b / l 00 gm. blood. A "real" group average presumably would have been lower than this. The results of the multitude of detailed comparisons and calcu lations made in the study will not be presented here. They can be summarized by sta tin g th a t, with one e x c e p tio n , the TEL and 'Y non-TEL groups (and all sub-groups) appear to have been almost identical in their health ex periences, with no s ta tistic a lly sig nificant or medically suggestive differences. The one facto r in which the TEL and non-TEL groups were found to differ is shown in Graph 8, which shows that a very small but very consistent greater number of absences per year due to p e rso n al i lln e s s for TEL workers than for non-TEL w o rk ers. As can be seen in Graph 9, the average duration of the absences for the two groups were essentially the same over the years. This same pattern was found for each of the various sub-groups ("high" and "low" urinary lead groups, "restriction" and "no restriction" groups, e tc .). Analyses made for each of the various diagnostic categories (as heart disease, intestinal disorders, etc.) failed to show th is differen c e betw een the TEL and non-TEL workers in any specific category. At the p re s e n t tim e , the re a so n for the observed sm all but c o n sistent difference in number of absences per worker per year is not clear. The possibility that it might be due to occupational absorption of lead must be considered. The fact that those workers with the highest long term urinary lead levels and those workers who have been on restriction did not differ in this respect from those with the low est long term urinary lead levels and those with no re s tric tio n s-- or from the group a s a w hole--w eighs som e what against this ( i . e . , no progressive dose:effect relationship), but does not rule the possibility out entirely. If the observed 0003813 3 S O u a S ( j t A e>c/ uim// cg> l S"L V NO L \r\j to o / Q <fc O o '.-.I s f4 * V\ ft Q) O Q) V , ~> Vi <j v> - A` 0 -Vo\ > X >f."- T f4-i"':1 V. X n> <y VQ) Vc* y IO Q Qj 4N 9 ft! oJ >- O :> A 1-v. s/ m j u o q ^ " ? l/ f z l* &2-&c> / MQ i> ? /ei/Qjr-t?J &? Z>n<Z ~>o't&?f/-*;oj p s ^ 'j &*&/>,%%{ -to^z-rr/?// ~ difference was due to occupational absorption of lead, the effect was present at the lowest levels of absorption covered in this study--and did not increase in magnitude up to the highest levels of absorption covered in this study. Other factors (differences in worker morale, differences in concern and caution about illn e s s , e tc .) could be involved, but no way of evaluating them has presented itself. Summary: An e x h a u stiv e study of e s s e n t ia ll y a ll recorded h e a lth d a ta on a group of TEL O perators em ployed for 20 or more years has shown them to be essen tially identical in health experiences to a matched group of non-TEL workers. The only observed difference was a consistently slightly greater frequency of absence due to personal illness on the part o f TEL w orkers. No sp e c ific d i s e a s e , d iso rd e r or organ system could be identified as being related to this observa tion. The difference must be considered to be real, but the > precise cause or mechanism involved is not obvious. The nature and magnitude of this finding is such that it is of academic interest to the physician, warranting further investi gation when a suitable approach can be formulated. Concern or action on the part of management or workers is not indi cated . IV. Overall Commentary An e x h a u stiv e se arc h has been made for e v id e n c e of a d v e rse health effects associated with work in the antiknock production area of the Baton Rouge Manufacturing facility of Ethyl Corpora tion. No adverse health effects that are of practical significance or concern have been found. The system of medical monitoring and control that has been in use since 1952 appears to be ade quate for the protection of the health of the workers, not only against the development of acute lead intoxication, but also against any unusual incidence of other specific diseases or shortening of life span. June 1, 1973 Theodore R. Robinson, M . D . , I . M . D . HE' 000881 S