Document bBNa98VQVjVNjByv3oMJ4Xm16

'130 . Annals New York Academy of Sciences 48. Dugois, 1\, P. Amblard, D. De Bionicourt A J. Leqrand. 1972. Acropalhle polyvinyliquc pcofcssionnelle. Bull. Soc. Franc. Dermatol. Svphiligr. 79; 197. 49. Eckardt, R. E. A R. Hindis. 1973. The health hazards of plastics. ]. Occupa tional hied. 7 St 808. 50. Edmondson, H. A., R. L. Peters, H. H. Frankel A S. Borowski. 1967. The early stage of liver injury in the alcoholics. Medicine 46i 119. 51; Europaciiemie. 1972. Handelsblatt GmbH. DUsseldorf, West Germany. -CumpanyrBaliimore, Md. 53. Filatova, V, S. A E. Stl. Gronsbero. 1957. Sanitamo-gigieniteskie usloviya iruda v proizvodslve polikhlorvinilovoi smolyi I meryl ikh ozdorovleniya. Gigiena Sanit. No. 1; 38. 5a. Filatova, V. L. I. Balakhonova A E. Su. Gronsbero. 1958. Gigicniieskaya kharakteristika proizvodstva khloristovo vinila. Gigiena Truda Prof. Zabolevaniya 2(1); 6. 55. Filatova, V. S.. E. Sil. Gronsbero, N. A. Smirnova, E. A. Stlilova & I. V. Oresckevic. 1965. Voprosyi gigienyi truda i sostoyanie zdorov'ya rabotikh, zanyaiyikli na proiivodstve latcksnovo polivinilkhlorida. Gigiena Truda Prof. Zabulevaniya P: 9. 56. Filatova, V. S. A V. A, Antonyuziienko. 1971. Gigicnitcskiye usloviya truda i professional'naya zabolevaemosl* rabotikh proizvodstva suspenzionnovo poli nvinilkhlorida v dinamike za ryad let. Gigiena Truda Prof. Zabolcvaniya 15(4); 57. Fisciier, J., II. Munosciienk A R. Wolf. 1965. Milzszintlgriphie mil l-Bromomerctiri (l"Hg)-2 hydroxypropan (BMHP). Foruchr. Gebiete Roenigensirahlen Nuklearmed. 103s 349. 58. Pisciirr, }., R. WOLF A H. Oamm. 1975. Dia Miluzlnilgraphle. Dlich. Arziebl. No. 7: 401. i9 fmlih n .4 Tiimnn nf th |lv^r In (if ih. T lm.,1 ftr-httr--Vrf " 9rd-cdiir-iH)r-fcipplm.Tm Cuuiptiiy. PhtiacUlphia, Par 60. Gitsios, C. T. 1971. Acro-osteolysis in PVC workers. Med. Bull. Stand. Oil Co. .>1(1}: hP. 61. GOnther, O. 1956. Die KunststoRc und Ihre irbeitsmedizinische Bedeutung. Zentr. Arbeitsmed.' 6i 156. 62. Harris, D. K. 1953. Health problems in the manufacture and use of plastics. Bril. J. Ind. Med. lOt 255. 63. Harris, D. K. A W. G. F. Adams. 1967. Acro-osteolysis occurring in men engaged in the polymerization of vinyl chloride. Bril. Med. J. 3i 712. 64. Hensculer, D., Ed. 1972/1973. Gesundheitsschldliche ArbcitsslolTe. Toxikolo- gisch-arbciismedizinischc Bcgrilndungen von MAK-Werlcn (Maximale Arbcits- plalz-Konzentralionan). Vcrlag Chcmle. Weinheim, West Oerniany. 65. Herri.e, K. 1963. Polyvinyichlorid. // Ullmanns Encyklopgdie der lechnischen Chemie. W. Foerst, Ed. 3rd edit. Voi. 14. Urban A Schwarzenberg. Miinchen, West Germany. 66. Hervieux A Tessier. 1959. Quelques observations d'exposition et d'intoltrance aux dfrivls vinyliques et aux rfsines lihoxyliques. Aren, Maladies Profess. 20i 61. 67. Ioer, F. L. 1970. Porttl hypertension in the presence of normal liver morphology. 68. Ann. N.Y. Acad. Sci. 170(1): 115. International Labour Office. 1971. Encyclopaedia of Occupational Health and Safety. Geneva, Switzerland. Vol. I: 387. 69, International Labour Office. 1972. Encyclopaedia of Occupational Hcalih and Safety. Geneva. Switzerland. Vol. U: 1467. fmeil, J.-f>i f!63. Halogrnilrd hydrocarbons; 1--AHpht7-d>t Industrial Hygiene ^aod'TusTkglU'gy.-'AaliTlt TaalaoUgyr Pt-W< Faaant U D. D. ItUI', p-*t frirr. HiLiiLL^ublwncrsrtfew-YorkrW^N* 71. Javitt, N. B. 1970. Clinical and experimental aspects of sulphobromophihaleln and related compounds. In Progress in Liver Disease. H. Popper A F. Schaffner, Eds. Vol. III. C-rune A Stratton. New York, N.Y. 72. Juoaii, 7. D., A. E. in. McLean A E. K, McLean. 1970. Biochemical mechanisms of liver injury m. I. Med. 49t 609. 73. JOliE, S. A C. . Laiioe. 1972. Sklerodermleartige HaulvcrBndcrungcn, Raynaud- Sypatom upd Akroosteolysen bel Arbcitern der PVC-hersteilenden Industrie. Dcu|. Med. Wcehsshr. 97s 1922. *00806^2 I99Dda Marstcller et al.; Splenomegalic Liver Disease 131 74. Kelly, R. E. 1973. Vinyl chloride and acrooslcolysis. J. Occupational Med. 15r 75. Kl8a5t8s.kin, G. 1969. Toxic and drug induced hepatitis. In Diseases of the Liver. L. Schilf, Ed. 3rd edit. 3. B. Lippincoit Company. Philadelphia, Pa. 76. Klinge, O. A H. W. Altmann. 1971. Morphologie toxischer Hepatosen. MUnch. Med. Wochschr. 113s 1529. 73 (1^------------------ -- 78. Kramer, C. G. A 7. E. Mutchler.<I97J) The correlation of clinical and environ mental measurements for workers exposed to vinyl chloride/Am. Ind. Hy|. Assoc. 7. 33; 19. __ J jWWSfSSfcleifSSS^MHufsBeS^^ISISnsflerosn med. 32; I. B0. Leake, C. D. 19)4. The role of pharmacology in the development of ideal anes thesia. 7. Am. Med. Assoc. 102; 1. ',, u 01 I I I'MIV. R. jCAA Tkfmiii im.l -T.^. i S .Hoj-i. iter Ifrnml ilIT~ 1( I .mriiLl|llr MaillTT POOn-- --lALrss-Gemnntyr 82. LipfvRe, M. J, 1972. Internationales Symposion der Werksiirzte der Chcmlschen Industrie, 27-29 April 1972, I.udwigshafcn. As cited in Stein <r al., 1973. 43. Lehmann, K. D. A F. Flurv, Eds. 1938. Toxikologie und Hygiene der lechni schen Lbsiingsmiucl. Julius Springer. Berlin, Germany. 84. Lester, D., L. A. Greenbero A W. R. Adams. 1963. Effects of single and re pealed exposures of humans and rats to vinyl chloride. Am. Ind. Hyg. Assoc. J. 24:265. 85. LinonER, H. 1973. Iutparoscopy in alcohol-induced liver disease. Gastroenterology 64i 842. 86. MacSwiin, R. N. M., 7. M. Vittirs, S. K. Ross, 7. Ferguson, 7. M. John stons A A. T, Sandison. 1973. Haemangio-endothelial sarcomi of the ifvtr. J. Pathol. 109t 39. 27i MalTEW, KrE. A R. UrXimwu. 196 H -Lidueirial- Toxicalag}' and Ouiuiutulcrgy ]%ran /<_ t1!ih;..i;^^i:r,ir,^UJ;TV"la U* *,|a,lt''*'1, *-!<-* iP' Publishing fiouipwiy. 88. Maltoni, C., M. Cresfi A P. 7. R. Ourcii, Eds. 1973. II International Symposium on Cancer Detection and Prevention, Bologna, April 9-12, 1973. Excerpta Mcdica In!. Congr. Ser. No. 275. 89. Marin, A., 7. Strauss, R. Miciiiels, J. P. Benoit, R. Baltie A C. Pierre. 1967. Acro-ostfolyse d'origine professionnelie (Travail pr6sent6 8 la Ugue Francaisc con ire le Rhumatisme, s/ancc du 18 janvier 1967). Rev. Rhumal. 34; 340. 90. Markowitz, S. S., C. 7. McDonald, W. ' ^ ^ *S. "K-e-r--z--n--e--r. 1972. Oc- cupaiionai acrooslcolysis. Arch. Derma 91. Marstellea, H. J., W. K. Lelbacii, R. Roiiner A G. Veltman. 1973. Chronk , C. E. Lanoe, H. G. schiden bci Arbeitern In der PVC-Produktion. Deut. Med. Wi 92. Mastromatteo, E., A. M. Fisher, H. Ci halation toxicity of vinyl chloride lo la goer. 1960. Acute inAm. Ind. Hyg. Assoc. J. 5i 394; Bull. Hyg. 36; 244. 93 Mtypae M R I9A9 Flrnipniinnal A Wilkins Cuilip4ity-~/6oc? t1--- nillimnrti htd~----94. McCord, C. P. 1970. A new occupation 12t 234. 95. MiKxeLSEN, W, P., H. A. Edmondson, Reynolds. 1965. Extra- and intrahepa (hepatoporial sclerosis). Ann. Surg. 162 96. MtsoeLD. V. H. J. Stolpmann A S. ! Vlnylchlorld-Polymcrisaic und/odcr di H 10 H 0) _____ 7. Occupational Med. G. Redeker A T. O. ision without cirrhosis ur Inloxikatlon durch l. Haul Gcschlechlskr. 48; 425. 97. Morris, J. S., T. Htut A A. E. Read. 19 (0 (0 id portal hypertension. Ann. Rheumatic Diseases 31: 316. 98. Nettleship, A. A W. J. Fink. 1961. Nec W < ; following ftijeclion of ihorotrasi. Am. J. Clin. Pathol. 35; 422. 99. Oettel. II. 1963. Gcwcrbeloxikologic und Physiologic einzclncr Polymerisaic. Polymcrisatc clilorierter Alhylcne. In Ullmanns Encyklopiidic der lechnischen > Am to 5 O ON f\J OS LO 18 unconstrained construction since it does not correspond to the theoretical model. A similar set of measurements were made on an undamped and damped chute. In this case, the room acoustics for the test sites were not comparable, leading to sound pressure level data which are not subject to direct comparison. The trends of this data do, however, confirm the results presented here. Conclusions A theoretical model of the impact noise reduction provided by damping treatments has been developed and successfully compared with field data from one installation. The model suggests that the reduction achieved depends on the addpd mass and stiffness of the damping treatment as well as the lost factor of the resulting system. In addition, the appropriate evaluation of the effectiveness of the treatment depends on the acoustics of the space, and a decision at to whether the source is single or repetitiyc impact For the case of a single impact in a large acoustically absorptive January, 1972 room, an appropriate measure of effectiveness is the peak noise reduction, which depends only on the change in the bending stiffness and mast per unit area of the surface. Most materials handling problems on the other hand, involve repetitive impacts over a short period of time, within a relatively reverberant room. For this case, because of the integrating properties of the structure and the room, a more appropriate measure of the effectiveness of the treatment is the energy noise reduction. The energy noise reduction is a function of the peak noise reduction and the change in system loss factor. The experimental results to date, support the theoretical model. Additional, more detailed studies of' impact sound from laboratory samples are now in progress which should provide additional substantiation. Reference I. Vcr, I. L.. ed C. I. Hotmor: banaioi of Sound Went and Solid Structure*. Char, II in Notto and Vlbroilo Control. L. Straask, Ed. McGraw-Hill, Haw York (1971). m a ~i o ***4/. .<c4>"': O CV !? Sv -> Tj ,,< 2 X V3 5 m x> > i-- > mCO Product Liability and Safety A new book Product Liability and Safety by Oeorge A. Peters (Coiner Publications, Ltd., 3066 M Street, N.W., Washington, D. C. 20007) is a twopart volume -- text and case law digest -- which details the concepts of liability and applies safety engineering principles to case examples of lawsuits and safety Incidents. By spanning the disciplines of law and engineering, the text demonstrates for professionals in each field how the growing number of product liability cases are indicative of changes in the objectives and procedures of designing and manufacturing and of the public skepticisms evident in the legal response to product accidents and malfunctions. The book previews what may be expected with the broadening responsibility for accidents: who may be touched by the increased liability, the major legal trends in product liability suits, and affirmative actions which can be taken to protect yourself from liability. In capsule form he defines the underlying concepts of liability: assumption of risk, comparative negligence, contributory negligence, discovery, expert witness, fraud, last clear chance and others. The textual coverage is reinforced by the Case Law Digest covering more than 4,000 leading cases in product liability classified by point of law and by product. The thorough, dual-disciplinary approach to product liability and safety make this book practical, educational and beneficial to both the legal and manufacturing fields. , ZQ08OCT2 * The Correlation of Clinical and Environmental Measurements for Workers Exposed to Vinyl Chloride C. O. KRAMER, M.D., and ]. E. MUTCHLER* Tht Dow Chtmlrol Corny**,. UitrimO, UiMoon e*440 ygfN motkoa l describee fur the slsllsltcal coaloHdalloe sad cotrclallea ef f ca.vtroaiaenlal measureMeals sad clinical fladlags uilag as aa exampie a group af healthy assla workers exposed rooclaeiy lo vinyl chloride for perlade ap lo 25 years. Retrospective }a estate the ready reveals several atalirllcally llgalflcael effects freer chronic exposeres lo vinyl chloride and (races of vlaylideae chloride. Introduction has not been applied, the feedback from For validating an industrial hygiene standard, it is essential to perform careful human experience could be expected to describe levels of exposure which have been and comprehensive studies of the possible shown to be either acceptable or marginally effects of substances on exposed workmen, in unacceptable. This information would be practice, however, very few substances have been the object of sufficient Rudy to furnish valuable to toxicologists because it would strengthen their skills in predicting from reliable guidelines. Today, specialists in experimental animal data effects of substances occupational health must recognize the need on humans. In a broader sense, it would be to develop programs which will better identify the relation between stresses acting on the useful in substantiating criteria to be used for industrial hygiene standards. human body in the work environment and For several years The Dow Chemical physical changes that can be measured Company's medical and environmental health clinically, to explain the significance of these changes and use the results to help refine our groups have been conducting concurrent medical and environmental surveillance of a guidelines for environmental control. Although toxicologists are constantly large worker population exposed to many different chemicals. The project described in predicting what exposures are likely to be safe for people, there will always be some doubt this paper analyzes the information already gained from concurrent surveillance and about their predictions until enough human relates it to the determination of acceptable experience has been gained to prove their levels of exposure. A method is described for accuracy. The "proof of the pudding" should the statistical consolidation and correlation of result from the correlation of good environmental measurements and clinical environmental measurements with the results of a well planned medical surveillance findings, using as an example a group of 98 healthy male workers who had been exposed program. It is likely that such feedback from human experience will differ from the animal routinely to vinyl chloride for periods up to 23 years. Retrospective in nature, the study experimental data in that it will not define a level of exposure which will actually cause injury, at least frank injury. However, except in cases where an industrial hygiene standard reveals several statistically significant clinical changes due to chronic exposures to vinyl chloride and smaller amounts of vinylidene chloride. By isolating these apparent effects a< Aiklrcii. D. C'liylfiii and Awk<M. K7| I SuulMffM MumI. Sotiffcrifjd, MfcAifR* 4107$ and examining them in the light of our medical interpretation, we have developed what appears lo be a promising technique for 19 January. 1973 20 retailng clinic*) information to worker exposurer to achieve a more refined industrial narcosis upon acute exposure. However, at least two industrial deaths have been reported from overexposure to vinyl chloride.* In a hygiene standard. controlled study, Lester, et alt exposed six volunteers for five-minute periods to 4,000 Vlayl Chloride Vinyl chloride (CH,-CHC1) ir a chemical compound of increasing industrial importance. U is a monomer used ar a chemical intermediate in the polymerization of polyvinyl chloride resin, in the production of copolymers such as Saran, and as a solvent. Animat Toxicity The toxicity of vinyl chloride has been reviewed by von Oettingen,' Mastromatteo, er alt and more recently by Torkelson, er alt and Lester, tt alt This gat is an anesthetic, and narcosis is the only reported effect of 8,000, 12,000, 16,000, and 20,000 ppm of vinyl chloride. The first signs of intoxication appear at 8,000-12,000 ppm. No other effects were reported. Baretta, er alt exposed human volunteers to 50, 250 and 500 ppm for 7 1/2 hours in an investigation concerned primarily with expired air studies. No clinical changes nor neurological responses were found in the thirteen volunteers upon thorough physical examination. Filatova and Gronsberg1 reported angioneurotic of spastic character in workers exposed to the monomer in a polyvinyl chloride polymerization process. Mr samples acute overexposure. Torkelson,1 Lester/ and their co-workers studied the chronic toxicity of vinyl chloride on rata. Torkelson and associates included rabbits, guinea pigs and dogs in a study of effects from repeated exposure, U., using controlled concentrations of 50-500 ppm. usually varied between 20 ppm and 315 ppm. Wilson, el alt reported several cases of acroosteolysir in hands of workmen working in vinyl chloride polymerization processes No vinyl chloride exposure estimates are cited, but the nature of the disorder and the circumstances of its appearance suggest that They found that repeated seven-hour exposure to 220 ppm caused micropathological changes in the Uven of rabbits, and at 100 ppm, noted slight but statistically significant Increases In the average weight of rat livers. Other animals were unaffected by 100 ppm. Using concentrations of 20,000 and 50,000 ppm, Lester found no evidence of effects on lungs or other vital organs upon repealed daily exposures lasting 92 days at the lower concentration and 19 days at the higher level. Like Torkelson, however, be detected some increase in relative weights of the rat liver and, in addition, of the rat spleen. The Committee on Threshold Limit Values (American Conference of Governmental industrial Hygienists), weighing both studies, concluded that "although the experimental data arc conflicting, the preponderance indicates a compound of relatively low toxicity with which a threshold limit of 500 the effect may have resulted from a "combination of physical insult, chemical insult, and personal idiosyncrasy." Dinman, et al.,M Cook, et at.," and Dodson, et gl.,u reported on a comprehensive epidemiological, industrial hygiene and clinical study of over 5,000 employees engsged in vinyl chloride and polyvinyl chloride manufacturing throughout the United States and Canada. A clear association of acroosteolysit and manual cleaning of polymerization reactors was revealed, with an expected prevalence of one case per 37 reactor cleaners. The study did not implicate vinyl chloride as the etiological agent but, using certain aawmptions about the monomeric content of polymer residue within the reactors, there appeared to be a semiquantitative correlation between (he prevalence of acroosteolysis and the degree of degaseing prior to vessel entry." Suciu, et al.t1 studied the clinical ppm is consistent."* Human Toxicity Few effects have been reported as a result of human exposure to vinyl chloride except for manifestations of s group of 186 male employees working in polyvinyl chloride plants. They reported the presence of the "narcotic syndrome," asthenic nervous American industrial Hygiene Association Journal 11 symptoms, Raynaud's syndrome and hepatomegaly, but did not furnish data regarding the number of exposures to vinyl chloride and other substances in the work environment. Environmental Aspects The Work Environment Subjects included in our investigation had worked in one or both of two manufacturing facilities which had been using vinyl chloride in polymerization processes In both plants the y environmental stresses of the work area were essentially equivalent. There were two airborne materials present in the work environment, vinyl chloride and vinyiidene chloride. The concentrations of vinyl chloride were much higher than those of vinyiidene chloride, due to the much larger quantities of vinyl chloride used and its greater volatility. During the first of two decades covered in the present study, the exposure of the workers to vinyl chloride and vinyiidene chloride were estimated solely by nonspecific combustion techniques.1*'1* The concentrations were expressed as vinyl chloride, although both materials were known to be present, in more recent measurements, infrared and gas chromatographic techniques have established that the vinyl chloride concentrations average 10 ppm, while virtually all vinyiidene chloride concentrations amount to lets than 5 ppm, and most frequently are detectable only in trace amounts. For this reason, ell exposure estimates used in this study have been indexed as "vinyl chloride." Our conclusions, however, mutt be viewed in the proper context -- that is, a work environment with two airborne materials: vinyl chloride in substantial amounts combined with very small amounts of vinyiidene chloride. It should be noted, however, that a continuous 90-day inhalation exposure of ran and guinea pigs, at a concentration of f ppm vinyiidene chloride,1* revealed no significant changes in hematologic, biochemical, pathologic and growth-rate parameters. Environmental Surveillance Industrial hygiene surveys of the operations n which the workers under study were exposed started in 1950. From that time until 1959, environmental surveillance was conducted on a regular basis, but uaing only the traditional techniques of grab sampling and portable analysers."'* Since 1959, permanent multipoint continuous monitors have been used to estimate the exposures received by the workers studied. The application of data processing and computer technology to environmental control hat allowed us to document the Intensity of exposures more thoroughly and validate our continuous monitoring technique by breath sampling surveys.*'11 The environmental sampling related to this investigation has focused on the exposure levels of men working in eight critical job classifications. Sampling for one or more of these classifications was performed in 1950. 1951, 1952, 1953, 1954, 1955, 1958, 1959, and each year thereafter. Before continuous monitors were installed in 1959, the periodic exposure estimates were based on job studies supplemented by the examination of several discreet samples gathered over a few days. In later surveys, the exposure estimates were based on hundreds of thousands of samples gathered on a continuous basis over long time periods using multi-point analyzers. Thus the quantity of environmental sampling has increased and the quality has improved over the years in a manner that parallels the intensification of the medical surveillance program. Suitable Air Quality Parameters Obviously, a study of the possible effects of repeated inhalation of an airborne material which varies in concentration require! the use of a quantitative expteaeion of air quality. We also recognize the need for an expression of air quality that will help characterize the tremendous variation in vinyl chloride concentration that may occur, together with a measure of central tendency. We base our choice, the "time-weighted average concentration" (TWA), on consideration both of the problem under study and of availability of data. For this study, from a practical viewpoint, the heterogeneity of the environmental sampling limits our choice of an air-quality parameter to the time-weighted 22 January, 1972 American Industrial Hygiene Association Journal 2J average concentration, which is a convenient expression for integrating a variable exposure pattern. However, we wish to point out that theoretically this expression has no relationship to the degree of toxic response. Bartlett and Carroll " note that, for agents passing through the respiratory membranes, as vinyl chloride apparently does, we know very little of how repeated or continuous exposure leads to chronic effects. However, since chronic effects could presumably be cumulative and progressive, a suitable parameter for the study of air quality would be the mean concentration, e.g., the timeweighted average concentration. As a result of the environmental sampling conducted since 19S0, yearly TWA estimates have been tabulated for each of the 98 individuals studied, following the work history of each man as he stayed within the group of critical job classifications during hit employment The result it a table of yearly exposure estimates for each individual. With such a table, a map's previous exposure history it available -- both on a cumulative dosage basis (ppm-years) and at a career timeweighted average exposure. Medical Aspects Those who have worked in the industrial setting appreciate the difficulties encountered in studying a population which is Subject to continuing change and often to mixed exposures. In actual experience it is race to encounter a stable population which has had exposure to a tingle environmental contaminant. The population in the present : study it typical in that the exposure has been mixed. Likewise, our clinical methods have varied both aa to frequency of examination . and use of certain laboratory testa l/ntil recently, our periodic medical examination consisted of a medical history, and a physical examination, including chest xray, timed vital capacity, urinalysis snd minimum hematology. To this basic examination we have added those particular laboratory tests which appear justified by the particular hazard to which the worker may have been exposed. The tests hate varied from year to year as the state of medical knowledge has changed. We now have a program in which all employees, in addition to this basic examination, receive a far more complete battety of tests. We include all individuals in our plant, regardless of the degree or type of exposure to hazardous materials By so doing, we hope to accumulate data that will be useful in establishing norms for our working population, and for providing better clinical data to be used in similar projects Darn on a large group of employees that would qualify as a control group would be very useful for a conventional comparison of mean clinical indices for the "control" population and the "exposed" population. Unfortunately we have no such comparable data. Moreover, this type of analysis has the disadvantage of masking variation within the "exposed" group -- variation which could be correlated with the degree of exposure if good environmental data were available. The experience discussed in this paper is based largely on our previous methods of acquiring data. At the moment we are seeking to establish a method with which we can study the data accumulated in the past. Over the years, our examinations, which have served the basic purpose of protecting' the health of individual employees, have resulted in the discovery and correction of some obvious abnormalities. However, leas obvious effects may have been missed. Though we had no ideal control group, we compared the results of the examinations on 66 of the individuals in the study group who had had examinations during 1965 and 1966 with a group of 605 employees from other departmenu who had had examinations in the same period. Ninety-five parameters of the history, physical examination and laboratory work were studied. This comparison was carried out by a test for difference between means, using a normal approximation. The summary of significant differences is shown in Table I. The study group showed an increased number of responses to the history item on asthma. This, however, was not reflected in a final diagnostic category, nor was any significant difference noted between the timed vital capacities of the study group and of the overall group The study group also showed an Factors in Which VC1 Group Differed SipuficuUI/ _______ from the "Control Group" (P<o,os) Number of Extent History; Asthms Stomach, liver, intestinal (rouble Kidney stone, bloody urine Nervous (rouble of sny sort Have you ever worked with radioactive substances Physical: Anus-rectum Identifying body msrki ^ VCl Croup, % *6 "Control Group, ' 60S 6.1 9.1 IS 7.7 1 B*7 increase in positive responses to the history item "kidney stone or bloody urine." Again, this was not reflected in the diagnostic categories. There was a decrease In number of responses to the history questions on "stomach, liver, and intestinal trouble" snd "nervous trouble of any sort." On physical examination, the only category in which more responses were recorded was that involving abnormalities of the anus and rectum. Again, since this finding was not borne out in the final diagnostic categories, it would indicate that the various examiners did not consider these findings to be of clinical significance. There was no difference in overall diagnostic categories except for diseases of the digestive system, where fewer specific diagnoses were recorded for the study group than for the comparison group. There were no group differences in the electrocardiograms or chest x-rays. Hand x-rays on the individuals in the "exposed" group showed no significant abnormalities and no case of acroosteolysis. For comparing the mean BSP of the study group with that of the comparison group only 116 measurements were available for the comparison group The mean BSP for the study groups was 2.73 (SO observations), and the mean for the control group was 2.89 (116 observations). Although all records were Individually reviewed for data which had not been processed statistically, no significant additional findings were noted. Considering the many factors studied, some differences would be expected. However, this conventional comparison of test means for the two groups does not suggest any basic difference between the two populations with regard to general health, and it appears that no significant disease has appeared in the study group as a result of work expouire. Statistical Conaelldalioa of Data for the Exposed Population Dependent Variables After the accumulated clinical data from the 98 men in this study had been compiled, there were 21 clinical parameters for which sufficient data existed to warrant inclusion in further statistical analysis The criterion for inclusion was as least one observation per man for 25 men for any given teat. The 21 clinical parameters are listed in Table II. Independent Variables In identifying factors which could explain some or all of the variation in the observed clinical variables, we recognize the need for including a record of age and obesity (important nonenvironmental variables), and the level and duration of exposure (essential environmental variables). Age was recorded to the nearest whole year. Obesity was defined as the ratio of actual weight to "standard weight." The level of exposure was expressed as the cumulative time-weighted average concentration. The product of TWA and timeon-the-job (TOI) gave a measure of the cumulative dosage. f00806frZ m m* it* * -K!i r<"A 24 l TABLE li Twenty-one Clinical Pftiameters Screened for Owrelelioa with Exposure _____________ Teat Physical Systolic Mood pressure DtMtotte Mood presence Timed vital capacity Chemical Bromsulphaleln (BSP) Icterus index Alkaline phosphatase Serum |lul oxel tran (SGOT) Thymol turbidity hoitia, serum total albumin globulin alpha I alpha 2 beta gamma AG ratio Hematological Hemoglobin Hematocrit Red Mood cells White Mood cells Prothrombin time Urine Specific gravity_________ Data Formal At this point wc had prepared two concurrent acta of data for each man: medical information and environmental information. All that remained was the individual matching proceaa and collective analysis. At the time of each clinical observation, both types of data for each man were registered in the following format: Man No., Date, Age, TOJ, TWA, Ht, Wt, Std Wt, Y, ... Y,, Where TOJ - timc-on-Job (time of exposure), yrs. TWA - Career time-weighted average exposure Std Wt - Standard (deaired) weight as tabulated by the Metropolitan Life Insurance Company." Y, - Clinical observation I, I-1, 2 .., 21. Statistical Analysis The technique used for extracting relationabipe hidden in the available data was January, 1972 -Step-wise multiple linear regression analysis." This procedure, made powerful by the advent of digital computers, systematically builds a mathematical model from a choice of Independent variable terms baaed on the fundamental independent variables. In the step-wise regression procedure, Ihe Independent variable (X,) most highly correlated with the response Is entered Into the model, and the coefficients are determined by the method of least squares. Using partial correlation coefficients, the next variable (X,) to enter the regression is thst whose partial correlation with the response is highest. Given the regression equation Y-ftX,, Xt), the method now examines the contribution X, would have made if X, had been entered first. Repeatedly, the step-wise method selects as the next variable in the regression the one most highly partially correlated with the response. At each stage, the "best" regression equation Y-f (X,, X,, ... X. ) is determined by the method of least squares, after checking the partial F criterion for each variable to verify the significance of each term included." The object of this technique is to express a relationship by some relatively simple mathematical function such as polynomial which containa appropriate variables and which approximates the true response of the dependent variable over some limited ranges of til the variables involved. Siiice this approach is empirical, the resulting equation might be considered to be physically meaningless; nevertheless, it may prove extremely valuable for predicting the values of some dependent variable from knowledge of other variables, at least under certain Mated restrictions In using the technique, it was kept in mind that, just because a particular functional relationship has been developed and a specific computational procedure ia followed, it cannot be concluded that a causal relationship exists among the variables After data had been accumulated and a strategy had been selected for analyst! of the information, the remaining step# could be broadly claasified as screening and refinement. Correlation Matrix The ftru step in analyzing the consolidated information was to esamine the linear ,American Industrial Hygiene Association Journal TABLE III Correlation of All Dependent Variables with All Independent Variables (P<0.05) Teal Age OB TWA Dose Physical Systolic blood pressure 4 4 Diastolic blood prasaura 4 Timid vital capacity -0 0 0 Chemical Oromaulphalain (BSP) 0 t Icterus index 004 Alkaline phucphelaae Scrum glut oxel tran (SGOT) 0000 0000 Thymol lusbidliy Protein, scrum total 000 0 albumin globulin 0000 alpha 1 alpha 2 beta gamma AG ratio 4 00 0 0000 0++ --0 00 0000 Hematological Hemoglobin Hematocrit Red blood cells White blood cells Prothrombin time -0 __ 0000 000 0000 0 00 0 Urine Specific gravity 0000 correlation matrix for all the independent and dependent variables available. This screening technique revealed several clinical variables that appeared to be related to exposure. The correlation matrix is shown in Table ill. Six clinical parameters of the 21 under Mudy showed significant correlations (P<0.05) with the exposure variables cumulative TWA and 23 cumulative dose. These were: systolic and diastolic blood pressure, bromsulphalein, icterus index, hemoglobin and beta-protein. Of these, three showed correlation with age and four with obesity. Three other clinical parameter! were significantly associated with age. The corralatlon-scrasnlng procedure helped us develop and show that the "independent" and "dependent" varieblea are interrelated. Table IV shows the correlation matrix (P0.03) for all the crucial variables, dependent and Independent. The general consistency of the relationships indicated among the variable! justified more rigorous analysis Development of Regression Models In the development of a linear regression equation for each clinical test Y in terms of independent variables age, obesity, TWA, and dose, we took the view that the complete let of terms from which a model would be chosen should include the independent variables themselves together with interaction or crossproduct terms which might be helpful In explaining variation in the observed variables For example, we allowed for the possibility of age and exposure operating together (interacting) in a manner which would be different from that of age and exposure acting independently. However, we faced two opposing criteria for selecting a predictive model: l.For utility and accuracy we wished our model to include as many significant table tv CorreiaHon OoemcUni Matrix - Crucial Variable! Age OB TWA Dost BPS BPp BSP II Aga 0 0 4 4 4 0 0 OB 0 4 4 4 4 0 TWA 0 0 4444 4 Doe* 4 4 4 4444 BPS 4- 4 4- 4 440 4444 40 isF 0 4 4 4 4 t 0 II 0 0 4 4 0 0 0 Hb 0 - - 0 0 0 0 (Tprotein 0 4 4 4 0 0 4 0 + ftallOr correiatlun tCaoi 0 No correlation V <0.05 - Nesative correlation P <O.OS Hb 0fVotefn 0 _ 00 00 04 00 0 "Z 9E O J a mmoBfz BFG36267 V *' i * o \ Jj'v; 26 January, 1972 TABLE V Wuwbw of Subjict* and Number of Clinical Tel within th Study Group Tee! Number of Subject* Told Number of A Number of Randomly Selected Obeervellone ________________ Obeervetlon* Systolic blood preceure Dtaetolic Mood procure Bromeulphalein Icterus index Hemoglobin Beto-pfotolfl__________________ 323 323 b2 30 103 3* 08 08 63 23 83 38 independent wiable lermt at poteible go that reliable valuer could be predicted. 2. For simplicity and cage of com munication, we wanted the equation to include aj few significant independent variable terms as possible. Operating largely from an empirical point of view, we drew up a list of 30 independent variable terms including transformations of the four basic independent factors. Since we had unequal numbers of observations for each individual in any given test, it was necessary to choose randomly one observation per individual for each test in order to weight each man equally. This random selection reduced the number of observations for each tear as indicated in Table V. Statistical Results The tesults of the regression analyses for each of the sis crucial clinical variables are given below; 1 Syndic Blood Pressure BP.-A.-i-B, (Age)* +(TWA) (Age) 1C, (OB)- D, 1 DiauoUe Blood Pressure BP. -- Af+Bt (Age)* (OB) * +C, (TWA) (OB) Bromtuiphaiein BSP-A.+B, (Age) (Dose) Icterus fades II-A.+B, (TWA)* Hemoglobin Hb-A.+B, (Age)" - CdTWAF Beta-protein Bcta-pfolcin-Ae+Bs (Dose)* Figures 1,2 and 3 show the regression responses for three of the above models, BSP, Icterus Indea and Beta-protein, respectively. Figure I. Reireuion model for bromeulphalein retention. Statistical Significance of Models An appropriate question is: What measures of precision can be attached to the regteaion models? Three useful indices art the standard error of regression, Se, the overall F-Statistic, and the coefficient of multiple determination. American Industrial Hygiene Association Journal .n Figure 3. Regression model for beta-piotein. ' R*. These measures of the "goodness of fit" for each model of the clinical variables are luted in Table VI. All of the regression models are significant ai the P-0.001 level, except the Icterus Index model, which is significant at the P-0.03 level. Utility of the Models The regression models must be used with discretion. Since the least square regression coefficients are adjusted for other variables in the regression procedure, attempting to predict the response by changing only one variable arbitrarily may be misleading. Because of this, we mutt specify the prediction range for each variable under investigation. Such prediction ranges are shown in Table VII. To relate the statiaticel results to the practical question of an industrial hygiene standard requires careful consideration. First, an acceptable workroom air concentration mutt allow for men working in the environment for an entire career, up to 43 years; our data are useful only over a 20-year span. For effects which are cumulative, as most of those isolated in this uudy apparently are, the last part of a man's career It the limiting consideration. In view of our data and their ranges, we can examine the clinical variables at TOJ-20, and Age-60, the highest legitimate values of our predictive parameters. In the case of blood pressure, obesity must be fixed alto if we are to predict the effect of the level of exposure, TWA. For this purpose, we hold "OB" constant at 1.06, the overall mean for the blood pressure data. The following functions result; Systolic Blood Pressure -136.80 + 0.034035 (TWA) Diastolic Blood Pressure -84.74 + 0.018843 (TWA) Bromtuiphaiein -2.12 + 0.034399 (TWA) Icterus Index -6.82 + 0.000000002309522 (TWA)* Hemoglobin -13.97 - 0.0000000457339 (TWA)* Beta-protein -14.15 + O.OOOOOI37I545 (TWA)* These clinical changes are tabulated in Table VIII at a function of TWA Discussion of Clinical Changes In reviewing Table VIII, we note six factors which relate empirically to exposure. Within TABLE vt Statistical aaelflcince of the Restesslon Models Model Systolic blood pressure Diastolic blood peaasur* BromsuJphaleln Icterue Index Hemotlobin Bale-protein___________ P<0.0Ol Number ot Observations Standard ' Error of Repression 9ft 1X9 9ft 7.6 6S I.S 2$ 1.6 19 0.S3 SB X6 Overall F-Stetlstlc 34. S3 (3;94)* 39.46 (2;9S)* 43.8S (1,69)* S.66 (1;23)** ft. 95 (3*.ft0)* 13.65 (l;S6)* Coafftrleat of Multiple Deterasiaetlaa 0.1*0 0.193 0.407 0.191 0.162 0.170 900806fcZ i 28 ligSSf illlk **wif .z r i -- -- 9 0 m *o*S-989 eoH^ee WMWIVIVI WOMMWW :;{9l OMWOO (tywsoci'Z January. 1972 the scope of thit study the predicted blood pressures, systolic nd diastolic, did not rise to levels which would be considered abnormal. The hemoglobin, though statistically decreased, does not fall outside the normal limits for our laboratory. The significance of the change in ratio of the beta-protein is not known. We are left with two factors which give tome cause for concern. The changes in the Icterus Index and in the BSP lend tome support to the hypothesis that some changes in liver function have occurred in a few individuals exposed at the higher levels. The BSP appears to be most significantly correlated with exposure. Within the study group were several individuals who, after approximately 20 yean of exposure with time-weighted exposures of approximately 300 ppm of vinyl chloride and smaller amounts of vinylidene chloride during the early part of their careers, demonstrated a tendency to develop changes in certain laboratory tests which appear to be related to their exposure. Reference to Figures 1-3 indicates that our interpretation of the clinical changes must be tempered by the fact that only a small number of individuals experienced the highest exposures. Two of the individuals showing the highest rise in BSP were recheeked in 1968. One had essentially normal laboratory findings and.the other showed persistent elevation of various liver function tests, even though both had been removed from further exposure since 1965. The individual whose liver function tests remained elevated had a history of hepatitis preceding his exposure, although his preexposure liver function tests had been normal. Whether his abnormalities represented a result of his exposure or independent sequelae of hepatitis cannot be ascertained. Certainly it would be desirable not to consider individuals with a history of hepatitis as candidates for prolonged exposure to vinyl or vinylidene chloride. Unfortunately, since many cases of subclinical hepatitis occur, there may always be some individuals in a working population who have had hepatitis. For mott individuals in the study, the highest exposure occurred in the early phases of their careers and their later exposures were much lower. In the final analysis, much weight had American Industrial Hygiene Association Journal I TABLE VIII Expected Response of Clinical Testsssa Function or Career TWA TWA. PPM Vinyl Chloride Tsl SyatoJic Mood pressure (Age = 60, ONES* 1.06) IMhuIuIU' hluod pressure (Age = 60, OBES- 1.06) Bromaulphaleln (TO! 30, Age * 60) Icterus Index Hemoglobin Beta-protein 0 136,6 SO 138.3 100 140.2 ISO 141.9 300 143.6 3S0 145.3 300 147.0 84.7 ns.7 86.6 87.6 88. S 89.4 90.4 3.1 6.8 14.0 14.1 3.8 6.8 14.0 14.3 S.6 \ 7.0 13.9 15.5 7.3 8.1 13.8 18.8 9.0 11.0 13.6 3S.1 10.8 X 13.3 X X beyond range or available data I3.S X 13.7 X 29 to be placed on the readings observed for those employees who experienced high exposure levels, especially during the period 1950-38. For example, the average timeweighted exposure level in 1950 was 155 ppm, whereas the average exposure level in 1965 was 30 ppm. Our findings suggest that repeated exposure to vinyl chloride at TWA levels of 300 ppm or above for a working lifetime together with a very low level of vinylidehe chloride may result in slight changes in certain physiologic and clinical laboratory parameters. The possibility of some impairment in liver function tests must be considered, even though no overt clinical disease was evident in any of the individuals studied. We shall continue our study, but suggest that similar studies to help clarify the effects of this material be performed for other worker populations exposed to vinyl chloride alone. Conclusions The present study offers a technique of judging exposure effects on a group of exposed workmen based on an analysis which is intended to account for individual levels of exposure rather than relying on a collective comparison with a so-called "control" population. The "exposed" group, especially when it is drawn from an industrial setting, will contain individuals subject to a wide range of exposures, and the mean clinical indices for the group may well mask significant individual differences within the exposed group that could be detected only by intra-group analysis. We have attempted to correlate the clinical manifestations of a group of men for which exposure data as well as clinical measurements were available. With this approach, the "exposed" group will contain tome individuals whose exposures are low enough to serve at "controls," The regression technique we have employed treats the exposure levels (Dote and TWA) as independent variables, thereby providing an open format that allows inclusion of any degree of exposure, including none. The advantage of regression analysis in this application lies in the ability to extract more substantial information on acceptable exposure levels by relating measured clinical changes directly to measured exposure. To use this method, good environmental and medical data must be gathered and consolidated concurrently in substantial quantity. We have demonstrated the use of thit statistical technique with a group of men exposed to vinyl chloride and trace levels of vinylidene chloride. In so doing, we have found some interesting apparent effects from chronic exposure to that system but, more importantly, the methodology looks promising as a needed improvement in our quest to make X) January. 1972 practical use of toxicological feedback from worker exposure*. We hope that others will offer further refinement* and suggestions that will help attain this goal Ackaowledgncals We wish to acknowledge the assistance of other members of the Medical Department and Environmental Research Laboratory of The Dow Chemical Company who, over two decades, gathered the basic information which has made this study possible. Our special thanks to go Mrs. Shirley Walker, R.N., who conditioned much of the medical data, to M. Gerald Oft for his suggestions with the statistical strategies, and to our supervisors and colleagues for their steady support. References 1. voa OrtiMSa. W.F.; Tkt Halogaaattd Hydrocarbon*; TosUUy aad PetmtM Damgan. U-1 Public Hmlih Service. PuMfcatieii 414. Ooverament Printlaf Office. WedUastoa. D.C. (1955). 2. Meetfoawiteo. fc. A.M. Fithcr. H. Cbrietle, md H. Pillar Aee InbelatlMi Toxicity at Viayt CMoridc Laboratory Atbuli. Amor. Id. Hn- Am*. A 21:194 (OcL IMO). 5. Torkeltoe, T.R.. P. Oyea. ea4 V.K. Rowe: The Tosiclty of Vlayl Chloride At Determined By Panewed Eayoiwe of Laboratory Animal*. Am*. tad. Hyg Am*. A 22:154 (Oa IMI). 4. Letter. D.. L.A. Oroeabers. aad W.a. Adams Effectt ofSingle aad Repeated Bipolaree of Huataat eed Rett to Vlayl Chloride. Am*, tad. Hn daeoc / **.265 (May IMS). 5. Committee oo ThrethoM Liaiit Values Documentation at Ttantmld Limit Voiutt, Rev. Ed.. Aetericea Conference of Qoverementel ladtWriel Hjgieein* Cincinnati. OMo (IMS). 6. Dtmxifcr, H.. Acddeaul Poieoalag by Vlayl Chloride: Report at Two Ceeee. Canadian Mod. Am*. A D.III (April IMP). 7. Bereue. E.D., R.D. Stewart, and J.E. Muubler: Moeitoriag Eipoaerea to Vinyl Chloride Vapor: Brewh Anelyria aad Continuous Air Saepltn|. Am*, tnd. Hn Altec. / 5*537 (1969) S. Filatova. U.S.. aad E.S. Oroatber|: Hygienic Workiaf Coodilioat <a Polyvinyl CMorlde Ter Plant* Git i Sunil id-42 (Jea 19)7). 9. Wiltoe. R.H., W.E. McCormick. C.F. TUHt. aad I.L. Creech: Occupaiioaal Acroottcolytit. J.A.M.A. 201:511 <At 1967). 10. Dinmaa, B.D.. W.A. Cook. W.M. Whiteboiiac. H.J. Ms*nuon. aad T. Ditchcck: Occupatioeil Acrootteolyii* Ae Epidemiological Study. Artk. Environ. Health 22.41 (Jaa 1971). 11. Cook. W.A.. F.M. Oiever, B.D. Diamen. aad H.l. Mefaueoa: Occupaiioaal Acrootteolytix Aa laduttrlel Hysieec Study. Artk. Environ. Health. 22:74 (Jea 1971). 12. Dodaoa. V.N., B.D. Dinmea, W.M. WMtehouM, A.N.M. Hear, aad H.J. Manueoa: Occupational AorooetoolyeU: A Cllnkel Study. Artk. Environ. JfoaMk 22.15 (Jaa 1971). 15. Socio, I.. J. Drcjmaa. aad M. ValaUi: Cbatrihutioat to , the Stady ol Affwtkae CeuMd by Vlayl CMorlde. kitdkim Inter* 15.941 (Atif 19*5). 14. FrcotorgM* J.A.. B.A. Joeee. L.J. Jenkins, Jr., aad J. Siegel: Effects oo Eaperboeoial Animal* of Loo*-Term labalatloa of Trlcbloroethyleac, Ctrboa Tetre- cbtoride. I.I.I-TricMoroetbeee, DichlorodiAeoro- rootbene, cod l.l-Dicbloroothyleoe. TosttoU omd Atft. /Harm. 10:210 (March 1967). 15. Petertoo. J.E., H.B. Hoyle, ead E.J. Schneider: The Aaalytit ol Air for Halogcaated Hydrocarbon CoalMBiaaoie by Moaat of Abaorptioo of Silica Ool. Am* lad. Hn Am*. Quart. 17:429 (Doc 1956). I*. Schaffer. A.W., and H.R. Hoyle: Nine Yeara Eiperleacc with the Dtvia Halide Meter. Am* tad. Hn- Am*. A 22.-95 (April IMI). 17. Patereoo, J.E., H.R. Hoyle, cod E.J. Scbooldar: The AppIlcatloB of Computer Science to laduttrlel Hygiene- Am*, fed. Hy$- Am*. A 22;110 (March 1966). . IS. Bertlcti. D.. Jr., ead R.E. Carroll: Air Quality Parameter! for Epidemiologic Studice. Arch. Environ. Health J6.1S2 (Fob. 1966). 19. DoairaMe Weight* for Meo of Apca 25 aad Over. MetropolUaa Lift leturaace Compeay. 20. Draper. N.R.. ead H. Smith: Apptiod Kegrettlon Analyek. Joha Wiley ead Son*. lac.. New York (1966). Received May 21. I*7l i Course on Effects of Nonionixing Radiations The Massachusetts Institute of Technology will present a special two-week ' program on Biological Effects and Medical Applications of Nonionizing Radiations, July 31-August II. 1972. The course will present the basic physics, biological effects, biomedical applications and hazards of ultrasound, laser, microwaves and magnetic fields. Presentation will be in manner to be suited to individuals with clinical and physical science backgrounds. The information will alio be related in context to the activities of the Federal Regulatory Agencies. Detailed information is available from the Director of the Summer Session, Room E19-356, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139. i Lead in Hair among Exposed Workers ABDEL.-AR1Z EL-DAKHAKHNY, PH D., and YASSIN M. EL-SADIK, M.O. o.pvmmm dompiM mhuk min ituiui. tfmii. hmia AkeemtHe Uelwrtity. AI.Mw.4rle, |,r, 1IAR. (0,a 1 performed o. ,7 It., expoK, worker., corr.lili.. , fo.., V3V kolwna I...I. of Us, la kalr aa, Ik. blockflakal aa, cllalcal n>,la^. A In, I. kalr af wore ikaa N pg/ raal, k (.atllnd a. a al,a af txn.iw taa, lava,. \ lalrodaclioa A wealth of information on the value, of lead in blood and urine of expoaed and non-expocd perton, to lead ha, been accumulated durin, thu century. On the other hand, little knowledge ha, been acquired concerning the concentration of lead in hair. Recently Barry and Moaman,1 in their udy of lead concentration in human tliauci among 69 cue, at poM-mortem have found that hair contained relatively high concentration of lead approximately 20 ppm. They suggened the importance of the study of lead in heir in medicolegal Investigation! for the determination of the severity of exposure. The purpose of thia nudy ia to determine the levels of lead in hair of expoaed worker, and to compare luch level, with tome laboratory and clinical flndingi in order to ihow the extent of lead hazard. Method The ttudy wai conducted during the year 1970-1971 on 67 worker, expoaed to lead, at four different factorial in Alexandria, and are distributed as follows: Plant lead reclamation Lead battery Tin can 1 Tin can II Number of worker* examined 12 20 as 10 From past environments! studies, it has been found that the four factories have vatying degrees of lead exposure. Exposures were excessive in the lead reclamation and the lead battery plants, and, mild in the two tin can factories. In this investigation, each worker was medically examined with emphasis on occupational history, looking for blue line occurrence in the gum, and, for tymptoms of colic aa well aa constipation. Blood haemoglobin waa determined by using the Sshli haemogiobinometer. As regards the biochemical testa, lead In blood and coproporphyrin in urine were de termined. As for hair, about O.2-0.5 gm were taken from different pent of the scalp of the examined worker. Since hair of expoied workers were likely to be contaminated by Iced from the working environment, every hair temple was soaked end shaken in a hot detergent for about 10 minutes. Then it was thoroughly washed several limes with distilled weter, with hot nitric acid 1% solution, and distilled water respectively. Hair was then dried in an oven at 103-110*C and was kept ia a desiccator ready for weighing. Wnehing with s detergent alone, proved insufficient to remove all lead contamination completely from the hair, especially with individuals exposed to environments high in lead. Our wuhing procedure was tested by collecting the nitric acid washings into separate containers and these were analysed for lead determination. In all tests performed, the third washing contained no lead at all. In this study, the USPHS Dithizone Method ** was used in the determination of lead in blood and hair. Coproporphyria in 800806^2 I