Document G5pby6XZnxRvEYjgqKg26XR7r

M r. F . C. Gauguah D irector of Safety The Sherw in-W illiam s Company 115th Street and C ottage G rove Avenue C hicago 28, Illinois ' '> ! D ear M r. Gaugush: Your le tter of May 27, to the attention of D r. C. M . P eterson , Secretary of the C ouncil on Industrial Health of the A m erican M edical A ssociation , concerning the value of the determ ination cf porphyrins in the urine of p erson s em ployed under conditions involving exposure to lead, as a m eans of estim atin g the extent and sign ifican ce of th eir exposure, was referred by D r. P eterso n to m e. I am glad to give you m y opinion on the m atter. I a lso m ake certain additional su ggestion s, fo r such u se as they m ay be to you. P erson s who have absorbed fa irly large quantities of lead and are sustaining a significant degree of interferen ce with the m etabolism o f hem oglobin on that account, ex crete abnorm al quantities of coproporphyrin III. U nfortunately, this reaction is not sp ecific in relation to lead , nor is there a graduated relationship betw een the rate of excretion of the coproporphyrin and the amount of lead absorbed. The p resen ce of highly abnorm al le v e ls of excretion of this substance, th erefore, when other cau ses-can be elim inated satisfactorily, is an ind ication, at b est, o f an e a rly m an ifestation of a toxic e ffe ct of lea d in the body. (See the a r tic le of P arkinson and Choiak (from th is L aboratory) in the A m erican Industrial H ygiepe A ssociation Q uarterly, 13:153, (Sept.) 1952.) That is to sa y that it is evidence of the e x isten ce of lead intoxication, although there m ay be no dram atic evidence of illn ess otherw ise. F rom the aspect of preventive m edicine, th erefore, this cannot be regarded as an altogether satisfactory procedure. A t b est it helps to warn one of the existen ce of prodrom al intoxication, and to enable him to head off m ore serio u s form s of the disease* f In p r a c tic e , th e p ro ced u re is ev en l e s s e ffe c tiv e than the fo reg o in g r em a rk s would ind icate. The varia b ility in the ex cretio n of coproporphyrins under norm al conditions is co n sid era b le, and the v a ria b ility in the resp o n se to the absorption of lead is a lso g rea t. T h erefore, it is d ifficu lt to be su re how the resu lts should be interpreted when one u se s highly p r e c ise m ethods of determ ination. The sh ort-cu t m ethods are not alw ays reliab le, and their m eaning is far from c lea r. The resu lt is that the procedure, lik e that of follow ing the m icro sco p ic changes in the blood (basophilic stipp ling, fo r exam ple) is not adequate. M r. F . C. Gaugush - (2) - June 23, 1955 Ideally, what one d e sir e s is a m ethod w hereby he can m easure the extent of the absorption o f lead its e lf, and, on the b a sis of p h ysiological know ledge and clin ica l exp erien ce, determ ine when it is that an individual approaches the point pf danger, with som e m argin of safety to sp a re. This is the purpose of the quantitative a n a ly sis of the u rin e. The m ethod has its sh ortcom in gs, in that the lim its of p h ysiological variation a re fa irly wide and m ust be counter balanced by carefu lly chosen m ethods and frequencies of sam pling and by expert interpretation of analytical resu lts on the background of sound knowledge of the physiology of the p r o c ess. Such knowledge is not w idely distributed, unfortunately and th erefo re certain rules of thumb have been substituted for it, to the disad vantage of a ll concerned. ; On the background of our co n sid era b le e x p e rie n c e , I a d v ise you that the pro cedure w hich you are now using (assum ing that your analytical m ethods are sa tisfa cto ry ) is m uch m ore effectiv e than that of the determ ination of porphyrins, or of any other procedure, with one exception to which I sh all refer la ter. If you. a r e m aking your o b serv a tio n s on the urine w ith su fficien t frequency, and if you a re obtaining proper sa m p les, analysing them properly and interpreting the resu lts properly, you now have a good tool for the purpose which you have in m ind, and you w ill be p rogressin g backw ard, if you abandon it in favor of a non-specifi^f^Sfc^S-S the determ ination of porphyrins by any m ethod. You can, how ever, im prove your procedure, by analysing the blood of your m en instead of, o r along w ith, their urin e. On the b asis of our present know led g e, it is p o ssib le to in terp ret the sign ifican ce of the lead concentration in the blood w ith v irtu a l cer ta in ty . It d oes not v a ry fro m hour to hour, ex cep t under c e r ta in known, con d ition s (sudden ab sorp tion of fa ir ly la r g e q u antities o f le a d , o r in r e sp o n se to the a d m in istra tio n o f BAL. o r FD T A ) and th erefo re it rep resen ts th e status of the individual in a very x-epresentative m anner, fro m the a s p e c t o f Hie g e n e r a l le v e l of le a d co n cen tra tio n in the bod y. One can s e t c r ite r ia fo r ab solu te sa fety and fo r v a rio u s d e g r ee s of danger, in te r m s of the lead le v e l in the blood, and, by adhering to th ese c r ite r ia , can avoid the occu rrence of lead poisoning in any group of exposed p erso n s. This can be done also by adequate study of the urine, but it is m ore troublesom e and also m ore co stly , sin ce m ore an alyses are required for the sam e degree of a c c u r a c y o f in ter p r e ta tio n . In p r a c tic e , w e in v e s tig a te th e lea d le v e ls in both blood and urine at in tervals which vary with the sev erity of the hazards of a p articu lar ind ustry, and on the b a sis of the inform ation obtained, we deal with the in d ividu als by tra n sferrin g them to job s involving le s s ex p o su re, o r, if need be, to jobs that give no exposure a t.a ll, m aintaining th ese situations until the individual has a su fficien t m argin of sa fety to return to h is form er job . This p roced ure goes hand in hand with m e a su r es of environm ental con trol, w hich, w hen accom p lish ed sa tisfa c to r ily , enable one to d isp en se w ith tra n sfers and rem ovals. M r. F . C . C-augush - (3) - .Tune 2 3 , 1955 T hese m atters m ay or m ay not be known to you or to your m edical people, but if you or your physicians (preferably the la tter, sin ce this is , 3trictiy speaking, a m ed ical problem ) would lik e to d isc u ss th ese m atters w ith m e and exam ine the evid en ce on w hich th ese statem en ts a re b ased , I should be glad to find tim e for the purpose. V ery truly yours, HAK ef C . C . : D r . C. M. P e t e r s o n Robert A . Kehoe, M. D. J