Document rxVzj93EdO0R8Y6bZxOZeN4X0

Ba l t imo r e Cit y Ho s pit a l s Fr ed er ic G. Hu bba r d d ir ec t o r 4940 EASTERN AVENUE BALTIMORE, MARYLAND 21224 Ap r i l 30, 1971 IN REPLY REFER TOs Dr . Robert A. Kehoe Co l l e ge o f Me d i c i n e , Eden and Bet hesda Aves. Ket t er ing Laborat ory Depar t m ent o f Envi r onm ent al Heal t h Un i ve r si t y o f Ci n c i n n at i Ci n ci n n at i , Oh i o 45219 Dear Dr. Kehoe: Ma n y t hanks f or your l et t er o f Ap r i l 7. I w oul d, i n t he f irst p l ace, have t o agr ee w i t h you and say t hat c l e ar - c u t c l i n i c a l sympt oms o f l ead p oi soni ng i n chi l d r en are v i r t u a l l y al w ays associ at ed w i t h bl ood l ead l evel s o f ap p r oxi m at el y 80 p g Pb/ 100 G w hol e bl ood or gr eat er. Ex c e p t i ons t o t his w oul d be chi l d r en w i t h sever e anem i a or pr i or br ai n dam age due t o ot her causes in w hi ch t he com p l exi t i es i nt r oduced by t he pr esence o f m ul t i pl e di seases makes t he assignment of sympt oms of t en d i f f i cu l t . In such chi l d r en, I w oul d be i n c l i n e d t o depend more upon t he response t o chel at i on t her apy and al so on t he response in t erms o f A L A or co pr opor phyr i n excr et i on i n r each i ng a d eci si on. Wi t hsr espect t o t he ver y m i l d sympt oms o f p oi soni ng w hi ch are subj ect i ve in nat ure, I f eel t hat w e ar e on much less f irm gr ound i n d e al i n g w i t h chi l d r en t han you are i n d e al i n g w i t h ad ul t s because o f t he d i f f i c u l t i e s i n assessi ng minor changes in b ehavi or and gast r oi nt est i nal f unct i on i n a t w o- ye ar o l d ch i l d . 1 am al so in good agr eem ent w i t h you on t he poi nt t hat t he r isk o f acut e sympt om at i c l ead p oi son i n g i ncr eases m ar ked l y as b l ood l ead l e vel s rise above ap pr oxi m at el y 80 pg Pb/ 100 G w hol e''b l ood , lj>uf t hat t he act ual occur r ence o f sympt oms and t he sever i t y of sympt oms cannot be correl at ^ 'cf ^ / f f h^ bl ood l ead l e vel s above t he 80 p g l evel . There is, o f cour se, i n chi l dr en t he ad d i t i onal e p i d em i ol ogi c f act or o f t he ve r y l ar ge dose t hat can r esul t f rom t he i ngest i on o f pai nt chi p s. This is qui t e di f f er ent , I t hi nk, f rom t he i ndust r i al si t uat i on i n whi ch, bar r i ng br eaks in envi r onm ent al cont r ol 't echniques, a r e l at i ve l y const ant l evel o f exposur e m ight be an t i ci p at ed . Not so i n t he c h i l d i n whom w e f i n d bl ood l ead l evel s can r ise at a p r eci pi t ous rat e w i t hi n a per i od of one t o t wo mont hs from a r e l at i ve l y saf e l evel t o a l evel associ at ed w i t h sympt oms. This must cer t ai n l y be due t o t he ve r y hi gh dose w hi ch such chi l d r en m ay i ngest . It is f or t hi s reason t hat we set a l evel o f act i on f or p r event i ve purposes w el l b el ow t he 80 p g l evel . 1 w oul d suspect t hat bl ood l ead l evel s bet w een 40 and 50 p g Pb/ 100 G w hol e bl ood ar e h i gh l y suggest i ve o f t he p r ob ab i l i t y t hat a c h i l d has an ad d i t i on al abnor m al sour ce o f l ead and t hat gi ve n suf f i ci ent t ime and cont i nued pi ca, he may absor b enough l ead t o cause c l i n i c a l l ead p oi soni ng. In Bal t im or e, w e ar e f or t unat e i n t hat t he Heal t h Depar t m ent w i l l t ake p r event i ve act i on on t he basis o f t he d i agn osi s o f "i ncr eased l ead ab sor p t i on" w hi ch t he Heal t h Depar t m ent now def i nes as a conf i r m ed bipod l ead l evel >50 p g Pb/ 100 Dr . R. A. Ke h oe Ap r i l 30, 1971 G w hol e bl ood. I b el i eve t hat i n t he minds o f most ped i at r i ci ans, al m ost no d i st i nct i on is made bet w een t he t erms "i ncr eased l ead ab sor p t i on" and "l e a d p o i so n i n g". This and t he ver y hi gh dose of l ead t hat chi l d r en may i ngest is at t he root o f most o f t he conf usi on. There is al so gr eat conf us ion am ong p ed i at r i ci an s because most are f or ced, at present , t o base t heir ac t i o n s on inaccur at e, an al y t i c al resul t s. I might st at e p ar e n t h e t i cal l y t hat report s o f l ead p oi soni ng in adul t s w i t h bipod l ead l evel s in t he 4 0 - 7 0 p g Pb/ 100 G w hol e bl ood r ange have al w ays r ai sed my su sp i c i o n ' t hat t he an al y t i c al r esul t s w er e l ow . In an y event , I hear t i l y agr ee t hat accur at e an al y t i c al r esul t s and t echni ques const i t ut e one of t he main st um bl i ng b l ock s t o t he adequat e management o f l ead p oi son i n g and it s pr event i on t oday. At t he moment , I am t r yi n g t o t ake on t his ungl am ordus, but I f ear, necessar y t ask. The ar ea o f gr eat uncer t ai nt y w i t h r espect t o pot ent i al adver se ef f ect s o f l ead is, in my mind, t he r ange of l ead absor pt ion associ at ed w i t h bl ood l ead l evel s in t he 50 t o 80 pg Pb r ange. This is a r ange associ at ed w i t h m et abol i c al t er at i ons in heme synt hesis. Wh i l e t he di st ur bance in heme synt hesi s is, w i t h r espect t o t he f or mat ion o f red bl ood cel l s, c l e ar l y r ever si bl e, it is al so possi bl e but not pr oven, t hat t he di st ur bance in heme synt hesi s may r ef l ect m et abol i c d e r angem ent s in ot her t issues and p ar t i cu l ar l y i n t he ner vous syst em w hi ch m ay not be r ever si bl e. And so t here is i n t he m inds o f m any t he quest i on o f w het her some subt l e ef f ect s w i l l occur i n t he d e v e l op i ng young c h i l d t hat ar e not m ani f est ed by t he usual c l i n i c a l i nd i ces. This i s an ar ea w h i ch 1 hope t o i nvest i gat e in t he com i ng year s. Pedi at r i ci ans in p ar t i cul ar are sensi t i ve t o t he p ossi b i l i t y of subt l e, d el et er i ous su b - c l i n i c a l ef f ect s i n t he ch i l d . This st ems l ar ge l y from t hei r exper i ence w i t h var i ous i nbor n errors o f met abol i sm, such as p henyl ket onur i a and gal act osem i a i n w hi ch sympt om at i c cont r ol is i nsuf f i ci ent and m et abol i c cont r ol is essent i al , i f t he pat i ent i s t o have a good pr ognosis. Li kew i se, it appear s in young chi l d r en t hat measl es, even in t he absence o f post -m easl es e nc ep h al i t i s, can be associ at ed w i t h i nj ur y t o t he br ai n. An d so I t hi nk it is pr oper i n pedi at r i cs t hat we concer n our sel ves w i t h t he su b - c l i n i c a l aspect s o f di sease processes. I do hope t hat t hi s answ ers some o f t he quest i ons posed in your r ecent let t br. Your s si ncer el y, JJCr ov