Document 8Oq7BJrJR3K4VXKoNznoEwqqk

Janu ary 4 , .1955 M r,' L ew is H. B o g ers Southern C alifornia A ir P ollution Foundation ?04 South Spring S treet A L os -Angeles 14, C alifornia D ear M r. Buffers: M r. C holak show ed m e your le tte r o f D ecem b er 15 in w hich you a sk for inform ation on the lead compounds in the exhaust gas of autom obiles, and on the other so u rces of le a d in the atm osp h ere. It seem ed b e st that I reply, despite the fact that we have m ade no observations on the exhaust g a s, and our knowledge of the proportional representation of variou s so u rces in the co m p o site so u rce of lead in the atm osph ere is based la r g ely on in feren ces which a re reason ab le but unproved. * The com position of the lead in the exhaust has been investigated by the D etroit L ab oratories of Ethyl' C orporation, but so far a s I know th e data h ave hot b een p u b lish ed . In g e n e r a l, it m a y b e s a id that th e lead burned in the engine is converted into sa lts by the cations a v a ila b le in th e m ix tu r e on th e b a s is o f a. n o r m a l e q u ilib r iu m . The h a lo g e n c a rr ie rs a re added to convert m ost of the lead to the ch lorid es and b rom id es, and thi3 is accom plished. In'addition, th ere is sulfate, carbonate, phosphate and som e n itrite, w ith perhaps m inute am ounts of other sa lts. The proportions vary with the com position of the fu el, but it is to be anticapted that the halogen sa lts greatly predom inate. A s you a r e aw are, no doubt, aviation gasolin e contains ethylene di brom ide a s the halogen' c a r r ie r , w hile autom obile gasolin e has both brom ide and chloride c a rr ie rs. The exhaust gas is the principal contributor of lead brom ide, lead chloride and lead ehlorobrom ide to the a tm o sp h ere. The nature of the oth er le a d com pounds in the atm osphere derived from so il, from the com bustion of coal and vegetation, from various industrial p rocesses, and from other, perhaps triv ia l, so u rces, is conjectural. We have only in d irect inform ation on the contribution made by the com bustion o f coal} when the City of Cincinnati put its sm oke reducing ordinance into operation a fter the la s t w ar, the lea d content of the atm osphere d ecrea sed gen erally to som ething m ore than half of its previous lev el. ;- I think, if I m ay aay so , that p resen t attem pts to estim ate the propor tional contributions m ade to the lead in the atm osphere in L os A ngeles M r . .L ew is H . R o g e r s - {2} - J an u ary 4 , 1955 w ill be highly specu lative and largely futile until and u n less sp ecific compounds or form s of lead have been identified and related to sp ecific so u rces. The potential sou rces have not been explored even qualitatively, so far as I know, by anyone, and assum ptions concerning them w ill be a bit naive to sa y the le a st, sin ce the situation th ere m ay d iffer appre cia b ly fro m th ose cliat m ay he encountered e lse w h e r e , b eca u se of d ifferen ces in the pattern and d irections of m ajor and m inor a ir currents and in the location , num ber and type of so u r c e s of p articu late lea d . Y/e h ave g iv e n so m e c o n s id e r a tio n fr o m tim e to tim e to m e a n s o f identifying variou s lead -b earin g m a teria ls in relation to sou rces, but w e ha ve not m ad e m u ch p r o g r e s s in th e d e v e lo p m e n t o r a p p lic a tio n o f such m ethods. 1 suspect that this could be done eventually if there w ere adequate rea so n s for so doing, but in view of the sm a lle r sig n ifica n ce of lead in the atm osph ere of urban cen ters (apart from sp ecific industrial e n v ir o n m e n ts )' a s a s o u r c e o fh u m a n ^ead a b so r p tio n , in c o m p a r is o n w ith the quantities which o ccu r regu larly in human food and b e v e ra g e s, the im petus fo r such work has been that of scien tific cu r io sity rather than u tility . To be a bit m ore sp ecific as to the am ounts of lead involved in the d a ily lif e of n orm al in d iv id u a ls, .if is fa ir to s a y that the am ount o f le a d in. the a ir b reathed in (not ab sorb ed ) by the a v era g e urban c itiz e n is app reciably le s s than 0 .1 m g. per day. Of this quantity som ething 'less, than'half; on the a v era g e, in a ll probability, is retained in the resp ir a to r y app aratus, the rem ain d er being carried, out of the body in the expired a ir . P r a ctica lly a ll of the lead of th is type that is retained in the lung is absorbed even tually, and part of that which is trapped in the upper resp iratory apparatus is sw allow ed, the rem ainder being exp ectorated or carried out with n asal d isch a rg es. Thus it m ay be teen' that a s e r ie s of variab les which rela te p rim arily to the s iz e of the p a rticles of lead com pounds in the atm osp h ere d eterm ine th eir fate in the body. It is reasonably certain , h ow ever, on the b asis of balance m etab olic exp erim en ts, that som ething le s s than 0. 03 m g. of lead p er day Is a b so r b e d fr o m th e a tm o s p h e r e (in C in cin n a ti); the am ou n t m a y w ell b e a s sm a ll as 0 . 0 1 m g. p er day, and it is not m uch different in o th er A m erica n c itie s , including L os A n g e le s, a s judged by the a v a ilab le data. '' In c o n tr a st, th e a v e r a g e am ount o f le a d tak en in b y th e a v e r a g e A m e r ic a n in.food and drink is approxim ately 0 . 33 m g. per day, this being the principal sou rce of h is regu lar absorption of lea d . Som ething of the order e f 1/10 of this quantity is absorbed into th e body daily under average conditions, the rem ainder being evacuated in th e fe c e s . 0004354 M r. L ew is H. R ogers - (3) - January 4, 19S5 The foregoing quantities of lead are taken ca re of quite adequately in the human econom y, ana m ere is good evidence that th ere is a satisfactory fa c to r o f s a f e t y . We a r e en g a g ed In d e te r m in in g , a m o n g o th er th in g s , in current experim ents on the m etab olism of lead in human subjects, the actual m agnitude of this factor of safety. I have gone to som e length in com m enting on sev e r a l asp ects of the situa tion in w hich you a re in terested , la r g e ly b eca u se th ere has been a s e r ie s of foolish and irresp on sib le statem ents concerning it in a number of so called new s r e le a s e s . It see m s the b etter part of w isdom not to augm ent th e se in the public p r e ss by fu rth er sp ecu la tiv e com m ents on the su b ject. S in cerely yours, , M K ef u*. O . . I r . Jo C n o la k R obert A . K olioe, M . D. .'