Document G5V4Gv7VmRXGXno1ZKOKwJQRr

V f' '! V' 'i '' ` " ` ' TBTREETHYL LEAD. NOTES ON THE DETERMINATION OF LEAD IN THE ATMOSPHERE. ------------------------------- .. . 'f - '4 . * 1 The f o ll o w i n g b r i e f 'comments a r e made i n r e l a t i o n t o t h e method d e s c r i b e d i n a 7 ; , i r e p o r t from Abadan (Development R ep o rt No. 8501). -L , , D espite the p re lim in ary t e s t of th e method d escrib ed in the r e p o r t, i t i s be- / ! lie v e d t h a t th e a b s o rp tio n of t e t r a e t h y l le ad vapour from th e atmosphere by means ' ' ? of T.Y.O. would be incom plete under th e co n d itio n s p r e v a ilin g in th e P.O.D. I t has been shown t h a t th e use of s im i la r s o lv e n ts (k ero sen e, m in e ra l o i l ) f o r t h i s p u r- " pose i s r e a s o n a b ly s a t i s f a c t o r y o n ly when th e c o n c e n t r a t i o n of t e t r a e t h y l le a d vapounr in th e a i r i s q u ite h ig h , and t h a t th e e f f ic ie n c y ,of th e a b so rp tio n drops o ff sh a rp ly , as the lead con cen tratio n in th e a i r dim inished. For t h i s reason the use of ahrab-:',-^ so rb in g medium which r e a c t s prom ptly w i t h - t e t r a e t h y l le a d (one c o n ta in in g bromine : or io d in e), i s recommended a s being n ece ssary . .. The e s tim a tio n of th e lead e x tr a c te d from th e a i r by th e ab so rb en t can be c a r - 7 rie d out by anyone of sev eral methods w ith s a tis f a c to r y accuracy provided the quan- ; t i t i e s of lead to be -dealt w ith are w ithin the range of the s e n s itiv ity of the in - . d iv id u a l method chosen. The a n a l y t i c a l e r r o r a s s o c ia te d w ith th e use of th e A.S.T.M. ' method D 526-39T as o u tlin e d in th e re p o rt from Abadan i s a p p re c ia b le , and can be ' ' reduced to p r a c tic a l in s ig n ific a n c e only by the c o lle c tio n of a sample th a t w ill con t a i n q u a n t i t i e s o f l e a d o f t h e o r d e r o f s e v e r a l mgms. I n g e n e r a l , t h e q u a n t i t i e s . o f l e a d d e a l t w i t h i n t h e r e p o r t a p p e a r t o have b e e n s u f f i c i e n t t o j u s t i f y th e u s e ... of t h i s a n a ly tic a l method. I t i s b eliev ed , however, th a t the r e s u lt s given in the ' ., r e p o r t tend to e r r somewhat on th e low sid e . The a n a l y t i c a l e r r o r would be q u ite . sm all as compared w ith t h a t r e s u l t i n g from the use of th e spmewhat i n e f f i c i e n t method of e x tra c tin g te tr a e th y l lead from th e a i r . . ' ' . : . \ ' ; ! ; , - -- > | 1 For th e reasons given above, i t seems probable th a t the co n d itio n s w ith r e s p e c t to lead exposure in th e c a n - f i l l i n g s e c tio n of th e P.O.D. were somewhat more severe than the data in d ic a te . This conclusion is e sp e c ia lly ju s tif ie d in connection with' the a n a ly tic a l r e s u l t s given in the Second In te rim R eport (D.R.No.8620). I t seems ,7 c e r t a in th a t any ty p e of in c re a se d v e n t i l a t i o n ivould have reduced th e le ad concen- . tr a tio n (as w ell as the concentration of p e tro l vapours) in the atmosphere of the 7 f i l l i n g s e c tio n . However, the d ata in Table 1 (D.R.8620) cannot be r e li e d upon : :f I m p l i c i t l y f o r t h e f o l l o w i n g r e a s o n s : - ( l ) The a i r s a m p le s were c o m p a r a t i v e l y s m a l l ; !.` (2) The q u a n t iti e s of lead found Were o u tsid e th e -ra n g e of s e n s i t i v i t y of th e a n a l- ; . y t i c a l method; and (3) In a l l p ro b a b ility th e e x tra c tio n of the te tr a e th y l lead : vapour from the a i r was incom plete. Moreover, i t would seem t h a t th e r e would be s ig n ific a n t v a ria tio n s in the lead content of the atmosphere a t d iffe re n t times and\ 7 in d iffe re n t p a rts of the f i l l i n g sectio n unless the v e n tila tio n had been designed in such a manner as to remove 'th e,v ap o rs from th e b u ild in g by p ic k in g them up a t t h e i r point of origin. '- ... -V/i The method f o r th e c o l le c t io n and d e te rm in a tio n of t e t r a e t h y l le a d as o u tlin e d ; i n t h e memorandum o f Dr. C a s s e l l s d a te d 1 6 th J u l y 1943 can be eocpedted t o y i e l d s a t i s - -factory re s u lts . The efficien cy of the absorption of t.e .l.fro m the a ir is high for even q u ite low co n ce n tratio n , w nile th e a n a ly tic a l procedure i s s u f f ic ie n tly accurate fo r the purpose. . ` ` . R o b e r t A. K ehoe, M.D. October 1943. .' HE 0010146 .