Document Qgjy00rjYGkOoo4y6d47R2DB4

FILE NAME: Ford (FD) DATE: 1971 Oct 20 DOC#: FD115 DOCUMENT DESCRIPTION: Memo - Preliminary Estimate of Airborne Asbestos Emissions from Brake Linings Inter Office Communication Scientific R e s e a rc h Staff O c to b e r 20, 1971 To: cc: Subject: M r. J. U. Damian E . Eichen ' E . D . M arande S. G ratch J. E . M ayer, J r M. Humenik, J r. J. V. Petrocelli 'D . A . Jensen P relim inary Estim ate of A irborne A sbestos E m issions fro m Brake Linings Some e x p e rim e n ts have b e e n p e r f o r m e d w ith the objectiv e of a s s e s s in g the quantity of asb esto s fib e r em itted to the a tm o sp h e re during autom obile braking. A p ro d u c tio n P into disc b rak e a s s e m b ly w a s used in the stu d y . S am ples of the lining w e a r dust w ere obtained during the lining burnish (break-in), during typical u s a g e c o n d itio n s (40 m p h sto p s a t 1 / 4 G d e c e l e r a t i o n an d 3 5 0 F r o t o r t e m p e r a t u r e ) , and d u rin g abnorm ally se v e re usage conditions (~ 800 F r o to r te m p e r a tu r e ) . Only sam p les fro m the typical usage te s t have been exam ined to d a te . During th ese te sts, tke a ir flow over the b ra k e , w heel and tire a sse m b ly w as carefu lly m atch ed to vehicle use conditions. F o r the ty p ic a l usage te s t, all of the a i r flow fro m the brake was exhausted through a sam pling grid netw ork w here m u ltip le-sto p sam ples were taken isokinetic ally at each grid c e n te r using a 0.45 m icro n M illipore filte r. A m a tc h in g f ilte r w a s used to sa m p le th e a ir su p p lied to th e b r a k e . The q u an tity of a sb e sto s fib er collected on the filte rs is in the p ro c e ss of being determ in ed by elec tron m icro sco p e exam ination, using a fiber counting technique developed in the labo r a to r y of D r. I. J . Selikoff, et a l. , a t the M t. Sinai School of M edicine in New Y ork. T h is p ro c e d u r e w a s d ev elo p ed sp e c ific a lly f o r th e d e te r m in a tio n of a s b e s to s content from atm ospheric sam ples. The filter exam ination experim ents are not yet com pleted. F urther r e p lic a tio n of the fib e r count r e m a in s to be d o n e on the ty p ic a l sage f i l t e r s tc ob tain the precision .: m easu rem en t d esired . A ppropriate quantitative reference s a m p l e s h a v e n o t y e t b e e n p r e p a r e d a n a cour-.ted - - t h u s , o t ............- e s t i m a t e of actur.1 - s b e s to s f i b e r c o u n t r e q u i r e d a r e l i a n c e on M t. -:-ua i--- > experience^ to e s tim a te a sb e sto s lo s s e s fro m the sam p les during sam p le p re p a ra tio n . N ev ertae- le s s , a prelim inary estim ate may be made of the am ount of asbestos fiber collected based on fib e r counts m a d e to d a te . E x a m in atio n of th e s e m e a s u re m e n ts indicates^ that a s b e s to s f ib e r p ro b a b ly c o m p r is e s le s s th a n 0.Q27 of the a irb o rn e w e a r dust an m a y b e a s low a s 0.0047<r f o r ty p ic a l b r a k e u s a g e . E x p r e s s e d i n t e r m s of th e a m o u n t of b r a k e lin in g w o rn aw ay , it a p p e a r s that l e s s th an 0.017c, and p e rh a p s a s little as 8 3 000118 // 177 PRODUCED BY FORD M r. J. U. Damian 2 October 20, 1971 0.002% of the w o rn lining b e c o m e s a irb o rn e a sb e sto s fib e rs . The r a n g e of e s tim a te s r e s u l t s f r o m the in h e r e n t difficulty of accu-a*M v m e a s u rin g sm all q u a n titie s of such fin e f ib e r s (300 A d ia m e te r) a n 7 f r o m the r e l J tive sim ilarity of asbestos count from the background and test filte r sam ples For e x a m p l e , th e t e s t f i l t e r f r o m t h e t y p i c a l u s a g e t e s t c o l l e c t e d a p p r o x im a te ly 1*4,5 x 10 g r a m s of a s b e s t o s f i b e r p e r c u b ic m e t e r of a i r s a m p l e d dow nw ind of th e b r a k e , w hile the corresponding background filte r collected about 13.5 x i o " 9 gram s p e r cubic m e te r of a ir supplied to the b ra k e . O ur re c o rd s re v e a l that asb fsto s in s u la tio n had been used on a s te a m pipe in th e d y n a m o m e te r a r e a about a week p r i o r to o u r te s ts and that o th e r a s b e s to s in su la tio n w as in sta lle d e lse w h e re in the building at the sam e fame. This m ay account fo r the relatively high background level of a s b e s to s , w hich is a t the u p p er end of the ra n g e m e a s u r e d by the M t. Sinai la b o ra to ry in the am bient a ir of the D etro it area (0.5 to 13.4 x i o ' 9 g ra m s p e r cubic m e te r). T h e re p o rt of th e ir findings h a s not y e t b e e n p u b lish ed . In c o n c lu sio n , alth o u g h only p r e lim in a r y r e s u l t s a re av ailab le a t thi* tim e , the concentration of asbestos in the effluent a ir fro m a Pinto disc brake u n d erg o in g ty p ic a l b ra k e u s a g e a p p e a rs to be le s s than 0 .0 1 % of th e brake lining w o rn aw ay. The lin in g w as found to c o n ta in about 42% a s b e s to s , hence the a i r borne asbestos collected w as le ss than 0.03% of the original asbestos content. . ur labo rato ry studies have shown that all visible asb esto s fibers at an active rubbing interface a re heated to incandescence at typical braking velocities. T he glow te m p e ra tu re (approxim ately 1450F ) is m o re th a n sufficient to deco m pose the asbestos to a nonfibrous fo rm . T his probably explains the ex trem ely low am ount * f ib r o u s a s b e s to s e m itte d f r o m the b ra Jc e . ' The am o u n t of f ib ro u s a s b e s to s re m a in in g w ith in the confines of th e b rak e and wheel assem b ly w as not d eterm in ed in this e x p erim en t. RLG:m s Roy L . G ealer C hem ical Engineering Departm ent . h o -- Q M echanical R esearch Departm ent 000119 PRODUCED BY FORD