Document 5bEwKOv31NgdjZ8xqKL4g9nbV

FILE NAME: Z< DATE: DOC#: Z< DOCUMENT DESCRIPTION WDZZZZ ---~ . ...... -- ....... .... UNITED STATES ENVlRONMENTAL :f-:~;r...' . PROTECTlON.A.GEt.r.:n:;::: ~ , .,. ~ WASHtNCTON.O.e. 20460 ocr (7 935 - OFFICE OF P:Jl.ICY. PLANNING ANO EVALUATION HEHOAANDUM SUSJECT: FROM: TO: . . Asbestos Exposure - Brakes and Ambient Steve Wel1~ Chief ~ S7t.-~~ Chemical Review and Analysls- Branch L~ypnon~uD~e~lpAisr:ees~ ~~ent Branch Alay Moll Regulatory Impacts Branch After careiulasbestos dust from examination of brake relining the and data on worker exposure to maintenance operations and on ig ambi utes ent are e x 0 pos .04 ure to asb ibers/~c est fo o r s. b r we ake h s ave. and decide 0.000 d 07 t hat fibe the rs/c b c est fo r a,bient exposure . Our r3asoning i s e~plained below. BJ;"ake Shops - on yoTrkheerreexispoasusriegntoifiacs~bnetstoams oiunntshoof pms odnoiitnogr1nbgrokdeatamaaivntaeinlaabnlcee. This data shows various levels of asbestos ~he operation involved {e.g., blowing dust exposure depending from brakes), the on distance from being done in the the actual ~hop. brake work an~ the The numbers ranged amount of f~om 29.8 brake work flee for a peak sample taken during (RohI et al, 1976) Ca high blowout of number even dust from"brake linings for this ope~atlon) to low numbers length) such as .002 flee (fibers greater for a tw-a for complete service of than 5 micrometers in front disk and rear d19ru8mQ k bAralklieesd anBdrak.0e01Shof~/c).e six fe~t outsIde of the work bay (Roberts, 0.04 fWleech,aveis daecrideeadsont.ahbalte theestinmumabtee-rocfhothseenebxypotshuerecoofntwraocrktoerrs, in shops doing workers during brake work. While the number may be low for the time actually engaged in brake repair and maintenance. we eXp'osure t.o the think th3t population it of relatively accurately refl~cts ~ll mechanics and workers in the repair shops. .. -2- A more accurate method of determination of such exposure ~ould involve determination of exposures of ~orkers during different phases of actual brake work, and calculation of the1~ exposure, and then addition of the rest of the exposed work force at levels that approximate background levels in the shop. Rou~h calculations show that this yields approximately the same average exposure. Ambient Exposure to Asbestos The purpose of calculating ambient exposure to asbestos is to include benefits not captured by the models. Thus, the ambient exposure calculation should be based on exposure data that does not includeeither exposure to friable asbestos in buildings (already banned) or asbestos floor tiles (a separate calculation). The calculation by the NAS (pg. 219, in Asbestiform Fibers: Nonoccupational Health Risks) is not valid for our purposes as it assumes a certain contribution to ambient from exposure to friable asbestos. Further, the calculation is flawed because the exposure measurement for uncontaminated indoor environments came from buildings with friable asbestos in other rooms. The resulting cross contamination yields figures that are not truly represent8~ive of uncontaminated indoor environments. The NAS figure for outdoor ambient exposure, 0.00007 flee, seems to be a reasonable figure. While this exposure undoubtedly has some component deriving from friable asbestos use in build- ings and so on, use of this ~igure will minimize the double counting problem. , c.c. Oebl OcbkO\llSki Al Jennings Rick Tins.orth -.