Document p5X0Q739ROrqqkeOGqMBOgXj

PLAINTIFFS EXHIBfT Afcw-M-' r* v Vi I *1 o latl/ tL>+Jr St.lj.oJUL 1 DOW CHEMICAL U.S.A. 3//1-6 TgjrwrrmitrssA-iTOi* RESTRICTED fM VUdTWI ftflOTtl CAT aft i cft tnkI fIt fAtM itwfw-v -- -- ANALYTICAL LABORATORIES itrsorr D* R. Beaman And H. J. Walker KL-AL76-60697 n?irTM~-- *-.**$ _September 29, 1976 "WtT DIFFICULTIES ENCOUNTERED IN TUB IDENTIFICATION OF ASBESTOS P;$f?RS.. ftV AWNAMLtlYWTItUgltNACTO.lMTCif*tAWSMIRSinM v.t.rCTUfVt mCZCSCtoP*____LiJJJSjr;_____ Urgt variation is often observed in inter-laboratory determinations of the asbostos concentrations in water.and air* The reasons for and means of minimising this ~~ variation are discussed* The fiber losses that occur, during sample preparation and filter extraction are .. large, and variable (10-60$) and depend on^ the fiber type / and extraction mothod used* Fiber losses can be minimized' by using short extraction times and/or gentle extraction techniques* Asbestos morphology is.distinctive but not sufficiently so to allow positive morphological identification in environmental samples* Selected area electron diffraction pattern# are often indistinct and the fraction of asbestos , fibers giving identifiable diffraction patterns depends on the fiber size distribution and instrumental parameters*' This problem is particularly serious in^atudying chryxotile/fib^ilr large vaHhMcnOn concentration are encountered when the sample contains- a-significant* numbcr;*of fiber eiumpeV bundles or networks because guidelines*. for ..costing, cojuplex .fiber: tf configurations have not been established* It is difficult _ to maintain good counting statistics when the quantity of* '* material analyzed corresponds to parts per billion of.asbestos and samples cf less than 100 ml must be used. When these problems ard avoided the variation'in multiple "analysis 'is generally better than 30.t.... ; -*. - *** -c j -theses CO _;U at i f >* ?*c? c* f- pfPyNP T'Af-u; ).(.UHUIhA ~C.ft.LTtt** f. ft. L V*m* *Cft.L Uilitiit Um4 ! S {# C.S.L. M SIS* *UU*4m"7 ' ` See Attached Distribution* Llat - -1.0. ___________ r*>V *a.~c* era u]> Ai**r*r u; ;n ;r - ,7rto :.*'O0 anv.i; n *:r i0`we ::***! 'iif- :alcs. '*1 -rs*3 ^ !#' > -j *.***.' b . > .. . j .u ; v * *' * ;S. .. ;.**i DOW 07141