Document v113XayBvOYgM6Qag3jy6vnXq

OCT 11 ,2005 15:44 FR CISTI ICIST 613 952 9303 TO 12145201181 I CHRYSOTILE ASBESTOS--LANCER ET AL i P. 10/16 355 i ibrils with lore often, 3d internal by polarized ing medium 'iscous liquid ition20; scan250X, 400X, magnification ndertaken at ocamined miual undigestspite the ap- prepared for Small splits washed resi zere pipetted of the latter >1 of distilled im were agiconds. Small esidues were L onto a polyed 200-mesh EM) locator ' allowed to grid for 15 solid materi3 liquid drop paper. actually setie polyvinyl the unaided i j : j I { Fig 3.--Chrysotile fiber size range (thickness, length); fibers several fibrils thick (A to F) to fibril bundles (6, H), Fibrils range from well-formed (A) to highly deformed (C). Fiber length ranges from several thousand Angstroms to several microns. eye. Only 9 of 248 squares of each grid were examined under the EM beam. The tech nique used in this investigation provides an answer to the qualitative question: is chryso tile a ubiquitous contaminant of the tissue examined? It is evident that only an in finitesimal fraction of lung tissue was scanned (conservatively estimated at 10- of the total lung burden). Quantitative studies are in progress; these will be useful for epi demiological investigations concerned with `he biological significance of the current qualitative findings. Instrumentation.--Identification and loca tion of asbestos fibers and fibrils required the use of the highest magnification available on the electron microscope (RCA EMU 3G). A fibril is defined as the smallest characteristic fiber unit of chrysotile asbestos, with a thick ness of 200 to 400 Angstroms. Scanning was done at magnifications of 31,OOOX with an acceleration voltage of 100 kv. Identification of chrysotile was confirmed using the 7X binocular attachment, or at 217,000X. Identification Criteria.--In order to justify identification of chrysotile asbestos as it ap pears after extraction from lungs, it was necessary to review and extend information concerning the morphological nature of chry sotile. The range of morphological character istics of chrysotile was studied in consider able detail, and the findings are described Arch Environ Health--Vol 22, March 1971 RECEIVED TIME OCT. 11. 2:43PM