Document ypmyEEm8OqJqY5N4nNVdg9Oxr

OCT 11 2005 15:47 RR CISTI ICIST 613 952 9303 TO 12145201181 CHRYSOTILE ASBESTOS--LANGER ET AL P. 14/16 359 platy particles idlcate location nee of partially ' means of EM. lie of chrysotlle material which in Suzuki and AS 1 men. Photographic stently gave imple visual . function of "ast, particle jested debris, difference in \ (Hunting obtained at different magni- electron beam (compare with naturally oc r,rations. At the low magnification shown in curring clay minerals). j the upper right of Fig 4, the number of fibers In the extracts examined, only three of 28 * and fibrils counted was only 45. However, cases showed what appeared to be asbestos when the magnification was increased photo bodies on the EM level. In each of these graphically, the count increased to 59. Occa three cases, asbestos bodies were observed sionally, even at the highest magnification, with the light microscope. Figure 7 shows organic debris (partially digested tissue) ob one of these bodies. The asbestos body is scures chrysotile from view. morphologically like asbestos bodies ob Some fiber fields were counted by scan- served by Suzuki and Churg25 and appears * ning and were then photographed; recount to be nucleated on chrysotile. It is a paradox ing of the fields photographed indicates that that, although asbestos bodies were readily they were initially "undercounted" (Fig 5). observed with the light microscope, very few The findings reported here are based upon were observed with the EM. The reasons 1 scanning values, and are not corrected for may lie in the preparation technique: the photographic results; the fiber and fibril water drop is drawn off the EM substrate by counts given, therefore, reflect minimum means of a wet filter paper; die moisture is I values. quickly and strongly "sorbed" into the blot There exists a close association of undi- ting material; nearly all of the larger parti I gested tissue and chrysotile fibers and fibrils, cles are "pulled" along with the water, as j Chrysotile fibrils occur not only next to, but evidenced by brown discoloration of the I in the midst of, partially digested tissue, wetted filter paper. It is likely that only the j Fibrils inside the undigested tissue tend to smallest and most highly surface-charged j be thin-walled and relatively small. -Clay particles remain attached to the substrate. ' minerals are present in the undigested tissue Diatom fragments, other fibrous materials as well. Asbestos "counts" from photographs including fibrous glass and amphibole asbes again demonstrated the presence of more tos types and sheet silicates were observed to chrysotile than could be counted directly on be present in the lung dust residues. The the screen. occurrence of fibrous particles (other than Figure 6 demonstrates the close associa chrysotile and currently unidentified) is rela tion of chrysotile with well-formed polygonal tively frequent. Diatom fragments, although plates, morphologically similar to clay and occasionally observed, were rare. talc minerals. This association is striking because chrysotile fibrils tend to be both Comment ` "surface-" and edge-sorbed." Sheet silicates 1 tend to have a negative surface charge and a Unaltered chrysotile is uncommonly found positive edge charge. This suggests that one as the core fiber in asbestos bodies removed of the following mechanisms is at work: (1) from lungs of people in the general popula The chrysotile fibrils possess a range of sur- tion. In an electron microprobe study of 16 t face properties. (2) Different sheet silicates cases from which such asbestos bodies were . are involved in the association. (3) Both 1 recovered and analyzed,18 none were chemi and 2. (4) The association is artifact. cally equivalent to unchanged chrysotile. Fif The morphology of the sheet silicates indi teen of 16 analyses, however, were consistent cates that they may be kaolinite (Compare with magnesium-leached chrysotile, and one I with kaolinite plates shown in Beutelspacher was consistent with amphibole (amosite). and van der Marei,81 Fig 19 to 32, pages 53 We have similarly examined asbestos bodies I to 59; Fig 259 to 260, Page 271; Fig 238, A from the lungs of a Canadian chrysotile and B, page 252. Several of the sheet materi miner and from hamsters injected with chry als resemble bentonites. Fig 130, page 137, as sotile, all of which gave results consistent well as labile chlorite. Fig 152 and 153, page with magnesium-leached fibers. 161). This association may be important in This could well have been predicted, in determining the origin of the chrysotile that biological environments would seem ide source. The nature of the pitted surface tex al for this. Indeed, with the rapid splitting of ture is likely artifact produced under the the fibers into their unit fibrils, the surface J RECEIVED TIME OCT. 1 Arch Environ Health--Vol 22, March 1971 2:43PM