Document aBEVnKDg1Mp9ar6rvOgYbVrVY

FILE NAME: RT Vanderbilt (RTV) DATE: 1995 June 16 DOC#: RTV 119 DOCUMENT DESCRIPTION: Letter from Univ of Maryland to US Gypsum RE Report on Tremolite in Vanderbilt Samples Downplaying Danger P t fI UNIVERSITY OF MARYLAND AT COLLEGE PARK ; DEPARTMENT OF GEOLOCY | I Mr. Charles Byers United States Gypsum 125 s. Franklin street Chicago, Illinois 60606-4678 ! j i June 16, 1995 ; I Dear Mr. Byers; j i I have reviewed the report, dated March 20, 1995 and written by A. W. struss on international Talc 325 from R.T- Vanderbilt. I have also examined a portion of the sample labeled International Talc 325 that you sent to me. S Mr. Struss's report has accurately identified tremolite and ' fibrous talc as the elongated minerals in the sample. He has also correctly concluded that while lizardite .is present in the sample, chrysotile asbestos is not. I also agree that tremolite particles that are longer than 5 micrometers, narrower than 3 micrometers with a length to width ratio of at least 5 are present in the j sample. However, I do not agree that these dimensions make these particles asbestos. Mr, Struss has applied criteria that are ` advocated by NIOSH for asbestos fiber counting on air filters. It is not really a definition but a set of criteria for counting . asbestos to obtain an exposure index and as such it is j inappropriate to apply to air filters unless asbestos is known to ! be present. In other words, this definitions tells the analyst which asbestos particles to count on air filters, but it does not 1 tell him which ones are asbestos. Furthermore, since the NIOSH : fiber counting criteria were designed for air filters, I would not ' apply them to bulk samples under any conditions. When examining a bulk sample for the presence of amphibole asbestos by optical microscopy, I look for the following characteristics of .a population of amphibole particles: l) Mean aspect ratio of 20:1 or greater for fibers longer than 5 micrometers, 2) very thin fibrils, usually less than 0.5 ' micrometers in width, and 3) parallel fibers occurring in bundles. If amphibole is present that does not display these properties, then it is not asbestiform. I have not yet found a sample of amphibole asbestos (identified by its hand specimen j characteristics) that does not display these properties under the Microscope (although I have found chrysotile that does not). I _ have enclosed a paper I wrote several years ago describing the ` DEPARTMENT OF GEOLOGY * UNIVERSITY OF MARYLAND AT C0U .EG E PARK, MARYLAND JC74J, USA OFFICE: 001) 4054365 . DIRECT LINE: FAX: 0 0 )1 3 )4 -9 ! WES000313 differences between amphibole asbestos and cleavage fragments which gives the basis for the criteria I have summarized above- I hope these comments are useful to you and help resolve the issue of Talc 325- I did not found asbestos in the sample and I believe your analyst will concur that the tremolite present in Talc 325 does not exhibit the properties I have described for the asbestiforra habit. cc: J. Kelse Sincerely yours, Ann G. Wylie Professor WES000314