Document BDbe6rbBXkqNNoeyD42yQzjE

FILE NAME: Raybestos-Manhattan (RBM) DATE: 1974 Jan 29 DOC#: RBM061 DOCUMENT DESCRIPTION: Letter to John Marsh from McGill Univ Dept of Epidemiology RE Asbestos Fibre Concentrations DEPARTMENT OF EPIDEMIOLOGY AND HEALTH m i UNIVERSITY STREET. MONTREAL K J J QUC., CANADA B4 McGILL UNIVERSITY Telephone # 392-8058 Area Code 514 January 29, 1974 M r . John Marsh Raybestos-Manhattan 205 Middle Street BRIDGEPORT, Conn. Cr < Dear Mr. Marsh, Further to our discussions on Friday, January the 25th, I would like to clarify one or two points which you raised. The method used to mount the membrane filters was that adopted by the British Occupational Hygiene Society. There are essentially two reasons for using this method. One, we were transporting samples considerable distances before countingr The British method calls for treatment of the filter at the site with a "plexi-glass in chloroform" solution which essentially fixes the fibres in place, reducing the risk of disturbing the particles before they reach the laboratory. Secondly, the American method calls for the preparation of a special solution containing dissolved membrane filter which must be fairly fresh when used, it requires some time for preparation and we have found that counts using the British and American methods are comparable. With regard to the sub-micron diameter fibres, we chose scanning electron microscopy rather than transmission electron microscopy because virtually all techniques for examining airborne dust using transmission electron microscopy involve transfer of dust from the filter to the electron microscope grid. This can lead to serious loss of fibres under some circumstances and the fibre is unlikely to be observed in the same condition as it was collected. Because we were interested in the actual airborne fibre concentrations. we decided to eliminate the possibility of fibrilisation etc. by collecting samples on nucleopore membrane filters and examining the samples directly. The airborne fibre concentrations at Plant 2, raise a serious problem. There is no doubt in my mind that it should be impossible for a man to be unknowingly exposed to fibre concentrations exceeding those permitted in an asbestos industry. As you know, we agreed in our contract that the results of our studies would not be published until one year from submission of the final report to Raybestos-Manhattan. In the meantime, I would like I1T1 PLAINTIFFS EXHIBIT 11 l : > OC''T~' >o to ensure that companies manufacturing asbestos aware that garments do exist which give rise to of asbestos in a man's breathing zone. I would you might have. safety garments are made fairly high concentrations appreciate any suggestions There are probably two further investigations which are worthwhile 1) Tests of specially treated (eg coated inside and out) asbestos garments both in the laboratory and in the field. Although the dust concentrations released by the garments which we tested at plant 1 did not exceed the 5 fibre/cc standard, some of them would exceed the 2 fibre standard if the work practice adopted at a particular plant required men to wear them more frequently than at this plant. 2) Further investigation of the Novatex material. Exactly where to go with this material will be known in about 2 -.:ceks when we have completed our tests. If you have any further questions concerning the report on Phase I or would like to discuss follow up studies on asbestos garments, please do not hesitate to contact me. Yours sincerely, i :,L /// G.W. Gibbs, MSc, MSc, PhD Assistant Professor GWG/ssn cc Dr. J. Magenheimer