Document rBa6JNrK67DX7voxO60Y3O6za

/3N W OMWiVNMam THE MOUNT SINAI MEDICAL CENTER ONE CUSTAVE L LEVY PUCE NEW YORK NY 10029 Mount Sum School ofMedicine "The Mount Sinai Hospital PER April U, 1979 Mr. Robert S. Magdelala, PresIdeat Hllfisk of America, Inc. 201 Kins Manor Drive Xing of Prussia, Penxmylvaniii 19406 SnnraiuMnial tauieu Utmim Cumaunf, Sanic Seiic Butfdu, <0 Kill lot tmtt N<u York, York 10029 ran/ eso-em Boar Mr. Kagdeloin: This will report the results of air sampling rests conducted, in October 1976, to determine cirrysotile asbestos concentrations dur ing brake repair -work. Our major objective was to determine the efficiency at Che Hllfisk Asbestos System utilising HEPA filters, particularly with regard to Bubsderoacopie asbestos fibers. Studies conduetad in our Laboratory and elasahera have demonstrated that free asbestos fibers present la brake drum dusts are predominantly shorter chan Sum la length, la particular, it was found Chat about ISt of the fibera is such dusts vara lui than 0.3vm in length, as determined by transmission electron microscopy. Thus, the optical microscopic technique used by 0SHA for determining asbestos levels in workplaces (in which only fibers Sum or longer are counted) would overlook a large numbor of asbestos fibers iu air samples. That is, the total asbestos exposure In terms of fiber number, mass sad surface area would be significantly greater than the levels determined using the 0SBA fiber-counting method. Therefore, it was of considerable interest to ua to have an oppor tunity to test the efficiency of the Hllfisk Asbeato-Clena System. To do this personal air sampling was carried out on the exhaust of a SEPA-filtered vacuum dust collector and, simultaneously, on a garage mechanic cleaning a brake drum with Che KiLflak brake en capsulation cylinder. Three such teats were mads, background air samples, also using personal air pumps, were taken. For each of the teats, a sample of settled dust was taken from the broke /drum. The dusts were analysed by x-ray diffraction in the tep-- aeon mode co quantitatively determine asbestos contents, using a technique previously published. Asbestos was found in all three sasplea, ranging from 2.52 to 4 JX by weight. The membrane filters were analysed by both transmission electron microacopy (XZ5,000) and by the standard OSSA fibor-counting technique, employing phase canCroat optical microacopy. The results sze as followst 007912 PRODUCED BY FORD