Document wDL8Rgv0y5ZqGMvOvjBJnMvVo

;jf| :}j>!;s j^fg ~j || PLAINTIFF'S EXHIBIT DUP-672 Ir O fw*"3' ndustrial hygiene news report 4 HlUr*oUVui,aauUir dl^SciM Mm rmmmUr Mar jaaetaiatf to toa 0.4, Cuutf*. MlU<41ffbwur44aMU> niamidmotonHn Cammltsmt tilu* *mW M.Mmla Caatmlltum WUUtm r. MtCtmitk 4frirt f* r/wwfl Volume IX July, 1966 - Number ` FINDIN11 GS RE...P..O.. RT1 ED 1IN1DUST _ STUDY IN ASBESTOS .T.. EXT"ILEi 1I1NDUSTRY Result* of environmental surveys of nine asbestos textile plants, which account for me than 80% of the workers In the Industry, have revealed that dust concentrations as met sured by implnger are gene rally'below the Threshold Limit Value, and that estimates relative dustiness from membrane filter samples were in good agreement with those made from Impinger samples by either concentration or body burden methods of group The following information on the U. S. Publie Health Service study was given by Jeren R. Lynch and Howard Z. Ayer of the Division ofOccupatienal Health (1014 Broadway, ( cinnatl, Ohio 45202) at the American Industrial Hygiene Association meeting May 16*2' A total of 1896 membrane filter samples and IU5 midget impinger samples were col lected using all of the usual and some of the less frequently used methods of sampli: for mineral dusts. To examine the relative variability of different count methods ef analysis, the variance ratio test was applied to the sample groups by different count methods In each plant and operation, tn all cases, the variance ratio test indicated that the difference between the standard deviations by the different methods was not significant (p >0.05) and that .none of the methods eould be considered less variable than the others. To Investigate this further, samples on which magnesium analysis for asbestos were performed were compared with total fiber counts made on the sac samples. Again, the differences between standard deviations were not significant, indicating that the variability observed is actually the variability of the environment Count*weight ratios obtained by magnesium analyses of membrane filters were 3, 000* fibers M0 gm or 5, 000 biers >8 p//igm or ll, 000 total fibers//igro. None of the sett of ratios exhibited any less dispersion than the others. A mass median fiber volume o 50obtained from electron micrographs, yielded a count-weight ratio of 8,000 fibers figm which was ef the same order ef magnitude as the ratio obtained by magnesium analysis. It was concluded that the implnger is as convenient as any other method and in view the large variance found in the environment, no less accurate than other measure ments; however, it is difficult to reconcile the basing ef the hygienic criteria on codominated by grains while the fibers are thought to be the causes of disease, la thi: respect the counting of fibers on membrane filters appears to have an advantage, ct pecially in Industries where asbestos is only a small fraction of the airborne dust. The relevance of magnesium analysis for asbestos is unknown and the method InvoT the use of sophisticated and expensive laboratory equipment; however, U is hoped t: the intensive study ef total and respirable mass concentrations made possible by th method, will lead to the development of a relevant and convenient mass sampling rr. .... . _. .... ....... .................... WR 0900513 12J DU 021910