Document jy8LzRV5q03zvk9zk1xMVO8pN

L. V. CRALLEY PITTSBURGH OFFICE MR. H. A. SJSMKBN ROCKDALE WORKS COfFIDENTIAL January 16, 1968 In connection with your letter erf January 12, 1968, concerning employees who use an asbestos-Luanite cement in crucible and trough liner repairs, we have Bade contact with Johns-Manvilie concerning their Ho. 352 cenent which we use. The asbestos component of this ceaent is crysotile. It contains no crocldolite. The above asbestos, if inhaled over a large nuaber of years in excessive amounts, will produce asbestosis. The current Threshold Limit Value is 5 million parts per cubic foot for a weighted 8-hour exposure. There is at present controversy over the allowable exposure to crocidolite, but since this is not involved in the cement now being used, it does not enter into the picture. Intermittent exposures to asbestos dust would not be expected to produce asbestosis unless the daily weighted average exceeds the TLV's. Even so, asbestosis from crysotile is not produced with in a short number of years njor is it possible to be exposed to enough dust during the handling of dirty clothes to give rise to a hazardous situation. In the repair of crucibles and troughs where asbestos dust is involved, it is desirable to correct the condition, when practical, by exhaust ventilation. However, some intermittent situations do not lend themselves to this approach and respirators must be worn. The respirators used for this purpose should be those approved by the Bureau of Mines for the protection against pneumoconiosisproducing dusts, that is those that would be adequate for pro tection against silica dust would also be suitable for asbestos dust. The Martindale respirator is not recognized as being suit able in this application. While it is effective for nuisance dusts, it is not recommended for either toxic or pneumoconiosisproducing dusts. Suitable respirators can be recommended by your Safety Director. However, should you wish us to comment on a particular respirator, please let us know. Dr. Dawson will be in touch with Dr. Richards concerning this subject. One of the things that disturbs us is the abundance of incorrect information now being circulated in relation to . asbestosis. Probably the most outstanding feature printed now in ndwspapers is cancer known as mesothelioma. Some researchers believe that crocidolite is responsible for the mesotheliomas. However, there is not enough information presently available to establish such a relationship and we must await further investi gation. On the other hand, many of the so-called asbestos bodies which are found on autopsy are probably in no way related to asbestos. We now know that many fibers, organic or inorganic, can produce these bodies and they are more and more being referred Z DEPOSITION I EXHIBIT I ARCH 18742