Document 6B4QD6Oaj1jReEQN9dRqjpm61

RE: SUBSTITUTES FORASBESTOS In his memorandum of April 9, 1973, "Re: Substitutes for Asbestos", Mr. T. B. Bonney points out the strong desirability of replacing the use of asbestos with other materials because of the very strict requirements of the asbestos standard. In the second paragraph of that memorandum, he also points out that some environmental control measures may be necessary with some of the proposed substitutes for asbestos that are presently under consideration or development. In our telephone conversation of last week, I recommended to you that where it is likely that there will be worker exposures to airborne dust related either to the original use of the substitute materials or to repair and maintenance work in connection with their use, we should obtain from the suppliers of these materials detailed information regarding their composition. If any of these materials contains free (not chemically combined) silica, it is important that we know whether this silica is crystalline or amorphous and in what proportion it is present. Only in the light of this information can a proper determination be made of the maximum safe levels to which a worker may be exposed. I believe that you agreed that it would be desirable to obtain this information in all applicable situations at an early point in our consideration of these materials to permit industrial hygiene, review of the composition and establishment of any required controls. We will be glad to be of any needed assistance in this matter. ROBERT P. CARTER RPC/map cc: Messrs. R. C. Hinkle, Badin Works P. V. Bonsignore, ATC R. E. Spear/R. G. LaBar, ATC G. H. Farrah/J. M. Plunkett, ATC L. D. Hart, East St. Louis M. J. Caprio, Pittsburgh - 19 R. J. Getty, Pittsburgh - 2k J. E. Hatch, Pittsburgh - 23 J. Z. Nelson, Pittsburgh - 7 O.P. V. w. Rieke, Pittsburgh - 2 G. R. Svany, Pittsburgh - 23 F. E. Mueller, Pittsburgh- 23 ALCOA 4110841716 tf.436t (mv ti e) FROM THOMAS B. BONNEY PITTSBURGH OFFICE 1 TO MEMORANDUM u April 9, 1973 RE: SUBSTITUTES FOR ASBESTOS* I Recently Dr. Mearl Stanton of the National Cancer Institute concluded as a result of animal experimentation that microscopic fibers of a certain size (0.5 - 5 microns diameter and less than 80 microns long) can cause cancer in rats, regardless of the fibers' chemical composi tion. Should this also apply to man, it would mean that any fibrous substitute for asbestos having fibers of similar dimensions would have the same hazard as asbestos. I I Furthermore, some of the proposed substitutes for asbestos: may contain crystalline or amorphous silica or other potentially harmful materials that will also require some type of environmental control On the basis of these two facts, the question naturally arises, 'If we are successful in finding substitutes for asbestos, will we be getting out of the frying pan and into the fire?" In our opinion, the answer to this question is, "Definitely No!" The present comprehensive standard for asbestos is exceedingly restric tive and expensive to those who would comply with it One must have extremely effective exhaust systems where dlust is ger-rated, establish a respirator program, observe restrictions 'in the ma: ner of handling and disposing, provide special clothing, comprehensively monitor dust concentrations every six months, provide median 1 examinations every year, post the area, appropriately label the raw material and maintain records. By contrast, all that is required to be in compliance with, for instance, the standard for amorphous silica is to keep the eighthour, time-weighted exposures below 20 million particles per cubic foot (mppcf). Even if comprehensive standards were eventually developed for substitute materials, we do not believe that these standards will be as restrictive as that for asbestos. Furthermore, the limit for asbestos is now 5 fibers/cc and it will be reduced to 2 fibers/cc in 1976. Compare either one of these figures with the 20 mppcf limit for amorphous silica which is equivalent to 706 particles/.c. Even 100% crystalline silica dust has a limit of 2.4 mppcf or 81 particles/cc. From these figures, it can be seen that the required engineering control for asbestos is much more stringent than for most materials that might be used as substitutes. If those actively seeking substi tutes have any questions about the toxicity of proposed alternatives, they can obtain answers from the Industrial Hygiene Division. Admittedly, Dr. Stanton's hypothesis does stand as a dark cloud on the horizon. But we must remember that his hypothesis is still unproven. Even Dr. Stanton cautions, "Direct application of our results to the problems in man would be unwise because the method of application and the high doses used are remote from the usual exposures of man to fibers, but how these materials exc-rt their carcinogenic effect is a critical problem, and current data seem ALCOA 411084 1717 r>43 (*. 1 Memorandum April 9, 1973 rap*; 2 adequate to develop a working hypotho;. s." 1 here are oilier da1 a in the ] i (.eratuii that controvert* Dr. Stanton's hypothesis and further work is contemptaled in this area. (mo , ah expeel a considerable period of time before the question finally settled. Even if the theory proves true (and we have* no reason to believe that it is at this time) there will be additional elapsed time before an appropriate standard can be written. Until a standard is written covering all fibers having thf critical dimensions, the asbestos standard will apply to ashes! - and to asbestos alone. It cannot be extrapolated to cover physically similar materials. Thomas B. Bonney TBB:mh cc: R. C. Hinkle, Badin Works P. V. Bonsignore, ATC R.E. Spear/R.G. LaBar, ATC G.H. Farrah/J.M. Plunkett, ATC L. D. Hart, East St. Louis M.J. Caprio, Pittsburgh - 19 R. J. Getty, Pittsburgh - 24 J. E. Hatch, Pittsburgh - 23 J. Z. Nelson, Pittsburgh - 7 0 P V. W. Rieke, Pittsburgh - 2 G. R. Swany, Pittsburgh - 23 R. P. Carter/File <11084 i7ie