Document 2RenGZKw2y5o5JQ7qVMR3d4Qg

TO MR. D. R. BARCH PITTSBURGH OFFICE - 8 O.P. April 23, 1973 RE: SUBSTITUTES FOR ASBESTOS 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 - 2h J. E. Hatch, Pittsburgh - 23 J. Z. Nelson, Pittsburgh - 7 O.P. V. W. Rieke, Pittsburgh - 2 G. R. Swany, Pittsburgh - 23 F. E. Mueller, Pittsburgh- 23 ALCOA (*tv n e> ALCOAO 000009743 FROM THOMAS B. BONNEY PITTSBURGH OFFICE TO MEMORANDUM April 9, 1973 RE: SUBSTITUTES FOR ASBESTOS 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 micr< ns long) can cause cancer in rats, regardless of the fibers' ch--m:c:i'i 'ompesition. Should this also apply to man, it would mean that. z- \ tilrous substitute for asbestos having fibers of similar dimension- wvuld have the same hazard as asbestos. Furthermore, some of the proposed substitutes for asbesto.* may contain crystalline or amorphous silica or other potentially harmful materials that will also require some type of environmental control Or. the basis of these two facts, the question naturally arises, If we are successful in finding substitutes for asbestos, will we be griting 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 mu.sr have extremely effective exhaust systems where dust is gi: rated, establish a respirator program, observe restrictions in the ma er of handling and disposing, provide special clothing, comprehenst .*ly rnonjt i dust concentrations every six months, provide medi- r.l exam.a nar ions wi.ry year, post the area, appropriately label the i.w material and maintain records. By contrast, all that is required to he in a'mpiiance 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 1' fibers/cc in 1976. Compare either one of these figures with the 20 ppcf 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 cl( ud 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 F-49e* (V. !!-*) ALCOAO 000009744 Memorandum ..April 9, 1973 Pagje 2 adequate to develop a working hypothesis." There arc other data in the literature that controverts Dr. Stanton's hypothesis ar.d further work is contemplated in this area. One oah expect a considerable period of time before the question is 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 tine before an appropriate standard can be written. Until a s-tandard is written covering all fibers having tie critiial dimensions, the asbestos standard will apply to asbes and to asbestos:, alone. It cannot be extrapolated to cover }o.\>n11 y similar materials. Thomas H. 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. F. Hatch, Pittsburgh - 23 J. Z. Nelson, Pittsburgh - 7 0 P V. W. Rieke, Pittsburgh - 2 G. R. Swany, Pittsburgh - 23 R. P. Carter/File ALCOAO 000009745