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Cl [24] Dement, J. M., Zumwalde, R. D., and Wallingford, J. M., Discussion paper: Asbestos fiber exposures in a hard rock gold mine, Ann. N. Y. Acad. Sci., 271, 345-353 (1976). (25] Swent, L. W., Herrin, G. R., Waterland, J. K., and Bell, R. F., Mortality patterns among hard rock gold miners exposed to an asbestiform mineral - a critique. Presented at American Industrial Hygiene Conference, New Orlenas, LA, May 26, 1977. [26] Langer, A. M., Mackler, A. D., and Pooley, F. D., Electron microscopical investigation of asbestos fibers, Environ. Health Perspectives, 9, 63-80 (1974). [27] Pooley, F. D., An examination of the fibrous mineral content of asbestos lung tissue from the Canadian chrysotile mining industry, Environ. Res., 12, 281-298 (1976). [28] Langer, A. M. and Selikoff, I. J., Chrysotile asbestos in lungs of residents of New York City, International Union of Air Pollution Prevention Association's Second International Clean Air Congress, Washington, D.C., December 6-11, 1970. [29] Nicholson, W. J. and Pundsack, F. L., Asbestos in the environment, in Biolo ical Effects of Asbestos, Proceedings of a Workin Conference, on, 1972, P. ogovsk , im re31, J. C. Gilson, and 3-C. Wagner, eds., RC c ent~f9c Publications No. 8, Lyon, pp. 126-130 (International Agency for Research on Cancer, 1973). [30] Rohl, A. N., Langer, A. M., and Selikoff, 1. J., Environmental asbestos pollution related to use of quarried serpentine rock, Science, 196, 1319-1322 (1977). [31] Miller, A., Langer, A. M., Teirstein, A. S., and Selikoff, I. J., "Nonspecific" interstitial pulmonary fibrosis: association with asbestos fibers detectbd by electron microscopy, N. Enal. J. Med., 292, 91-93 (1975). ' [32] Miller, A., Teirstein, A. S., Bader, M. E., Bader, R. A., and Selikoff, I. J.; Talc pneumoconiosis: Significance of sublight microscopic mineral particles, Am. J. Med., 50, 395-402 (1971). (33] Masson, T. S., McKay, F. W., and Miller, R. W. , Asbestos-like fibers in Duluth water supply. Relation to cancer mortality, J. Amer. Med. Assn. , 228, 1019-1020 (1974). [34] Ashcroft, T. and Heppleston, A. G. , Asbestos fibre concentration in relation to pulmonary reaction, in, Biolo ical Effects of Asbestos, ~Proceedin _s of a W~~orkin Conference, Lyon, 1972, P. ogovs i,-O-Timbell,~T i soGan .~ C A a gner, eds. , TA1(C 3cientf?T-c Publications No 8, Lyon, pp. 236 (International Agency for Research on Cancer, 1973). [35] Doniach, I., Swettenham, K. V., and Hathorn, M. K. S. , Prevalence of asbestos bodies in a necropsy series in East London: Association with disease, occupation, and domiciliary address, Brit. J. Ind. Med., 32, 16-30 (1975). [36] Fears, T. R., Cancer mortality and asbestos deposits, Amer. J. Epidemiol., 104, 523- 526 (1976). [37] Stanton, M. F., Fiber carcinogenesis: Is asbestos the only hazard? Editorial, J. Nat. Cancer Inst. , March 1974, 633-634. oN W '.+ 131 a° N b

t DISCUSSION J. DEMENT: I'.d like to make several observations dealing with a couple of points. First of all, Dr. Cooper pointed out that the Homestake mine study dealt with exposure to very short fiber lengths, and that's certainly true. However, you failed to point out that in most industrial settings, as high as 99 percent of the fibers, of chrysotile especially, are shorter than five pm in length with very typical lognormal distributions which follow closely to the Homestake study. Secondly, a couple of comments with respect to the Homestake study. In its publication, NIOSH did in fact recognize the possible contributory effects of free silicate exposures for non-malignant respiratory disease. Our study ascribed the cancers predominantly to fibrous grunerite exposures. With regard to the McDonald study, I'd also like to make a couple of comments. First of all, it was a group from a Veterans Association with 21 years minimum employment at Homestake, but not necessarily underground mining. The copy of the Homestake paper, which I have been given, does not indicate whether or not they were miners or surface workers. Homestake operates several above-ground facilities. One must question whether or not 21 years requirement isn't a selective population, especially with regard to the data we saw from Dr. Nicholson today where he indicated that even one month carries with it an excess risk. Thirdly, we at NIOSH of course do realize the importance of the study as evidenced by our increase in the scope of the study, mainly to get a larger cohort to study. I would like to express a bit of gratitude for your pointing out that lack of evidence should not be taken as lack of effect. W. COOPER: With respect to the proportion of individuals underground, I can't answer that question. I think that the criticism of limiting it to individuals who had worked for 21 years or more is not a valid criticism. Actually, these were not retired miners, and even a study of retired miners is not necessarily a bad study; Enterline has developed the arguments pro and con very well. The fact that members of this club had been there for 21 years is not very different from, the basis that Selikoff and Hammond used in selecting their population of insulating workers, which was limited to those who had their initial exposures, or rather had been insulators, 20 years or more. The same processes of selection which keep an insulating worker working for 20 years keep a miner working 21 years; I do not think that this is a valid criticism. As to whether or not the paper ascribes the non-malignant respiratory disease to asbestos or to silica, I think it is unmistakable. The paper, as I recall, does not use the word "silicosis," except in describing the population as having come from a Public Health Service study of silicosis. I will read from the conclusion: "The observed excess of malignant respiratory disease can therefore be attributed to asbestos, singly or in combination with cigarette smoke, and that of non-malignant respiratory disease can therefore be ascribed to asbestos with a possible additive role from low exposures to free silica dust." That's a direct quotation from the report, so I think the implication is that the non-malignant respiratory disease is asbestosis. 132