Document zdnjOqewzz5GnZ3kML4pKyyyg

Internal Memorandum Date August 21, 1973 To Distribution Letter No. From V. M. Spurgeon Subject PRESENTATION AND CORRESPONDENCE ON ASBESTOS Plaintiffs' Exhibit BX 5064 F.csftaicli Lalaar.-ncricr. SoLrthliolU. M.cn'n.ir. Attached are copies of documents received on August 17 from the Friction Materials Standards Institute. On first reading it appears that the experts are not in agreement. The fact that ingested or inhaled asbestos is harmful to health is not questioned. What Drs. Selikoff and Lewinsohn are both saying, in effect, is that the safe exposure levels, if any, are not known. The various parties differ in the rigor, and hence the cost, of the protective measures to be adopted. To some, Dr. Selikoff appears to be an overzealous crusader. In fairness to him it should be realized that an epidemiologist has to be a crusader in order to .be effective in his work. Further, it is not a tenable position to advocate that rigorous control methods should be postponed until safe exposure levels are established. It is not possible to establish them, since well-designed experiments on human subjects are both impermissible and impractical in this matter. .. In such a situation it is better to err on the safe side, pushing ahead with our programs for control of asbestos In our factories, for labeling our aftermarket friction materials, and our search for new fibrous reinforcing materials. . - 10 ^ Jf VMS/ew Distribution: ACSG (Troy) ACSG CSouth Bend) J. V. Armstrong D. Bitondo B. B. Burton G. T. Burton A. Capsalis L. D. Ferguson M. G. Jacko R. S. Kiuak T. Liu C. E. Miller S. K. Rhee L. B. Taplin A. B. Van Rennes F. W. Aldrich C. N. Menz J. R. Farron B. W. Klein J. J. Lukas E. T. Pyles E. A. Sheridan  ft i.'DARfiS INSTITUTE, IiC., E. 21D ROUTE 4, PARAMUS, II.J.07073 August 14, 1973 TO: MFIBERS OF ASDESTOS STUDY COMMITTEE Your Chairman, Mr. I. ii. Weaver, has sent the enclosed papers for distribution to the Committee. 1. Presentation Dr. I. J. Selikoff to the American Industrial Hygiene Association on May 21, 1973 (Includes Question 4 Answer Sessicn). 2. Letter from II. C. LetJinsohn and S. holmes of Turner Brothers Asbestos of July 12, 1973 to J)r. Selikoff, 3. Letter from II. Swetonic, Asbestos Information Association U.A. to J. 11. Dtender of OS'l'> dated July 24, 1973. (Forwarding Dr. Selikoff's allegations and the comments of Lewinsohn and Holmes). 4. Letter from G. F. Scannell, OS11A, of July 31, 1973, to M. Swetonic acknowledging receipt and advising on distribution of enclosures. 5. Mr. Swetonic letter of August 3, 1973 covering distribution of correspondence to members of A1A. Hr. Swetonic*s letter of August 3, 1973 to the AIA Membership summarizes the presentation and review of a tall: Dr. Selikoff gave to the American Industrial Hygiene Conference in Boston, Massachusetts, on Hay 21, 1973. In essence. Dr. Selikoff is attacking the 2 fiber/cc asbestos exposure level in the work place as being too loose. This is the 2 fiber limit that goes in effect in 1976 (not the 5 fiber limit now in effect). For your information. LVDrllz Enc. E. U. Drislane Executive Director TcryfC'rsrn^u Icf CV^*w rvn * 1*** rk^trir mr%r\r*-^--.-a Presentation on Asbestos by . . Dr. Irving J. Selikoff st . . American Industrial Hygiene Conference Boston, Massachusetts . May 21, 1973 ' " This year, 1973, marks 50 years since the examination of the first case of death due to asbestosis. Dr. Cooke in Leeds described this fatal disease in 1924. He might well have been asked the question which points a dilemma in which ve still are. 'f he had been asked what exposure of this asbestos textile worker resulted in her fatal pulmonary fibrosis, he would have had to say, "I don't know." Because 20 years ago when she began work in this textile factory, no dust counts were done. Nov?, the dilemma, that he faced is still very much with us at this time . because the disease that we are now seeing is the result of ex posures at a time when v*e were hot alerted and environmental measurements were not made. We find this a. great difficulty in . ' ft our own work and perhaps it may be well demonstrated by the first slide, which I will read to you in'view of the circumstances. This is a slide of the x-ray results in 1,000 employee workers in the New York area examined by us and it demonstrates that out of 725 people v/ith less than 20 years from onset of exposure, most had normal :c-rays. When they were abnormal, they tended to ;nset of exposure, of the over -300 men so examined, few had ' :ormal x-rays; and when they v;ere abnormal, not infrequently, ihe fibrosis was extensive. So the 20 year rule which was found .c in 1924 is present with us today. The description of lung cancer, 1935, and subsequently of pleural mesothelioma in 1954 and after wards, in 1955 of peritoneal mesothelioma and subsequently of other tumors, has done nothing to resolve this question because they too have had this difficulty which we still, face. We have found it so in our studies. ' ` .: . F^r example, in the New York area, we have been following 632 r- oars of the Asbestos Workers Union; these are the. insulation workers, who were on the union roils or. January 1, 1943. 'You will see in this slide that for the first 10 years from 1943 to 1947 and 194S to 1952, the total number of deaths was almost exactly what was expected. It was not until after this 10 year period had passed that we began to see the extraordinary mortality patterns that are still with us. We found, for example, that after 20 years wherein there should have been 6 or 7 deaths of cancer in the lungs and pleural mesothelioma, there were 45. There should have been ' . 9 or 10 deaths of cancer of the stomach, colon and rectum. There were three times as many, 29, and, of course, there were 12 deaths of asbestosis v?here none had been expected. Yet, as we go longer .th this group - we have followed them nov? through December 31,. 1971 (and the .no are unpublished data; I thought you night find i len interesting) - we have found that of the- survivors of this }43 group, there should have been another 85' deaths, but 168 =ve occurred. There should have been 4 or 5 deaths of lung ancer. There were 42. There should have been no deaths of .esotheliona, v;hich almost never occurs in the general population, here were 25. There was the small increase, 3 or 4 times increase In gastro-intestinal cancer and the asbestosis deaths, so that ;he longer -we go from onset of exposure, the more, evident the risk appears. . | :**- have, in order to further study this question, undertaken a i__>nd study and these are the first reports of this second"study, not yet published. *' On January 1, 1967, we registered every single union insulation worker in the United States. There were 17,800 members of this ' union on that date, and Dr. Eamnond and I have followed "them from January 1, 1967 through December 31, 1971. These are the results found in that study. .. . ' ' i - Whereas, there should have been- 805 deaths among then, given their ages, there .actually were almost 1,100. And,, once again, the r lung cancer death rate was extraordinarily increased. Whereas -.hera should have been 44 expected, 213 bronchogenic carcinomas w.tually occurred. There should have been.no deaths of mesothslicm. there were 77. There should have been a small number of gastro intestinal deaths; there were 3 tines as many as expected. .ir.a, of course, there should have been no deaths of asbestosis, which doesn't occur in the general population, and'there were 78. Khen we analyze these deaths by duration from onset of work, ' among these 17,800 men, we found that in the group less than 15 years from onset of exposure, there was no significant increase 'n * in either lung cancer or mesothelioma. V?e did*not see one mesothelioma in less than 15 years from onset- of work, although we were observing almost 10,000 men in this category. On the other hand, once the 15 years passed, we found that the ratio of expected to observed deaths was 5, 6 and 7 times; now the mesothelioma deaths began to be seen. ' ___ Ke have also looked to see whether this was-* so in an asbestos products factory making insulation and many other products. To >h study this, we'made a list of every single production worker in this plant on January 1, 1959 who had on that date worked at least 20 years. Ke have followed this group, 689 people, through December 31, 1971. And, once again,'we have found-that whereas there should have been 8 or 9 deaths of respiratory cancer, there were 35; of these 27 were lung cancers, 8 were pleural mesothe liomas, 7 were peritoneal mesotheliomas,`and the same increase, a modest increase, in gastro-ir.testinal cancer and asbestosis. Finally, to try to get some sense out of the duration from onset versus the actual exposure, because most of the men in the three' i %> ;ohorts that I have just reported to you had worked continuously and in one group, v;e were able to find a very significant differ- snce in the amounts of work. This was a factory which opened in June, 1941, to ma3;e insulation for the U. S. Navy. Nine hundred ' thirty-three men were employed for the first fime, for Ml to M5. The factory closed in-1954. Some 11 men .worked for only 1 day. They didn't like it. Some worked tintil the plant closed in t '54. Follovring this group of 933 people (it is a darn good plant -- they got their Army-Navy "E".) , we have found tkat in these 933 men there should have been 300 deaths by the end of '71; there actually were. 484. And, once again - it's almost monotonous - i same 7 times increase in lung cancer, pleural mesothelioma, peritoneal mesothelioma, gastro-intestinal cancer and asbestosis. But, of these men, approximately one-third worked for less than 3 month's. One-third worked from 3 to 11 months, and one-third worked for more than a year. We have found that although the ' ' '` l- . group with more than a year of exposure had a very significantly greater ratio of expected to observed deaths# 11 times as many lung cancers as expected, still even less than 3 months of work was enough to give a 3 or 4 times increase in bronchogenic carci noma provided they lived long enough - provided you looked at them 30 years later. Now all of these data indicate that what v/e are seeing now, the current mortality experience, is the result of -he inadequately controlled exposures of the past. However, the i . ;. , problem is with this long latent period, how ^ou find out what the exposures of the past were to relate them to the cpidemiological evidence of disease at the present time. Unfortunately, in the United States we are at a loss for this. There are no * , sets of dust counts and resulting disease observations, from the first case reported in the United States in 1930, to permit judgment here of acceptable levels. There are two approaches. Both have been used. First of all, if there were measured dust levels 20 years ago, and if we could identify the population exposed to those levels 20 years ago, we could make some, corre lations. One, of course, would be asbestosis. The other approach has been to take dust measurements now and get seme sense of hov: these measurements now relate to what existed in practice 20, 30 and 40 years ago. This has been done but there are significant differences with this technique*. First of all, in the past very, few dust counts were done.. The current techniques, membrane filter methods, phase microscopy, etc. were not used at that time. For example, the Ur-e^sen1 study. Also at that time all particles were counted rather than only fibers, and as we try to . convert particles, per cubic foot to fibers per cc, the results are . #* unfortunately uncertain. We have, on the other hand, had some . measurements of what exists today in the construction industry with the use of insulation material, and we have found in using ' fibers per cc, that in general some/.here around 5 to 10 fibers l per cc exists in these environments. Ke don't really know whether this was true 20 years ago.- There are 4 studies that provide evidence. First, there is the original study of Dr. Fleischer and his colleagues in the U. S. Navy shipyards, published in *'4 6 and done in '44 and '45. A. different instrument was used and a time weighted average of 25 fibers per cc-could.be obtained, but other glass fibers and so forth were included. Murphy and Ferris and their colleagues have looked at shipyard data published in '62 and '71 and they came to somewhere around 10 fibers per cc. Ealoe and ffooper, in San Francisco insulation workers, have come to iround 6 fibers per cc. And in 'our laboratories, looking at con struction -work in shipyards throughout the United States, we have found exactly what Balzer and Cqoper have found; somewhere around 6 fibers per cc. But this is reconstruction. And we don't really *. ** * know that this existed 20 years ago. While this is the dilemma that we faced, we thought that 6 fibers per cc, somewhere around that, 10 fibers per cc', existed in the past but we weren't sure. We know what the disease is; I've just shown it to you. Therefore we .were all very much impressed and grateful when the British Occupational Hygiene Society gave us the answer. % .. '* In 1968, the British Occupational Hygiene Society published a report stating that 4 fibers per cc or 2 fibers per cc would likel be safe. The basis for their report was the report of their sub- `. a committee on asbestos published in -the Annals of Occupatior.al Hvci s. , 1966. It read, "The results of recent work, the study of *I hn F. Knox and Steven Holmes, have been made available to -the * i mmittee by the asbestos industry and it is on these recent jsults that the new.standard is primarily based." What they ame to is that it would be safe to have 100 fiber years, such s 2 fibers per cc for 50 years or 4 fibers per cc for*25 years, he work of Dr. Knox -and Dr. Holmes {they were both members of his committee) was v.alid. Dr. Knox was Chief MeI dical Officer l .f Turner Brothers Asbestos Company in Rochdale and Dr. Holmes ;as their Industrial Hygiene Scientist. . ' .. : bases for these data were then published by the British, Occupational Hygiene Society. -Dr. Knox had-x-rayed all production * .*% workers at Turner Erothers Asbestos Company in Rochdale as of - June 30; 1966. There were 931 workers in this plant, of whom a large number had been more than 10 years in their employ. They had done dust counts, very good dust* counts, from 1951 on, and therefore we had a population, for the first time, Where dust 9 ** counts could be related to clinical evidence of disease. In the departments where the dust counts were 10 to 15 fibers per cc, of the large number of'workers there employed, 7 showed some x-ray .' * abnormality.which could have been asbestosis. On the other hand, . of 70 or 80 people working at 3 to 4 fibers per cc, only one was -`ported to have an abnormal x-ray. This -being so, the subcommittee ,'hirV ` did not review the data but reviewed the numbers ' "* . . ; < . *t.i . '-viv.iv.-v/VjVa%>>>:o^vawX`.'^v submitted to it, then reviewed the data given^ it and decided that since only one worker, exposed for 20 years or more at 4 fibers per cc shov:ed evidence of asbestosis, that half that level, 2 fibers per cc, would be prudent and safe. And if I .were oh that committee, I would have come to exactly1the same conclusion. When these data, this conclusion and this recommendation reached the United States, it did, as Isay, impress all of us. So much so that on February 28, 1969, Howard Ayer sent a letter, containing this statement, to 28 asbestos companies and 50 state health depa-rtments: "From these standards (that is, the British Occupational 'ygiene Society recommended standards), one would gather-that concentration below 2 fibers per cc are probably safe." A fair . *S statement. Indeed when the criteria document was submitted by KIOSJI last year, 1972, it stated, "The development of a standard for asbestos dust in Great Britain and the evaluation made by the British Occupational Hygiene Society Subcommittee on Hygiene Standards for Asbestos, v?hich considered data to reduce the risk * * * of asbestosis, was given-great weight in the development of this asbestos standard." That is the origin of the 2 fiber per cc standard. Two fibers per cc obviously is 2 million fibers per ' cubic meter. A working man inhales somewhere around 8 to 10 cubic . meters of air in an eight-hour working day, which means that we have told him that he can safely inhale with an uncertain, unmeasured - *< -. retention, somovrhcre around 20 million fibers longer than 5 microns . * . I * !., * ** . . > in an'eight-hour day. As Mr. Dement has just told us, anywhere from 20 to 99% of fibers are smaller than 5 microns, and therefore . the total number .of fibers of all sizes is somewhere around 20 to 40 billion. . : *_ Now some new data has recently appeared which- 1 thought might be of interest to you. In 1968, Dr. Knox retired as Chief Medical Officer of Turner Brothers and was replaced by a young South ' 'I African, Dr. Hilton Lewinsohn. .Dr. Lewinsohn has re-x-rayed all of the workers at Rochdale "in December, 1970. The populations, . howi ever, were not entirely identical. Dr. Knox had examined --o-r.l'v men in the scheduled areas - that is, the production areas, 913 - whereas Dr. Lewinsohn included all employees, including the office personnel, and therefore had a larger number. To .some extent ycu could say that this diluted the population, but I think it was a wise-thing to' do. Also, some of the people working there in 1966 were no longer employed; obviously they had retired or died and some new workers had been added. The very large majority, of course, were in both surveys. Dr. Lewinsohn reported the results of his . December 1970 re-x-ray of the Rochdale personnel in the Royal Society of Health Journals in 1972. Dr. Lewinschn's data are on this slide. ' :s . It demonstrates that of those with, let's say, 20 to 29 years from onset of exposure, of 114 x-rayed, 51 had abnormal x-rays. . together, total abnormalities were 55% of all people who had t i I ' . s reached 20 to 29 years from onset, and of these, actual pulmonary fibrosis was seen in 21 out of 114. Of those who had reached 30 to 39 years from onset, 78% had abnormal x-rays, and 17 out of the 42 had actual pulmonary fibrosis. Of those 4 0 to 4 9 years, there was too small a number to show. ; When we put these two sets of data together,, we'can find that as of 400 fiber years. Dr. Knox had found, in reading the films, that somewhere around 7 or 8% had abnormal x-rays, whereas in the same population a different film reader had found that somewhere between 40 to"' 50 % had abnormal x-rays. There is obviously a considerable 'iscrepancy in the two sets of film readings. Nov/ when these dis- ,_epancies were discussed with our British" colleagues, last October in Lyon, France, Dr. Eolmes made the following statement: "Thus, the information, although the best available at the time, was, to say the least, scanty for the purpose. And some of us who were .. * I ' associated with it have become increasingly concerned With the authority with which it has become invested in the international field (meaning the United*States). The time has therefore probably arrived for an up-to-date reappraisal of the original data." I have communicated with Dr. tewinsohn in the ^Last three weeks and am informed that there are definite plans to undertake this reviev; in the future. It has not yet been done. .' ' t> conclusion, then, as a result of these new data from Turner Brothers Asbestos Company, we can say that if the 1972 report of , . \ ! ' tne Chief' Medical Officer of Turner Brothers Asbestos Company correctly represents the disease incidence associated v?ith prior !* ` !` levels of asbestos exposure in the company, then the asbestos standard of the Department of Labor places U. S. asbestos workers at serious risk of irreversible, often fatal disease, and in my opinion, it should immediately be reconsidered. . Unfortunately, then, I feel that we are in the same dilemma still - after 50 years - that Dr. Cooke found himself in 1923. Thank you very much.' ' 1 l--ii.. r*T % ..** PRCVALCHCE OF X-RAY EVIDENCE OF ASBESTOS IS. IK ASBESTOS TEXTILE WORKERS : . ' QUESTION AND ANSWER SESSION . FOLLOWING DR. SELIKOFF'S PRESENTATION I * Q. In the asbestos products factory in which men employed for only three months were found to have a significant increase . in lung.cancer, were smoking histories obtained? . (Dr. Selikoff) A. The answer is "Yes", and those data are- now being analyzed, but I would be amazed if we found any lung caniers or any more than a trivial number among those who* did not smoke cigarettes. We have failed to see any significant increase in the incidence of lung cancer among asbestos workers who . do r.ot smoke cigarettes. We have been following 2,066 non- "smoking insulation workers from January 1967 through 1971 and we have only seen two lung cancers among them. On the other hand, of 9,590 cigarette smoking insulation workers, we have found 14 5 lung cancers whereas only some 3 0 were expected. Bronchogenic carcinoma is almost limited to ciga rette smoking .asbestos workers. This is not true of peritoneal mesothelioma; it is not true of asbestosis; and it is pr-'bably, although our data is too scant yet to be sure, it`Is probably" not true cf pleural mesothelioma. -But of lung cancer - there is no question - this will not occur by and large among asbestos . workers who do not smoke cigarettes. . . 0. I would like to ask Dr. Selikoff if he thinks the new standard should include both a total dust count - if there is a new standard - both, a total dust^ count and a per cent fiber count. At least in our experience, we seem to vary comparatively. A . standard set on one rather than the other could' be quite mis- leading. <. * : * % . ' A. Ray Murphy has asked me a very embarrassing question. He asked me to give an opinion where I can't give it even on fiber counts. : He row asked me whether 1 would do it on total counts rather ' tnan just fibers. The answer is, "I don't know." But I'm . .not very impressed (if 1 can upstage Duncan Holiday a bit who is going to review this tomorrow morning) - we're not very impressed with asbestos standards which rely upon dust counts being done. May I give you some data? Very depressing data, if you think these are depressing. On June 7, 1972, the asbestc standard came into effect. And it said that every company usir.c asbestos had to do at least one dust count, one dust count, in the next six months. That is, by December 6. YJe, on December 7, did a survey of insulation workers in the United States anti we now have some 5,0C0 odd replies. Each nan was asked about . , i '!* . I V * the dust counts that he personally had seen in the six months when every company was supposed to do a dust count'. In the United States insulation industry, fewer than 3 of the in sulation workers' saw even one dust count done from June 7 to December 6, 1972. Obviously then, dependence upon dust counting as a means of control in this unusual industry has many deficiencies. q. 'it is really one question in two parts,: perhaps. The fibers at the Turner Asbestos Company (Knox-Holmes study), what were these and could you comment, would you comment on the possible differences that"*you think may be between crocido'lite and chrysotile and amosite? A. The fibers in Turner Erothers, since it was la textile ope*aticn, were largely chrysotile. We can give you no information :oncerning crocidoiite because none of the workers studied b-* us had any crocidoiite exposure. They had chrysotile exposu :e ar..\ "`many of them had amosite exposure. Indeed, in the plants, in the factory making the Wavy insulation, this was almost entirely amosite. o our data apply only to amosite and to chrysotile and, unfortunately, I can give you no information on..the relative ' hazard of crocidciite. I would suggest, however, that if cro` ciaolite is more dangerous than amosite,or chrysotile, it is going to be almost as bad as bis-chloromethylether. (Laughter) Q. Dr. Selikoff, are you aware of a particular type of asbestos fiber mined in Ontario called Headman? fibers which have been found to be relatively inert, by Paul Gross and others? *' t~ .. A-. I presume that you mean the fibers mined in Quebec, not Ontario. (No, mined in Headman Mine in Ontario.) Ho, I do not know these particular fibers and I vxmld be delighted to know of an asbestos fiber which is comparatively inert. ' Q. . They claim - and Paul Gross and others have done experimental work - and they have found that this particular fiber which is chrysotile has been, .in experimental work, found to be inert. A. Well, I would be delighted to see those, indeed I'd be delighted to see those in industrial use. Thank you. Dr. Selikoff. 'ZTJ fi Ns'.vall CU-- limited ECL/iW 12.7.73. Professor Irving J.Selifcoff, Mount Sinai School of Modi cine, Fifth Avenue and 120th Street, KEV YCLT-: IT! 20029, U.S.A. . ' . . .. . . r Dear Professor Selikoff, . . .. ' * . Ve have recently received a transcript of a tape recording of your address to the American Industrial Hygiene Conference in Boston on 21st May, 1973 vhich was cent to us because of its references to our vopk. If the copy enclosc-d herewith is a true representation of that address and the gral.-h shown by you, we nust tell you that ve find your assumptions and conclusions to be eitrezely misleading. ' '~ . The Case cade at the end of your paper appears to rest on the fact that the data which forced the basis of our Eygiene Standard^- was scanty. You then attempt to extract'data fron the Figures in ECL's publication^ in order to show a discrepancy between the original data and these Figures. Ve are astonished at your having ccnnunicated the contents of a private correspondence to the meeting vhich you addressed without having obtained'our agreement. Ve axe also very displeased at the manner in which you have used the information we provided in order to launch what seers to us to be a political campaign in the USA aimed at discrediting our Hygiene Standard for asbestos. Ve cannot accept the implication that the ECL publication allows doubt to 'fie iTast on the validity of the BOSS Standard and are of the opinion that such a conclusion is unwarranted. Comparisons such as those you have made between the Ecox data end the ECL data are invalid for the following reasons j-- 1. The paper by ECL was not intended to justify or ' verify the 2CH5 Standard, and no reference is made in this paper to environmental duct measurements. The . . results presented in HCL*s paper were preliminary results and in the discussion section it vas clearly stated . that 'from the information currently available only . tentative opinions can be expressed . Ve are /cont........... .. ZZLi lnduslriolPfoductsUd 2. surprised therefore that you have been able to read far norc into the incomplete picture presented than the author was able to do or even intended to do. 2. The populations reported by Knox and HCL were not identical nor were 'the very large najori'fer' of asbestos workers ' ccanon to both surveys', as you suggested. 'Office personnel' were net included. The population studied by HCL consisted of workers in the recognised asbestos ardas, together with maintenance, quality control and research staff. 3. Knox reported on 290 men (not 913 as stated by you) with at least 10 years exposure since l3t January.1933. when the Asbestos Industry Regulations 1951 took effect, and who were still in the Company's employ on the JOth June,l?o6. HCL on the other hand has analysed .the X-rays of a such larger population (l,2S7) as of November,1970 irrespective of date of first eaployment; sore were in fact first employed befor 1st January,1935* 4. Ehcx sub-divided his population according to..actual ' cumulative exposure whereas ECL's was sub-divided by decades elapsed since first crop-sure, irrespective of the actual number of.years exposed. In view of these basic differences and others which we will point out in due course, we fail to see how you derived the relationship between cumulative exposure and percentage of individuals `affected on the graph . which you showed (copy attached). The heading on' ... the graph is obviously misleading as ECL at no stage in hio report equated the radiological changes with 'asbestosis'. ` 5* Because it was possible to estimate dust exposures for the Knox population, the B0E5 Sub-Committee were able to arrive at figures for cumulative exposure expressed in . fibre year3/ce. J.'o such exercise va3 ever attempted by ' HCL. This is a further invalidation of the graph since you have attempted to relate radiological features described by ECL to what ve can only regard as speculative exposure data. ** 6. Knox only recorded X-ray changes as being present which are possibly asbestotic, after taking the whole clinical picture into consideration. 'Radiological changes considered significant included those of increased general opacity of the lower lobes, blurring of the . cardiac outline, pleural thickening and adhesions' /cent -3- 6. Cont/, HCL on the other hand attempted to analyse Ms radiological findings according to the UICC/lLO classification, an entirely different set of criteria, and took no account of the clinical picture as a whole. 7. The BOES sub-coccittee decided that basal rales were the 'key syrpten' since all the men with X-ray changes, by the Xnox criteria, had basal . rales, but some with basal rales had no X-ray changes. 1 .JJCL points out in his paper that . he has not yet attenpted to correlate physical signs and X-ray changes. 8. Ve are obliged to point out that the use of the words 'pulmonary fibrosis' by ECL in his paper ' may have misled you, as they were used to describe . . snail opacities which prior to the advent of the BlCC/lLO classification nay have been regarded as consistent with fibrotic changes. The use of this tens does not allow for sub-division into profusion and type of opacity as is now possible with' the UICC/lLO classification. For simplicity in presentation, HCL greuped- all cases showing evidence of these changes together, irrespective of severity. Knox only included X-ray changes consistent with the clinical diagnosis of asbestosis. It is not possible to say, frem the data that ECL_ has compiled, how cany' persons would fulfil the criteria for a clinical diagnosis of asbestosis, and to attempt to illustrate these two very different sets of data on the same graph is simply nbt remissible. The clinical significance of the radiological changes observed cannot as yet be defined* , Tou' appear to have ignored completely'the fact that the number of cases of asbestosis in 19^8 among 355 employees (nen and women) exposed for 10 years or more ' since 1933 in Rochdale and still employed, wa3 1.120 (i.e. 4 cases)3 as compared with Kerevether's finding of 44.40 (i.e. 59 cases) among 133 workers _ exposed 10 yearn or more in the same industry in 1929.5 This lower incidence has occurred in spite of the fact that the Fneumoconiocis Medical Panels are better equipped to diagnose asbestosis than Kerewether was. In addition, during the years immediately following 1933i there still was substantially greater exposure in certain job3 than in more recent times. /cont. ;* -4< 8. Coat..... _ 'In view of your consents and our previous correspondence we should like to rerind you that ve are iSi the process of reviewing and bringing up to date`all the available data, and hope to ' present it for publication in the near future. Dr.Eolnes' remarks at Lyon were never intended to . suggest that"the E0H5 Standard was not strin-tent^enough. The BOHS Standard is 100 fibre years/cc and therefore application of a 2 f/ee lirit for periods of less .than 50 years_has_th_e_ effect of providing an ample safety cargin. The BOHS* Sub-comrittee, of which we are both Berbers, recently reviewed the Hygiene Standard.*? for Chrysotile Asbestos**' in the light of the latest available data and recommended that no change he cade at the present tire. `. ' Ve are forwarding a copy of this letter to the President of the American Industrial Hygiene Association, the Chairman of the ACCIH, the Director of IIICSH and also the Asbestos Information Association of Korth America in view of their obvious interest in this important subject. Tours sincerely. E.C.lSyillSOHlI, M.B. B.Ch. D.I.E. .* Chief Medical Officer. S.HOLMES, Chief Health Physicist. Enel KE7TREHC3S 1. Eygicne Standards for Chrysotile Asbestos ` Dust - Araaals of Occupational Hygiene 19SS. ' 2. The Nodical Surveillance of Asbestos Vorkers Boyal Society of Health Journal, Aprilj1972. 3 Report on effects of asbestos dust on the lungs ' and dust suppression in the asbestos industry - Nerevether A Price. HM30 1930. 4. Annals of Occupational Hygiene Tol.l6, 1973*