Document V3DMRgEQvdLaZM1N8LrLMdmdj

j: ,/ \ AU::,. _.w..L Industrial Products Ltd CTT773 TURNER ZT7\f & NEVVALL i-T---j UNITED HCL/fctf 12.7.73. Professor Irvine J.Selikoff, Mount Sinai School of Medicine, Fifth Avenue and 110th Street, HE'/ YORK 2JY 10029, U.S.A. Dear Professor Selikoff, Ve have recently received a transcript of a tape recording of your address to the American Industrial Hygiene Conference in Poston on 21nt Hay,1973 which was sent to us because of its references to our work. If the copy enclosed herewith is a true representation of that address and the graph shown by you, we must tell you that we find your assumptions and conclusions to be extremely misleading. The case made at the end of your paper appears to rest on the fact that the data which formed the basis of our Hygiene Standard^- was scanty. You then attempt to extract data from the Figures in IlCL's publication^ in order to show a discrepancy between the original data and these Figures. Ve arc astonished at your having communicated the contents of a private correspondence to the Eeeting which you addressed without having obtained our agreement. Ve are also very displeased at the manner in which you have used the information we provided in order to launch what seems 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 ECD publication allows doubt to be cast on the validity of the ECUS Standard and are cf the opinion that such a conclusion is unwarranted. Comparisons such as those you have made between the Knox data and the KCL data are invalid for the following reasons :- 1. The paper by ECL was not intended to justify or verify the DOES Standard, and no reference is made in this paper to environmental cuot measurements. The results presented in HCL's paper were preliminary results and in the discussion section it was clearly stated that 'from the information currently available only tentative opinions can be expressed . Ve are /cont 11:/. Industrial Products Lid HO. lie;: `>0 *2 /TO !-n\-'tnd -2- surprised therefore that you have been able to read fax more into the incomplete picture presented than the author va3 able to do or even intended to do. 2. The populations reported by Knox and HCL were not identical nor wore 'the very large majority' of asbestos workers 'common to both surveys', as you suggested. 'Office personnel' were not included. The population studied by HCL consisted of workers in the recognised asbestos areas, together with maintenance, quality control and research staff. 5. Knox reported on 290 men (not 913 as stated by you) with at least 10 years exposux-e since 1st January,1933* when the Asbestos Industry Regulations 1931 took effect, and who were still in the Company's c-mploy on the 30th June,1966. HCL on the other hand has analysed the X-rays of a much larger population (1,237) as of November,1970 irrespective of date of first employment; some were in fact first employed before 1st January,1933* 4. Knox sub-divided his population according to actual Cumulative exposure whereas KCL's was sub-divided by decades elapsed since first exposure, 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 HCL at no stage in his report equated the radiologica.l changes with 'asbestosis'. 5. Eccause it was possible to estimate dust exposures for the Knox population, the BOHS Sub-Committee were able to arrive at figures for cumulative exposure expressed in fibre ycars/cc. ho such exercise was ever attempted by HCL. This is a further invalidation of the graph since you have attempted to relate radiological features described by IICL to what ve can only regard as speculative exposure data. 6. Knox only recorded X-ray changes as being present which are possibly asbestotio, after taking the whole clinical picture into consideration. 'Radiological changes considered significant included these of increased general opacity of the Icu.'r lobe3, blurring cf the cardiac outline, pleural thickening and adhesions*.^ /cont -3- 6. Con t/< * HCL on the other hand attempted to analyse his 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 ECUS sub-committee decided that basal rales were the 'key symptom' since all the men with X-ray changes, by the Knox criteria, had basal rales, but some with basal rales had no X-ray changes.* HCL points out in his paper that he has not yet attempted to correlate physical signs and X-ray changes. 8. We are obliged to point out that the use of the words 'pulmonary fibrosis' by HCL in his paper may have misled you, as they were used to describe small opacities which pricr to the advent of the UICC/lLO classification may have been regarded a3 consistent with fibrotic changes. The use of this term 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 grouped all cases shewing evidence of these changes together, irrespective of severity. Knox only included X-ray changes consistent with the clinical diagnosis of asbestosi3. It is not possible to say, from the data that HCL has compiled, how many persons would fulfil the criteria for a clinical diagnosis of asbcstosi3, and to attempt to illustrate these two very different sets of data on the same graph is simply not permissible. The clinical significance of the radiological changes observed cannot r.s yet be defined. You. appear to have ignored completely the fact that the number of cases of asbectosis in 168 among 535 employees (men and women) exposed for 10 years or more since 1933 in Rochdale and still employed, was 1.12Jo (i.e. 4 casos)3 as compared with Kerewether's finding of 44.4>j (i.e. 59 cases) among 133 workers exposed 10 years or more in the same industry in 1929*^ This lower incidence has occurred in spile of the fact that the Pneumoconiosis Medical Panels are better equipped to diagnose asbestosis than Merewether was. In addition, during the years immediately following 1935> there still was substantially greater exposure in certain gobs than in more recent times. /cont, -4- 8. Cont In view of your comments and our previous correspondence we should like to remind you that ve are in 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.Holmes' remarks at Lyon were never intended to suggest that the BOHS Standard was not stringent enough. The B03S Standard is ICO fibre years/cc and therefore application of a 2 f/cc limit for periods of less than 50 years has the effect of providing an ample safety margin. The 30HS Sub-committee, of which wa are both members, recently reviewed the Hygiene Standards for Chrysotile Asbestos^ in the light of the latest'available data and recommended that no change be made at the present time. Ve are forwarding a copy of this letter to the President of the American Industrial Hygiene Association, the Chairman of the ACGIH, the Director of MI OSH and also the Asbestos Information Association of North America in view of their obvious interest in this important subject. Yours sincerely, H.C.LEMIKSOIDT, M.B. B.Ch. D.I.H Chief Medical Officer. S.HOLMES, Chief Health Physicist Enel: REFERENCES 1. Hygiene Standards for Chrysotile Asbestos Dust - Annal3 of Occupational Hygiene 1966. 2. The Medical Surveillance of Asbestos V/orkcro Royal Society of Health Journal, April 1972. 3. Report on effects of asbestos dust on the lung3 and dust suppression in the asbestos industry Merewether & Price. HUSO 19J0. 4. Annals of Occupational Hygiene Vol.lb, 1973