Document 6VLQj9ZGVgBN163JkoyO4b13

ASBESTOS INTERNATIONAL ASSOCIATION (Limited by Guarantee) * GLOUCESTER PLACE, LONDON WiH jHL, ENGLAND MEMORANDUM ~ f,i. TO: Asbestos Producers Advisory Panel Medical Advisory Panel FROM: Director General cc Executive Committee OUR REF.: A1A/5/FIB 7 December 193A TREMOLITE ID CHRYS07ILE the attained report on a meeting, together with a paper by Dr. Hodgson on Tremolite in Chrysctile, are forwarded for information. In essence, research is being conducted at the IOM* into the possibilities of testing commercial chrysotile tremolite content. This matter would appear to be of considerable significance to chrysotile miners. You will be kept informed. Sir Neville Stack Encs. Notes on a Meeting Paper by Dr. A.A. Hodgson * Institute of Occupational Medecine, Edinburgh, Scotland BE6g|y ep DEC 1 0 1984 AO 130C a t LEWINSOHN, M.D. UCC 017480 NOTES ON A MEETING BETWEEN DOCTORS ELMES, HODGSON AND BROWNE REPRESENTING THE ASBESTOSIS RESEARCH COUNCIL AND SIR NEVILLE STACK, DIRECTOR GENERAL OF THE ASBESTOS INTERNATIONAL ASSOCIATION, TO DISCUSS ASPECTS OF THE PROBLEM OF TREMOLITE CONTAMINATION OF ASBESTOS FIBRE 122 November 1984) Doctor Browne began by explaining the background of the present meeting. At the last meeting of the Scientific Committee of the A.R.C. much time had been spent in discussing recent research which had suggested that tremoiite, which was a regular contaminant of chrysotile may be an important cause of some of Che morbidity associated wich the mining, milling and manufacture of chrysotile. He had been in correspondence with Professor MacDonald, who confirmed that research was being carried out in his Department on the adverse health effects of cremolite, both in vermiculite miners in Montana and in chrysotile miners and textile workers in Quebec and Charleston respectively, as well as examining lung fibre burdens of a wide range of cases in mesothelioma throughout Canada, to assess Che importance of tremoiite in causation. Some of Che results of his work are being presented at the conference on "Inhaled Particles", next September. Doctor Elmes gave further details of research indicating tremoiite as an important cause of asbestos-related disease. He discussed Che views of the A.R.C. chat an attempt should be made to produce a practical commercial test for assessing the tremoiite content of chrysotile. The possibility of producing such a test method was already being explored by Doctor Hodgson in conjunction with the Institute of Occupational Medicine at Edinburgh. Some research funding was being made available by the A.R.C. but this research seems to be of great importance to the asbestos industry, particularly the mining industry and it was felt that the A.I.A. should be urged to participate. He also said that some manufacturing Companies were already beginning to frame a policy of restricting imports of chrysotile co chose areas where the tremolice content was known to be minnimal. It was felt that Che International Asbestos Industry should be made aware of this development. Doctor Hodgson had prepared a valuable paper for the meeting, outlining what was known about tremoiite as a contaminant of chrysotile and discussing possible schemes for both identification and the separation of tremoiite from chrysotile. He pointed out that a wide range of samples of fibre would be required for research on this subject. He mentioned one or two possible sources, one of which was Central Asbestos and undertook to look into the possibility of obtaining fibre from this source. But it was emphasised that collaboration from the mining industry members of the A.I.A. would be very helpful. He and Doctor Elmes gave details of main problems associated with the assessment of the tremoiite content and of the health problems associated with it. The Vanderbilt talc mine was quoted. Apparently this contained up .to 50Z of cremolite but much of it in a massive and splintered form. In Zimbabwe many serpentines were incorrectly labelled tremoiite. Chrysotile in the Cobi Desert was said to contain up to 17! of tremoiite. In conclusion. Sir Neville Stack undercook to report the substance of the meeting co che relevant Committees of the A.I.A. UCC 017481  ITi; IK CHRYSOTi./: A. A. HODGSON It is established that trenolite fibre has high ranking as a carcinogen, and its biological effects are strongly suspected in its association with chrysotile, vemiculite and talc, in some but not ail occurrences. Tremolite is not now mined on a commercial scale, the largest producer in Korea having closed some years age. Exploitable deposits occur in aklstan, and in northern Italy where a valuable long fibre tremolite is believed tc be extracted fron tine to tine. '-resence ri trenolite in chrysotile Ifrere is growing concern about the trer.clite content of chrysctiles in cc!cnercja! use, but as far as is known studies have never been made tc establish the presence cf tremclite in chrysotile on a quantitative basis. It ifc the nurjeae cf these nctes to outline the properties ancl ether relevant information concerning both cf tr.ese fibres, in order to assist towards a quantitative scheme for separat ing and identifying the trer.clite, 'The presence cf tremclite in chrysotile should he regarded as ubiquitous, even tc very small quantities, because the paragenesis cf these minerals, which ay-lies also vC vemiculite and talc, leads to such ? conclusion, as explained later. The ubiquity cf tremclite is not upheld by such qualitative researches as have been made cn the minerals associated with chrysotile. Butler 1960^ found tremclite in only 6 cut of 128 samples of varicus o chrysctiles, and Gcsseye and Kahn-Weinheiner 1971" feund trenolite in 1 cut cf 56 samples, that particular cne not having been detected by Butler. Both these investigations were made by X-ray diffraction !.aR.`iV . Reasons for the sparse location of tremclite in these samples a;'-ear to be two-fold. Although tremclite may be widespread in chrysctiles and serpentinite rocks, it is unlikely to be distributed uniformly. The very small samples taken for XRD could well be unrepresentative, and the chance that sny cne sample contains trenolite in detectable amounts nay be less than cne in three. Secondly, and more importantly, the direct analysis, cf such samples by XRD is hampered by detection limits fer trenolite of about 1 . factions of tremclite less than this would be completely unobserved. Any method for the quantitative analysis cf trenolite in chrysotile must there fore have as its first stage a means cf concentrating the trenolite, to lift its content in any residues well above the detection limits of XRD and other techniques, and if possible tc concentrate it towards ICC r'. UCC 017482 0 -.elation to TI Vs 3he following table sets cut the concentration of tremolite in tens cf f/ml, which will apply at various levels cf Tl v fox chrysotiie and at various assumed trendite contents. possible tremolite content cf chrysotiie at t; V fer chrysotiie of 2 f/ml 1 f/ml 0.5 f/ml trenc 3ite count,f/ni. is: 1 C .02 O.f 1 C.C05 2 i-.fl f .1 2 (..Cl 5 , .If f .05 c .025 If C .21 f .if ( .05 the most part the tremclite count is negligible and is below current v: 7s for crrciriclite. However trend ite is the most intransigent cf a] 3 asbestos fibres and this distinction is a natter cf bio3.OEi.cai signifi cance in relation to chrysotiie. Chrysotiie fibre inhaled into the lungs can be partially cleared by a dissolution jxocess, leaving any associated tremolite tc become concentrated in lung tissue. Thus, while at the sane tine natural lung clearance takes dace presumably at the same rate for both types of fibre, the relative ;reportions of tremclite and chrysotiie will chenge, and the effective count of tremclite at lung burden jevei will progressively increase by several, if not many, tines the figures calculated above. Ceclog" and mineralogy Serpentines and ultimately chrysotiles are products of the thermal metamorjhism cf both ultrabasic rocks with high magnesium contents, and siliceous dr ionites containing magnesium and calcium. Tremclite is an early product cf the metamor;hisn of dolomites (hence tremclitic marbles}, but equally it is an accessory mineral along with talc, brucite, magnetite and etc. in the serpentinization of ultra- basic rocks. The latter are usually low in calcium content and consequently the generation of tremolite, of which calcium is an essential part, is limited. On the other hand the dolomites have high calcium contents, and ultimate serpentini2ation may be expected to yield pro;ortionately high amounts c-f tremclite. There is a broad belt of serpentinized ultrabasic rocks in the northern Hemisphere stretching from Canada to Russia and Siberia. The serpentines cf 'iinbabwe have a similar origin. Serpentinized dclcmites are character istic of the Mediterranean area, and also of the northern and eastern Transvaal in South Africa. Chrysotiie deposits, large and small, are UCC 017483 AO 1 303 1 located in all these geographical areas, and it follows that these deposits might be expected to contain greater or lesser proportions of tremolite, depending on their regional siting. Mining and milling Any chiysotile deposit can be expected to contain some tremolite. Apart from its random distribution throughout the deposit, tremolite may occur in pockets, fairly easy to distinguish and hence avoided in mining operations, since it would be considered to degrade the quality of the end product. The more general distribution of tremolite throughout a chrysotile deposit cannot be avoided, and any large scale separation of small amounts of tremolite from chryeotile fibre ie hardly practical or even poaaible in the Initial stages of extraction. However asbestos milling and grading prooeaees must to Borne degree bring about a differentiation between the two types of fibre. The grading of asbestoB fibre is essentially a serial screening and air-lifting process, with longer fibres being lifted first and shorter fibres passing each screen to the next stage. Tremolite has a distinctly higher density than that of chrysotile, and it follows that tremolite fibres have a lesser chance of being air-lifted than have chrysotile fibres, and similarly a greater chance of being screened out. Hence there Bhould be some concentration of tremolite in shorter grades of chrysotile, and of course in tailings. Chemistry Tremolite and chrysotile are highly distinguishable from each other in terms of chemical and thermal properties. Tremolite is the most acid resistant of all aabeatoa fibres, while chrysotile possesses complete lack of acid resistance, and indeed can be leached by water. Much of the chemistry concerning the acid resistance of asbestos fibres la well known*, and it is only necessary here to summarize those aspects which may be of help in formulating a scheme tovards a quantitative analysis for tremolite in chrysotile. The relative acid resistance curves for asbeBtoa fibres refluxed in 4N HC1 show that ohrysotile decomposes with a 58 % weight loss in i hr., while tremolite has a 4 weight loaa under the same conditions. All the MgO and HjO contents of chrysotile are removed leaving a siliceous residue. The tubular morphology of the chrysotile remains, but the residue is amorphous to X-ray and EM beams. Tremolite may lose up to 22 5 of its Ca content, these ions being picked off at the ends of cation chains. The lose of other ions is neglig&bla. These aredrastic conditions, and it is possible to reduce the concentration of sold without any effect an the decomposition of the chrysotile, but with 40f304 UCC 017484  & reduction in the removal or Ca2+ from tremolite. Rates of reaction are proportionately decreased with reduction in acid strength, although there is little difference in reaction rates in changing from IN to 0.1N HC1. Uiie may be an important factor in setting up a scheme to extract chrysotile if many samples are to be involved, but at the same time low acid concentrat ions will have minimal effect on the decomposition of tremolite- 35ie kinetics of the acid decomposition of chrysotile have been reported in detail by Atkinson and Rickards 1971** and by Monkman 1971. In these investigations the chryeotile was ground to a high surface area, which to some extent may be a disadvantage when attempting to preserve the integrity of any tremolite which nay be present*3ie rate of reaction of HgSO^ on chrysotile is slightly greater than that of HC1 of the same normality. In this context the choice of H^SO^ may be the better one, because the effect of the SO.^" ion may be to suppress the o+ ^ removal of Ca from tremolite, CaSO being insoluble, 47 Chrysotile is vulnerable to alternating acid and alkaline conditions . Hie reaction of acid removes Mg2+ but leaves a layer of orthosilicic acid which effectively controls the rate of diffusion of the reaction acid into the inner layers of the chrysotile. Hie orthosilicic acid can hovever be removed in s consecutive reaction with NeOH to give sodium silicate in solution. After each consecutive stage m a series of such extractions the residues require to be washed to remove soluble magnesium saltB and sodium silicate. In suit able conditions of acid concentration thie may be a way of completely remov ing chryeotile with negllgable effect on tremolite residues. Tremolite will not is any way react to alkaline solutions. Talc is a frequent accessory mineral in chrysotile and its presence may interfere with the final determination of tremolite contents. Talc is insoluble in acids and therefore will accumulate in extraction residues. If the talc content is high and the tremolite content is low, the former may obscure the latter in the final analysis. One refinement to the extraction method which might be considered involves the heating of the sample specimen. ChryBotile dehydroxylatee and forms a highly disorganised forsterite at about 600C; talc begins to debydrcxylate at about 700C; and tremolite remains stable up to about 950C ( a higher temperature than any other type of asbestos). Hie advantage of pre-heating chrysotile to 600C lies in its extreme vulnerability to acid decomposition, since there is little residual crystal structure left at this temperature. A0l30b UCC 017485 1 Further, regarding the presence of talc, this mineral can be assessed quantitatively byZR analysis, and it has been reported that the XR spectra of many of the minerals associated with chrysotile are rendered less complex O by pre-heating them to certain temperatures . Other possible extraction techniques Hie density of tremolite is 2.9 to 3.2, that of chrysotile 2.55. It is therefore experimentally possible to differentiate between the two minerals by heavy liquid separation, using a medium of suitable intermediate specific gravity. It would be usual to apply this technique to relatively small samples and to make a final separation of the heavier mineral by centrifuge. Complete separation of tremolite from chrysotile might be difficult because of the entanglement of one type of fibre with the other. Again talc may interfere, and samples containing talc may require a secondary heavy liquid separation. Hie density of talc is 2.65 to 2.9, indicating a slight overlap here between the densities of talc and tremolite. However, the method may be useful as a preliminary assay of samples, to determine approximate tremolite contents. Following similar lines, it should be possible to obtain a separation of the tvo minerals, ehxyaotiie and tremolite, by a bench scale flotation process. It is relevant to note in this connection that Cyprus Industrial Minerals Corp. in USA have used a flotation process for the beneficiation of Sew q York state talcs, which are notorious for their high tremolite contents. Anionic surfactants will disperse chrysotile fibres and will also effect a partial, spontaneous, fibrillation of the asbestos. In principle this should lead to the release of tremolite, and permit the separation of both chrysotile and talc by a flotation method. Hie application of anionic surfactants to chrysotile is an essential step in the wet dispersion process for making chrysotile yarns, as outlined by Gettins and Mallon 1971^, Heron and Huggett 197111 (all four authors associated with TBA), and Otcruma 12 and Take 1975 . For the purpose of this present exercise it will be use ful to approach TBA to ascertain whether there is any feasibility in- applying wet dispersion and flotation techniques to the separation of tremolite from chryaotile. Identification of tremolite by UV light 9 Hie Cyprus Ind. Hin. Corp. patent , referred to above, cites an optical sorting method in which tale ore contain ing tremolite is sorted under UV radiation of wavelength 250 to 340 m, In which the talc fluoresces white and the tremolite fluoresces oranor red. Hie principle might be applied to chrysotile/tremolite mixes to give a preliminary indication of high or low levels of tremolite content. AO 1306 UCC 017486 6 Outline schemes for eeparatiry tremollte from chrysotile On face value, a chemical separation scheme appears to be absolute, but if many samples are to be investigated it will be tedious and time consuming, unless an automated means of extraction of the chzysotile can be devised. Choice of sample sizes will be Important, due to the uneven distribution and variable content of tremollte in chrysotiles from different sources. A preliminary assay of samples by heavy liquid separation or by tTV screening (if practical) may be necessary. The following stops are foreseen in setting up an analytical procedure. 1. Confirm experimentally that chzysotile fibre can be fully decomposed into soluble products, by using alternating acid and alkaline conditions, and by selecting an optimum reaction regime as indicated in the literature. AsseeB the decomposition of pure tremollte under the same conditions. 2. Determine what advantages lie in pre-milling or pre-heating the samples. 3. Investigate a procedure for the preliminary assay of samples by heavy liquid separation or by UT screening. 4. Draw up plans for an automated bench rig to decompose the chryBotlle and leave a residue of tremollte. 5. Prepare an order of sample sizes (l to 10 gm ?) according to likely tremolite content, and according to choice of final quantitative assessment. 6. Investigate the interference due to other insoluble minerals, particularly talc, in the final assessment of residues, 7. Consider the choice of one or more methods for the final analysis of residues XRD for positive identification of tremolite from all samples! IR for quantitative assessment of talc in the presence of tremollte; gravimetric evaluation of large residues; EDXA (Ca content) for the evaluation of tremolite in small residues. Two further approaches should be considered: (a) If chxysotile samples contain considerably more than 1 % trasollte, it should be possible to analyse them directly by XHD/EDXA, particularly if a set of calibrated mixes has been prepared and examined beforehand. To obtain a statistically acceptable result it would be necessary to assess a number of aliquots of the unknown. (b) Die feasibility of a flotation technique for separating tremolite and chxysotile should be examined as a separate issue. A flotation method would replace chemical separation, and could probably be the means of separating off any interfering talc along with the chzysotile. The T&N &01307 UCC 017487 1 elutriation method, as used In -the testing of asbestos fibres, could probably be adapted without difficulty to the partition of chxysotile and talc from tremolite, after preparation of the samples with suitable surfactants. References 1. 2. 3. 4. 9. 6. 7. 8. 9. 10. 11. 12. K. A. Butler. The physical and chemical characteristics of serpentine rocks and minerals. PhD thesis. University College, Cardiff, 1980. A. Gosseye, P. Hahn-Weihheimer. A comparative study of asbestos minerals. 2nd International Asbestos Conference, Louvain, 1971 E.J.V. Whittaker (Oxford University). Advisorycommunication to Cape Asbestos Fibres Ltd., 1978. A. A. Hodgson. Fibrous Silioates. Royal Institute of Chemistry, 1965. A. V. Atkinson, A. L. Rickards. Acid decomposition of highly opened chzysotileB. 2nd International Asbestos Conference, Louvain, 1971> L. J. Monkman. Some aspects of the reaction of chrysotlle with inorganic and organic acids. 2nd International Asbestos Conference, Louvain, 1971* P. F. Holt, S. G. Clark. Nature, Lond., i960, 185, p. 237. E. Martinez, R. B. Haagensen, H. L. Lovell. Investigation of the quantitative determination of minerals in serpentine end asbestos samples by infra-red spectroscopy and thermo-analysis. 1 Bt International Asbestos Conference, Oxford, 1967. US Patent 3837582. Beneficiation of New York State talc. Cyprus Mines Corp., 1974. (now Cyprus Industrial Mineralb Corp.) R. B. Gettins, F. J. Mallon. Adsorption of surface active agents on chxysotile asbestoB. 2nd International Asbestos Conference, Louvain, 1971 G. F. Heron, R. Huggett. Dispersion based textiles. 2nd International Asbestos Conference, Louvain, 1971- T. Otouma, S. Take. Effect of anionic surface active agents on chxyBotile 3rd International Asbestos Conference, Quebec, 1975- Proceedings of the International Asbestos Conferences are not readily available end the authors referenced above did not necessarily publish elsewhere. Copies of the relevant papers can be obtained from AAB if so desired. A. A. B. 30.IO.1984. Copies: Chairman, ARC Research Committee 3 Institute of Occupational 2 Medicine UCC 017488