Document wg90r4qyqLkxa5r2Vp05g42KQ

f lliE ASUi STOS INTORMATION COMMITTEE Memo tot H D S Hardie Esq AIC Sub Committee /Dr S Holmes Dr V J Smither Front Mr V P noward Vednesday 14th April 1976 The AIC decided at its last meeting that we should produce a leaflet setting out the facts on mesothelioma as ve understood them. I should be grateful for your comments on the enclosed draft* lv V P HOWARD Secretary VPH/JG Enc O i  Q u V DRAFT MESOTHELIOMA Nov that there is general acceptance of the adequacy of the current standards to protect workpeople from the risk of contracting asbestosis and lung cancer* the major area of expert concern is in the risk of another disease* mesothelioma. The cause of this concern is the reporting of cases which are allegedly the result of relatively slight exposure to asbestos. They are sometimes adduced to challenge the adequacy of the precautions incorporated in Government regulations and recommended by the asbestos industry. It will take time*perhaps several years* before va can be completely certain of the effectiveness of the current UK standards* but there are pointers which should encourage us to persevere with them. '/ * t , A DEFINITION Mesothelioma is a malignant tumour. It affects the pleura* the lining of the chest vail* or the peritoneum* the lining of the abdominal cavity* where the stomach lies. There is no known treatment. * g INCIDENCE Mesothelioma has attracted a great deal of public attention in recent times* but It is nevertheless a rare disease. The number of new confirmed cases has never exceeded 200 in any one year in the UK, compared with over 30,000 cases of lung cancer reported every year. , [ : | j THE CAUSE At least 15JC of British eases appear to be "spontaneous*, i.e. to display no clear causation. The remainder have in the past occurred in people exposed to asbestos dust* evinoing symptoms of the disease at any time from 15 to 50 years slnoe first exposure. Most were exposed at work. Some were exposed because they lived close to an asbestos factory many years ago when asbestos dust was allowed to escape into the surrounding atmosphere, some because husbands brought dust home on their vorkclothee. There seems little doubt of the association* since pathologists at post mortem have found a burden of asbestos fibre in the patient*' lungs* much higher than found in the general population. t fl u 2- -- ' * There is, hovever, considerable doubt of the asbestos association in the case of people vho have only been exposed as a result of their hobbies, or living in or near buildings incorporating asbestos materials. There are many reasons for this doubts 1 The evidence of exposure is based on recollection of incidents long ago. Few people have this kind of total recall. Frequently the evidence of exposure is Incomplete because it is based not even on the patient1s ovn recollections but on that of his relatives, vho will rarely have been able to provide a complete occupational) history. 2 The corollary of this is that recorded casual exposures may in fact have Involved other quite heavy exposure unbeknown either to the patient or to his relatives, vhich only the most thorough Investigation would bring to light. 3 The casual "hobby" or "domestic" exposures are not supported by corroborative evidence of asbestos fibre bodies, asbestos fibres or pleural plaques observed in the lungs at necropsy^It is therefore always possible that many, perhaps most,of these casual cases should more properly be added to the 15~-of "spontaneous" mesotheliomas. WHAT TYPE OF FIBRE? * Mortality studies have been undertaken in many countries among populations of workers exposed to asbestos. They reveal increasing evidence that the risk of contracting mesothelioma differs with the type of asbestos. It la greatest with one type of croeldollte (blue asbestos) from a particular area in South Africa, less with amosite and apparently less with chrysotile. It has never been associated with anthophyllite^*^. A DIFFERENTIAL STANDARD The standards associated with the 1969 Asbestos Regulations recognise this difference by applying very much more stringent controls to work with croeldollte (blue) than are applied to the other types of fibres. Vhereas the standard for the latter is 2 fibres per millilitre of air (2 f/ml) the standard for croeldollte is 0.2 f/ml^ The asbestos Industry itself, when first appraised of British experts* ? anxieties over croeldollte, decided in 1968 to phase it gradually out of use la its processes. Since 1970 no croeldollte fibre has been imported into this country. Vork which now Involves croeldollte is to largelyAthe repair or dismantling of old installations vhich contain it. There is an obligation under the Regulations to give ths Factory j -3.'Inspector 28 days* notice before such vork commences, so that he can be assured that all the proper precautions are being taken. GROUNDS FOR CONFIDENCE Cases of mesothelioma occurring today as a result of asbestos exposure do not reflect current vorking conditions and should not be adduced to impugn the adequacy of today's British threshold standards. Certainly the occupational and near-occupational exposures of a previous generation, vhich gave rise to the mesotheliomas reported today, vere vastly greater than those encountered in any vorkplace vhich satisfies the current Regulations. And they have included crocidolite exposure vhich for all normal asbestos vork is a thing of the past. DOSE-RESPONSE RELATIONSHIP This confidence is reinforced by the groving body of evidence that for mesothelioma* as for asbestosis and lung cancer* a dose-exposure relationship exists. This means that the likelihood of contracting the disease is related to the length and severity of the exposure'**^ It appears that in most cases vhere the exposure has been short* e.g. of the order of 5tfvpeks*it may veil by today's standards have been Iheavy^^. In the^cases vhere crocidolite (blue) has not been involved* {the exposure has been heavier still. A RISK TO THE PUBLIC? All the evidence of an association between mesothelioma and air pollution in the neighbourhood of factories relates to conditions many years ago* when chryeotile, amosite and crocidolite vere all in use in many factories, and when asbestos emissions into the atmosphere vere often inadequately controlled. Measurements taken in the urban atmosphere nowadays reveal amounts of asbestos fibre vhich are so Infinitesimal as to be negligible* at least 1,000 times less than would be acceptable for factory vork^^. Measurements taken in buildings vhich incorporate asbestos materials in their structure have sbo(7vn) levels of asbestos fibre w--hi-c--h---d--o-- n---ot-*p1lace the occupan,ts at risk*1 *. Thus there is no risk to the general public at present. from these low levels of exposure to asbestos^). Care should of course be exercised in do-it-yourself vork on asbestos products in the home* but the normal use of asbestos products should not be a cause of anxiety. i 1 Mesothelioma Register 1967*8 . M Greenberg and T A Lloyd Davies British Journal of Industrial Medicine 1974. 31* 91*104 2. Report of the Advisory Committee on Asbestos Cancers to the Director of International Agency for Research on Cancer Lyon, October 1972* 3. Department of Employment Technical Data Note 13 (revised) Standards for Asbestos Dust Concentrations for use with the Asbestos Regulations 1969* 4. Cancer among workers in the Asbestos Textile Industry Muriel Newhouse "Biological Effects of Asbestos" pp 203. IARC October 1972. * 5* The Medical Risks of Exposure to Asbestos Muriel Newhouse, The Practitioners, September 1968. 6* Chrysotlle Asbestos in Urban Air A L Rickards and D V Badami o Nature, Vol 234, 12 November 1971* . 7* Dust Survey carried out in Buildings incorporating Asbestos-Based Materials in their Construction J C Byrom, A A Hodgson and S Holmes, Annals of Occupational Hygiene, Vol.12 pp 141-143*