Document Dgo0bRVGd66qyg9VpXXej2V5

: Comparison BHwaanMorewether'jFIndlngsIn 1929 and' Prevalorico of Asbestosis In l975.* ,4J"> ? , v.,-.,. i ** EwpIoyM* 'NO ' ,, . Ni..Casts' . ExppsaJ Certified. Gro" . `IrtcUwce ' uV T>r 3 45 'Only cases ol asbestosis in receipt ot Industrial Injuries Benefit are included in the 1975 figures. t3 cases with more than 20 years exposure were lirst exposed before 1933 (Table IVI. No/. ' -Examined. 230 , 84 .'/. 1 28 .. ", . 21 / . . .363 Ho. of Cases ' Diagnosed-,... 36 27 15 17' .95 , 156 ^SSg 32 1 'M1 '536,. " 809 26 2 `9 The Advisory Panel did record, however, that although they were inclined to accept the growing use of asbestos as the most probable explanation of the increase in cases, "conversely there is no evidence pointing to a decrease in the attack rate in the in dustry as a whole although there is such evidence in certain im portant asbestos using factories." In 1969. new regulations known as the Asbestos Regulations 1969 were made in the U.K. and they took effect in May 1970.'2 These regulations recognized two things, among many others, namely, the importance of their application to both manufacture and usage of asbestos products and the acceptance of a level of dustiness below which there was no hazard to health. The latter principle was acknowledged by the publication of "Hygiene Stan dards for Airborne Asbestos Oust Concentrations for Use with Asbestos Regulations 1969" in Technical Data Note 13 (Rev.).11 Technical Data Note 13 states that where the dust concentra tion is less than 2 fibres/ml, HM Factory Inspectorate will not seek to enforce the substantive provisions of the Regulations. This figure is derived from the simple assumption that in order to ac cumulate an exposure limit of 100 fibres/ml during a working life time, the dust level should not exceed an annual average of 2 fibres/ml .'.50 years x 2 f/ml = 100 f. years/ml., 50 years x 4 f/ml = 100 f. years/ml. etc. 'Adequate' Occupational Exposure History In the determination of an adequate occupational exposure history it is necessary to ascertain the type of asbestos fibre in use. There are four main varieties in commercial use, namely: Chrysotile -- white -- 95% world production. Crocidolite -- blue -) Amosite -- brownish -) 5% of world production. Anthophyllite -- brownish -) It is accepted that all varieties of asbestos can give rise to asbestosis. Asbestosis might be complicated by the development of carcinoma of the lung, and the risk of this complication is multiplied many times by cigarette smoking. Before discussing the clinical features of asbestosis, one further difficulty in obtaining an adequate occupational exposure history requires reference. Merewether attempted to quantify the dusti ness in the textile branch of the industry but was only able to pro duce a rough guide. The respirability of asbestos dust, because it is composed of fibres and not of spherical or uniform particles, depends upon its aerodynamic behavior which is related to fibre diameter and falling speed. It was not until suitable instruments became available in the late 19401s and early 1950's that routine environmental monitoring could be introduced into industry. The British Occupational Hygiene Society made use of dust measure 608 ments and clinical data from a Rochdale asbestos textile factory^ its first attempt to set "Hygiene Standards for Chrysotile Asbes Dust" in 1968. Prior to this the only standard recorded was in t U.S.A. and was 5,000,000 asbestos particles per cubic foot as mea sured by means of the midget impinger. The BOHS Standy recommended a cumulative dust exposure limit of 100 fibre ye` per cubic centimeter. This would allow a 1% risk of developin basal rales, which were considered as the earliest physical sig' due to the effects of asbestos exposure. In the medical surveillance of asbestos workers in Britain we; now concerned with two populations for follow-up, narmi|! those people who have worked in the industry when dust me*' surements were not made and when variable dust control mea. sures were taken and those who have entered since May 19j when new improved conditions were demanded by new regula tions and when environmental monitoring could be added to't,J data for epidemiological evaluation. HM Chief Inspector of Fa lories in his Annual Report, 1974,' states, "139 new cases o' asbestosis were recorded by DHSS during the year. These cdf^ tinued to reflect conditions in past years when the long-term.ef fects of asbestos dust on the Health of Workers was not fully prcciated. The latent period for this disease is such that anntj figures cannot yet be expected to reflect improved conditions fp lowing the introduction of new legislation in 1970." What constitutes an adequate occupational history? There is iif sufficient evidence available from industry to enable this questii} to be completely resolved, but such evidence as there is allow certain standards to be set in the hope of reducing the risk an, providing a base-line for further study. (B.O.H.S. 1968). Physical Signs of Pulmonary Fibrosis Where exposure is known, the presence of asbestos bodies an fibers in sputum is of little importance, since their presence simp'!., confirms exposure and their absence does not indicate freedonj from disease. The presence of basal rales (crepitations or crackles) and finger clubbing have long been accepted as important clinic findings in conjunction with a history of asbestos exposure. TfT British Occupational Hygiene Society's Committee on HygietC Standards, in their publication 'Hygiene Standards for Chrysptife Asbestos Dust' considered basal rales as the "key symptom." 3^ crackles are characteristically of high pitch and occur in .end: inspiration, persisting after coughing and most prominent in th dependent areas of the lungs. It is important to establish that the crackles are persistent art,, not due to other diseases resulting in pulmonary fibrosis. Until it is possible to record lung sounds and preserve gra records, the presence or absence of these fine crackles remainfi? Asbestosis/Lewinsti