Document 2j8M634p10xgjB0MgzpQzbjNa

: Health hazards of as'Casios J. C. GILSON* Inhaled, fibres of asbestos can cause fibrosis of the lungs and two kinds of cancer. Protection of asbestos workers calls for monitoring and controlling their working environment and linking these records with records of their health HISTORICAL Asbestos was (tic first inorganic fibre in be used in compo sites. More than 4000 years ago clay pou in Finland were sttengUicited by adding inihopiiyllite Fibres'. In classical times asbestos cloth was used to preserve the ashes of the eminent. The oldest known piece of asbestos doth from (hr Sew World, dating Trom about |T40. is a small purse mad: of tremolite m the Sir Hans Sloane collection of minerals in the British Museum (Natural History). The modern asbestos industry is about 100 years old, suning nearly simultaneously in Canada and die USSR, bn: it was not unif 30 vears later that the first medial reports appeared iai France and England, indicating that there might be a specific type of damage to the lungs following inhalation of the dust. By the late 1920s it was dear from surveys made in this country and in USA1-1 that a high proportion of older workers in the asbestos textile industries were becoming severely disabled by a specific type of chest disuse due. to the dust. This was named asbestosis. .. DISEASES CAUSED BY ASBESTOS DUST Research carried ou: in (lie 1930s. supported by ihe greatly expanded investigations during the last 15 yesrs into (lie types of disease caused by asbestos, now.piovides a much dearer pic.uie of she specific hazards and how damage to health can b; avoided in the future. Table I lists she diteascs. Ttih 10-..em swim br iitxnoi dun - Ajjsttnu Cave- CoiM fturoit'i of iuftgi BfOflctiiai Oungl MttoiMioma Skin Asbtsiovs In asViii.vj the Just causes scarring and thickening of the tii.iic, of :!;c lung The two pirn particularly affected r- !:t: jit jns.-jici I respiratory btttich;olc>l r.cic tin;. branch i: :o the tv.-imtul in sacs (the :lvc,i!i|. mil ;!.c M:l-.c iu tin.- lung Irleuiat. The thickening of the t;"UC- h\ the .-->euus dutt affects me lunciior.she ::r.IT-: I'.uintc v.Ticil lii1llv` i.':lij;-.-J V !i.: e i -.i;i n-{ m i> lew Hun nuiuisi. lln- : "-ICC .iu>*.i. t ill. I Ciiwl-.il '-. ' 1.'ji i'.:. Iiu.l I. become stiffer than normal so that the compliance is reduced. The thickening in the alveolar walls, when the disease is extensive, also reduces (be gu transfer for oxygen, so that the blood leaving the hmg is no (ongei folly saturated with this (it The transfer of arbon dioxide from the blood to the air in the lungs is not, however, appre ciably affected. Tlw reduced oxygen transfer is panly compensated for by ait increase in the frequency ofbreath ing so shat the subject notices breathlessness on slight exertion. These alterations of htnj function are used to assist in diagnosis of asbestosis and measure the severity of the damage. ishesio<is takes a number of yean to develop, even under very dusty conditions, but once established it is a progressive disease not materially affected by avoiding fuithei dust exposure. The less the dust exposure, the longer intern! before the onset of disease, the kit its severity; and the kst chance of being affected. Thia-dose response relationship is used to fix the acceptable dust levels - threshold limit values - for those working with asbestos. The article by Holmes in this issue describes how these standards are applied in practice. Prevention by avoiding expnsurrs to a dangerous quantity of dust is an essential step towards (he safe use of asbestos. Asbestos cancers Some years after the recognition of asbestosis as an impor tant problem in the asbestos textile industry, articles began to appear ir. the medical journals* suggesting an association between asbestosis and lung-cancer. A survey in 1955 firmly aaaabSsked that those who hid worked its the. asbestos textile industry before the improvements in dust control, jniiuduce'd in the 1930s. had a 10-fold excess risk of developing lung cancel1. The survey, however, also indicated that the imptcveinent in dust control introduced at a p-articubi factory after 1933 had very materially reduced the risk. Later surveys at this factory have confirmed this*. . The lung cancers seen in asbestos woikers are simiiai to lltose caused by cigarette smoking. Recent research inu'icaves that" thcie is likely to he a tyncigistic effect of cigarette smoking and exposure to asbestos dust1. The precis quantitative inter-relationship between asbestos, cigarette*. and other factors it not fully established, but p.vrfni evidence indicates that those who smoke cigatcitcs and uic c.\po>cd to asbestos duu have a risk of developing It:.: .'ar'ci at least fifty times cicitcr tlinr. ncn-smoceis " i- * ire nm i'\jui,ed l,i asbestos dust. 'n the last IS veaic ihric has been much new informsil-uiii Hie bit. Uriwcen cspii-ur: to asbestos n.J .!i`.--t.V.-j pievi.(,.,|f rC!\ liK tyn.-cancer affecting Use