Document 1NGg5kR0MDR3Q3xo00Jb2Jxo

05 PatholQ9ica1 mechanisms For various; diseases in relation to uptake of asbestos in the human body (sec chapter* VIIj, ix, X) a direct relationship has to be accepted; a precise explanation of the pathological mechanism is not available. Develop*!*.*:.t of Juny fihrcu;ii. ir. ashestosis may originate from asbestos fibre;, penetrating the alveolar epithelial cells, interfering with cell- and en?y:..c ae t J vi ty (Beck ct a) 1972, 1975). This leads to the conclusion that, the fibre form is the most important factor - this will be discussed further or. in this chapter. Asbestoses may develop fron exposure to alj four important types of asbestos, regardless of the dimensions of the inhaled fibres, the longer ones however seem to be more pathogenic. In relation to the asbestos induced excess incidence of cancer^ Gilson (1973) lists the following factors: dose and duration (see chapter X); ty:** of fibre; age; r.ex; occupation; and cofactors (particularly smoking). The four important of asbestos apparently differ in their biological effects, as well a*. in their deposition in the lungs, bpidemi ol ogi c*l evidence lead;; to the conclusion that the incidence of bronchial cancer as seen in ashes* tosis, does not depend upon the typ._* of asbestos but mainly on the dose le vel. However, in view of the established fact that there is a multiplicative effect between cigarette smoking and exposure to asbestos dust the state ment that in occupationally exposed populations an excess incidence o! bron chial cancer is only associated with ashestosis needs reassessment. The incidence of mesothelioma is linked to the *:ypt of asbestos. There is a general agreement that the risk of mesothelioma is Jbre^v^lated in the order crocidolite > amosite > chrysotile > anthophyl 1 i te; OS* mao.-jj t ede of the difference between, for example, crocidolite end chrysotile i* -r.'t well establJshed. l.ewinsohn (1974) presented a review of studies, centered around this theme. Amphibole fibres usually have a rectolinear shape in contrast to the 'curly" shape of chrysotile (sec chapter I). Amphibole fibres therefore may penetrate more efficiently through lung tissue, and reach the pleura rela- eonj 075*. PRODUCED FY FORn