Document pqJ85NE9zzbRNV33MV168xGd

19P FROM: TO:16182590886 224 INDUSTRIAL CARCINOGENESIS AND TOXICOLOGY due to a maintained mechanical irritation produced by the insoluble amphibolc, or to a chemical effect brought about by the dissolving silicate. It may be recalled that Alden and Howell (1944) stated that amosite needles are capable, where embedded in epithelial tissue in the skin, of eliciting a non inflammatory epithelial proliferation. This statement was made from obser vations on amosite workers who developed hyperkeralotic epithelial thicken ing after penetration by a small splinter-like fibre. X-ray examination and biopsy show no evidence of a foreign body in these " corns Solubility of asbestosis bodies More work is required on this problem especially quantitative studies of the solubility of asbestos types in a variety of conditions, together with an identification of the products after solution. The question is not one of explaining fibrosis of tho lung by a chemical process, for this is ulmo&t decisively negatived by the undoubted fact that tbe smallest particles of asbestos have not in fact produced a fibrosis In the experience of most investigators. The question is rather one of finding a product of solution which, by entering the modified squamous epithelium of the lung, or by changing its environment, can lead to de-dilTerenliution or to tumour for mation. The majority of pulmonary tumours in men are anaplastic or undifferentiated or (epidermoid) squamous epitheliomala and they con stitute a type of new growth in the lung which has hitherto eluded the experimentalist. Probably the only claim to have induced a true cancer in the lungs of mice was that made by Nordmanrt and Sorge (1941) who exposed 100 mice to undefined asbestos dust and stated that 20 per cent of the animals developed cancer. There is considerable doubt, however, whether the evidence presented i$ really acceptable. In fact, cancer of the lung (truly so called--not adenomas as found and induced in mice) has not hitherto been produced by inhalation of any material W H Smith (1952) in a very forceful consideration of the experi mental aspects or cancer of the lung concludes " that wc are singularly illequipped for the experimental study of one of the chief problems of human cancer ", Until this charge is successfully answered we may for practical purposes regard asbestos or u derivative ot asbestos as a probable co-carcinogen in that proportion of cases of diffuse fibrosis of the lung in which the necessary preparedness of the lung has been brought about, probably endogenously Such a view has, ill Icust, the merit of loss sterility than the common panacea for carcinogenic dilemmas, irritation AROMATIC AMINES Of tire few identifiable chemical agents which may without doubt be accepted as standing in the line of causality of particular types of human neoplastic disease, certain aromatic amino intermediates in the dyestuffs industry occupy the most interesting and, from tho point of view of the experimentalist, the most fruitful position. Not only have they been repeatedly reported in