Document 2J8L2gN8aEXx7gM65Oj6o84or

V IMKC CANCER IN ASBESTOS MINERS it KW reliable criK-riiol b)' which one calk anticipate arciuugvuicii) aud. at is wdl known, relatively minute changes in the structure ol a chemical careinegtn are suffi cient to dimmish or eliminate ctrdnugeuic "scheduled" areas, by which is meant. "thue areas where processes arc carried on which Were scheduled under the Asbestos Industry Regulations of 1931 as being dusty." action. There is, funlicniiurc, a complete lack I ( asbestos it iinleed to be regarded as a carcinogen, the need it fdt to demonstrate some property which cut be regarded as something more than inertness.** These authors advance the theory that, until some more experimental evidence of direct carcinogenesis by asbestos or a decumiositUm product of it can bo obtained, asbestos might be considered as a "co-carcinogen" which only induces a further de velopment of a preneoplaslic condition brought about by something independent of the asbestos, such as an endogenous faemr. Thus the literature, while tending in sujipnn the thesis that asbestosis is in some way related to the development of lung oncer, is by no means unanimous.. Alto gether, it is perhaps more confusing than enlightening. A careful review shows that the majority of the reports are clinical and not epidemiological. They lack many ele-' ments necessary for the application of epidemiologicd tedtniques to their content, and most of the authors do oot make claim to having done so. What has happened is that succeeding authors have drawn conclu sions and generalised beyond (he scope of the works which they quote. Nowhere, for of definition of terms as used in the pub lished Tiiemure. For example, the term "asbestosis." as used, may refer to changes observable only by microscopic examination ol the lung tissue, or it may mean a radiologically detectable condition. Most of the published reports obviously included women among their cases, but some of them do not give the number or pro|rtion of women involved in the study. There is also a lack of tmifnrmity as to whxt type of exposure most studies have draft with. Of 99 cases enumerated by Hueper** in 1955, only 10 appear tu have originated in the United Stales, and 7 in Canaria. Some of the earlier reports ap parently included asbestos miners, but it can be' assumed, since 82 of the 99 cases had originated in England, and since no asbestos mining operations are carried an in that country, that most of the reported eases have involved workers in the textile or fabricating industries. Such factors as smoking habits, family history of cancer, length of time in the industty, and age of the individual ease are also notably ahsent in the majority of these reports. example, have we found references to population of asbestos workers, although several authors who have quoted the ob served incidence of hing cancer in autopsies of persons who aljo haif.ajbtiloni imply With' this understanding of the limita tions of the existing literature with respect to epidemiologfatl generalisation, it may be nf value to consider in somewhat more de tail some representative earlier publications, that this incidence applies to asbestos work a few of which were referred to briefly ers, generally. We have likewise been above. unable to find any study which actually calculated the incidence of lung cancer among a population of persons who had asbestosis, and not just those who oune to autopsy. With the exception of n taper V *VI,M none of those reviewed five any data oil exposure and dust concentraliuns, and cveu Doll's paper merely mentions One of the most detailed studies and one which deserves the most serious considen- tion is that reported by Doll" in 1955. This study reviews causes of death among asbestos workers based on coroners' roc- unis. It abu allsuipl.. i. uk iimc In- studying records ol men who worked for at least 20 years in exposed situations. PnM--Trtui /v 61$ w