It seems that every advance in science has its naysayers who are pulled along screaming and kicking. Garrett Schepers (76), then work-ing as an American pathologist, was originally from South Africa. He related his own experience at the New York Academy of Sciences meeting:
As a boy, I lived not far from Kuruman for a number of years. One could not imagine a more healthy territory. However, there is a particular irritating type of grass in the area (Klitsgras), whose seeds burrow into every garment they cling to, as these seeds are armed with fine barbs. Surely, when the wind blows, as often it does in Kuruman, some of these minute barbs may be inhaled. I wonder whether some of these fiber structures reported in the lungs of persons in that area may not represent reactions to grass barbules. I offer this Klitsgras theory of Kuruman mesotheliomatosis in order to clear the hurdle created by the discovery of this rare disease in such abundance in persons with such little meaningful exposure to asbestos.
Perhaps the South African pathologists will now have their turn to make mincemeat of my theory. [p. 599]
Also at that meeting Schepers stated:
Perhaps the South African pathologists will now have their turn to make mincemeat of my theory. [p. 599]
Also at that meeting Schepers stated:
My first impression is that there is now less certainty that asbestos inhalation is associated with pulmonary neoplasia than there was 10 or 20 years ago.
Perhaps this is due to greatly reduced dust exposures. Asbestos may after all prove to be carcinogenic only in overwhelming dosage. Thus, the high preva-lence of neoplasia which was reported several decades ago may be a function of the severity of exposure rather than an indication of high carcinogenic potency. I suspect that in the final analysis the carcinogenicity of asbestos will be rated as of low order. Perhaps carcinogenicity will prove to be a correlate of
asbestosis rather than a specific biological function of the mineral asbestos. This may be the crux of the matter. In all cases of asbestos-associated lung cancer that I have personally studied (the number now exceeds two dozen), there invariably was well-established asbestosis. Not only was the asbestosis of marked degree in the areas where the cancer arose, but there generally was evidence from serial chest x-rays that asbestosis had been present in the lungs for a protracted period. [p. 595]
asbestosis rather than a specific biological function of the mineral asbestos. This may be the crux of the matter. In all cases of asbestos-associated lung cancer that I have personally studied (the number now exceeds two dozen), there invariably was well-established asbestosis. Not only was the asbestosis of marked degree in the areas where the cancer arose, but there generally was evidence from serial chest x-rays that asbestosis had been present in the lungs for a protracted period. [p. 595]
Ian Webster (77), who was J.C. Wagner’s brother-in-law and a well-respected pulmonary pathologist, still stated that there were unsolved problems in the relationship between asbestos and malignancy in a paper he published in February 1973 in the South African Medical
Journal. Webster remained skeptical as to why this previously rare tumor seemed to be found primarily only in direct relationship to cro-cidolite exposure. Webster suggested that some other factor, possibly mineral, must be present to explain the high incidence of mesothelioma
in a very localized area of South Africa. He looked at exposure to asbestos and the association with 232 cases of pleural mesothelioma.
Almost all the individuals had been exposed to Cape Blue asbestos and only two miners had been exposed to amosite as far as could be dis-cerned. Thirty-two cases occurred where there was no evidence of any asbestos exposure, presumably having environmental exposure. There
were only two cases related to exposure to amosite out of 232 confirmed cases of mesotheliomas. He stated, “Furthermore, it is difficult to con-ceive of amosite in the intermediate group of asbestos fibers causing malignancy, as suggested by Wagner et al when there are so few cases in the employees of the amosite mines.” He goes on to say, “The pro-duction of amosite far exceeded that of Cape Blue asbestos. It is sug-gested that more attention should be paid to the determination of the nature of the substance of the Cape Blue areas and not in the Transvaal Blue, and apparently limited to the areas where amosite is mined.” The same opinion had been offered earlier, in 1969, by George Wright (78), one of America’s most respected investigators in occupational pul-monary disease, who in his review, “Asbestos and Health in 1969,” stated, “That something other than, or in addition to, asbestos plays a role in mesothelioma formation seems inescapable.” Wright accepted asbestos as a cause of mesothelioma but felt there was a “tolerable level of airborne asbestos fiber which does not cause an undue risk of devel-opment of mesothelioma.” He later states that “the tolerable level was substantial.”
Journal. Webster remained skeptical as to why this previously rare tumor seemed to be found primarily only in direct relationship to cro-cidolite exposure. Webster suggested that some other factor, possibly mineral, must be present to explain the high incidence of mesothelioma
in a very localized area of South Africa. He looked at exposure to asbestos and the association with 232 cases of pleural mesothelioma.
Almost all the individuals had been exposed to Cape Blue asbestos and only two miners had been exposed to amosite as far as could be dis-cerned. Thirty-two cases occurred where there was no evidence of any asbestos exposure, presumably having environmental exposure. There
were only two cases related to exposure to amosite out of 232 confirmed cases of mesotheliomas. He stated, “Furthermore, it is difficult to con-ceive of amosite in the intermediate group of asbestos fibers causing malignancy, as suggested by Wagner et al when there are so few cases in the employees of the amosite mines.” He goes on to say, “The pro-duction of amosite far exceeded that of Cape Blue asbestos. It is sug-gested that more attention should be paid to the determination of the nature of the substance of the Cape Blue areas and not in the Transvaal Blue, and apparently limited to the areas where amosite is mined.” The same opinion had been offered earlier, in 1969, by George Wright (78), one of America’s most respected investigators in occupational pul-monary disease, who in his review, “Asbestos and Health in 1969,” stated, “That something other than, or in addition to, asbestos plays a role in mesothelioma formation seems inescapable.” Wright accepted asbestos as a cause of mesothelioma but felt there was a “tolerable level of airborne asbestos fiber which does not cause an undue risk of devel-opment of mesothelioma.” He later states that “the tolerable level was substantial.”
No comments:
Post a Comment