Tuesday, August 25, 2015
The History of Mesothelioma
Ian Webster, 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 crocidolite
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 discerned.
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 conceive
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 production
of amosite far exceeded that of Cape Blue asbestos. It is suggested
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,
one of America’s most respected investigators in occupational pulmonary
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 development
of mesothelioma.” He later states that “the tolerable level was
substantial.”
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