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1/8/2009
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| Our 1990 article reported on recent papers in the peer-reviewed literature and
two international symposia, one at the International Agency for Research on
Cancer (2) and the other at Harvard University (3), all concluding that
chrysotile fibers are less active than amphibole types (crocidolite, amosite,
tremolite) of asbestos in the causation of mesothelioma in man. In his summary
of the IARC meeting, Sir Richard Doll, an eminent epidemiologist, concluded
there is the difference between the effects of chrysotile and amphiboles, which
is so great in relation to mesothelioma that it is possible to argue that
chrysotile does not cause mesothelioma at all (2). This observation has been
supported by numerous peer-reviewed papers and working groups subsequently
(4-6). |
| Mesothelioma, a fatal cancer usually found on the lining of the lung, is
specifically recognized in Ontario—as is asbestosis—as arising from
exposure to asbestos. Mesothelioma is written into the Compensation Act
as a Schedule 4 Disease. |
| In stating that a threshold of effect has never been found for asbestos, Rall
stands behind the outdated one fiber can kill theory of carcinogenesis.
However, Rall fails to mention data supporting a threshold for chrysotile in
lung cancer (11, asbestosis (12), and mesothelioma (13) as well as a panel
report from the Health Effects Institute-Asbestos Research (HEI-AR) detailing
animal and in vitro dose-response studies exhibiting no-observed adverse effect
levels (NOAELs) for asbestos (14). Our recent work documents a dose-dependent
increase in asbestos-induced proto-oncogene activation in mesothelial cells with
no induction at lowest concentrations of fibers tested and an enhanced potency
of crocidolite asbestos in comparison to chrysotile (15). |
| The Monfalcone area, in northeastern Italy, is a small industrial
territory (population about 60,000), with a large shipyard.
Between October 1979 and April 1992, ninety-two malignant
mesotheliomas were diagnosed at the Monfalcone Hospital. The
series included 84 men and 8 women, aged 42 to 89 years (median age
68 years). There were 89 pleural and 3 peritoneal
tumors. Seventy patients (69 men and 1 woman) had worked in the
shipyards; six were seamen, and four insulators. Five men
had been exposed to asbestos in various industries; six women had
histories of domestic exposure, and one woman had a
history of possible environmental exposure. The latency periods
(intervals between first exposure to asbestos and diagnosis of
the tumor) ranged from 20 to 65 years (median 52 years). Latency
periods among insulators were significantly lower than
among shipyard workers, as well as lower than among the other
categories (. |
| In order to provide estimates of the accuracy of death certification
of malignant pleural mesothelioma in Italy, the causes of
death of a series of ascertained cases were investigated. The study
included 523 cases of pleural mesothelioma diagnosed in
1984-1988 by 88 hospital departments and clinics. Vital status at 7
May 1990 was ascertained for 92.7% of subjects. The
overall concordance between pathological diagnosis and death
certification was about 75%.
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Med Lav 1994 Mar-Apr;85(2):157-60 |
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