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1/8/2009
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| 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stands behind the outdated one fiber can kill theory of carcinogenesis.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 (. |
| A series of 421 malignant pleural mesotheliomas, diagnosed in the
Trieste-Monfalcone area, northeastern Italy, were reviewed.
A large majority of the patients had been employed in naval work
(shipbuilding, maritime trades, and dock work). Latency
periods (time intervals between first exposure to asbestos and
death), showed wide variations from one occupational category
to another. Such variations were attributable, but only partly, to
differences in the intensity of the exposure to asbestos. Various
family cases were identified, including people with and without blood
relationships. The data, obtained in the studies on
Trieste-Monfalcone mesothelioma, suggest that interactions between
asbestos and other factors play a considerable role in the
pathogenesis of asbestos-related mesothelioma.
___________________________________________________________
Med Lav 1997 Jul-Aug;88(4):310-5 |
| Following the finding of an unexpected cluster of mesotheliomas in
textile workers, a surveillance system of malignant
mesotheliomas was implemented in the region of Tuscany, Italy. This
article reports on the investigation of 124 cases of
mesothelioma diagnosed and reviewed by the Institutes of Morbid
Anatomy and Histopathology at the Universities of Florence,
Pisa, and Siena between 1970 and 1988. A complete occupational and
asbestos exposure history was assessed through a
semi-structured questionnaire directly administered to resident cases
of Tuscany or, if deceased, to their closest living relatives,
for a total of 100 interviews. The hypothesis of past occupational
asbestos exposure was verified and documented.
Seventy-two cases have been classified as occupationally exposed to
asbestos; four were classified in the category of possible
domestic exposure to asbestos. For two others, the role of other
risk . |
| 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). |
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