One interesting study is called, "Radiological
abnormalities and asbestos exposure among custodians of the New York
City Board of Education" by Levin, S.M.; Selikoff, I.J. – Annals of the
New York Academy of Sciences; (United States); Journal Volume: 643.
Here is an excerpt: "Six hundred sixty custodians employed by the New
York City Board of Education underwent examination from 1985 through
1987 for asbestos-related disease and other general medical conditions
by the clinical staff of the Division of Environmental and Occupational
Medicine of the Mount Sinai School of Medicine of the City University of
New York. Two-thirds of the men (no women were examined) were 20 or
more years from onset of any custodial work, with 44% having had at
least 20 years of employment as custodial workers in New York City Board
of Education schools. Twenty-four percent had begun custodial work in
buildings 30 or more years earlier. Findings among them were of
particular interest since asbestos-related disease might forecast what
might be expected among school custodians with less seniority. Since the
Board of Education, in selecting custodians for examination, had chosen
only custodians currently employed, the study group comprised men still
working in the school system. These, then, represented a survivor
population’. Although a considerable amount of clinical information was
obtained, abnormalities on chest X-ray consistent with asbestos-induced
scarring were used as the key index of disease resulting from exposure
to asbestos. Since scarring of the lung tissue may be present but
undetectable on standard chest radiographs (a relatively insensitive
diagnostic technique), the prevalence of abnormality on X-ray film
represents a conservative estimate of the actual burden of scarring lung
disease in the group. Such changes are indicative of previous asbestos
exposure, however, and provide evidence of an increased risk of later
asbestos-related malignancy. Overall, abnormalities on chest X-ray
consistent with asbestos-related scarring were found in 28% of the men
examined."
Another study is called, "Magnetic lung measurements in relation to
occupational exposure in asbestos miners and millers of Quebec" –
Environmental Research Volume 26, Issue 2, December 1981, Pages 535-550
by David Cohen, Thomas S. Crowther1Graham W. Gibbs2 and Margaret R.
Becklake. Here is an excerpt: "Abstract – Fe3O4 particles
(ferrimagnetic) are usually attached to asbestos fibers
(nonferrimagnetic) in the chrysotile asbestos mining and milling
industries; therefore, a magnetic measurement of Fe3O4 in the lungs of
workers in these industries could help determine the amount of asbestos
which has been inhaled and retained in their lungs. As a first
assessment of this method, magnetic measurements were made of Fe3O4 in
the lungs of 115 miners and millers in Quebec. These measurements at an
industrial site were found to be feasible and practical; however, the
amount of Fe3O4 seen in the lungs of those with welding exposure was
large enough to mask the Fe3O4 contributed by asbestos, and this
subgroup was considered separately. For the remainder (nonwelders), the
amount of Fe3O4 was plotted against a total dust exposure index
(asbestos and other dust) estimated for each worker. Although the
correlation between these quantities was not high, it was statistically
significant at the 1% level. Because retained asbestos is likely to
increase with increasing exposure to total dust, this correlation
suggests that a magnetic lung measurement of a chrysotile miner or a
miller does reflect, to some extent, the amount of asbestos in his lung.
There was considerable scatter in the data, partly due to individual
variations in deposition and clearance, to which this method is
sensitive. When the data of only the nonsmokers were plotted, the amount
of Fe3O4 was greater than for the total group of nonwelders. This is
consistent with previous findings that less dust is deeply deposited in
the lungs of smokers, due to constriction of small airways."
Another study is called, "The histopathology and ultrastructure of
pleural mesotheliomas produced in the rat by injections of crocidolite
asbestos." By Davis JM. – Br J Exp Pathol. 1979 Dec;60(6):642-52. Here
is an excerpt: "Abstract – Primary tumours of the pleural cavity were
produced in rats by the intrapleural injection of crocidolite asbestos.
Their histological structure as seen with both light and electron
microscopy was very variable and tumours frequently contained elements
of both connective-tissue and epithelial type. In some instances the
connective-tissue elements predominated from the start and the earliest
tumour nodules consisted mainly of pleomorphic connective-tissue cells
with only a few layers of cells more nearly epithelial in type on the
surface. This pattern was largely retained when tumour nodules increased
in size and coalesced, but in the deeper layers of advanced tumours the
pleomorphic connective-tissue pattern was often replaced by a more
uniform spindle-cell form. Other tumours were more predominantly
epithelial in type, showing either a papillary pattern with rounded
epithelial cells growing in solid columns, or a vesicular form in which
large tissue spaces, often intracellular, were lined by very thin layers
of extended cell cytoplasm. Whereas early tumours showed only one
histological pattern, the more advanced stages often exhibited areas of
all 3, so that there seemed to be some degree of histological
mutability. The spindle-cell areas of advanced tumours frequently showed
evidence of direct invasion of the surrounding tissue but this was
never seen with the epithelial forms of rat mesothelioma."
If you found any of these excerpts interesting, please read the
studies in their entirety. We all owe a debt of gratitude to these fine
researchers.
