Tuesday, August 25, 2015
Properties of Asbestos Associated with Carcinogenic Potential
The carcinogenic potential of asbestos fibers has been linked to their
geometry, size, and chemical composition. Because of the increased
potential of long (>5mm) fibers to cause mesothelioma and fibrosis after
intrapleural or intraperitoneal administration to rodents , health
concerns for long respirable fibers [World Health Organization (WHO)
criteria: length >5mm, diameter <3mm] are considerable .
In addition to size, the chemical composition of fibers plays an important
role in determining the durability, biopersistence, and biodegradability
of asbestos types. The greater durability of amphiboles
compared to chrysotile appears to be one of the principal reasons for
their greater carcinogenic potential. Amphibole fibers persist at sites of
tumor development and may serve as stimuli for neoplastic growth of
cells . Studies on the retention of asbestos fibers in lung tissues
of asbestos workers show that concentrations of amphibole fibers
increase with durations of exposure, whereas chrysotile concentration
does not . Studies also indicate that the lung fiber content of amphiboles
is less than that required for chrysotile in the induction of
mesothelioma . The persistence of the amphibole fibers at the site
of tumor formation is important to both tumor induction and promotion
because the mean latency period between initial exposure to
asbestos and the development of mesothelioma is around 30 to 40 years
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