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 (24), health concerns for long respirable fibers [World Health Organization (WHO) criteria: length >5mm, diameter <3mm] are considerable (25).
In addition to size, the chemical composition of fibers plays an im-portant role in determining the durability, biopersistence, and biode-gradability 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 (26,27). 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 (28). Studies also indicate that the lung fiber content of amphi-boles is less than that required for chrysotile in the induction of mesothelioma (29). The persistence of the amphibole fibers at the site of tumor formation is important to both tumor induction and promo-tion because the mean latency period between initial exposure to asbestos and the development of mesothelioma is around 30 to 40 years (19,30).
In addition to size, the chemical composition of fibers plays an im-portant role in determining the durability, biopersistence, and biode-gradability 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 (26,27). 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 (28). Studies also indicate that the lung fiber content of amphi-boles is less than that required for chrysotile in the induction of mesothelioma (29). The persistence of the amphibole fibers at the site of tumor formation is important to both tumor induction and promo-tion because the mean latency period between initial exposure to asbestos and the development of mesothelioma is around 30 to 40 years (19,30).
Properties of Asbestos Associated with Carcinogenic Potential
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