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CDC/ John Wheeler, Ph.D., DABT
Janice Haney Carr
Agency for Toxic Substances and Disease Registry (ATSDR) - Asbestos
Note the elongated crystalline structure, and how the fibrils are arranged in both bundles, and as singular serpentine units. See PHIL 11034 through PHIL 11066, for additional photomicrographic views of this material.
The levels of asbestos in air that lead to lung disease depend on several factors. The most important of these are (1) how long you were exposed, (2) how long it has been since your exposure started, and (3) whether you smoked cigarettes. Cigarette smoking, and asbestos exposure increase your chances of getting lung cancer.
There is a scientific debate concerning the differences in the extent of disease caused by different fiber types and sizes. Some of these differences may be due to the physical and chemical properties of the different fiber types. For example, several studies suggest that amphibole asbestos types (tremolite, amosite, and especially crocidolite) may be more harmful than chrysotile, particularly for mesothelioma. Other data indicate that fiber size dimensions (length and diameter) are important factors for cancer-causing potential. Some data indicate that fibers with lengths greater than 5.0µm are more likely to cause injury than fibers with lengths less than 2.5µm. (1µm is about 1/25,000 of an inch.) Additional data indicate that short fibers can contribute to injury. This appears to be true for mesothelioma, lung cancer, and asbestosis. However, fibers thicker than 3.0µm are of lesser concern, because they have little chance of penetrating to the lower regions of the lung