Dimensions of elongated mineral particles: a study of more than 570 fibers from more than 90 cases with implications for pathogenicity and classification as asbestiform vs. cleavage fragments

ABSTRACT

Asbestos is well-recognized as the cause of a variety of disorders of the respiratory tract, including neoplastic as well as non-neoplastic conditions. Fiber dimensions and biopersistence are important determinants of the pathologic response, and analytical electron microscopy is a powerful technique for determining the fiber content of lung tissue samples. For decades our laboratory has examined lung tissue samples counting fibers measuring 5 µm or greater in length. More recent observations have indicated that fibers 10 µm or greater in length are pathogenic, and that a length of 10 µm and diameter less than 1.0 µm are useful features for distinguishing asbestiform fibers from cleavage fragments. We examined more than 570 fibers from more than 90 cases to determine the dimensions of fibers that might be classified as asbestos. The vast majority of fibers classified as amosite or crocidolite met the criteria for length greater than 10 µm and diameter less than 1.0 µm. However, a significant proportion of fibers classified as tremolite, actinolite, or anthophyllite did not meet these criteria. These findings have important implications for the identification and classification of elongated mineral particles, both in terms of pathogenicity as well as classification as asbestiform vs. cleavage fragments.