Friday, September 02, 2005

Short Thin Asbestos Fibers and Mesothelioma

BrooklynDodger was raised in the era when students were taught to wonder why asbestos caused fibrosis and lung cancer, while silica only fibrosis. Now, silica is also known to be carcinogenic to humans. Within asbestos risk assessment, long fibers were thought to be the hazard, with short fibers to be ignored. That’s the “Stanton” hypothesis. There’s also the claim that chrysotile asbestos [white asbestos from the great white north] while the nasty amphiboles that no one uses anymore were the hazard.

You would think by now that everything was known about asbestos, and especially everything about asbestos and mesothelioma. Not so, important new data are being published even now.

These investigators got tissue from 168 mesothelioma victims. The investigators found “(1) long, thin asbestos fibers consistent with the Stanton hypothesis comprised only 2.3% of total fibers (247 / 10,575) in these tissues; (2) the majority (89.4%) of the fibers in the tissues examined were shorter than or equal to 5 microm in length (9454 of 10,575), and generally (92.7%) smaller than or equal to 0.25 microm in width (9808 of 10,575). (3) Among asbestos types detected in the lung and mesothelial tissues, chrysotile was the most common asbestos type to be categorized as short, thin asbestos fibers...”

The full text wouldn’t download to see if there were cases with no crocidolite or amosite fibers. And whether any of the mesothelioma victims had no asbestos in tissue.

The occupational health issue revolves around correlation of the long fibers seen on phase contrast microscopy and the short thin fibers which are invisible in environmental sampling. Figuring out the small fiber exposure where PCM gives non detectable results is still an issue.


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Int J Hyg Environ Health. 2005;208(3):201-10.

Short, thin asbestos fibers contribute to the development of human malignant mesothelioma: pathological evidence.

Suzuki Y, Yuen SR, Ashley R.

Department of Community and Preventive Medicine, Mount Sinai School of Medicine, 1 Gustave L. Levy Place, Box 1057, New York, NY 10029, USA. yasunosuke.suzuki@mssm.edu

Based on animal studies, long and thin asbestos fibers (> or =8 microm in length and < or = 0.25 microm in width) have been postulated to be strongly carcinogenic inducing pleural malignant mesothelioma, while shorter, thicker fibers have been postulated to pose a lesser risk (Stanton hypothesis). The objective of this study is to test the validity of the Stanton hypothesis through direct pathologic analysis of human mesothelioma tissue. Digested bulk tissue samples, or ashed 25 microm thick sections, or both, were prepared from lung and mesothelial tissues taken from 168 cases of human malignant mesothelioma. In these tissues, 10,575 asbestos fibers (4820 in the lung and 5755 in mesothelial tissues (1259 in fibrotic serosa and 4496 in mesotheliomatous tissue)) were identified by high-resolution analytical electron microscopy. Dimensions of these asbestos fibers were measured in printed electron micrographs. Results were as follows: (1) long, thin asbestos fibers consistent with the Stanton hypothesis comprised only 2.3% of total fibers (247 / 10,575) in these tissues; (2) the majority (89.4%) of the fibers in the tissues examined were shorter than or equal to 5 microm in length (9454 of 10,575), and generally (92.7%) smaller than or equal to 0.25 microm in width (9808 of 10,575). (3) Among asbestos types detected in the lung and mesothelial tissues, chrysotile was the most common asbestos type to be categorized as short, thin asbestos fibers. (4) Compared with digestion technique of the bulk tissue, ashing technique of the tissue section was more effective to detect short, thin fibers. We conclude that contrary to the Stanton hypothesis, short, thin, asbestos fibers appear to contribute to the causation of human malignant mesothelioma. Such fibers were the predominant fiber type detected in lung and mesothelial tissues from human mesothelioma patients. These findings suggest that it is not prudent to take the position that short asbestos fibers convey little risk of disease.

2 comments:

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