Friday, August 18, 2006

Asbestos, the Magic Mineral

The title of this post comes from the sign on the Johns Manville Pavilion at the 1939 World's Fair. No kidding. Asbestos has gotten a bad rap in more recent years, to the point of being banned in most consumer products, but how bad is it? Well, it depends. Asbestos is a naturally occurring mineral, and comes in two forms: serpentine, of which the only subtype is chrysotile (white asbestos), and amphibole, of which there are several subtypes. The most common subtypes are amosite (from the acronym AMOSA--Asbestos Mines of South Africa), and crocidolite. Chrysotile fibers are curly, while amphibole fibers are straight. The amphiboles are the bad actors, more likely to cause asbestosis (scarring of the lungs), lung cancer, and malignant mesothelioma, a rare cancer of the lining of the chest or abdominal cavity, seen almost exclusively in patients with asbestos exposure. Asbestos alone doesn't increase risk of lung cancer much, but the combination of cigarette smoking and asbestos exposure increases the risk about a hundred fold. Fortunately, most of the asbestos in commercial use in years past--about 95%--was chrysotile, which is less likely to have adverse health effects. The EPA doesn't distinguish between the chrysotile and more dangerous types, nor is there any such distinction in asbestos litigation. I don't mean this as an apologia for the asbestos industry. There's no question many, many people who worked in mines, mills, and shipyards have had their lives cut short by asbestos-related disease. The reaction may be a bit overdone, though. Was it necessary to give up completely on a naturally fireproof, durable material (chrysotile) in favor of synthetic substitutes? I don't know.

Well, what I really wanted to talk about is misinformation. If you Google asbestos, you'll see a lot of web sites that refer to the Greek geographer Strabo and the Roman historian Pliny the Elder (and sometimes Pliny the Younger) as the first people to recognize the adverse health effects of asbestos in the first century A.D. They are variously credited with observing that slaves working in asbestos mines or who wove cloth out of asbestos didn't live long, or that they developed breathing problems. At none of these sites have I seen credible documentation backing up these assertions. I found one well-researched paper, "History of asbestos discovery and use and asbestos-related disease in context with the occurrence of asbestos within ophiolite complexes," by Malcolm Ross and Robert P. Nolan(www.rpnolan.com/html/HistoryAsb.pdf). This article contains about everything you'd want to know about asbestos, and more. The authors knock down the idea that ancient writers understood the health effects of asbestos, and they cite a letter to Lancet in 1990, which my friendly local medical librarian retrieved for me. The authors of that letter, entitled "Asbestos and the Romans," make a succinct and convincing argument that people who say the ancient Romans knew the health effects of asbestos are talking through their hats.

Veritas!

1 comment:

Drugs-about.com said...

Edward J.

Some more info about classes and pharmacotherapy of Mesothelioma and others medical conditions of Neoplasms:
Drugs-about.com - ICD-10 - Mesothelioma

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