Part 2 of 2
Conservative U.K. journalist Christopher Booker, writing in a recent issue of The Telegraph, stated that "white asbestos," or chrysotile, is a virtually harmless substance – and not at all implicated in mesothelioma or other forms of asbestos-related cancer. He quotes studies commissioned by that country's own Health and Safety Executive to prove his point – specifically, the Meldrum study of 1996, which stated that "very few cases of mesothelioma can be reliably ascribed to chrysotile," and the Hodgson and Darnton study published in 2000.
Chrysotile may be less harmful than amphibole asbestos – but both the historical record and the medical evidence show that it is far from "harmless."
It is true that chrysotile asbestos fibers, which are relatively soft and curly, act differently than hard, spear-like amphibole fibers once they enter the lungs and other organs. Whereas amphiboles impale themselves into lung tissue, chrysotile fibers act more like abrasive steel wool, irritating and scratching up the inner surfaces of the air sacs, or alveoli. Over time, scar tissue builds up, reducing the victim's lung capacity. This non-malignant condition is known as asbestosis. The good news is that once the patient is removed from the asbestos environment, the progression of the disease stops.
The bad news is that once the damage is done, it is irreversible. Contrary to Mr. Booker's claim in his 12 March piece in The Telegraph, chrysotile does not simply "dissolve." But does it cause cancer like amphibole asbestos?
The fact is that medical researchers are not in absolute agreement on this subject. Writing in the journal Environmental Health Perspectives in 2010, then-assistant Surgeon General Richard Lemen quoted a 2009 study by team of French oncologists in which "...epidemiological evidence has increasingly shown an association of all forms of asbestos (chrysotile, crocidolite, amosite, tremolite, actinolite, and anthophyllite) with an increased risk of lung cancer and mesothelioma."
It is worth noting the above mention of tremolite as well as the latter two asbestiform minerals listed (actinolite and anthophyllite). Crocidolite and amosite are the technical names of blue and brown asbestos respectively, and accounted for about 5-10% of all commercial asbestos used worldwide. Tremolite was never mined nor exploited for commercial purposes. However, tremolite is a form of "hard" amphibole asbestos. It was a common contaminant of the chrysotile that came out of the W.R. Grace Mines in Libby, Montana as well as another non-asbestos product of that operation, a building insulation material known as vermiculite.
This said, it is also worth noting that in the 1980s, a number of mesothelioma patients were found to have only chrysotile fibers in their lungs. The conclusion here is that while mesothelioma cancer due to chrysotile exposure alone is rare, it indeed happens. More often, it may be due to tremolite contamination.
In either case, Mr. Booker and other naysayers would do well to dig a little deeper before dismissing chrysotile as "harmless."
Booker, Christopher. "Billions to be Spent on Nonexistent Risk." The [UK] Telegraph, 13 Jan 2003.
Bowker, Michael. Deadly Deception (New York: Touchstone, 2003)
Churg, A. et. al. "Lung Asbestos Content in Chrysotile Workers With Mesothelioma." American Review of Respiratory Disease, vol. 130 no. 6 (Dec. 1984).
Hodgson, J.T. and A. Darnton. "The Quantitative Risks of Mesothelioma and Lung Cancer in Relation to Asbestos Exposure." Annals of Occupational Hygiene, vol. 44 no. 8 (Dec. 2000).
Meldrum, M. "Review of Fibre Toxicology." Health and Safety Executive Chrysotile Institute (U.K.), 1996.
Straif, K, et. al. "A Review of Human Carcinogens, Part C – Metals, Arsenic, Dusts and Fibres." The Lancet Oncology, vol. 10 no. 5. Quoted in "Chrysotile Asbestos and Mesothelioma" by Richard Lemen (Environmental Health Perspectives, July 2010).