Asbestos from Libby a far more toxic variety


The asbestos contaminating the vermiculite ore from the W.R. Grace & Co. mine in Libby was tremolite. Its fibers are far more toxic, and it produces 10 to 100 times more scarring, than the more widely used chrysotile asbestos. The fibers are like microscopic needles or spears, which, because of their sharpness, become imbedded in lung tissue. Over time, the fibers become infected and create scar tissue in the lungs and the pleura, which is the lining of the lungs and the chest cavity.

The pleura, when healthy, is thinner than a balloon and as flexible. As the scarring spreads, the pleural lining becomes hard, ultimately rigid as a football and about the thickness of a navel orange rind. This limits the ability of the lungs to expand and exchange oxygen. Fluid that can accumulate in the chest makes breathing increasingly difficult and can lead to suffocation.

Asbestos exposure causes three diseases: asbestosis, which is a scarring of the lining of the lung, lung cancer and mesothelioma, a rare and fast-killing cancer found in the lining of the heart, diaphragm, lungs or chest.

Dr. Alan Whitehouse was a Spokane, Wash., pulmonologist who began treating Montana miners in the early 1980s. The pattern and progress of their disease differed from what he was seeing in about 500 workers from the Hanford Nuclear facility whom he was examining for asbestos disease. In effect, Whitehouse's patients were a living laboratory permitting him to compare disease from chrysotile fiber, which had sickened the atomic workers, with tremolite, which was causing the disease in Libby.

When government physicians responded to Libby's health disaster in 1999, they were skeptical of Whitehouse's contention that not only were the miners sick and dying but so were their family members and neighbors.

It was long held that asbestos disease was contracted only during a working career of 30 to 40 years by those exposed to heavy concentrations. There were no recorded cases of second-hand exposure causing disease in families or others. But that was with chrysotile, not tremolite.

By 2002, public health experts were convinced that Whitehouse was correct in that tremolite manifested unique clinical signs.

Grace and its experts are fighting the government's contentions that new rules and diagnostic techniques are needed to analyze and handle exposure to tremolite. The company has repeatedly claimed that reports of tremolite's dangers were overstated, and that its vermiculite products, which might be contaminated with tremolite, present no danger to consumers.

Baltimore Sun Articles
Please note the green-lined linked article text has been applied commercially without any involvement from our newsroom editors, reporters or any other editorial staff.