Asbestos – a generic name for six different silicates commonly used in industrial and building trades – has long been known for its resistance to heat, fire, electrical current, moisture and corrosive chemicals. For this reason, it was commonly found in and around chemical plants in insulation, on work surfaces and even in workers’ own protective clothing.
One type of asbestos particularly known for its acid resistance was amosite, more commonly known as “brown asbestos.” The brown color was due to the presence of iron; most was imported from South Africa. Because of its non-corrosive properties, amosite was quite useful in chemical plants.
Most of the asbestos used in the U.S. was of the “white” variety, or chrysotile. Perhaps as much as 300 million tons of chrysotile has been used in construction and industrial applications in the U.S. since the 1930s.
The main difference between amosite and chrysolite lies in their respective shapes; while chrysotile fibers are softer and have a curly shape (like a microscopic metal spring), amosite fibers are amphiboles – long, hard and needle-like. Although amosite and other amphibole asbestos have been banned for most uses, they are still present in many buildings. Additionally, the chrysolite type of asbestos is still legal in the U.S., and in the past has often been contaminated with the amphibole tremolite. At present, there is a bill pending in the U.S. senate to ban most uses of asbestos, and phase out others over a period of 2 – 4 years. This bill, S.742 is expected to pass when it comes to the senate floor in the fall of 2007.
A Glaring Record
DuPont, one of the largest chemical companies in the world, was fined $70,000 in 1999 for failing to record 117 occupational injuries and illnesses among its employees over the previous two years. The company’s own records show that management was concerned about asbestos liability as far back as 1966; in 1980, the company went so far as to submit a written request to a physician who had performed physical examinations for company employees that he remove the word asbestos from the rubber stamp used to apply identifying markings to x-rays.
Studies as far back as 1979 have shown that chemical plant workers suffer from abnormally high rates of asbestos-related diseases such as asbestosis or the deadly asbestos cancer mesothelioma. Studying several sizable groups of chemical plant workers, the researchers found “chest x-ray abnormalities (small irregular opacities and/or pleural changes) of the type known to be induced by asbestos”. Symptoms of asbestosisand indicators of pre-cancerous conditions were discovered in nearly 60% of the 185 workers studied. It was noted that “prevalence [of symptoms] was significantly higher in those employed 20 or more years”.
The common chrysolite asbestos was touted by representatives of Union Carbide (a subsidiary of Dow Chemical) as “safe” because of its curly structure and relative softness. However, researchers at the Mount Sinai School of Medicine found little difference in the effects of chrysotile and amphiboles; in addition, a study in the Oxford Journal of Medicine showed that chemical plant workers suffering from mesothelioma were in fact exposed to chrysotile that was contaminated with significant amounts of tremolite, a type of amphibole.