Asbestos is a mineral rock with a chemical composition of mostly silicon, water, and magnesium. Most asbestos fibers are long, thin, strong, flexible, fireproof, and resistant to chemical attack. Of the six varieties of asbestos fibers found in nature, only three are commonly found in construction materials: chrysotile, amosite, and crocidolite. Chrysotile, the variety most often found in building materials, absorbs water readily, which allows for easier removal. Chrysotile was commonly used as a binding and strengthening agent in plastics, cement, and insulation. Extremely long chrysotile fibers were woven into fire- and heat-resistant cloth.

Asbestos is a carcinogen, and medical reports indicate a single fiber can cause lung cancer. There is little health risk if the material is fully intact and is properly maintained; but it can quickly turn dangerous if any of the fibers become friable and airborne, and are inhaled.

Asbestos has been used in a...