USE Domestically used asbestos fibers are technically classified into seven quality categories or grades. The four commercially important forms of asbestos are chrysotile, amosite, anthophyllite, and crocidolite. Chrysotile, amosite, and particularly crocidolite all have extremely high-tensile strengths and are used extensively as reinforcers in cements, resins, and plastics. Chrysotile fibers are soft and flexible, whereas crocidolite and amosite fibers are hard and brittle. Asbestos has been used in more than 5,000 products, including roofing, thermal and electrical insulation, cement pipe and sheet, flooring, gaskets, friction materials, coatings, plastics, textiles, and paper products.
Major research is currently under way to develop and determine suitable substitutes for asbestos.
The CBI Aggregate was between 100 million and 1 billion lb. U.S. imports of asbestos have declined since 1980. The primary routes of potential human exposure to asbestos are dermal contact, inhalation, and ingestion. Asbestos is used so widely that the entire population is potentially exposed to some degree. Worker exposure is a concern in the mining and milling of asbestos, during the manufacture of all asbestos products, and in the construction and shipbuilding industries.