What is Asbestos – Asbestos Element Definition
Asbestos is the name for a group of naturally occurring, hydrated silicate minerals with fibrous appearance. Included in this group are the mineral chrysotile, crocidolite, anthophyllite, and some of the tremolite-actinolite and cummingtonite-grunerite series. All except chrysotile fibers are known as amphibole. Most commercially mined asbestos is chrysotile. Asbestos element occurs in water exposed to natural deposits of these minerals, asbestos mining discharges, and asbestos-cement pipe.
The physical dimensions of asbestos fibers rather than the type are more important in health effects, with the shorter, thinner fibers more highly associated with cancer by inhalation. Human occupational and laboratory animal inhalation exposures are associated with the cancer, mesothelioma, found in lung, pleura, and peritoneum. An NTP study also observed gastrointestinal cancers in rats dietarily exposed to intermediate range fiber (65 percent of the fiber larger than 10 um, 14 percent larger than 100 μm) for their lifetime. Epidemiologic studies of asbestos element in drinking water have had inconsistent results, but there are suggestions of elevated risk for gastric, kidney, and pancreatic cancers (Cantor, 1997). The USEPA based its 1/1,000,000 cancer risk estimate and the MCLG and MCL on 7 × 106 fibers/L > 10 micron observed in the NTP rat study (USEPA).
