Between 10 and 100 times the corresponding value or between 0.01 and 0.1 times that value, respectively, and so on. The committee also attempted to provide a sense of the quality of these judgments. Most is probably excreted rapidly, but the amount that moves into the body is not known. It is not known whether peritoneal mesothelioma results from ingested asbestos, inhaled asbestos, or both. What little epidemiological information exists does not demonstrate an increased mesothelioma risk associated with ingested asbestos.
Ingested asbestos is more likely to be excreted rapidly than is inhaled asbestos.
Crocidolite use has been on the decline and confined to well-contained applications. In the United States, its use is already less than one-tenth that of chrysotile, and its occurrence is also low with respect to chrysotile. On the other hand, many investigators believe that equal exposures to crocidolite and chrysotile will result in more cancer from the former, possibly from crocidolite's greater ability to penetrate to the lung and its greater stability once there, rather than from a fundamental difference in potency at the site. Thus, the lower risk assessment is due almost entirely to much lower likelihood of significant nonoccupational exposures. Most other forms of asbestos have been shown to cause cancers if introduced into the lung in sufficient quantity.