Asbestos: Still a Carcinogen

Asbestos is an important cause of human illness. Clinical and epidemiologic studies have established incontrovertibly that asbestos causes cancer of the lung, malignant mesothelioma of the pleura and peritoneum, cancer of the larynx, and certain gastrointestinal cancers. Asbestos also causes asbestosis, a progressive fibrotic disease of the lungs. The risk of these diseases increases with cumulative exposure and also with the length of time since the first exposure

Asbestos is a generic term applied to a group of minerals, all of them fibrous. There are four commercially important forms: chrysotile, crocidolite, amosite, and anthophyllite. Chrysotile is the most important. It accounts for more than 95 percent of current world production. Nearly all asbestos used in North America has been chrysotile from the province of Quebec, Canada

All forms of asbestos are carcinogenic. All have been shown in clinical, epidemiologic, and laboratory studies to be fully capable of causing lung cancer, mesothelioma, and the full range of asbestos-related diseases. Although crocidolite appears to be two to four times more potent than chrysotile or amosite in its capacity to induce mesothelioma, all forms appear to be equally potent in their capacity to cause cancer of the lung.

New use of asbestos has almost completely ended in the United States and in most other developed nations as the result of government bans and market pressures. Those forces were stimulated by the landmark epidemiologic studies of Selikoff and colleagues6 and by the release of information on the carcinogenicity of asbestos that had previously been suppressed by the industry.7 By contrast, extensive and aggressive marketing of asbestos by Canada and other exporting nations continues in the developing world, where sales remain strong.