Silica, Silicosis, and Lung Cancer: A Response to a Recent Working Group Report

• Published in: Journal of occupational and environmental medicine 2000-07, Vol.42 (7), p.704-720
• Main Authors: Hessel, Patrick A., Gamble, John F., Gee, J. Bernard L., Gibbs, Graham, Green, Francis H.Y., Morgan, W. Keith C., Mossman, Brooke T.
• Format: Article
• Language: English
• Subjects: Animals; Autopsy; Biological and medical sciences; Carcinogens - adverse effects; Causality; Chemical and industrial products toxicology. Toxic occupational diseases; cristobalite; Humans; Inorganic dusts (pneumoconiosises) and organic dusts (byssinosis etc.); Lung cancer; Lung Neoplasms - chemically induced; Lung Neoplasms - epidemiology; Medical sciences; Occupational health; ORIGINAL ARTICLES; Quartz - adverse effects; Radiography; Rats; Research Design; silica; Silicon; Silicon Dioxide - adverse effects; Silicosis - epidemiology; Silicosis - pathology; Toxicology
• ISSN: 1076-2752; 1536-5948
• DOI: 10.1097/00043764-200007000-00005

The relationship between crystalline silica and lung cancer has been the subject of many recent publications, conferences, and regulatory considerations. An influential, international body has determined that there was sufficient evidence to conclude that quartz and cristobalite are carcinogenic in humans. The present authors believe that the results of these studies are inconsistent and, when positive, only weakly positive. Other, methodologically strong, negative studies have not been considered, and several studies viewed as providing evidence supporting the carcinogenicity of silica have significant methodological weaknesses. Silica is not directly genotoxic and is a pulmonary carcinogen only in the rat, a species that seems to be inappropriate for assessing particulate carcinogenesis in humans. Data on humans demonstrate a lack of association between lung cancer and exposure to crystalline silica. Exposure-response relationships have generally not been found. Studies in which silicotic patients were not identified from compensation registries and in which enumeration was complete did not support a causal association between silicosis and lung cancer, which further argues against the carcinogenicity of crystalline silica.