Beryllium carcinogenesis.
Beryllium is a proven bone carcinogen in rabbits, and proven pulmonary carcinogen in rats. Median effective doses or concentrations can be computed only with considerable uncertainty; they appear to be in the 10 mg area (as total dose, in divided intravenous injections, expressed as Be for zinc beryllium silicate) for rabbits, and in the 20 alpha/m3 area (as atmospheric concentration for inhalation exposures lasting for at least three months, expressed as Be for beryllium sulfate) for rats. It is also proven that, at least from inhalation, guinea pigs do not develop beryllium cancers. Epidemiologic studies in humans are thus far unconfirmed but do not show increased cancer morbidity among beryllium workers. Current research is aimed at explaining the mechanism of carcinogenic action in the susceptible species, which seems to involve nucleic acid transcriptional interference, or the species specificity, which seems to involve immune mechanisms. No experiments were reported thus far besides the carcinogenesis studies to show that beryllium is a chemical mutagen. In the species thus far tested, there appeared to be mutual exclusion of development of a delayed (cell-mediated) hypersensitivity to beryllium and development of neoplasia from beryllium. Further research on this subject might lead to new possibilities in the understanding of cancer susceptibility.