Beryllium Metal Solubility in the Lung, Comparison of Metal and Hot-pressed Forms by in vivo and in vitro Dissolution Bioassays

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Abstract
The solubility of two industrial forms of beryllium, i.e. particles of metal powder and particles of hot-pressed beryllium, was investigated using in vivo and in vitro models. In the in vivo model, baboons and rats were used and were injected via the trachea with amounts of beryllium equivalent to 100, 500 and 1000 fold the maximum permissible concentration (MPC) recommended by the US Occupational Safety and Health Administration. In vivo experiments showed that in both species the daily beryllium solubility rates were about 5 x 10-6 for metal particles and that in rats the daily beryllium solubility rate was about 5 x 10-5 for the hot-pressed particles. During the 10 months of the experiment with baboons, urinary excretion of beryllium was proportional to the amount administered. With regard to results for the in vitro models, the outcome of the acellular dissolution test using a serum simulant was not consistent with the in vivo results, though a cellular model using cultured macrophages showed the same trends in the dissolution rates for the two forms of beryllium as those observed in vivo. This result suggests that a cellular rather than an acellular dissolution model would be better at predicting solubility of beryllium compounds in the lungs.