Action by government agencies which have been taken pertaining to curtailment of open-air test firings of high-performance solid rocket motors utilizing beryllium (Be) powder as a fuel are summarized. More recent analytical and biological test data indicate that exhaust products from Be motors are essentially insoluble and hence present little health hazards so that safety can be assured by adherence to reasonable control standards. A critical review of existing restrictive measures is recommended in light of present toxicological information. (Author).

Results of long-term studies on rats and rabbits, injected intratracheally with well-characterized key samples of beryllium oxide prepared by calcining beryllium hydroxide for 10 hours at 500, 1100 and 1600 C, respectively, show clearly that there is a definite gradation in biological response depending upon the oxide administered. Thus, the oxide calcined at 500 C was highly active as judged by histopathological examination of the lungs, incidence of tumors, and translocation of beryllium from the lungs to other tissues. In contrast, the oxide calcined at 1600 C showed only minimal effects. Dose-response studies were carried out, using carefully prepared subsamples of 'respirable particle size' (1 to 5 microns) of the three key oxides; results showed a definite gradation in response which diminishes with decreasing dosages of the administered oxide. Investigations on motor exhaust products show that some samples have chemical, physical, and toxicological properties similar to the beryllium oxide calcined at 1600 C. On the other hand, other samples are heterogeneous, contain considerable quantities of water-soluble beryllium, and vary in toxicity. The mechanism of toxic action of beryllium oxide was investigated through study of chemical and physical properties, solubility and adsorption studies, serum electrophoretic analyses, and immunological experiments. Suggestions are made for further studies. (Author).