[Biological activity of Bulgarian zeolite rocks].

An evaluation of the biological activity of Bulgarian zeolite rocks was made by the methods in vivo and in vitro. The results pointed out to specific biological effect--cytotoxic and fibrogenic--most strongly expressed for clinoptilolite followed by mordenite and erionite. The clinoptilolite is characterized by strong cytotoxic effect in comparison with dust of calibrated quartz DQ-12 which confirms the lack of correlation between cytotoxicity and fibrogenicity for some types of dust. On the basis of the results a temporary hygienic norm for clinoptilolite dust--2 mg/m3 is proposed.