[Hygienic regulation of yttrium, terbium, ytterbium and lutetium fluorides in the air of the workplace].

The study (experiments on animals and on culture of rats' peritoneal macrophages) covered fluorides of rare-earth metals (REM) assigned to yttrium group--yttrium, terbium, ytterbium, lutetium. Fluorides of REM have low toxicity and cumulativity, induce no local irritation of skin and eyes. Fluorides of yttrium, terbium and lutetium, if administered into stomach, result in specific intoxication (fluorosis). Fluoride of ytterbium did not cause such intoxication. According to short-term tests of cytotoxicity, the foreseeable fibrogenic danger for ytterbium fluoride is moderate, for fluorides of yttrium, terbium and lutetium is mild. The authors recommend to control the level of yttrium, terbium and lutetium fluorides in the air of workplace through the MACs for the fluorides at 2.5 mg/cu m (maximal single concentration) and 0.5 mg/cu m (average shift concentration), the level of ytterbium fluoride as moderate fibrogenic dust at 6 mg/cu m.