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58454 
Journal Article 
The acute mammalian toxicity of rare earth nitrates and oxides 
Bruce, DW; Hietbrink, BE; DuBois, KP 
1963 
Yes 
Toxicology and Applied Pharmacology
ISSN: 0041-008X
EISSN: 1096-0333 
5 
6 
750-759 
English 
14082480 
Acute toxicity studies were conducted on the rare earth nitrates and oxides. The approximate LD50 values for the rare earth nitrates given intraperitoneally to mice ranged from 225 mg/kg to 480 mg/kg, and for rats the values ranged from 210 mg/kg to 335 mg/kg. Rats were able to tolerate 1000 mg/kg of the rare earth oxides given orally or by the intraperitoneal route. When the salts of rare earths were administered orally to rats, the LD50 values ranged from 2750 mg/kg to 4200 mg/kg. With the exception of the transition elements for which the oral LD50 values were greater than 5000 mg/kg, the compounds generally exhibited an increase in toxicity with increasing atomic weight.

Intravenous toxicity studies in rats showed that the light lanthanons are highly toxic to rats and an appreciable sex difference in susceptibility was observed. The nitrate salts of cerium, praseodymium, neodymium, and samarium were from 7 to 11 times more toxic to females than to male rats. In contrast, erbium nitrate, a member of the heavy lanthanons, did not show the marked sex difference in toxicity to rats.