Subchronic toxicity study of yttrium nitrate by 90-day repeated oral exposure in rats
Concerns regarding the adverse effects of long-term exposure to low levels of rare earth elements (REEs) from foods on human health have arisen in recent years. Nevertheless, no official acceptable daily intake (ADI) has yet been proposed for either total REEs or individual REE. In accordance with the Organization for Economic Co-operation and Development (OECD) testing guideline, the present study was undertaken to evaluate the subchronic toxicity of yttrium, a representative heavy REE with higher contaminated level in foods in China, to achieve a no observed adverse effect level (NOAEL) which is a critical basis for the establishment of an ADI. Yttrium nitrate was orally administered to rats at doses of 0, 10, 30 and 90 mg/kg/day for 90 days followed by a recovery period of 4 weeks. The following toxicity indices were measured: mortality, clinical signs, daily food consumption and weekly body weight; urinalysis, hematology, blood coagulation, clinical biochemistry and histopathology at the end of administration and recovery periods. No toxicologically significant changes were found in any yttrium-treated group as compared to the concurrent control group. Under the present experimental condition, the NOAEL in rats was thus set at 90 mg/kg for yttrium nitrate, i.e. 29.1 mg/kg for yttrium.