Abstract
There is little information on environmental hazard of nanomaterials due to its unique physicochemical properties and biological interactions. In the present study, acute toxicity tests for fullerene C60 using aquatic organisms were conducted to investigate the effects of the substance on the aquatic ecosystem. An aqueous suspension of fullerene C60 (500 mg/L) which included nano-sized particles was prepared by grinding with sugar candy and polyoxyethylene hydrogenated castor oil for the tests. A 96-h acute toxicity test with medaka (Oryzias latipes), a 48-h acute immobilization test with Daphnia magna and a 72-h algae growth inhibition test with Pseudokirchneriella subcapitata were conducted using this aqueous suspension of fullerene C60 according to the existing OECD test guidelines . As a result, the 96-h LC50 (median lethal concentration) for medaka, the 48-h EC50 (median effective concentration) for D. magna and 72-h EC50 for algae based on the growth rate (0-72 h) were estimated to be larger than 2.15, 2.25 and 2.27 mg/L, respectively. However, in the algae test, the growth rate (0-72 h) was significantly inhibited in the groups exposed to 0.0551-mg/L and higher concentrations of fullerene C60. This result indicated that the 72-h NOEC (no observed effect concentration) based on the growth rate (0-72 h) was estimated to be 0.0178 mg/L.
