Impacts of Longer-Term Exposure to AuNPs on Two Soil Ecotoxicological Model Species

The production, use and disposal of nanoparticles (NPs) has been increasing continuously. Due to its unique properties, such as a high resistance to oxidation, gold NPs (AuNPs) are persistent in the environment, including the terrestrial, one of the major sinks of NPs. The present study aimed to assess the effects of AuNPs (from 10 to 1000 mg/kg) on two OECD standard ecotoxicological soil model species, Enchytraeus crypticus and Folsomia candida, based on the reproduction test (28 days) and on a longer-term exposure (56 days), and survival, reproduction, and size were assessed. AuNPs caused no significant hazard to F. candida, but for E. crypticus the lowest tested concentrations (10 and 100 mg AuNPs/kg) reduced reproduction. Further, AuNPs' toxicity increased from the 28th to the 56th day mainly to F. candida, as observed in animals' size reduction. Therefore, longer-term exposure tests are recommended as these often reveal increased hazards, not predicted when based on shorter exposures. Additionally, special attention should be given to the higher hazard of low concentrations of NPs, compared to higher concentrations.