Toxicity of different zinc oxide nanomaterials at three trophic levels: implications for development of low-toxicity antifouling agents.

Since zinc oxide (ZnO) nanomaterials are used in antifouling and antibacterial solutions, understanding their toxic effects on different aquatic organisms is essential. In the present study, we evaluated the toxicity of ZnO nanoparticles of 10-30 nm (ZnO NPI) and 80-200 nm (ZnO NP II), ZnO nanorods (width of 80 nm, height of 1.7 microm) attached to the support substrate (glass, ZnO NRG) and not attached (ZnO NRS), as well as zinc ions at the concentrations ranging from 0.5 mg/L to 100 mg/L. Toxicity was evaluated using the microalga Dunaliella salina, the brine shrimp Artemia salina and a marine bacterium Bacillus cereus. The highest toxicity was observed for ZnO nanoparticles (LC50 ~ 15 mg/L) and zinc ions (LC50 ~ 13 mg/L), while the lowest toxicity found for ZnO nanorods (NRG LC50 ~ 60 mg/L; ZnO NRS LC50 ~ 42 mg/L). The presence of the support substrate in case of ZnO nanorods reduced the associated toxicity to aquatic organisms. Smaller ZnO nanoparticles resulted in the highest Zn(2+) ion dissolution among tested nanostructures. Different aquatic organisms responded differently to ZnO nanomaterials, with D. salina and B. cereus being more sensitive than A. salina. Toxicity of nanostructures increased with an increase of the dose and the time of exposure. Supported ZnO nanorods can be used as a low toxicity alternative for future antimicrobial and antifouling applications. This article is protected by copyright. All rights reserved.