title: Chronic ZnO-NPs exposure at environmentally relevant concentrations results in metabolic and locomotive toxicities in Caenorhabditis elegans.
abstract: ZnO nanoparticles (ZnO-NPs) are emerging contaminants that raise the concerns of potential risk in the aquatic environment. It has been estimated that the environmental ZnO-NPs concentration is 76 μg/l in the aquatic environment. Our aim was to determine the aquatic toxicity of ZnO-NPs with chronic exposure at environmentally relevant concentrations using the nematode Caenorhabditis elegans. Two simulated environmentally relevant mediums-moderately hard reconstituted water (EPA water) and simulated soil pore water (SSPW)-were used to represent surface water and pore water in sediment, respectively. The results showed that the ZnO-NPs in EPA water has a much smaller hydrodynamic diameter than that in SSPW. Although the ionic release of Zn ions increased time-dependently in both mediums, the Zn ions concentrations in EPA water increased two-fold more than that in SSPW at 48 h and 72 h. The ZnO-NPs did not induce growth defects or decrease head thrashes in C. elegans in either media. However, chronic exposure to ZnO-NPs caused a significant reduction in C. elegans body bends in EPA water even with a relatively low concentration (0.05 μg/l); similar results were not observed in SSPW. Moreover, at the same concentrations (50 and 500 μg/l), body bends in C. elegans were reduced more severely in ZnO-NPs than in ZnCl2in EPA water. The ATP levels were consistently and significantly decreased, and ROS was induced after ZnO-NPs exposure (50 and 500 μg/l) in EPA water. Our results provide evidences that chronic exposure to ZnO-NPs under environmentally relevant concentrations causes metabolic and locomotive toxicities implicating the potential ecotoxicity of ZnO-NPs at low concentrations in aquatic environments.
authors.affiliation: Department of Bioenvironmental Systems Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan.
authors.forename: Chi-Wei
authors.initials: CW
authors.lastname: Huang
authors.affiliation: Department of Bioenvironmental Systems Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan.
authors.forename: Shang-Wei
authors.initials: SW
authors.lastname: Li
authors.affiliation: Department of Bioenvironmental Systems Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan. Electronic address: vivianliao@ntu.edu.tw.
authors.forename: Vivian
authors.initials: V
authors.lastname: Hsiu-Chuan Liao
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000187:drug effects*; D053758:Nanoparticles / Q000633:toxicity*; D012987:Soil / Q000737:chemistry; D018675:Toxicity Tests; D014867:Water / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D015034:Zinc Oxide / Q000633:toxicity*
chemical_list: D012987:Soil; D014874:Water Pollutants, Chemical; D014867:Water; D015034:Zinc Oxide
keywords: Caenorhabditis elegan; Chronic exposure; Emerging contaminants; Environmentally relevant concentrations; Locomotive toxicity; Metabolic toxicity; ZnO-NPs