Abstract
Increased industrial application of nanotechnology has potential to increase nanoparticle contaminations in aquatic ecosystems. However a large knowledge gap exists on influence of nanoparticles on fish populations inhabiting receiving waters. The present study reports the effects of exposure to aquatic suspensions of titanium dioxide nanoparticles (TiO2 NPs, anatase, particle size <25nm: 0, 1, 10 mg l-1, for 7 and 14 days) on some haematological/ innate immune responses and histological structure of gills, liver and intestine of Nile tilapia, an economically important freshwater fish in tropical regions. The results show that TiO2 NPs exposure conditions were not lethal to Nile tilapia but lead to blood parameter alterations and histopathological changes in the organs. Upon exposure of fish to both concentrations of TiO2 NPs for 14 days, erythrocyte counts, haemoglobin levels, total leucocyte counts and percent neutrophils in the peripheral blood were increased significantly (P <0.05) in comparison to the control fish. Despite increases in neutrophils, total phagocytic and myeloperoxidase activities of the blood of fish exposed to 10 mg L-1 TiO2 NPs were depressed significantly (P <0.05) whereas respiratory burst activity was not altered. Serum lysozyme activities in the fish exposed to 10 mg l-1 TiO2 NPs were elevated significantly (P <0.05) compared to the controls. Histological changes seen in the tilapia exposed to TiO2 NPs were epithelial separation, mucous cell proliferation, hyperplasia and lamellae fusion in the gills; hepatocytes with vacuolations, pycnotic nuclei, apoptosis and necrosis in the liver; eroded villi epithelium, reduction of mucous cells and degeneration of mucosa of the intestine. Although blood parameter alterations seen in Nile tilapia can be considered as physiological responses of the fish to cope up with the TiO2 NPs induced stress, observed organ pathologies could lead to serious health implications. Hence, detail studies with a range of environmentally relevant levels are warranted to investigate chronic effects of TiO2 nanoparticles on health of fish populations in the receiving water bodies. We recommend use of Nile tilapia as a tropical fish model for further studies on nanotoxicity.DOI: http://dx.doi.org/10.4038/sljas.v17i0.6852 Sri Lanka Journal of Aquatic Sciences Vol.17: 1-18
Highlights
The properties of engineered nanoparticles that make them useful in a wide range of industrial applications have led to concerns on their potential impact on human and environmental health (Scown et al 2010)
Upon exposure to the aqueous suspensions of TiO2 NPs, opercular movement rates of Nile tilapia were significantly increased in comparison to the control fish during the observation period (Fig. 1)
Available acute toxicity data of TiO2 NPs on the tested fish species indicate low acute toxicity of TiO2 NPs within the exposure period studied: the 48-h LC50 for Pimephales promelas >500 mg l-1, the 96-h LC50 for Oncorhynchus mykiss > 100 mg L-1 and no lethal effects on Danio rerio were observed below 500 mg l-1 (Menard et al 2011)
Summary
The properties of engineered nanoparticles that make them useful in a wide range of industrial applications have led to concerns on their potential impact on human and environmental health (Scown et al 2010). Titanium dioxide nanoparticles (TiO2 NPs) are one of the abundantly produced and mostly used engineered nanoparticles in industrial applications. Nano-TiO2 is photoinducible, redox active and a generator of potential reactive oxygen species (ROS) at its surfaces in the presence of UV light (Armelao et al 2007) or in the absence of UV light (Reeves et al 2008). The toxicity of nanoparticles is generally governed by properties such as particle size, shape, and surface properties (Kahru and Dubourguier 2010). The aquatic environment is at risk of exposure to these nanoparticles, as it acts as a sink for most environmental contaminants
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