Abstract:
Due to widespread use of titanium dioxide nanoparticles (nano-TiO2) in many industrial
applications, significant release of nano-TiO2 to the environment can occur which may
eventually reach aquatic ecosystems. Hence biological impacts of nano-TiO2 to the aquatic
fauna especially fish under chronic exposure need to be explored. Nile tilapia, Oreochromis
niloticus is used as a bioindicator for evaluating toxic effects to environmental substances in
tropical waters. The aim of the present study was to assess the potential genotoxic effects of
water-borne nano-TiO2 on Nile tilapia under chronic exposure conditions. Fish were exposed
to a range of nano-TiO2 (<25 nm, anatase) concentrations viz 0.1 mg/L, 0.5 mg/L and 1.0 mg/L
along with the controls for 21 days and genotoxic effects were evaluated weekly by
micronucleus assay and Comet assay using peripheral erythrocytes. Even though micronuclei
induction in the erythrocytes was higher in the fish exposed to the lowest nano-TiO2
concentration (0.1 mg/L) at 7 and 21 days of exposure, a statistically significant concentrationresponse
pattern was not observed (P > 0.05). Comet assay revealed that DNA damage in
erythrocytes of Nile tilapia could be induced by nano-TiO2 even at 0.1 mg/L level (P < 0.05)
by 21 days of exposure. Compared to micronucleus assay, Comet assay was more effective in
detecting genotoxic effects on Nile tilapia. The results indicate that nano-TiO2 exposure could
lead to genotoxic hazards to the fish populations in the contaminated water bodies.
