Disruption of zebrafish (Danio rerio) reproduction upon chronic exposure to TiO2 nanoparticles

As common engineered nanomaterials, TiO2 nanoparticles (nTiO2) are usually perceived as non-toxic, and have already been widely used in many products and applications. Such a perception might have been shaped by some short-term studies that revealed no/low toxicity of nTiO2 to cells and eco-relevant organisms. However, given the ultimate release of nTiO2 into the aquatic environment, which can act as a sink for engineered nanoparticles, their long-term impact on the environment and human health is still a concern and deserves more research efforts. Here, for the first time, we demonstrate that chronic exposure of zebrafish to 0.1 mg L−1 nTiO2, can significantly impair zebrafish reproduction. For instance, there was a 29.5% reduction in the cumulative number of zebrafish eggs after 13 weeks of nTiO2 exposure. Thus, we provided timely information on indicating a serious risk of reproductive impairment of environments contaminated with low levels of nTiO2 on aquatic organisms, leading to alterations in population dynamics and aquatic ecosystem balance, and thus warrants a careful scrutiny on toxicity assessment of nTiO2, especially their long-term impact.

Research highlights
► Long-term exposure to low concentrations of TiO2 is toxic to zebrafish.
► TiO2 may act on primary follicles directly and/or subsequently interfere with vitellogenin synthesis.
► Reproductive impairment may lead to alterations in population dynamics.
► A careful scrutiny on the long-term impact of NPs is needed.