An environmentally relevant concentration of titanium dioxide (TiO2) nanoparticles induces morphological changes in the mouthparts of Chironomus tentans.

ABSTRACT

The present study was carried out in order to assess the influence of environmentally relevant concentrations of TiO2 nanoparticles (E171 human food grade) toxicity on the freshwater midge Chironomus tentans. Tested concentrations were 125, 250, 500, 1000, 2000 and 4000 mg of E171 TiO2 per 1 kg of sediment, for the experiment aiming at life trait toxicity observation; and 2.5, 25 and 250 mg of E171 TiO2 per 1 kg of sediment for the experiment aiming at mouthpart deformity observation. The experimental design was constructed for the sediment dwelling chironomid larvae according to OECD guidelines. For the first time, a geometric morphometric approach was used to assess the deformities in chironomid larvae as sublethal implications of nanoparticle exposure. The present study showed a concentration-response relationship between the TiO2 concentration in the substrate and the TiO2 intake. The mortality and emergence ratio was affected at concentrations >1000 mg/kg. Geometric Morphometrics revealed the tendency of the mentum teeth to narrow and elongate and the mandibles to widen, as well as the loss of the first inner tooth, with a TiO2 concentration rise. The variability of morphological changes observed in the mouthparts indicates that C. tentans could be used as a bioindicator in nano-TiO2 monitoring.