Ana Picado^a, Liliana Moita^a, Susana M. Paixão^a, Luis Silva^a,

Mário S. Diniz^b,c, Elsa Mendonça^a

^a LNEG-Laboratório Nacional de Energia e Geologia, I.P. Estrada do Paço do Lumiar 22, 1649-038 Lisboa, Portugal

^b REQUIMTE, Departamento de Química, Centro de Química Fina e Biotecnologia, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal

^c IMAR-Instituto do Mar, Departamento de Ciências e Engenharia do Ambiente, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal

The widspread use of titanium dioxide nanoparticles, e.g: self-cleaning surface coatings, solar cells, water treatment agents and topical sunscreens, increase the environmental exposure.  Research on the safety, fate, behavior and biological effects of these particles on organisms and ecosystems are needed  once ecotoxicological data are still scarce. The main purpose of this work was the evaluation of effects of TiO₂ nanoparticles (TiO₂-NP) using a battery of aquatic assays, covering different trophic levels. TiO₂-NP (Aeroxide® P25) with two phase composition of anatase (65%) and rutile (35%) were used to prepare aqueous suspensions. Routine endpoints in bacteria, alga, crustacean and fish as well as tissue histological observations in fish were studied. Results on the EC₅₀ for the tested organisms showed no acute toxicity for the bacteria Vibrio fischeri and no effect on a 21 day survival test with the fish Carassius auratus. Toxic effects were observed for the alga Pseudokirchneriella subcapitata and the crustacean Daphnia magna, being the alga the most sensitive. Fish tissue histological observations showed the presence of TiO₂-NP aggregates in the intestine lumen but their internalization by intestine cells was not confirmed. Although different responses at sublethal or lethal levels can be expected from different organisms when exposed to TiO₂-NP, it seems that NP can put aquatic ecosystems at risk.

Project funded by Fundação para a Ciência e Tecnologia, PTDC/CTM/099446/2008