Release of TiO2 Nanoparticles from Sunscreens into Surface Waters: A One-Year Survey at the Old Danube Recreational Lake

Monitoring data are necessary for the future production of engineered nanomaterials and the development of regulations for nanomaterials. Therefore, it is necessary to develop methods that reliably detect and quantify nanomaterials in real-world systems at expectedly low concentrations. In this work we tested several methodological approaches to detect titanium dioxide nanomaterials released from sunscreen products into the Old Danube Lake (Vienna, Austria), which is heavily used for recreational activities like bathing and water sports during the summer season. During a 12-month period suspended particulate matter (SPM) was collected from the lake and analyzed using a combination of complementary techniques. By sampling at a location approximately 50 m from the nearest bathing area and at one meter depth from the water surface, we focused on the potentially mobile fraction of the released nanoparticles. We were able to identify titanium dioxide nanoparticles stemming from sunscreens in the suspended matter of the lake using electron microscopy. Bulk analysis of SPM clearly shows an increase of Ti-containing particles during the summer season. These analyses, however, are not able to distinguish sunscreen nanoparticles from natural Ti-bearing nanoparticles. Therefore, Elemental ratios of Ti with Al, V, Ga, Y, Nb, Eu, Ho, Er, Tm, Yb, and Ta as determined by ICPMS and ICPOES, in combination with single particle ICPMS analysis were applied to establish local background values. The observed mild increase of Ti elemental ratios, compared to spring background values indicates that the residence time of released nanomaterials in the water column is rather short. Overall, the advantages and disadvantages of the methods used to detect and characterize the nanomaterials are discussed.