The use of sunscreen to protect our skin against the damaging action of intense solar irradiation has become part of daily life particularly in the tropics. An increasingly controversial discussion, however, arises from modern sunscreen formulation's possible health risk. Widely used organic ultraviolet (UV) filters were reported to diffuse through intact human skin. Water streams containing elevated levels of these compounds affect the gender ratio of fish, snails and micro-organism in contaminated rivers, lakes and even seaside water. These health concerns have provoked development and application of inorganic UV filters to partially replace or minimize the use of organic filters with potential oestrogenic activity.

The rapidly increasing use of such nanoparticulate titania or zinc oxide pigments has initiated a debate about a possible penetration of these tiny particles through the human skin. The large production volumes of cosmetics directly entail the question whether the release of persistent inorganic nanoparticles into the environment may be harmful for our ecosystem. While both human health concerns and ecotoxicological investigations are under way, requiring several years to completion, the only timely alternative to a wait-and-see attitude is a proactive search for alternative sunscreen pigments circumventing above risks.

Here we show the one-step production of a new class of bio-degradable inorganic pigment nanoparticles with an UV radiation absorbance potential comparable to currently used titania. Our results suggest the substitution of currently used persistent inorganic UV filters in modern sunscreen formulations through such biodegradable compounds thus avoiding potential harm to both the environment and the human organism.

References

[1] T.J. Brunner, R.N. Grass, W.J. Stark, Chem. Commun., 13, 1384-6 (2006).

[2] S. Loher, W.J. Stark, M. Maciejewski, A. Baiker, S.E. Pratsinis, D. Reichardt, F. Maspero, D. Günther, Chem. Mater. 17 (1), 36-42 (2005).

[3] S. C. Halim, L. K. Limbach, T. J. Brunner, S. Loher, E. K. Athanassiou, R. N. Grass, N. Osterwalder, N. A. Luechinger, F. Koehler & W. J. Stark, in review (2008).