Sunscreens have long contained bulk particles of zinc and titanium oxides as their active ingredients to absorb or reflect damaging ultraviolet light. In contrast to chemical absorbers, such as octyl methoxycinnamate, the oxides work over most of the ultraviolet band. These oxides appear white on the skin, but at a nanoscale they are clear.
There are concerns that these nanoparticles could be harmful. In vitro tests have demonstrated that they can penetrate human cells. However there are gaps in the knowledge. We don’t know for example, if these nanoparticles are absorbed through the skin.
Maxine and her colleague Prof. Brian Gulson of Macquarie University, Sydney, are carrying out the first study of human volunteers under real-life conditions—a five-day study to see whether zinc from sunscreens applied to the skin shows up in the subjects’ blood or urine.
In a three-year experiment, Maxine and her team will test three commercially available sunscreens on hairless mice, doing pathology and molecular tests on internal organs. “That experiment represents a worst case scenario because mouse skin is more penetrable than human skin,” Maxine says.
The experiments are investigating whether the nanoparticles have long-term harmful effects and what could be done to reduce these effects.
Contributed by the National Enabling Technologies Program of the Department of Innovation.
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