![]() Simon James, research fellow at the Australian Synchotron, recently showed that immune cells collect and break down zinc oxide nanoparticles. "They don't get past the outermost dead layer of human skin cells, of which millions are shed each day." "There's a negligible penetration of sunscreen nanoparticles," says Paul Wright, toxicology expert at RMIT University. The current weight of evidence suggests that such nanoparticles do not do this. The potential for metal oxide nanoparticles in sunscreens to cause harm primarily depends upon the ability of these objects to penetrate the skin. You're more likely to slather yourself in it, better protecting your skin from sun damage. ![]() ![]() So in the fight against skin cancer, nanoparticle formulations are onto a winner. "Another advantage is that, at the nanoscale, ZnO and TiO2 feel 'lighter' on the skin," says Megan Osmond-McLeod, researcher at Australia's Commonwealth Scientific and Industrial Research Organisation ( CSIRO), "rather than heavy and cakey." And in comparison to other UV filters, they are more stable – requiring less reapplication – and are low irritant and low allergen materials. The reason traditional sunscreens look white when you rub them onto your skin is because particles of this size reflect visible light. But when these sunscreen ingredients are manufactured into nanoparticles – usually 25 to 50 nanometres wide – they behave differently.ĭespite clumping together when mixed into sunscreen, nanoparticles of titanium dioxide and zinc oxide not only retain their highly effective UV light-absorbing capacity, but also absorb and scatter visible light, rendering them transparent on the skin. Bulkier particles of zinc oxide and titanium dioxide have been used in sunscreens for decades to reflect or absorb cancer-causing ultraviolet light.
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