Although no adverse effects of nanoparticle sunscreens on humans have yet been found, there is concern that there may be undiscovered health issues for nanosized particles. The chemical industries have assumed that if large particles of a substance are safe, nanosized ones will be too, and the U.S. Food and Drug Administration (which must approve all active ingredients used in sunscreens sold the United States) bases its approval process on the identity and concentration of a chemical substance, not the size of the particle.
A growing body of evidence, however, suggests that the safety of nanoparticles can't be taken for granted just because larger particles of the same substance have been proven to be safe. Nanoparticles are useful precisely because they don't always act in the same ways as their larger counterparts. With sunscreens, the concern is that the nanoparti-cles could penetrate the protective layers of the skin and cause reactions with ultraviolet light that cause damage to DNA in cells. In 2003 the European Scientific Committee on Cosmetic and Non-Food Products (SCCNFP) concluded that titanium dioxide nanoparticles are safe for cosmetic use, but suggested the need for more tests on the safety of zinc oxide nanoparticles.
In response to this issue, many researchers are calling for full examination and safety testing of nanoparticles as if they were completely new chemicals, as well as clear identification of nanoparticles in ingredients lists of consumer products.
For more information about the NanoSense program, see www. nanosense.org
NANO ACTIVITY: SUNSCREENS AND SUNLIGHT ANIMATIONS, ADAPTED FROM SRI INTERNATIONAL'S NANOSENSE UNIT
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