Say No to Nanoparticles in Sunscreen
Safety Profile of Nanoparticles
Mineral sunscreens are capturing an increasing segment of the sunscreen market due to their many advantages over chemical sunscreens. The one drawback to using them has been the white cast the sunscreen leaves on the skin, so it is no surprise that consumer demand for more appealing products led to advances in controlling particle size, shape and distribution.
Thanks to nanotechnology, companies are now able to offer products that the public doesn’t mind wearing. On the downside, nanoparticles in sunscreen has given rise to a host of questions vis a vis safety issues
. This because we know so little about the behavior of nano-sized versions of materials like zinc oxide and titanium dioxide that have been used for years in bulk form.
Penetration of Nanoparticles
For some time now, companies have argued that this concern is overstated, since tests show that nanoparticles are not absorbed past the epidermis. However, an elegantly designed test
by Dr. Brian Gulson et al from Macquarie University demonstrated that tracer zinc showed up in blood and urine samples taken from test subjects, indicating that zinc oxide oxide nanoparticles were indeed being absorbed.
This begs the question of whether nanoparticles of titanium dioxide are also absorbed past the epidermis
(as one would infer from the Gulson study), and, if they are, what the biological pathways and endpoints of such particles might be.
A recent study
from the Institute of Clinical Pharmacology, Department of Pharmacology, Huazhong University of Science and Technology, Wuhan, China, found in their tests on hairless mice that TiO2 particles did penetrate past the epidermis, reached different tissues and caused pathologic changes to organs, most notably the skin and the liver.
Studies such as these (besides sounding the rather urgent call for more studies) indicate the clear superiority of zinc oxide, even in smaller sizes
, in terms of overall safety. Zinc oxide applications, even when absorbed, result in relatively harmless biological pathways and endpoints.
To quote Dr. Gulson:
“Maybe with young children where you’re applying it seven days a week, it could be an issue but I’m more than happy to continue applying [20% zinc oxide sunscreen] to my grandchildren.”
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