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Environment and Occupational - Human Health Risk Assessment of TiO2 and ZnO Nanoparticles Found in Sunscreen

The use of nanoparticles (particles with size at most100 nm) such as titanium dioxide (TiO2) and zinc oxide (ZnO) in sunscreens is one of the most common applications of nanotechnology in consumer products. These nanoparticles act as physical blocks to provide protection from ultraviolet solar radiation, a known cause of skin cancer. TiO2 and ZnO nanoparticles are preferred in sunscreens over other chemical UV absorbers because they provide broad-spectrum protection and are better tolerated with respect to skin irritation and sensitization.

Widespread use of these nanoparticles in sunscreens has raised concerns about their potential to cause toxic effects in humans.  Concerns regarding use of nanoparticles in sunscreens stem from the studies that have demonstrated the ability of ZnO and TiO2 nanoparticles to create free radicals and cause damage to cellular DNA, particularly in the presence of UV light. However, manifestation of these effects depend on the ability of TiO2 and ZnO nanoparticles to penetrate the skin and reach dermal cells. Although no conclusions can be drawn regarding absorption of these nanoparticles from damaged skin, several studies have now shown that ZnO and TiO2 nanoparticles are not absorbed through the intact skin into the bloodstream. Taken together, the data presented in this assessment suggests that there is minimal risk to human health from use of TiO2 and ZnO nanoparticles in sunscreens. In addition, given the broad-spectrum protection imparted by TiO2 and ZnO nanoparticles against the harmful effects of UV radiations from sun such as skin cancer, the benefits may outweigh the risks.

Currently, there is no legal requirement for manufacturers to indicate the presence of nano-scale ingredients on product labels. Although there is no need to avoid using sunscreen that contains nanoparticles, consumers should still be able to choose for themselves. Therefore, mandatory labeling of nanoparticles in sunscreens is recommended. In addition, active engagement with public through channels such as social media may help to increase public awareness of the harmful effects of sunlight and provide helpful information regarding presence of nanoparticles in sunscreens

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Contributor:             Pallavi Gupta
Last reviewed:         October 31, 2016


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