As is generally known, all sunscreens—chemical or mineral, nano or non-nano—are regulated by the U.S. Food and Drug Administration (FDA) and other national regulatory bodies, and have been found to be safe. Chemical sunscreens have been used by the public for more than 65 years, and mineral sunscreens for more than 20 years. However, there is a growing public hysteria about the possible risks nano-sized particles in sunscreens pose.
This fear has been promoted mainly by NGOs such as Friends of the Earth (FOE) and its allies, even in the face of overwhelming evidence from independent panels of experts that nanoparticulate titanium dioxide and zinc oxide are safe sunscreen actives. Nanoparticles and nanomaterials are ubiquitous. They are present in the atmosphere, and have presumably been there for hundreds of millions of years. Animals, including humans, have evolved in their presence.
To gain some perspective, consider the extent to which individuals are exposed to nanoparticles every day. Inhalation is, by far, the most significant route by which nanoparticles reach internal organs. According to a report by the Royal Society and Royal Academy of Engineering, there are estimated to be between 106 and 108 nanoparticles per liter of air, and the average person inhales between 500,000 and 50 million nanoparticles with each breath—i.e., about 6 million to 300 million nanoparticles per minute.
Also, nanoparticles are major components of clays and soils. Milk contains nanoparticles, and ricotta cheese consists of suspensions of nanoparticles. These are present in the body as protein molecules and enzymes; indeed, humans cannot live without them.
Nanoparticles of carbon were first manufactured nearly 100 years ago, The fact that sunscreen ingredients are nano-sized should not frighten anyone—after all, it could be said that humans are made up of a collection of nanoparticles known as proteins. Interestingly, the FOE campaign focuses exclusively on sunscreens and cosmetics using zinc oxide and titanium dioxide nanoparticles while ignoring sunscreens containing molecular UV absorbers, which themselves have dimensions that qualify as nanoparticles. In fact, it is arguable that all active ingredients used to absorb UV radiation in sunscreens are actually nanomaterials and should be classified as such.
This paper reviews important issues regarding classifications for UV actives. It also emphasizes the need for a uniform classification and labeling system to cover all nano ingredients. The definition of nanoparticles is not questioned here; however, the selective manner by which regulatory agencies apply the definition to different materials is.