Nanoparticles in sunscreens

Sunscreens made with mineral active ingredients, such as zinc oxide and titanium dioxide, generally score well in EWG’s ratings, because they provide strong sun protection with few health concerns and don’t break down readily in the sun.

To create mineral-based sunscreens that are both usable and effective, manufacturers often use nano-size versions of these minerals – materials measured in nanometers, or billionths of a meter – to increase clarity and SPF. More research is needed to fully understand the extent to which nanoparticles may harm cells and organs if they’re introduced into our bodies. But many studies have produced no evidence that zinc oxide or titanium dioxide nanoparticles can cross the skin in significant amounts.

For instance, one real-world study tested the penetration of zinc oxide particles on human volunteers who applied sunscreens twice daily for five days (Gulson 2012) but found less than 0.01 percent of either form of zinc entering the bloodstream.

Other studies sponsored by the Food and Drug Administration and the European Union concluded that neither zinc oxide nor titanium dioxide nanoparticles penetrate the skin (NanoDerm 2007, Sadrieh 2010). A study by Italian researchers focused on the potential for nanoparticles to cross damaged skin and found no evidence it happens (Crosera 2015).

But it may be dangerous to inhale or ingest nanoparticles. The lungs have trouble clearing small particles, which may pass from the lungs into the bloodstream. Once swallowed, nanoparticles – from lip sunscreens, for example – can damage the gastrointestinal tract, although there are no studies to suggest consumers swallow enough zinc oxide or titanium dioxide for this to pose a concern.

The FDA is proposing additional tests for sunscreens in powder and aerosol form to ensure no nanoparticles or small particles are released that could damage the lungs (FDA 2019).

EWG strongly discourages the use of loose powder makeup or spray sunscreens containing titanium dioxide or zinc oxide of any particle size.

Regulation

The use of nanoparticles in cosmetics poses a regulatory challenge, because their properties may vary tremendously, depending on their size, shape, surface area and coatings. We don’t know everything we’d like to know about their performance, because manufacturers are not required to disclose the qualities of the particles used in their sunscreens.

Many companies sell products advertised as containing non-nano titanium dioxide and zinc oxide. These claims are misleading. Although particle size varies among manufacturers, nearly all would be considered nanomaterials under a broad definition of the term, including the one the FDA proposed in 2011 (FDA 2011b).

More research and more specific FDA guidelines are essential to reducing the risk and maximizing the sun protection of mineral sunscreens. FDA sunscreen rules allow any type of titanium dioxide or zinc oxide to be used in sunscreens (FDA 2011a). To ensure the safety and effectiveness of nanomaterials in sunscreen, the FDA should restrict forms of zinc and titanium that would provide inadequate UV protection, or that could be activated by UV rays and damage skin cells. Yet even with the existing uncertainties, we believe zinc oxide and titanium dioxide lotions are among the best sunscreen choices on the American market.

EWG’s favorable rating of nanoparticle sunscreens is not an endorsement of nanomaterials in all consumer products. EWG has urged the FDA to carefully review the safety of nano-size particles in cosmetics products and to evaluate skin and lung penetration and the potential for greater toxicity to body organs (EWG 2007, 2011). In the case of sunscreens, the potential for human exposure at the consumer level has been carefully studied, and unlike other consumer products with nanomaterials, sunscreens play an important role in UV protection.

Worker and environmental safety

EWG remains deeply concerned about the general lack of oversight of nanotechnology and associated risks to consumers, people with workplace exposures and the environment. Government regulators should exercise strong oversight to ensure that the production, use and disposal of nanomaterials does not harm workers and the environment.