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Nanoparticles in Sunscreens

Sunscreens made with zinc oxide and titanium dioxide generally score well in EWG’s ratings because:

  • They provide strong sun protection with few health concerns;
  • They don’t break down in the sun; and
  • Zinc oxide offers good protection from UVA rays. Titanium oxide’s protection isn’t as strong, but it’s better than most other active ingredients.

Nanoparticles in American sunscreens are either titanium dioxide or zinc oxide.

Zinc oxide is EWG’s first choice for sun protection. It is stable in sunlight and can provide greater protection from UVA rays than titanium oxide or any other sunscreen chemical approved for use in the U.S.. Years ago, zinc oxide sunscreens, often seen on lifeguards’ noses, were famously white and chalky. Today, sunscreen makers use zinc oxide nanoparticles to formulate lotions with less white tint.

A number of companies sell products advertised as containing “non-nano” titanium dioxide and zinc oxide. These claims are generally misleading. While particle sizes vary among manufacturers, nearly all would be considered nanomaterials under a broad definition of the term, including the definition proposed in 2011 by the federal Food and Drug Administration (FDA 2011b). For example, Antaria, a popular supplier of zinc oxide, initially claimed it was selling a “non-nano” form to sunscreen makers. But under pressure from Friends of the Earth Australia, it acknowledged that its zinc oxide would be considered a nanomaterial requiring special labeling in Europe (Antaria 2012, Friends of the Earth 2012). There is even less dispute about titanium dioxide. According to the available information, it must be delivered in nanoparticle form to render a sunscreen reasonably transparent on the skin.

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

More research and more specific FDA guidelines are essential to reduce the risk and maximize the sun protection of mineral sunscreens. Yet, even with the existing uncertainties, we believe that zinc oxide and titanium dioxide lotions are among the best choices on the American market.

Here’s why:

  • The shape and size of the particles affect sun protection. The smaller they are, the better the SPF protection and the worse the UVA protection. Manufacturers must strike a balance: small particles provide greater transparency but larger particles offer greater UVA protection. The form of zinc oxide most often used in sunscreens is larger and provides greater UVA protection than titanium dioxide products that appear clear on skin.
  • Nanoparticles in sunscreen don’t penetrate the skin. Some studies indicate that nanoparticles can harm living cells and organs when administered in large doses. But a large number of studies have produced no evidence that zinc oxide nanoparticles can cross the skin in significant amounts (SCCS 2012). A real-world study tested penetration of zinc oxide particles of 19 and 110 nanometers on human volunteers who applied sunscreens twice daily for five days (Gulson 2010). Researchers found that less than 0.01 percent of either form of zinc entered the bloodstream. The study could not determine if the zinc in the bloodstream was insoluble nanoparticles, therefore the European regulators concluded it was most likely zinc ions, which would not pose any health risk (SCCS 2012). Other FDA- and European Union-sponsored studies concluded that nanoparticles did not penetrate the skin (NanoDerm 2007, Sadrieh 2010).
  • It is unlikely that nanoparticles in sunscreen cause skin damage when energized by sunlight. Titanium dioxide, and to a lesser extent zinc oxide, are photocatalysts, meaning that when they are exposed to UV radiation they can form free radicals that damage surrounding cells. Nanoparticle sizes of these minerals are more affected by UV rays than larger particles.

    Sunscreen manufacturers commonly employ surface coatings that can dramatically reduce the potential for photoactivity, with data suggesting that they reduce UV reactivity by as much as 99 percent (SCCNFP 2000, Pan 2009). In sunscreens, problems may arise if particles are not treated with inert coatings, if the coatings are not stable, or if manufacturers use forms of zinc oxide or titanium dioxide that are not optimized for stability and sun protection. However, tests of living skin from human volunteers and animal testing suggest that these hazards are not a concern for human safety because the free radicals that are generated by nanoparticles on skin are quenched by the skin’s own antioxidant protections (Popov 2009, Osmond 2010).

    Information from suppliers suggests that U.S. sunscreen formulators generally employ the appropriate forms of zinc oxide and titanium dioxide in their products. Recent studies from other countries indicate that manufacturers do not always use sunscreen-grade minerals (Barker 2008, Friends of the Earth 2012). Since manufacturers are not required to make this information public, the extent of these problems is difficult to gauge. The European Union reviewed 15 types of coated titanium dioxide in sunscreen and concluded manufacturers could use any of these forms in their products (SCCS 2013b). They specified that other types will also be allowed as long as manufacturers can provide data demonstrating their safety. For zinc oxide sunscreens, both coated and uncoated particles are allowed (SCCS 2014).
  • Nanoparticles could cause lung damage when inhaled. Inhalation of nanoparticles is dangerous for many reasons. EWG strongly discourages the use of loose powder makeup or spray sunscreens using titanium dioxide or zinc oxide of any particle size.

    The International Agency for Research on Carcinogens has classified titanium dioxide as a possible carcinogen when inhaled in large doses (IARC 2006b). The lungs have difficulty clearing small particles, and the particles may pass from the lungs into the bloodstream. Insoluble nanoparticles that penetrate skin or lung tissue can cause extensive organ damage.

    Nanoparticles in lip sunscreens can be swallowed and might damage the gastrointestinal tract, although there are no studies to suggest that consumers swallow enough zinc oxide or titanium dioxide to pose a concern. The risks are less if digestion alters the properties of the particles reaching the intestines. There are lots of uncertainties about the degree of risk. We know that titanium dioxide has been used for decades as a colorant in commonly eaten foods, including doughnuts and M&Ms, and a recent study found that these particles would be classified as nanoparticles (Weir 2012).
  • Do current federal sunscreen regulations ensure the safety and effectiveness of sunscreen minerals? No. The U.S. government has not enacted regulations, guidelines or recommendations on particle characteristics that would maximize sun protection and minimize health risks. As a consumer you are not likely to find detailed information about nanoparticles on product labels or from companies that make these products.

Nanoscale zinc was only recently approved for use in European sunscreens, except in sprays and powders (EU SCCS 2012). In early 2018, the European safety agency confirmed that there was not enough information on nano titanium to allow it to be used in sunscreen sprays (EU SCCS 2018).

EWG maintains ongoing vigilance in its assessment of sunscreen safety. At present, all available evidence suggests that zinc oxide and titanium dioxide can be safely used in sunscreen lotions applied to healthy skin. The weight of evidence indicates that both zinc oxide and titanium dioxide pose a lower hazard than most other sunscreen ingredients approved for the U.S. market.

EWG’s favorable rating of nanoparticle sunscreens is not an endorsement of nanomaterials in commerce. EWG has urged the FDA to review carefully the safety of nanosize particles used 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. Unlike other consumer products with nanomaterials, sunscreens play an important role in cancer prevention.

Worker 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 do not harm workers and the environment. More than 50,000 tons of nanoparticle titanium dioxide were produced in 2010 (Future Markets 2011), yet few rules govern the use of protective equipment and other controls to limit inhalation or ingestion during product formulation. A more thorough and complete assessment of worker risk and environmental outcomes is urgently needed.

Environmental safety

When zinc oxide and titanium dioxide nanoparticles wash off skin, they enter the environment, with unknown effects. The implications of nanoparticle pollution for the environment have not been sufficiently assessed (Börm 2006).

The potential negative environmental effects of nanoscale and conventional zinc and titanium should be carefully studied and weighed against the environmental impact of other UV blockers. Sunscreen ingredients have been shown to damage coral, accumulate in fish and the environment, and disrupt hormones in fish and amphibians (Buser 2006, Danovaro 2008, Giokas 2007, Kunz 2004, Kunz 2006, Weisbrod 2007).

For all sunscreens, including nanoscale zinc and titanium, there is an urgent need to carry out thorough environmental assessments so that regulators have the data they need to begin to control hazards associated with widespread use of these and other chemical ingredients in personal care products.


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About the ratings

EWG provides information on sunscreen products from the published scientific literature, to supplement incomplete data available from companies and the government. The ratings indicate both efficacy and the relative level of concern posed by exposure to the ingredients in this product - not the product itself - compared to other sunscreens. The ratings reflect potential health hazards but do not account for the level of exposure or individual susceptibility, factors which determine actual health risks, if any. Methodology | Privacy Policy | Terms & Conditions

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