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EWG 2014 Sunscreens Database
 
 

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;
  • zinc oxide offers good protection from UVA rays – titanium oxide less so, but better than most other active ingredients.

Nanoparticles found in American sunscreens are either titanium dioxide or zinc oxide. Within the broad family of nanoparticles made from these two minerals the effectiveness of sun protection and the potential for health concerns varies. The properties of nanoparticles can vary greatly by size, shape and coating.

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 in the U.S. (Schlossman 2005). 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 “non-nano” titanium dioxide and zinc oxide. These claims are generally misleading. While there is variation in particle sizes among these manufacturers, nearly all of their ingredients 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 are among the best choices on the American market.

To reach this conclusion, we have attempted to answer five basic questions about their safety.

  • Do the shape and size of the particles affect sun protection? Yes. 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 the titanium dioxide products that appear clear on the skin.
  • Do the nanoparticles in sunscreen penetrate the skin? No. Some studies indicate that nanoparticles can harm living cells and organs, but the large number of research studies conducted to date have produced no evidence that zinc oxide nanoparticles can cross the skin (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 the zinc from either particle size entered the bloodstream. A follow up study applied the same two sizes of nanoparticle zinc oxide in lotions to the skin of hairless mice, which have much thinner skin than humans. It found that the zinc atoms from these lotions became distributed throughout the mice. The overall zinc concentrations in the blood and internal organs did not change. (Osmond-McLeod 2013). While neither study could determine if zinc nanoparticles penetrated the skin the weight of evidence indicates zinc ions and not particles that traveled through the skin (Osmond-McLeod 2013).

    When the FDA and the European Union studied the issue, they concluded that nanoparticles did not penetrate the skin. (NanoDerm 2007, Sadrieh 2010).
  • Could nanoparticles that penetrate the skin cause skin damage when energized by sunlight? Possibly but unlikely, since the materials don’t penetrate deep enough in skin to reach living skin cells.

    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 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.

    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 the best forms of nanoparticles in sunscreen (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. However, tests of living skin from human volunteers and animal testing suggest that these hazards are not a concern for human safety because nanominerals rarely penetrate to living cells and because free radicals that are generated are quenched by the skin’s own antioxidant protections (Popov 2009, Osmond 2010).

  • Could nanoparticles cause internal damage if they penetrated skin or were inhaled? Yes. Inhalation of nanoparticles particles is dangerous for many reasons. EWG strongly discourages the use of loose powder makeup or 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 high 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 this is happening. 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 for decades been used 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 risk. As a consumer you are not likely to find detailed information about the nanoparticles on product labels or company websites.

Nanoscale zinc was only recently approved for use in European sunscreens, except in sprays and powders (EU SCCS 2012). FDA sunscreen rules assume that any type of titanium dioxide or zinc oxide can be safely used in sunscreens (FDA 2011a). In order to ensure the safety and effectiveness of nanominerals in sunscreen, the FDA should restrict forms of zinc and titanium that provide inadequate UV protection or that could be activated by UV rays and damage skin cells.

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 cosmetic 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 on the environment have not been sufficiently assessed (Börm 2006).
The potential negative environmental effects of nano-scale 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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