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Nanotechnology - Summary

When we began our sunscreen investigation at the Environmental Working Group, our researchers thought we would ultimately recommend against micronized and nano-sized zinc and titanium dioxide. After all, no one has taken a more expansive and critical look than EWG at the use of nanoparticles in cosmetics and sunscreens, including the lack of definitive safety data and consumer information on these common ingredients, and few substances more dramatically highlight gaps in our system of public health protections than the raw materials used in the bizarre and burgeoning field of nanotechnology. But 18 months, 800 products, and nearly 400 peer-reviewed studies later, we find ourselves drawing a different conclusion, and recommending some sunscreens that contain nano-sized ingredients.

Consumer Reports 2007 testing of eight sunscreens showed that consumers can be protected from UV radiation using products free of nano-scale ingredients like zinc and titanium. We expected to find this as well, but we took our study two steps further than Consumer Reports to be certain. We looked not only at whether or not products provide broad-spectrum UV protection, but also at which sunscreens break down in the sun, and at the full range of potentially hazardous sunscreen ingredients that can absorb through the skin and into the body to pose other risks. Our answers changed.

Our study shows that consumers who use sunscreens without zinc and titanium are likely exposed to more UV radiation and greater numbers of hazardous ingredients than consumers relying on zinc and titanium products for sun protection. We found that consumers using sunscreens without zinc and titanium would be exposed to an average of 20% more UVA radiation — with increased risks for UVA-induced skin damage, premature aging, wrinkling, and UV-induced immune system damage — than consumers using zinc — and titanium-based products. They contain four times as many high hazard ingredients known or strongly suspected to cause cancer or birth defects, to disrupt human reproduction or damage the growing brain of a child. They also contain more toxins on average in every major category of health harm considered: cancer (10% more), birth defects and reproductive harm (40% more), neurotoxins (20% more), endocrine system disruptors (70% more), and chemicals that can damage the immune system (70% more).

We also reviewed 15 peer-reviewed studies on skin absorption, nearly all showing no absorption of small-scale zinc and titanium sunscreen ingredients through healthy skin. We found that studies investigating absorption through damaged skin are not available, but that is also the case for nearly all of the 17 sunscreen chemicals approved for use in the U.S. And in contrast to zinc and titanium, studies show that some traditional sunscreens like oxybenzone and octinoxate definitely absorb into healthy skin — in large amounts according to some studies — and act like estrogens in the body, raising risks for breast cancer, and showing effects like hormone-driven uterine damage in other studies.

In the balance and when it comes to sunscreen, EWG researchers found that zinc and titanium-based formulations are among the safest, most effective sunscreens on the market. The easy way out of the nano debate would be to steer people clear of zinc and titanium sunscreens with a call for more data. In the process such a position would be implicitly recommending sunscreen ingredients that don't work, that break down soon after they are applied, that offer only marginal UVA protection, and that, far from having 15 studies demonstrating no penetration, definitively soak into the skin, into the blood, and into the organs.

If this were nano-containing eye shadow, blush, or body glitter our position would be different — it's not needed, it's not protecting your health, so don't use it. But sunscreen is a product meant to protect us from exposure to a known human carcinogen, UV radiation, responsible for a huge fraction of the more than one million cases of skin cancer diagnosed in this country every year.

For all sunscreens, nano and not, we have called for more safety studies, more data to understand when and in what amounts they penetrate the skin, and science-based assessments of health risks, so that everyone from consumers to health officials at FDA will know that we have the best possible products on the market. And for nano-scale ingredients we have called for full labeling so consumers can make informed choices. But we don't have any of that right now.

If sunscreens have gotten safer or more effective over the years, it is not because of FDA. PABA is out of products not because FDA took action on this potent skin-damaging chemical, but because manufacturers reformulated after enough consumers complained about allergic reactions. FDA still allows PABA in sunscreen, but companies know that it is too risky to use.

The sunscreen market may transition to progressively safer chemicals as time goes on, but these changes should be spurred by solid, final FDA safety standards requiring sunscreens to be proven safe and effective before they are sold, not by health complaints filed by consumers after dangerous products go on the market and into widespread use. We certainly hope that five years or even one year from now we have even safer, more effective sunscreen products to recommend, with more definitive data behind them.

EWG conducted our sunscreen study because we have no comprehensive sunscreen safety standards in place in this country. FDA has been drafting these standards for 29 years, but has not finished. And FDA has failed to get effective sunscreens on the market here in the U.S. that are widely available in other parts of the world. We think people need to know what products to use while we all wait for FDA to finish the job they need to do. EWG will continue to advocate for better safety standards and more safety studies for sunscreens - from nano-scale on up.

Ultimately, consumers make their own choices, and those wishing to avoid zinc and titanium can choose the "no nano" search option on our website to see the best of the rest.

More About Nanotechnology

Nanoparticles are incredibly small particles — measured in nanometers (nm), or one-billionth of a meter — whose size gives them unique physical and chemical qualities. But it also raises questions about their effect on human health and the environment, as they are more chemically reactive and more easily absorbed by the body. Although most people know little about nanoparticles, they are already widespread in products, including sunscreens.

The Australian government recently estimated that nanoparticles were prevalent in Australian sunscreens. 70% of titanium sunscreens, and 30% of zinc sunscreens were formulated with nanoparticles (smaller than 100 nanometers in diameter) (TGA 2006). Nano-scale titanium has been available for use in sunscreen since 1990 and nano zinc since 1999, and are suspected to be widely used in US sunscreens. Little is known about the industry, but an estimated 1,000 tons of nanoparticles were used in sunscreen worldwide during 2003-04 worldwide (Borm 2006).

The European Union and Australian cosmetic regulatory bodies have reviewed the toxicity of zinc and titanium nano-ingredients in sunscreen. In 2000, the EU found that nanoscale titanium does not pose toxicity concerns including dermal penetration, cytotoxicity, phototoxicity, and genotoxicity (SCCNFP 2000). The same panel decided in 2004 that zinc sunscreen formulations posed potential penetration concerns as well as possible DNA damage (SCCNFP 2004). In 2005, they called for additional study by manufacturers to evaluate these concerns (SCCP 2005).

The Australian Therapeutic Goods Administration completed a review in 2006 and concluded that the weight of evidence showed no skin penetration to viable skin sells-negating lingering toxicity concerns (Australia TGA 2006). The US Food and Drug Administration (FDA) accepted zinc oxide for use in sunscreen in 1999, but didn't consider the safety of the nanoscale forms of the ingredient that were just beginning to be commercially available.

In 2006, a coalition of advocacy groups petitioned the Food and Drug Administration to consider the health and environmental risks of nanomaterials in consumer products. The group specifically requested that FDA consider sunscreens containing nano-sized particles to be new drug products and that all nano-sunscreens be recalled until this drug approval was complete (ICTA 2006). The cosmetics industry responded that FDA has no authority to regulate nanotechnology, and that there is "scant evidence demonstrating that nanomaterials present unique safety issues" (CTFA 2006).

Zinc and Titanium benefits for UV protection

Zinc oxide and titanium dioxide are excellent UVA blockers. They are also 2 of only 4 UVA sunscreen chemicals used in US. Alternative UVA sunscreens are available in Europe but not approved by FDA. As it stands the only other U.S.-approved sunscreen with UVA-I protection are avobenzone and Mexoryl SX, both of which are highly unstable in most sunscreen formulations. Two EU-approved UVA blockers, Tinosorb S and Tinosorb M have been used in Europe since 2000 and are under evaluation by FDA. Zinc offers the best UVA protection of all current sunscreen chemicals, with titanium a close second.

There is some laboratory evidence that smaller particle zinc and titanium offer improved UV protection compared to conventional-sized counterparts. The peak UV shielding for titanium is by particles in the 60 to 120 nm size range (Popov 2005). The best UV shielding for zinc is by particles in the 20 to 30 nm in diameter (Cross 2007). However, a more important factor in their use is their appearance on skin. Prior to the 1990s larger zinc and titanium particles were used that left a white tint on consumers' skin and didn't adhere as well to skin. Nowadays the typical size range for titanium in sunscreens is 10-100 nm and zinc is 30 to 200 nm (Nohynek 2007), at these sizes both zinc and titanium give off less whitish tint and form a smoother barrier on skin.

Current evidence suggests that nanoparticles are widely used in sunscreens. However, they are rarely noted on product labels. The Australian government estimated that 70% of titanium sunscreens and 30% of zinc sunscreens in Australia are formulated with nanoparticles (Australia TGA 2006). In the US, Consumer Reports recently tested 8 sunscreens and found zinc or titanium nanoparticles in each one, even if they were not labeled (Consumer-Union 2007). Of the sunscreens EWG assessed, 2 zinc sunscreens and 0 titanium sunscreens included the term "nano" on the label.

Some sunscreenmakers voluntarily use non-nano zinc and titanium in their products. Until FDA requires appropriate labeling it will remain difficult for consumers to clearly distinguish which ones contain nano-size particles if they care to avoid them. In the interim the easiest way for a consumer to judge the particle size of the zinc or titanium in their sunscreen is by the tint that it leaves on skin when applied. A good rule of thumb: If your zinc or titanium sunscreen goes on clear it is nanosized.

Safety concerns of nanoparticles

The potential benefits to UV protection must be balanced against concerns that nanoparticles might be unusually toxic to body systems. This is based on the properties that make them most useful in commerce-the high surface reactivity of tiny particles and their ability to penetrate body tissues. Two hotly debated questions about the safety of nanoparticles in consumer products are the amount of human exposure and the effects of nanoparticles inside the body.

Titanium Dioxide

Author	Skin Type	Conclusions	Particle Size	Particle Coating
Gamer 2006	pig	No penetration	30-60 nm	silica or methicone
Mavon 2007	human volunteers	Penetration to upper layers of stratum corneum. NP in skin furrows or follicular opening may be mistaken to epidemal compartment	20 nm	no information
European Commission 2000	pig, human, in vitro tests	No penetration beyond stratum corneum. No TiO2 was detected in the follicle, viable epidermis or dermis	14nm-200 mm	coated and uncoated TiO2
Gottbrath 2003	human volunteers	Sunscreen particles tested. No penetration of particles beyond upper layers of stratum corneum	N/A	no information
Dussert 1997	human, in vitro	Penetration limited to upper layers of stratum corneum	50 - 100 nm	no information
Gontier 2004	mouse, pig, human, in vitro tests	TiO2 detected in the intercellular spaces between corneocytes of the outermost layers of the stratum corneum. No penetration into livng skin.	Nanoparticles	no information
Menzel 2004	Pig skin, in vitro	Particles in/on stratum corneum; minimal penetration into stratum granulosum. No penetration into living skin.	45-150 nm needles	no information

Zinc Oxide

Author	Skin Type	Conclusions	Particle Size
Gamer 2006	pig	1.5 to 2.3% of particles penetration	80 nm, with 90% <160 nm
Cross 2007	human skin, in vitro	No particles in epidermis or dermis	15-30 nm
Dussert 1997	human skin, in vitro	Penetration limited to upper layers of stratum corneum	20-200 nm
Gontier 2004	mouse, pig, human skin, in vitro	No penetration into living skin	N/A

Nano zinc and titanium toxicity

The safety of nano-titanium has been fully cleared by the EU cosmetic regulatory body and by Australia (SCCNFP 2000; TGA 2006). Nano zinc has not been fully approved in Europe (SCCP 2005), but is used in Australia (TGA 2006). In their review the EU raised concerns that zinc caused UV-activated DNA damage (SCCP 2005), although a follow-up study by industry found that damage was not UV-related (Dufour 2006). The EU decisionmakers have not yet formally responded to this study.

The primary toxicity concern of nanoparticles is free radical generation. This can provoke intense oxidative stress, inflammation and damage proteins, lipids and DNA (Nel 2006; Oberdorster, Maynard 2005) The particular chemical and coating of the nanoparticle have a lot to due with its toxicity to living systems. Zinc and titanium have both been shown to provoke some oxidative stress to tissues-especially when catalyzed by UV light (Hidaka 2006). On the skin, nano zinc and titanium extracted from sunscreens are activated by UV light to create reactive oxygen species damaging skin DNA and cell structures (Hidaka 2006). Titanium hydroxyl radicals produced on by UV irradiation provoke in DNA damage and cell damage (Dunford 1997; Uchino 2002; Sayes 2006; Wang 2007). Different coatings, such as magnesium, have been shown to greatly reduce UV reactivity of nano titanium (Wakefield 2004).

Oral intake is a potential concern for nanoparticles in sunscreen when they wash off consumers and enter swimming pools and reservoirs. Lip products with SPF protection are also a concern. Our analysis include 23 lip products with zinc oxide and 91 products contain titanium dioxide. A few studies have investigated gut absorption of nanoparticles and generally found low uptake. Some studies show gut absorption of titanium particles 150-500 nm (larger than typically used in sunscreen) (Bockmann 2000; Jani 1994). These particles reach the liver and spleen (Bockmann 2000; Jani 1994). More detail about uptake of small particles can be gleaned from radioactive metal studies, which found no passage from the gastrointestinal system to other organs (Kreyling 2002).

Sunscreen chemicals are some of the most studied nanoparticles, and appear to have low penetration through skin (Nohynek 2007). (described more fully below) Until the consequences of nanoparticle exposure are fully studied, EWG urges manufacturers to label the particle size of zinc and titanium used in their formulations to allow consumers who want to avoid nanoparticle exposures options to do so.

Skin penetration

The current weight of evidence suggests that nano zinc and titanium do not penetrate the skin. These studies use mouse, pig or human skin samples as test materials. The outer layer of skin, the epidermis, is a made up of dead skin cells that protect the living cells below by serving as a barrier to absorption of chemicals. At least 15 laboratory studies have tested nano-zinc and titanium penetration through intact skin, each finding that very few particles, if any, penetrate living skin (Baroli 2007; Cross 2007; Gamer 2006; Lademann 1999) as well as reviews by (Australia TGA 2006; Borm 2006; Nohynek 2007; SCCNFP 2000). The most recent study offered by industry found no titanium particle penetration and 1.5 to 2.3 % penetration by nano zinc, though the study is difficult to interpret because of laboratory contamination (Gamer 2006).

Regions where skin is thinnest — lips, underarms, eyelids and inner thighs are potentially more sensitive than the palms of our hands and feet. Places like joints, where skin is flexed and stretched are regions that are more porous for nanoparticles and other chemicals. Children and the elderly have thinner skin than adults. The outer layer of skin can also be sun damaged, abraded or rubbed off. Sunscreen is commonly used on sun-damaged skin. These factors call for caution when interpreting tests showing low penetration of a chemical in laboratory conditions.

Several recent studies have found that other types of nanoparticles penetrate through intact skin. Some additional factors such as mechanically movement (Tinkle 2003; Rouse 2007), particle charge/surface coating (Ryman-Rasmussen 2006; Nohynek citing Kohli 2004), or ultrasound can facilitate penetration (Paliwal 2006). Manufacturers must also account for penetration enhancers (Pont 2004; Paliwal 2006) which may increase skin permiability. Hair follicles make up 0.1% of the skin surface but can be portals for deeper movement into skin. Skin penetration studies for zinc and titanium from sunscreen commonly note follicular accumulation but not penetration (Lademann 2005; Lademann 2006; Lademann 2007).

Occupational exposure during manufacturing

The inhalation of nano-particles appears to be the most harmful of all potential human exposures. While a low concern for consumers, the production of small particles and their formulation in sunscreen both result in potentially intense worker exposures orders of magnitude more intense than via consumer products. There are significant concerns that workers handling nano materials during product formulation are not currently receiving adequate protection from nanoparticle exposures (Maynard 2005).

Nano-size particles in ambient air are a common form of air pollution, and are well documented to provoke oxidative damage to lung tissue, to enter the bloodstream where they impact the heart. Gojova specifically found that inhaled zinc nanoparticles lead to inflammation and cell death for heart endothelial cells (Gojova 2007).

The particle size of inhaled titanium particles may have profound impacts on its toxicity. Nano-scale titanium particles have been shown to be less toxic than nano nickel or cobalt (Zhang 1998). Mice inhaling titanium dioxide particles 19 to 21 nm for a period of weeks showed emphysema-like lung damages as well as altered gene expression (Chen 2006) However, a study testing particles of 2 to 5 nm diameter showed only moderate but reversible inflammation of lung tissue (Grassian 2007). Inside the body titanium particles 20 nm in diameter are 36-times more powerful at provoking an inflammatory response than particles 200 nm in diameter (Oberdorster 2000).

Both nano zinc and titanium should be more carefully assessed in relationship to occupational exposures.

Nanoparticle toxicity to ambient environment

Both nano zinc and titanium nanoparticles may impact the external environment (Adams L.K. 2006; Adams L.K. 2006; Hund-Rinke 2006). Each metal has strong antibacterial properties, and potential to provoke oxidative stress in the ambient environment. Their impacts to living systems have not been exhaustively assessed. As a recent nanotechnology review concluded, "No studies to date have been done on protists, fungi, plants, birds, reptiles, or amphibians, and the only mammalian studies have been carried out using laboratory species" (Borm 2006).

Nanoparticles will likely absorb to sediments in the water column. Thus potentially impacted species microorganisms and filterfeeders who would take in nanoparticles suspended in the water column. Nano titanium particles bind with cadmium in water sediments and lead to increased cadmium absorption for fish. There was a 146% increase in cadmium accumulation over a 25 day exposure period (Zhang 2007). A separate study concluded Nano fullerenes deplete antioxidant defenses in fish (Oberdorster 2004), and leads to lipid peroxidation in the brain and liver (Zhu 2006).

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