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My sunscreen says it has nano particles in it, should I be concerned?
Environmental Working Group is among the many advocacy groups who have raised concerns about whether the rapidly expanding use of nanotechnology poses risks to human health or the environment. Many zinc and titanium sunscreens contain nanosize particles, even when they are not on the label.

Although we expected to reach a different conclusion at the outset of our sunscreen investigation, when we balanced all factors important in sunscreen safety, we found many zinc and titanium-based sunscreens that our analysis shows are among the safest and most effective sunscreens on the market. Our product ratings reflect our concern about the very real dangers of cancer and other health hazards from sun exposure, balanced against concerns about the potential health hazards of sunscreen ingredients. Read our full assessment of zinc and titanium sunscreens here.

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 sunscreens without zinc and titanium could accelerate by an average of 20% the skin damage, premature aging, wrinkling, and UV-induced immune system damage linked to UVA exposure, compared to zinc and titanium sunscreens. 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).

Zinc oxide and titanium dioxide are stable compounds that provide broad spectrum UVA and UVB protection, while the available studies consistently show very little or zero penetration of intact skin by these compounds, indicating that real world exposure to potential nano sized particles in these products is likely very low (Borm 2006). The sun protection benefits, in contrast, are very high.

EWG's rating of zinc and titanium-based products as among the safest and most effective sunscreens available in the U.S. today should not be interpreted as an endorsement of nano-materials in general. We remain deeply concerned about the overall safety and oversight of nanotechnology as well as impacts to workers and the environment.


Benefits:

UV exposure is damaging to health, and Zinc and Titanium offer broad spectrum UV protection.
Zinc and titanium are 2 of only 4 UVA blockers used in the US. Alternatives including Tinosorb S and Tinosorb M are available in Europe but not approved by FDA for use in the U.S. As it stands, the only other U.S.-approved sunscreen with UVA-I protection are avobenzone and Mexoryl SX, both of which are unstable in most sunscreen formulations (i.e., they break down in the sun).
In 15 peer-reviewed studies, nanosize zinc and titanium were shown not to penetrate through unbroken skin at concentrations exceeding 1.5%. A recent review for the EU decision-making body found that, "There is currently little evidence from skin penetration studies that dermal applications of metal oxide nanoparticles used in sunscreens lead to systemic exposure" (Borm 2006).
Zinc oxide poses a low level of concern based on currently available science: it is well studied and is a necessary nutrient to humans.

Concerns of zinc and titanium in sunscreens:

No studies have tested nanosize zinc and titanium penetration through fragile or damaged skin. Conventional zinc is widely used on damaged skin including diaper ointment and burn treatment. However, other nano-scale particles have been shown to penetrate when skin, especially when it is repeatedly flexed.
U.S. regulatory framework has lagged far behind industry in addressing the impacts of nanotechnology. Due to inadequate labeling requirements, consumers have no options for avoiding products containing nanoparticles.
Nanoparticle production poses serious concerns for workers, especially particle inhalation, which available science indicates is likely the greatest human hazard for nanoparticle exposures. Occupational production is virtually unregulated in the U.S.
Nanoparticles, including zinc and titanium, are potentially toxic to the environment. Like all sunscreen ingredients their use in sunscreens results in releases of the chemicals through production, users' contact with water, and as waste.