What’s better than a day at the beach? A day at the beach and not being miserable for the next several days because of sunburn! That’s where the modern miracle of sunscreen comes into play. Did you know many sunscreens are products of nanotechnology? An advisory statement from the Australian Government’s Therapeutic Goods Administration, Safety of Sunscreens Containing Nanoparticles of Zinc Oxide or Titanium Dioxide, describes the properties of these sunscreens. One property is the familiar white color of these compounds, which can be made transparent by reducing the zinc oxide, or ZnO, particle size down to nanoparticles. However, this means the surface area ZnO particles is increased, and that means greater potential for chemical reaction with skin cell proteins, for example. Further, these nanoparticles may be more reactive to UV radiation.

On Monday, February 18, 2008, ABC Science Online posted a story, titled Tests on Sunscreen Nanoparticles ‘Reassuring,’ about research conducted in Australia. In the first study, researchers used a form of ZnO that contained a nonradioactive form of Zn, which differentiated it from all naturally occurring forms of Zn. This allowed the researchers to track whether the material was being absorbed by skin cells and transferred into the blood stream and excretory system. The researchers found “very little” ZnO was absorbed by the skin.

The second study included testing the toxicity of ZnO to immune cells. While the researchers found the ZnO to be quite harmful to the immune cells, they also found that high doses would be necessary and that the body would most likely eliminate the ZnO before damaging levels accumulated.

An ongoing study involves treating shaved mice with sunscreen containing ZnO nanoparticles and then testing their organs for ZnO levels. A future study is planned involving the impact of UV light on the toxicity level of the nanoparticles in sunscreen products used by lifeguards for a week.

An interesting aspect is that sunscreen formulations vary. It is possible that a given combination of compounds affects whether the nanoparticles are absorbed into the skin and to what degree they get metabolized. One of the researchers would have preferred to test commercially available sunscreens, rather than the generic type provided. He quotes an industry insider as saying “if you find something untoward about this then this could cause our products to be taken off the market plus could destroy the industry full stop.”

How to Turn This News Event into an Inquiry-Based, Standards-Related Science Lesson

The concepts of nanotechnology and properties of ZnO are related to the Physical Science content standard of the National Science Education Standards, which mentions that middle school students associate certain properties with specific materials. It also states that the sun’s energy “arrives as light with a range of wavelengths, consisting of visible light, infrared, and ultraviolet radiation.” Ask students why they should wear sunscreen. Ask if they know what elements or compounds might be in those lotions that protect them. What is the substance actually protecting them from? Lead them to the concept of the high energy UV rays which damage cells. Depending on your students’ background knowledge, you may want to mention that UV radiation works to denature some proteins and can cause DNA to mutate.

Ask students if skin cells are living. How do they know? Lead them to the idea that skin cells grow and reproduce, a characteristic of all living things. That means they take in substances and get rid of substances. The smaller the substance, the more likely it will be able to enter cells. What if the protective material in sunscreen, ZnO, was on a nano scale? Would you be concerned about using it on your skin? Why or why not?

Share the articles with your students. You could withhold the part discussing ongoing or future research studies and ask them: What do you think still needs to be investigated? How would you propose that be done? Lead them to design a “fair test” with the potential to yield meaningful results.

Here are some additional resources that are part of the NSDL Middle School Portal collection to facilitate your instruction regarding sunscreen, skin and UV radiation: What’s That Stuff? (scroll down and click on Sunscreen); Skin; Quick Take . . . on Sunshine, Rainbows and the Electromagnetic Spectrum; SPF 30: Exposing Your Students to Science

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