• Abilities of technological design

Science in Personal and Social Perspectives:

• K-4: Personal health
• 5-8: Risks and benefits
• 9-12: Personal and community health

Vocabulary

Nano is the scientific term meaning one-billionth.  (1/1,000,000,000)  It comes from a Greek word meaning “dwarf.”

A nanometer is one one-billionth of a meter. One inch equals 25.4 million nanometers. A sheet of paper is about 100,000 nanometers thick. A human hair measures roughly 50,000 to 100,000 nanometers across. Your fingernails grow one nanometer every second. (Other units can also be divided by one billion. A single blink of an eye is about one-billionth of a year. An eyeblink is to a year what a nanometer is to a yardstick.)

Nanoscale refers to measurements of 1 – 100 nanometers.  A virus is about 70 nm long. A cell membrane is about 9 nm thick. Ten hydrogen atoms are about 1 nm. At the nanoscale, many common materials exhibit unusual properties, such as remarkably lower resistance to electricity, or faster chemical reactions.

Nanotechnology is the manipulation of material at the nanoscale to take advantage of these properties. This often means working with individual molecules.

Nanoscience, nanoengineering and other such terms refer to those activities applied to the nanoscale. “Nano,” by itself, is often used as short-hand to refer to any or all of these activities.

Materials

• Handout/resource pdfs

For each pair of students:

• A dab of sunblock with nanoparticles of zinc oxide (e.g. CVS Sunblock with Zinc Oxide Spf 45+)
• A dab of zinc oxide ointment, a non-nano sunblock (e.g. CVS Zinc Oxide Ointment)
• 2 squares of black construction paper
• 2 cotton swabs
• Particle Size handout

Background

Sunblocks containing nanoparticles are one of the most common applications of nanotechnology. Nanotechnology takes advantage of special properties at the nanoscale. For example, the nanoparticles in sunblock are invisible to the human eye because they’re smaller than the wavelength of visible light.

How can you tell if you sun protection product contains nanoparticles? Check the ingredient list on the product. Ingredients such as avobenzone, oxybenzone, or PABA are chemical sunscreens that do not contain nanoparticles. If the product includes zinc oxide or titanium dioxide, it is a mineral sunblock that probably contains nanoparticles if it is also labeled as “goes on clear” or “invisible.”

Although the public and manufacturers often use the words ”sunblock” and “sunscreen” interchangeably, they technically refer to two different types of sun protectants. Sunblocks refer to sun protectants that contain minerals such as zinc oxide or titanium dioxide. They block about 99% of UV radiation, but non-nano formulations are opaque in nature and users rarely apply the amount recommended for effective protection as a result. Sunscreens refer to chemically based sun protectants, few of which individually protect against both UV-A (320–400 nm) and UV-B (290–320 nm) radiation and are usually combined into broad-spectrum products. Although chemical sunscreens also degrade when exposed to UV light, they are more transparent than traditional mineral sunblocks when rubbed on the skin. In light of this, chemical sunscreens tend to be more popular than mineral sun blocks, even though mineral sun blocks are better at blocking UV radiation and are better for the skin because they do not degrade.

When the diameter of a zinc oxide molecule is reduced below the wavelength of visible light (380–780 nm), the nanoparticle no longer scatters visible light so the substance containing the mineral will look transparent. However, the particles are still larger than the wavelength of ultraviolet light and the chemical composition of the particle is not altered, so zinc oxide does not lose its ability to absorb UV radiation.

Nanoparticles used in sun blocks are some of the most extensively researched topics in nanotechnology. Although Australian and European governments have approved the use of nanoparticles in sunblocks, cosmetics are not regulated by the U.S. Food and Drug Administration (FDA). It is often difficult to tell which commercially available products contain nano and non-nano mineral formulations, since cosmetics companies are not required to indicate whether nanoparticles are present in their product.

To date, toxicity studies have shown that nano-zinc and titanium based minerals do not penetrate the outer later of healthy skin and are largely safe to use. However, a possible penetration risk remains in areas where skin is thinner (i.e. lips, underarms, eyelids and at the joints) or if skin has been damaged by prior sun exposure or other physical trauma. Additionally, the elderly and young children may have a higher risk of skin penetration, as these age groups tend to have thinner skin. The primary health concern about nanoparticles is that if they are exposed to UV radiation they can generate oxygen free radicals; these can cause oxidative stress and inflammation as well as damage proteins, lipids and DNA.

Procedure

SAFETY: To avoid potential reactions due to allergies or sensitivities, caution students against applying the ointment or sunblock to their skin.