From SPF to SNF (Sunscreen Nano

Facts)

Cathleen Burke Karen Trickett

MathScience Innovation Center Nanotechnology Fellows

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Part 1:

The Energy of Light

The Sun

The sun’s electromagnetic spectrum consists of seven types of radiation with different quantities of energy and differing wavelengths including:

RadiowavesMicrowaves Infrared wavesVisible light Ultraviolet raysX-rays Gamma rays

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The Electromagnetic Spectrum

www.dnr.sc.gov

Ultraviolet Light

•Includes wavelengths between 380 and 10 nm

•Can not be visualized by the human eye

•Can be absorbed by skin cells and the energy from them can damage DNA in the cells which absorb them

www.abstract.desktopnexus.com

Types of UV light •UVC light Filtered out by the atmosphere

•UVB light Absorbed by the upper epidermis

•UVA light Absorbed into the lower layers of the epidermis as well as the dermis

www.ewg.org

Is all UV light Bad??

No!

Small amounts of UV light are needed for strong bones and good health!

www.homeschooling.gomilpitas.com/explore/skeleton.htm

So what is the problem with UV light?

Increasing amounts of UVA and UVB light are reaching the surface of the Earth due to the destruction of the stratospheric ozone layer

Absorbed UVB light causes sunburns

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Absorbed UVA light penetrates deep into the epidermis where cells called melanocytes are found. This triggers the melanocytes to produce the pigment melanin which results in a tan.

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but those tanning rays are actually causing damage to skin, leading to:

Many people think suntans give you a healthy appearance

•Premature wrinkles •cataracts

•Changes to DNA that can lead to skin cancer

www.sheknows.com

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Malignant melanoma - the most serious type of skin cancer. Results from deeper penetrating UVA rays which damage melanocytes.

Basal cell carcinoma - appears on the upper layers of the skin due to overexposure to UVB rays

Squamous cell carcinoma - also appears on the upper layers of skin due to overexposure to UVB rays

Types of Skin Cancers

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Sun Protection

Sunblocks and sunscreens are used to protect againstthe sun’s damaging rays.

The active ingredients in sunscreens either absorb,block or scatter UV rays www.shutterstock.com

Sunscreens

•17 active ingredients are currently approved for use in sunscreens in the U.S

• 2 categories of active ingredients: 1)inorganic minerals– zinc oxide

(ZnO) and titanium dioxide (TiO2)2)Organic chemicals – are padimate

O, oxybenzone, and methoxycinnamate

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In the past, most available sunscreens have protected against UVB (burning) rays with mixtures of up to 3 chemicals that block various UVB wavelengths Recently, broad spectrum sunscreens have become available which add UVA protection by adding Oxybenzone or avobenzone

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Sun Protection Factor (SPF)

Measures the length of time skin is protected against exposure to UVB light.

Higher SPF’s protect against burning longer.

SPF’s vary from as low as 2 to over 100.

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Sunblocks with ZnO and TiO2 protect against the entire range of UV wavelengths

without the use of chemicals. So, why don’t more people use them?

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The solution:

Nanotechnology!! Nanotechnology is a relatively new science which involves the creation of products that contain nano-sized materials in the range of 1 – 100 nanometers.

At these tiny sizes, many particles often exhibit unique chemical, physical and biological properties that are different from larger particles of the same type.

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How small is a nanometer?

A nanometer (nm) is a billionth of a meter

Compare this to some objects you may be familiar with:

•Thickness of a sheet of paper = 100,000 nm

•Width of a single DNA molecule or a cell membrane = 3 nm

•A red blood cell = 6,000 nm wide

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To change the usual opaque white color of sunblocks with zinc and titanium oxides, the particle size of these 2 minerals has been reduced to nanosize – 5 to 20 nm!

As nanoparticles, both zinc oxide and titanium dioxide are transparent.

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Sunscreen manufacturers have been using nanosized TiO2 since 1990 and nanosized ZnO since 1999.

Today over 300 sunscreens on the market contain nanosized mineral particles

www.action.foe.org

Part 2:

Risks vs. Benefits

Controversy Concerning Nano SunscreensSome concerns about sunscreens containing nanoparticles include:

1) Safety concerns regarding nanosized particles

2) Lack of labeling requirements which inform consumers that the product they are using contains nanoparticles.

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Safety Concerns

Nanosized ZnO and TiO2 particles may be small enough to be absorbed into the lower layers of living skin cells where they may be activated by light to react in a way which is unsafe for living tissue.

Nano-sized particles, due to their small size, are more reactive than their full-sized counterparts.

These nanoparticles, upon absorbing UV light, have been shown to emit free radicals which can cause damage to biomolecules such as DNA inside cells.

www.stu.westga.edu

While only a small amount of data is available on the safety of nanoparticles in sunscreen, the weight of current data seems to suggest that these particles do NOT get absorbed into healthy skin when applied in lotion form.

More research needs to be done to definitively address this safety concern.

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Nanoparticles may wash off sunbathers’ skin and enter the environment

Additional Safety Concerns

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A study published in Scientific American (March 2009)concluded that nanosized TiO2 particles substantially affect the cell wall of E. coli bacteria in very small quantities(10 – 100 mg/L) after less than 24 hours of exposure.

Both zinc and titanium are known to have strong antibacterial properties

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This micrograph displays visually the results of this study.

www.sciencecodex.com/titanium_dioxide _nanoparticles

In another study conducted at Utah State University and the University of Utah, beneficial soil bacteria were shown to be damaged by Silver, Copper Oxide and Zinc Oxide particles even at low levels of exposure.

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Since concerns about these sunscreens haven’t been fully addressed, many feel that labeling of sunscreens that contain nanoparticles should be mandatory.

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What do you think??

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References:

Tanning http://kidshealthorg/teen/safety/safebasics/tanning.html#

TGA Fact Sheet – Sunscreens http://www.tga.gov.au/npmeds/sunscreen-zotd.htm

Sunscreens/Sunblocks. American Academy of Dermatology http://www.aad.org/public/publications/pamphlets/sun_sunscreens.html

“Nanoparticles in Sunscreen Damage Microbes”. Cimitile, Matthew. Scientific American. March 24,2009.

Tanning: Is it Safe? www.csulb.edu/divisions/students/nrc/health_topics/TanningIsitSafe.htm

Sunscreen www.skincancer.org/sunscreensExplained.html