Ultraviolet Sun Protection: How Low Can You Go

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Ultraviolet Sun Protection How Low Can You Go?
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SPFs and Sunscreens

• SPF
• SPF stands for sun protection factor, which
  indicates the effectiveness of sunscreens.

• Sunscreens
• Sunscreens protect the skin by absorbing or
  scattering UV radiation.
• Molecules in the sunscreen absorb radiation much
  like melanin.
• Sunscreen manufacturers combine ingredients to
  increase protection and absorption.

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Sunscreen Ingredients

• The first sunscreens were made with PABA, but
  soon PABA was discontinued in use because it
  stained clothes and caused allergic reactions in
  some people.
• Last year Padimate O, a derivative of PABA, was
  found to oxidize DNA and produce free radicals
  that break DNA strands.
• Titanium dioxide and zinc oxide cause similar DNA
  strands to break.

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Ultraviolet Radiation

• Ultraviolet radiation makes up a fraction of
  sunlight but packs more energy than visible
  light. Some UV radiation (better known as UVC
  rays) is absorbed by the ozone layer in the
  atmosphere. However other UV rays (UVA and UVB)
  still reach the earth and can cause damage to the
  skin.
• According to the American Academy of
  Dermatology, most sun exposure occurs before a
  person is 20.

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The Human Skin

• Human skin has several layers - the outer layer
  (the epidermis) and the middle layer (the
  dermis).
• The epidermis contains a thin section of dead
  cells.
• The dermis contains capillaries, sweat glands,
  hair follicles, and nerves.
• Between the two layers are two sets of cells
  basal cells and melanocyte cells.

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A Different Way of Testing

• Manufacturers tested their sunscreens with an
  actual human experiment.
• The manufacturers placed a mask, with small
  holes, on a volunteers back to allow exposure of
  UV radiation to the skin at various times.
• Researchers then timed how long it takes for the
  skin on the volunteers back to turn red. After
  24 hours the skin was examined for redness.
• Sunscreen was then applied to the skin and
  re-exposed to UV radiation. After another 24
  hours the skin was examined to see which time
  interval produced the same redness as unprotected
  skin.
• SPF Minimum time to produce redness with
  sunscreen
• divided by
• Minimum time to produce redness without
  sunscreen

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Purpose

• To determine which sunscreen and SPF will permit
  the least amount of ultraviolet radiation from
  permeating through its layer.

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Hypothesis

• When testing the top three sunscreens with
  ranging SPFs from 4-45, Banana Boat with an SPF
  of 45 will reject the most ultraviolet radiation.

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Materials

• One large cardboard box
• One ring stand
• Two ring clamps
• UV light sensor
• Light sensor attached to Logger Pro
• Various sunscreens with ranging SPFs
• Micro-slides
• Small piece of cardboard
• Duct tape
• Cotton swabs
• Kimwipes

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Procedure

• Build the apparatus and then cover the apparatus
  with a light tight box.
• Collect various sunscreens with ranging SPF
  numbers.
• Swab a light film of sunscreen over the middle of
  a micro-slide. Place the slide on the little
  piece of cardboard. Align the UV sensor, lotion,
  and light sensor stick at this point.
• Prepare computer for data collection. Using the
  Vernier file, set up a data table using 300
  second on the horizontal axis.
• Place a piece of duct tape over the short
  wavelength side, exposing only the long
  wavelength screen. Turn on the UV sensor and
  immediately close flap. Make sure sides are
  taped down securely. Click on the Collect
  button to begin collecting data.
• Stop collection after 5 minutes and record the
  minimum and maximum number at 1 minute and at 5
  minutes.
• Prepare another slide for testing.
• After testing with the long wavelength screen is
  completed, tape the long wavelength screen with
  duct tape and begin testing with the short
  wavelength screen using the same procedure.

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Banana Boat SPF 30 Data(long wave-length)

• Original radiation of long wave-length 543
• Trial 1
• After I minute
  After 5 minutes
• -201 maximum
  -218 maximum
• -19 minimum
  -.7 minimum
• Trial 2
• After 1 minute
  After 5 minutes
• -125 maximum
  -152 maximum
• -59 minimum
  -7.5 minimum
• Trial 3
• After 1 minute
  After 5 minutes
• -79 maximum
  -124 maximum
• -10 minimum
  -.5 minimum

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Coppertone SPF 45 Data(short wave-length)

• Original radiation in sort wave-length 156.25
  
• Trial 1
• After 1 minutes
  After 5 minutes
• -46.0 maximum
  -58.5 maximum
• -.5 minimum
  -.5 minimum
• Trial 2
• After 1 minute
  After 5 minutes
• -49.75 maximum
  -69.0 maximum
• -.5 minimum
  -.5 minimum
• Trial 3
• After 1 minute
  After 5 minutes
• -73.75 maximum
  -73.75 maximum
• -.25 minimum
  -.25 minimum

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Conclusion

• I discovered, by completing my ex-periment, that
  my hypothesis was partially correct. Banana Boat
  30 was the best sunscreen for blocking UVA rays,
  but Coppertone 45 was the best sunscreen for
  blocking UVB rays.

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Thanks to the Teachers

• Id like to sincerely thank Mr. Bill Palmer, Mr.
  Mike Kelly, and Mrs. Jennifer Swain for all their
  help throughout the past four weeks at Summer
  Ventures. I have leaned a gracious plenty from
  these three teachers, and I have thoroughly
  enjoyed working with them in the laboratory.

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Thanks to the Writers

• Id like to thank the following sources for
  providing information for my research project
• May 1998 edition of Consumer Reports
• June 6, 1998 edition of the Science News
• April 1998 edition of the ChemMatters Journal