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Sunday July 14, 2024


Definition of Terms

SPF (Sun Protection Factor)

SPF refers specifically to sunscreens. It is an indexed number based on the amount of UV radiation necessary to turn sunscreen treated skin red compared to untreated skin. Some other facts:

1) The protection a certain SPF provides depends on your skin type. For example, SPF 10 means you can stay in the sun for ten times longer than it takes you to burn. If a fair-skinned, blond headed person burns in five minutes under the noon day sun, an SPF 10 would enable her to to remain outside for fifty minutes before burning -- ten times longer than without sunscreen. A darker-skinned individual who might burn in 20 minutes without sunscreen could stay out for 200 minutes.

2) Good protection depends upon correct use of sunscreen. Apply it 20 minutes before going outside, remembering to re-apply frequently because activities like wiping your brow cause it to rub off. Recent research has shown that kids often got their worst sunburns of the season while wearing high SPF sunscreen. The reason seems to be complacency: they thought they were protected but forgot to reapply...

3) SPF relates only to UVB protection. There is no agreed upon standard for UVA protection in the USA. Therefore, be wary of "broad spectrum" claims on sunscreens. Although many sunscreens actually do protect against UVA rays, there are a few which do not.

UPF (Ultraviolet Protection Factor)

UPF refers to the amount of UV rays blocked by apparel and fabrics. Some facts about UPF:

1) UPF is a transmission test: A fabric gets exposed to a UV source that simulates the sun's rays at noon. The amount of UV rays blocked by the fabric is measured by a device called a spectrophotometer. The UPF rating refers to how much UVR is blocked. For example, a UPF 50+ blocks 97.5% of the sun's UVA and UVB rays.

2) UPF measure both UVB and UVA rays.

3) Darker colors are better UV absorbers than lighter colors -- they have a higher UPF. Therefore, a black shirt will block more UV rays than a white shirt.

4) Beware of companies touting products with a UPF 100. UPF 50+ is the highest rating permitted by any National Standard in the world -- including the new US Standard. Companies claiming higher UPF numbers are doing so for marketing purposes and are mis-leading consumers.

5) Manufacturers often use SPF & UPF interchangeably when promoting the sun protection their products offer. This is mainly because research shows that there is much confusion about what these terms mean. UPF is the correct measurement for fabrics.

An SPF 15 rating is not the same as a UPF rating of 15 -- the two numbers are not interchangeable.

6) Just as a number of factors can influence the SPF ratings in sunscreens, the fiber type, weave, color, construction, humidity and wetness, stretch and wear and tear are factors that can also influence UV protection in fabrics. In order to obtain a UPF rating on any fabric, manufactures will need to submit a sample from each fabric color and style for UV testing.

EPF (Eye Protection Factor)

A rating scale (1 to 10) applied to sunglasses EPF 10 glasses offer the highest protection.

UV Rays

The shortest-wavelength and most damaging portion of the UV spectrum. The ozone layer completely blocks out the UVC rays. Without the protection of the ozone layer, the sun's UVC radiation would threaten life on Earth.

The longest-wavelength portion of the UV band (in the range 315 nanometers to 400 nanometers), UVA is not blocked by the stratospheric ozone layer, and reaches the ground in relatively large amounts. It is the least damaging of the three, but far from harmless. UVA rays penetrate to the inner layer of the skin (dermis) where it can damage blood vessels, DNA, and compromise the skin's physical support system, contributing to premature aging and wrinkling of the skin. Recent studies show that it may be more damaging than originally thought.

UVB rays (in the range of 280 nanometers to 315 nanometers of the electromagnetic spectrum) are more damaging than UVA rays, but, because they are effectively blocked by the ozone layer (less than 1% of the sun's energy that reaches the surface), they are less abundant. UVB rays are more prevalent in summer. UVB light affects only the outer layer of the skin (epidermis). They are more energetic than UVA, cause sunburn much faster and are the single-most major cause of skin cancer.

Definition of Terms
  • SPF
  • UPF
  • EPF
    UV Rays
  • UVC
  • UVA
  • UVB
  • Skin Cancer Facts
  • Basal cell
  • Squamous cell
  • Malignant melanoma
  • How to treat sunburn
    The UV Index
  • Where you can find more info
  • UVR and your Skin
  • what does your skin do?
  • epidermis
  • dermis
  • How each UVR penetrates (A,B,C) skin and what it does
  • Damage and Effects
  • How Skin becomes cancerous
  • Other Medical Considerations
    The OZONE
  • Ground Level Ozone
  • Stratospheric Ozone
  • Time of day
  • Time of year
  • Latitude
  • What affects the Ozone layer's effectiveness?
  • Altitude
  • Weather conditions
  • The Ozone Hole
  • The Sun
  • The Sun
  • Sunspots
  • Solar flares
  • Solar wind
  • Solar prominences
  • Sun Fun Facts
  • Did you know?
  • Astrology
  • Scientists can now see the far side of the Sun.
  • Is it possible the Sun has a heartbeat?
  • Cool links - just for Kids!
  • Passport to knowledge
  • Sun Kids
  • Spacelink
  • Star Child - A Learning Center for Young Astronomers
  • Backwoods Home Magazine
  • Kids books about the sun (fact and fiction)