UV Radiation - What makes an effective sun protective garment?

In the spirit of providing education and developing awareness and in order to help our CAKOON customers STAY SUN SAFE - we would like to offer the following information, helpful tips, and useful guidelines as presented by expert references including the EPA  and ARPANSA (Australian Radiation and Nuclear Safety Agency).

The sun radiates energy across a broad spectrum of wavelengths.  Ultraviolet (UV) radiation, which has a shorter wavelength than either visible blue or violet light is responsible for sunburn and other adverse health effects.  Fortunately, for life on Earth, our atmosphere's stratospheric ozone layer shields us from most UV radiation.  What gets through the ozone layer, however, can cause the following problems, particularly for people who spend substantial time outdoors:

• Skin cancer
• Suppression of the immune system
• Cataracts
• Premature aging of the skin

UV waves injure cells in the epidermis (outer layer) by diffusing into the inner layer and causing an enlargement of vessels.  Blisters can occur due to too much exposure.  If there is overexposure, blisters can leave scars or can cause skin cancer.  Because of these serious health effects, you should limit your exposure to UV radiation and protect yourself when outdoors.

Types of UV Radiation

Scientists classify UV radiation into three types or bands - UVA, UVB, and UVC.  The stratospheric ozone layer absorbs some, but not all, of these types of UV radiation:

• UVA:  UVA is the most commonly encountered type of UV light.  UVA exposure has an initial pigment-darkening effect (tanning) followed by erythema if the exposure is excessive. Atmospheric ozone absorbs very little of this part of the UV spectrum. UVA is needed by humans for synthesis of vitamin D; however, overexposure to UVA has been associated with toughening of the skin, suppression of the immune system, and cataract formation. UVA light is often called black light.  Most photo therapy and tanning booths use UVA lamps.
   
• UVB:  UVB is typically the most destructive form of UV radiation because it has enough energy to cause photochemical damage to cellular DNA, yet not enough to be completely absorbed by the atmosphere.  UVB is needed by humans for synthesis of vitamin D; however, harmful effects can include erythema (sunburn), cataracts, and development of skin cancer. Individuals working outdoors are at the greatest risk of UVB effects.  Most solar UVB is blocked by ozone in the atmosphere, and there is concern that reductions in atmospheric ozone could increase the prevalence of skin cancer.

• UVC:  UVC is mostly absorbed by the ozone layer, but some does reach the Earth's surface.   UVC is almost never observed in nature because it is absorbed completely in the atmosphere, as are Far UV and Vacuum UV.  Germicidal lamps are designed to emit UVC radiation because of its ability to kill bacteria.  In humans, UVC is absorbed in the outer dead layers of the epidermis. Accidental overexposure to UVC can cause corneal burns, commonly termed welders' flash, and snow blindness, a severe sunburn to the face.  While UVC injury usually clears up in a day or two, it can be extremely painful.

UV Levels - Adjusting Factors and Considerations

The level of UV radiation that reaches the Earth's surface can vary, depending on a variety of factors.  Each of the following factors can increase your risk of UV radiation overexposure and its consequent health effects.

The ozone layer absorbs most of the sun's UV rays, but the amount of absorption varies depending on the time of year and other natural phenomena. That absorption also has decreased, as the ozone layer has thinned due to the release of ozone-depleting substances that have been widely used in industry.

The sun is at its highest in the sky around noon.  At this time, the sun's rays have the least distance to travel through the atmosphere and UVB levels are at their highest.  In the early morning and late afternoon, the sun's rays pass through the atmosphere at an angle and their intensity is greatly reduced.

The sun's angle varies with the seasons, causing the intensity of UV rays to change.  UV intensity tends to be highest during the summer months.

The sun's rays are strongest at the equator, where the sun is most directly overhead and UV rays must travel the least distance through the atmosphere.  Ozone also is naturally thinner in the tropics compared to the mid- and high-latitudes, so there is less ozone to absorb the UV radiation as it passes through the atmosphere.  At higher latitudes, the sun is lower in the sky, so UV rays must travel a greater distance through ozone-rich portions of the atmosphere and, in turn, expose those latitudes to less UV radiation.

UV intensity increases with altitude - there is less absorbing of the damaging rays. At higher altitudes your risk of overexposure increases.

Cloud cover reduces UV levels but not completely.  Depending on the thickness of the cloud cover, it is possible to get burned on a cloudy summer day though it may not seem very warm. You can even increase your risk of long-term skin and eye damage.

Some surfaces, such as snow, sand, grass, or water can reflect much of the UV radiation that reaches them and because of this reflection, UV intensity can be deceptively high even in shaded areas.

How UV PROTECTION is measured:

Ultraviolet Protection Factor (UPF) is a measure of the protection provided by clothing fabrics.  The fabric is exposed to a UVR lamp that simulates the sun's intensity around noon.  The amount of UVR blocked by the fabric is then calculated.  Inclusion of the biological effectiveness of UVR in the calculations ensures that sufficient weighting is given to the UVB wavelengths and that the UPF can be applied readily to exposure situations involving people.

Sun Protection Factor (SPF) is a measure of the protection provided by sunscreens.  SPF is the ratio of the UVR dose that is required to produce a perceptible reddening of skin treated with sunscreen compared to untreated skin.  Use of sunscreen of at least SPF 15 is recommended for any areas of the body exposed to UVR.

Eye Protection Factor (EPF) is a measure of the protection provided by sunglasses and other eyewear.  EPF is the ratio of UVR dose to the unprotected eye to that of the protected eye.  EPF has a numerical rating scale from 1 to 10 used to classify how well a lens blocks UVR.  Sunglasses with an EPF rating of 9 or 10 transmit almost no UVR.

Most sun protective garments rely on the fabric's natural ability to block UVR (ultraviolet rays).  Sun protective garments are not usually specially treated, although chemical treatments are available. Laboratory testing determines how effective a material is at blocking UVR and this is often stated on the garment label as a UPF rating. The UPF rating of a material can be determined by placing it under a UVR lamp and measuring the amount of UVR that passes through the fabric. From this UVR transmission data the UPF rating can be calculated.

The UPF rating indicates how much the material reduces UVR exposure.  For example, a material with a UPF rating of 20 would only allow 1/20th of the hazardous UVR falling on its surface to pass through it.  A garment made from this material would reduce UVR exposure on the areas of skin it covered by a factor of 20. The UVR protection offered by different types of fabrics varies considerably and depends on the factors listed below.

Several factors determine how effective garments are at reducing UVR:

• Composition of the fabric: Different materials such as cotton, polyester, and nylon have different natural UVR-absorbing properties.  
• Weave density: Less UVR passes through tightly woven or knitted fabrics.  As shown below the smaller the spacing between the individual fiber strands the higher the protection.

The World Health Organization (WHO) developed this standardized method for reporting solar UV-Indexes.  The UV-Index is designed to provide the public with a numerical indication of the maximum potential solar UVR level during the day - the higher the number the higher the solar UVR hazard.  The UV-Index allows for cloud cover and other environmental factors and is used worldwide for reporting UVR levels.  UV-Index values are grouped into exposure categories of low, moderate, high, very high and extreme with corresponding color codes.  UV-Index values are related to UVR exposure as shown in the table below.  By following some simple precautions shown in the table below you can reduce your risk of sun related damage.

Click Here for the UV Index in your area. 

What are the risks from UVR exposure?

Over-exposure to UVR can cause sunburn, skin damage and skin cancer.  UVR exposure also places our eyes at risk of photokeratitis, photoconjunctivitus and cataracts. The most obvious short-term effect of over-exposure to UVR is sunburn, also known as erythema.  The more UVR exposure, the worse the sunburn becomes.  A person's cumulative exposure to UVR along with the number of severe sunburns they have received, especially during childhood, increases their risk of developing skin cancer.  Skin cancers affect people of all skin types.
 
Sun exposure causes the outer layers of the skin to thicken.  Long-term exposure can cause skin to wrinkle, sag, and become leathery. 
 
Melanoma, the least common of the skin cancers is the most dangerous, and reported cases of melanoma are growing each year.  Malignant melanoma may be related to severe exposure to solar UVR at an early age, and may appear without warning as a dark mole or other dark spot on the skin.  Any concerns regarding moles or skin spots should be referred to a doctor.
Prolonged exposure to solar UVR can have serious consequences for the eyes. Cataract is one of the most common types of eye damage.  Cataract is the clouding of the lens of the eye, which is responsible for focusing light and producing sharp images.  Without intervention cataract can lead to blindness.  Wearing wrap around sunglasses and a broad brimmed hat can prevent most of the UVR from reaching the eyes.
 
The sensitivity to sunburn can vary between different parts of the body.  The neck, face, ears, and trunk tend to be more sensitive than the limbs.  These parts of the body are at more risk from UVR exposure.  Our lips have thinner layers of skin than the rest of the body.  They have no sweat or oil glands so they can dry and crack easily in the sun.  There are lip balms available that contain sunscreens.

Many forms of protection are available to reduce your exposure to solar UVR.  The best protection is to avoid going outdoors during the middle of the day.  When outdoors, wear clothing with good body coverage, use a hat, sun/UV umbrella, sunglasses, and sunscreen.  The following strategies can reduce your UVR exposure:

• Avoid going outdoors when the sun is at its highest.  UVR peaks between 10am and 2pm (11am to 3pm during daylight-saving time).  This practice can dramatically reduce your UVR exposure;
• Wear clothing that covers the head, arms and legs as well as the body;
• Wear a broad-brimmed or legionnaires style hat to shade the eyes, face, ears and back of the neck;
• Apply at least SPF 15 and preferably SPF 30+ sunscreen to all areas of your body not covered by clothing.  Reapply sunscreen every two hours, even on cloudy days.  Reapply sunscreen after swimming or perspiring as it does wear off.  The greatest problem with sunscreen as UVR protection is that most people apply it too thinly and do not receive the full protection;
• Wear sunglasses when outside.  Choose a style of glasses such as wrap around, that prevent the UVR reaching your eyes from the sides;
• Choose shaded areas where you cannot directly see the open sky or carry a sun/UV protection umbrella.  Even if you are out of the direct sun, UVR can still reach you from the open sky.  UVR can also reflect from some surfaces such as beach sand, white paint, light colored concrete, snow and water, increasing your UVR exposure;
• Remember that if the temperature drops it does not mean that the UVR level has also decreased.

SPECIAL PRECAUTIONS FOR CHILDREN:  Protect children from excessive sun exposure with a sun/UV umbrella, suitable clothing, hats, sunglasses, and sunscreens.  Young children are unaware of the dangers.  Apply sunscreen liberally and often to children following the directions on the Does clothing offer good UVR protection?

Can you feel UVR?

When people state that the sun has "sting in it" they are confusing infrared (IR) radiation with UVR.  The skin detects IR radiation as a sensation of heat but it does not detect UVR.  If enough UVR exposure has occurred to cause sunburn, the damaged skin may become more sensitive to IR.

Solar ultraviolet radiation (UVR) levels are generally not related to temperature.  There can be high UVR levels even on cool days unless there is considerable cloud cover.  UVR and temperature peak at different times of the day.  UVR is usually highest around midday but the temperature is often highest later in the afternoon.  In general, there is a misconception that high temperatures and UVR intensity are related as most people tend to get sunburned when temperatures are lower.  People tend to assume they require less protection from the sun when temperatures are lower.  The intensity of UVR can be high on cool clear days as well as hot days during certain times of the year.  Without knowing the level of UVR people may incorrectly use temperature as a guide to the level of sun protection required.

What is described as windburn is often actually sunburn. Overexposure to UVR can increase the skins sensitivity.  One can argue that there is no such thing as "windburn" and that the wind may dry the skin - but it does not burn it. 

SKIN CANCER FACTS

• More than 1.3 million people each year are diagnosed with skin cancer. 
• Skin cancer is the most common type of cancer in the United States
• According to the American Cancer Society, 80% of skin cancers could be prevented by adequately protecting skin from the sun's rays.

• More than 90 percent of all skin cancers are caused by sun exposure, yet fewer than 33 percent of adults, adolescents, and children routinely use sun protection.
• A person's risk for skin cancer doubles if he or she has had five or more sunburns.

For more information about skin cancer Click Here