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UPF = SPF for clothing

Understanding Sun Protection Clothing


from REI http://www.rei.com/expertadvice/articles/sun+protection.html

see also WikiPedia FTC


More and more outdoor clothing now carries a UPF rating. What does this rating mean?
Why should you care about sun protection clothing?
We provide a quick summary followed by a more in-depth look from several leading dermatology experts.

Sun Protection Basics

1. Sunlight includes rays of invisible ultraviolet (UV) radiation, and overexposure to UV rays can lead to sunburn, accelerated skin aging and skin cancer. Sunscreen and your clothing offer the main forms of significant UV protection.
2. All fabrics disrupt UV radiation to some degree. Clothing that does the best job carries an Ultraviolet Protection Factor (UPF) value. UPF ratings range from 15 (good) to 50+ (excellent).
3. Some individuals have an elevated need for UPF-rated clothing, including:

  • Fair-skinned, sun-sensitive people
  • Children
  • People spending extended time at high elevation, in equatorial regions or on reflective surfaces (such as snow or water).

4. Not everyone needs to wear UV-protective clothing to guard against sunburn. People with "average" to darker skin types rarely get a sunburn on skin covered by clothing, even if they're wearing a basic T-shirt. Even so, UPF-rated clothing enhances everyone's protection against UV-related health risks.

  • Q: What is UPF?

A: Ultraviolet Protection Factor (UPF) is a rating system used for apparel. It indicates how effectively fabrics shield skin from ultraviolet (UV) rays. The higher the UPF number, the greater degree of UV protection a garment offers.

UPF is similar to SPF (Sun Protection Factor), the rating system used for sunscreen products. UPF gauges a fabric's effectiveness against both ultraviolet A (UVA) and UVB light. An SPF number pertains only to a sunscreen's effectiveness against UVB rays, the sunburn-causing segment of the ultraviolet spectrum. Most sunscreens include ingredients that shield skin from UVA rays, but sunscreen makers have yet to agree on how to measure that protection.

  • Q: What is in sunlight that puts our skin at risk?

A: In addition to visible light and other spectrums, sunlight includes invisible ultraviolet radiation (UV-R). Overexposure to the UV spectrum has been linked to skin cancer, accelerating skin aging and sunburn.

Three types of UV rays exist:

  • UVA (320-400 nanometers, or one-billionth of an inch): Causes premature skin aging, wrinkling and potentially skin cancer. Penetrates skin more deeply than UVB rays. Can impact skin during any hour of daylight. Can penetrate clouds and untreated glass.
  • UVB (290-320 nm): Causes sunburn; also contributes to premature skin aging and potentially to skin cancer. Causes most impact between 10am and 4pm. Can penetrate clouds, but not glass.
  • UVC (200-290 nm): Deadly to humans. Fortunately, it is absorbed by atmospheric gases before it reaches the earth's surface.


Excessive UV radiation weakens the body's immune system in addition to causing cancer. According to the American Cancer Society, skin cancer is the most common form of cancer in the United States—an estimated 1 million nonmelanoma cases are diagnosed annually. The majority of skin cancer cases, up to 90%, are sun-related.

Many skin-care experts believe clothing shields skin more effectively from UV light than sunscreen. Key reasons: Many of us often apply sunscreen lotions too thinly, giving our skin less protection than the sunscreen's available SPF rating, and we neglect to reapply it.

  • Q: How do I interpret UPF ratings?

A: UV-protection claims for clothing were first formalized in the 1990s in Australia, where skin cancer is a widespread concern. Researchers there developed the first fabric testing procedures for UV transmission and created a UPF rating system (see chart below). Clothing manufacturers have since voluntarily adopted this system.

UPF Range Protection Category Effective UV-R Transmission (%) UPF Rating
15-24 Good 6.7-4.2 15, 20
25-39 Very Good 4.1-2.6 25, 30, 35
40-50, 50+ Excellent Less than 2.5 40, 45, 50, 50+

Basically, a UPF rating of 50 indicates the fabric of a garment will allow only 1/50th (roughly 2%) of available UV radiation to pass through it. A garment rated UPF 25 permits roughly 4% (1/25th) UV transmission.

The higher the number, the better the protection the fabric offers. Any fabric that allows less than 2% UV transmission is simply labeled UPF 50+.

All fabrics in some way impact the transmission of UV radiation. You may read that fabrics "absorb" UV rays, but that wording implies that fabrics somehow soak up UV radiation like a sponge. That's not exactly the case. When ultraviolet radiation and textiles interact, the energy of UV rays is changed. UV radiation is converted to heat, a transformation that renders most rays harmless. Some garments, depending on factors such as construction, dyes and fabric treatments (explained later in this article), do a better job at this than others.

The original Australian rating system stipulates that garments made with fabrics rated below UPF 15 cannot be marketed as UV-protective. So where does a white cotton T-shirt rate? Many Web sites estimate it falls between UPF 5 and UPF 8, meaning it could allow as much as 20% (one-fifth) of available UV radiation to pass through.

While no doubt true in some cases, many newer T-shirts are treated with "optical brightening agents." These OBAs, appearance-enhancers for white fabrics, also boost disruption of UV radiation. Most common household detergents also include OBAs, so repeated launderings will increase the fabric's accumulation of brighteners and thus increase its UV-protective ability. Some experts estimate that such shirts may offer a UPF of nearly 15.

  • Q: Which skin types are most vulnerable to UV radiation?

A: The FDA publishes the following guide to skin types:

Type Sun History /// Example
I Always burns easily, never tans, extremely sun sensitive skin /// Red-headed, freckles, Irish/Scots/Welsh
II Always burns easily, tans minimally, very sun-sensitive skin /// Fair-skinned, fair-haired, blue or green-eyed, Caucasians
III Sometimes burns, tans gradually to light brown, sun-sensitive skin /// Average skin
IV Burns minimally, always tans to moderate brown, minimally sun-sensitive /// Mediterranean-type Caucasians
V Rarely burns, tans well, sun-insensitive skin /// Middle Eastern, some Hispanics, some African-Americans
VI Never burns, deeply pigmented, sun-insensitive skin /// African-Americans

Fair-skinned individuals (Types I and II) commonly embrace UPF-rated clothing as an effective method for shielding their sun-sensitive skin. Yet people with any skin type can benefit from having their skin covered with UV-protective clothing to guard against the less-obvious risks (aging and skin cancer) associated with UV rays.

Children also can benefit from UV-protective clothing. The Centers for Disease Control and Prevention (CDC) reports that just a few serious sunburns can increase a child's risk for developing skin cancer later in life. Clothing is a reliable form of sun protection for children, particularly for those who are not fond of sunscreen lotions.

UV-protective clothing also makes sense for outdoor-oriented people of any skin type who plan to explore areas with increased UV intensity, such as high elevations, equatorial regions, or areas in close proximity to reflective surfaces (water, sand, snowfields).

An overall UV protection strategy includes the use of sunscreen, wearing UV-protective clothing and limiting the amount of time you expose yourself to UV radiation.
How Sun Protection Clothing Works

  • Q: What makes some fabrics more effective at disrupting UV rays than others?

A: There are a variety of factors:

  • Construction: Dense, tight construction (either weaves or knits) minimizes the spaces between yarns, which in turn minimizes the amount of UV light that can pass through. Some tightly constructed UPF-rated garments use vents to boost air circulation and help the wearer stay cool. Thicker fabrics also help reduce UV transmission.
  • Dyes: It is the specific type of dye (and the concentration in which it is used) that impacts a fabric's UV transmission, not its color. Some dyes deflect more UV radiation than others, and some absorb none at all—including black dyes. How can one know what kind of dyes are used in individual garments? The only tip-off is if the garment carries a UPF rating. Clothing engineered for UV protection may use high concentrations of premium dyes that disrupt UV light. Such dyes include "conjugated" molecules that disrupt UV radiation. The higher the concentration of such dyes, the darker the garment becomes. But ultimately color has no influence on UV rays. Note: Pigment-dyed fabrics, which include a resin that creates a powdery look and feel, get high marks for UV protection.
  • Treatments: Chemicals effective at absorbing UV light may be added during processing. Specialized laundry additives, which include optical brightening agents and newly developed UV-disrupting compounds, can boost a garment's UPF rating.
  • Fiber type: Polyester does an excellent job at disrupting UV light (due to hydrogen- and carbon-based benzene rings within the polymer). Nylon is good. Wool and silk are moderately effective. Cotton, rayon, flax and hemp fabrics (natural fibers composed of cellulose polymers) often score low without added treatments. However, unbleached or naturally colored cotton performs better at interacting with UV light than bleached cotton.
  • Stretch: If a garment is stretched 10% or more beyond its normal dimensions, spaces between yarns are widened and its effectiveness against UV light may be reduced up to 40%.
  • Wetness: A fabric's ability to disrupt UV radiation is usually reduced when wet, though the reasons why are not completely understood. Wetness may cause a 30% to 50% reduction in a fabric's UPF rating.
  • Condition: Worn or faded fabrics are less effective against UV light.

Q: Before a UPF rating is assigned to a garment, how is it tested?
A: The first UPF testing procedure, developed in 1996, was the Australian/New Zealand test method (AS/NZS 4399).

Procedures were later developed in the United States: American Association of Textile Chemists and Colorists (AATCC) Test Method 183 and American Society for Testing and Materials (ASTM) D 6544. A UPF labeling guide (ASTM D 6603) has also been adopted. The European Committee for Standardization (CEN) has also created standards.

Typically during these tests, UV light is transmitted through a garment's fabric and measured by a radiation-measuring device, either a spectrophotometer or spectroradiometer. In most cases, the fabric is tested dry and without being stretched. The fabric's ability to absorb UV light is then calculated and a UPF value is assigned.
Q: Who regulates UPF clothing?
A: In the U.S., the Federal Trade Commission monitors UPF advertising claims. If a manufacturer's claims are questioned, the FTC can investigate the testing methods that were used to ensure that they support the claim. Most manufacturers and retailers voluntarily follow one of more of the AS/NZS, AATCC and ASTM standards, testing methods and labeling guidelines.

REI uses an independent lab to test fabric samples from its apparel line according to the AS/NZS standard. To ensure accurate and representative UPF labeling, the lightest color of an REI garment style is always tested (since darker colors using higher concentrations of UV-absorbing dyes generate higher UPF values). Sometimes all colors of a particular style are tested.
Q: How does laundering affect UPF-rated clothing?
A: A study paper on the effects of repeated laundering of UPF-rated clothing was published in November, 1998, in Textile Chemist and Colorist, an industry journal.

The paper's conclusions assert that "repeated home launderings (regardless of whether or not the detergent contains an OBA optical brightening agent, the compound commonly found in household detergents, mainly to "keep whites white") does not reduce the UPF rating of a woven or knitted fabric of cotton, polyester, or nylon. On the contrary UPF ratings are enhanced or remain unchanged by repeated launderings up to 20 times."
Q: Most people cannot recall ever getting sunburn on skin that was covered by clothing. So why wear UPF-rated clothing?
A: UPF-rated clothing can optimize any person's protection against UV transmission.
But is it essential that every person who spends any time outside wear such clothing? No.

"You might get fine UV protection from a regular piece of clothing," says Dr. Martin A. Weinstock, professor of Dermatology and Community Health at Brown University Medical School and the chairman of the Skin Cancer Advisory Group of the American Cancer Society. "But with UPF-rated clothing, you're assuring that protection."

Your skin type and your location on the planet both influence your need for UV-protective clothing.

"The lower your skin type number, the more vulnerable you are to UV radiation," Weinstock told REI.com, "and the more intense the UV rays, the more careful you have to be in protecting yourself."

Any skin type, Weinstock adds, may benefit from wearing UV-protective clothing in equatorial regions, at high elevations, or on reflective surfaces such as snow.

Children, who sometimes find sunscreen unappealing and resist its use, may accept the use of UPF-rated clothing more cheerfully. This can help minimize the accumulation of sun exposure during childhood years, which medical experts have linked to an increased risk of developing skin cancer later in life. The National Cancer Institute reports "studies have consistently shown that increased cumulative sun exposure is a risk factor for nonmelanoma skin cancer."

UPF-rated clothing originated in Australia. Due to its proximity to the equator, Australia experiences some of the world's most intense UV exposure. Other factors make Australians highly vulnerable to UV light: A generally clear atmosphere in the southern hemisphere; depleted ozone over Antarctica; a close pass to the sun during the earth's orbit in January, the height of Australia's summer. As the earth tilts at that time of year, sunlight coming through the Antarctica's ozone hole lands on Australia.

In Florida, the state on the U.S. mainland closest to the equator, Dr. Susan Weinkle says she has seen fair-skinned patients experience pigment change on skin that had been covered by nonspecialized clothing.

Weinkle, an Assistant Clinical Professor of Dermatology at the University of South Florida in Tampa, says she has encountered visitors or residents who wear a standard T-shirt as a skin shield while playing in the ocean or a swimming pool. This leaves them, particularly if they have sun-sensitive skin, at risk for sunburn.

"It's not a severe sunburn," Weinkle says, "but the skin nonetheless does get impacted. I've kayaked in the middle of the day in July wearing UPF-rated clothing while using sunscreen on exposed areas of my body. Afterwards I could not tell the difference between the two areas.

"That's just an anecdotal example," Weinkle says, "but it's helped make me a big proponent of sun-protective clothing. You don't have to be a mole and live in a hole to stay safe in the sun. You just have to make good choices."

To do so, Weinstock advises, know your skin and properly anticipate the level of exposure you'll be giving it. "The best clothing to wear may depend if you're fishing in Alaska or skateboarding in Hawaii," he says.

Location indeed matters. A 2002 study by a National Cancer Institute scientist shows that is not unusual to see notable differences in UV intensity between two relatively close locations. New Orleans, for example, receives 20% more UVB each year than Atlanta.

"Even in Rhode Island," Weinstock says of his northerly home state, "someone who's out sailing all day may be wearing an old, worn T-shirt and have no protection on under the shirt. With the sun's reflection off the water, he's bathing in intense UV light all that time. I think he should be concerned about the exposure he's getting."

Still, Weinstock acknowledges, in many circumstances a standard T-shirt is adequate for shielding the average skin types from sunburn and other impacts of UV light. "You just might not get all the protection you want," he says.

"Companies aren't being devious when they offer UPF-rated clothing," adds Weinstock. "They're just offering you your best assurance of staying protected from UV light."
Q: Won't wearing pants and a long-sleeve shirt feel uncomfortable during warm days?
A: Think of the attire commonly associated with desert-dwelling people.
Lightweight, loose-fitting, sun-shielding body coverings have been worn from head to toe for centuries.

Is it possible UPF-rated clothing may feel warmer, especially when you're active? Yes, due to tighter construction and possibly its darker color.

Yet today's modern fabrics—moisture-wicking, quick-drying, highly breathable, engineered for optimal ventilation—make it surprisingly efficient and comfortable to shield skin from UV light while you participate in aerobic outdoor pursuits.


Page last modified on 01 February, 2012


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