What is UPF

Wicked Catch Sun Protection Basics - Understanding Sun Protection Clothing

  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. People spending extended time at high elevation, in equatorial regions or on reflective surfaces (such as snow or water) have an elvated need for UPF-rated clothing.

UPF & Skin Types

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.

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. Clothing manufacturers have since voluntarily adopted this system.

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.

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: 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.

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."

"The lower your skin type number, the more vulnerable you are to UV radiation," Weinstock says, "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 water.

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.

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."

"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."

Researched and written with assistance from researchers and experts in the areas of dermatology, textiles and government regulation. Many advisors to this article declined to be quoted directly due to professional, governmental or academic restrictions.