GENEVA — The World Health Organization late last month kicked off an educational campaign intended to convince people to take more seriously the health risks posed by exposure to the ultraviolet rays in natural sunlight, which cause sunburn and can be a contributing cause of skin cancer. WHO scientists reacted warmly to a proposed European Union action that would impose standards on clothing marketed as protecting the wearer from the sun’s rays.

While all clothing provides some measure of protection from ultraviolet rays, scientists have found that many factors, including fabric density and construction, can influence how well a garment protects the skin it covers. The EU is considering requiring clothing makers to prove their wares have a sun protection factor of 40 if they wish to market them as effective protection from UV rays.

The SPF system, best known as a measure of the efficiency of sunscreen, is essentially a multiplier. A lotion or garment with an SPF of 10 extends by 10 times the amount of time the wearer can remain in the sun before beginning to burn — so a fair-skinned person who might begin to burn in strong sunlight within 15 minutes could remain safely in the sun for 150 minutes, or 2 1/2 hours, when protected by SPF 10 sunscreen. Wearing clothing with an SPF of 40, which would meet the proposed EU standards, would allow the same person to remain safely in the sun for 10 hours.

Research by scientists in Australia, the U.K., the U.S., Switzerland and other countries with large light-skinned populations — who are considered most at risk — has shown that the level of protection can vary widely between fabrics and garments.

Eva Rehfuess, WHO scientist on UV radiation, said the development of UV protection standards for clothing is "a welcome development because it can help people in high UV climates or high UV exposure to protect themselves better."

The WHO estimates that UV radiation is responsible for between two million to three million cases of skin cancer worldwide each year, including 132,000 malignant melanomas.

Solar radiation may also be responsible for over two million cases of blindness due to cataracts, out of a worldwide total of about 12 million to 15 million cases, it said.As part of its campaign, the WHO is proposing an index system to rate the strength of UV rays at any given time. The index runs from 1 to as high as 18.

Mike Repacholi, WHO coordinator for radiation and environmental health, said, "A high index will indicate there are high UV levels and high skin damage can occur."

Numbers below two, which would describe very cloudy or wintery conditions, are considered low risk for exposure to UV light. Moderate risk is 3 to 5, high risk is 6 or 7 and very high risk is 8 to 10. Anything over 11 is considered extreme risk, such as the conditions that might be experienced on a sunny day in the U.S. or Western Europe between 10 a.m. and 2 p.m.

The closer to the equator one gets, the higher the potential risk becomes. In New York, the risk rating might only get as high as 10, while in Texas it could hit 15, and in equatorial countries it could reach 18.

The objective of the WHO offensive is to try to get all countries using a uniform index to measure solar UV radiation and to recognize the index "as they recognize the weather" and "use as another parameter to protect themselves," said Repacholi.

The UV index does not correlate directly with the SPF index.

Scientists in Australia in 1997 developed the first standard for SPF metrics in fabric and over nine million garments with hangtags giving ultraviolet protective factor ratings have been sold. The rating applies to the fabric, not the garment itself, leaving it to the wearer to recognize how much skin the garment covers.

The standard, which is voluntary, indicates the rating may change with stretching, wetting and wear.

Colin Roy, who developed the standard along with other researchers at the Australian Radiation Protection and Nuclear Safety Agency, said he and his associates faced major difficulties in trying to formulate the standard.

For example, they found that "the stretching of both knitted and woven fabrics will cause a decrease in UPF," he said. The actual drop in UV protection is very dependent on the fabric used, with the reduction "greater for knitted rather than woven materials," he added.The Australian research showed that wetting a fabric can decrease its protective properties, especially for light-colored fabrics, and that a washing might lower a garment’s level of protection.

Meanwhile, researchers at the U.K.’s National Radiological Protection Board in Glasgow, Scotland, and Chilton, England, caution that while clothing is a source of protection against UVR, "its effectiveness is not fully quantified."

"Both the structure of a fabric…and its color can have a large influence on its UVR protection," they reported.

In the case of the pending EU standard, manufacturers and or retailers that put EU logos or claims on their products will only be able to do so if the product has been tested according to the standard, said Colin Driscoll of the National Radiological Protection Board.

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