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UV-Protective Textiles Standards by Kathryn L. Hatch
As having out-of-doors leisure time became a symbol of success, having tanned skin became socially desirable. Clothing styles changed and new social mores made it acceptable to cover less skin with fabric. Therefore, there was greater exposure of the skin to the sun’s radiation. As sun exposure increased, so did rates of skin cancer. Today, there are over one million new cases of skin cancer each year in the United States, making it the most prevalent form of cancer. Such increasing rates of skin cancer around the world as well as within the United States, especially among people with fair skin, has caused a re-examination of the use of clothing as a means to prevent sunlight from reaching the skin. Interest has soared in measuring the ability of fabric to block sunlight (especially its ultraviolet rays, which are responsible for tanning and burning), in quantifying the amount of UV protection provided by various fabrics, and in using that information to label clothing/fabric as UV protective. The U.S. standard definition for UV protective textile is any textile (fabric or product made from fabric) “whose manufacturer and/or seller claims that it protects consumers from ultraviolet radiation, claims the reduction of risk of skin injury associated with UV exposure, and/or uses a rating system that quantifies the amount of sun protection afforded.” Clothing, fabrics to be made into clothing, fabrics for tents, awnings, baby carrier covers, and other “shade” products may be UV protective textiles. Standard setting organizations around the world are engaging in writing standards for textiles so that companies who manufacture products they want to label as being UV protective can make a legal claim that they are. World Involvement Standards Australia/New Zealand (www.standards.com.au) led the way in 1996 with the publication of AS/NZS 4399:1996, Sun Protective Clothing—Evaluation and Classification. This comprehensive standard includes a) a definition for UV protective clothing, b) a detailed procedure for determining the UV transmittance of fabric, c) the formulas required to calculate UPF (ultraviolet protection factor) and percent of blocking from the UV transmittance data, and d) directions for taking those UPF or percent block numbers and determining the singular UPF or singular percent block value to appear on a label in the consumer marketplace. This number is called the label UPF. Standard AS/NZS 4399 also establishes three categories of protection—excellent, very good, and good. The category in which a specific fabric belongs depends on the label UPF value. A fabric must have a UPF of 15 to be classed as UV protective. The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) issues a certification label to those manufacturers who test and label their fabrics according to AS/NZS 4399. From the publication of the Australian/New Zealand standard in 1996 until today, American, British, Canadian, European, South African, and multinational groups have engaged in writing UV protective textile standard documents. Specific standard setting organizations at work include ASTM and the American Association of Textile Chemists and Colorists (AATCC) (United States), the European Commission for Standardization (CEN) (European), the British Standards Institution (BSI) (Britain), the Canadian General Standards Board (CGSB) and Commission on Illumination (CIE) (multinational). Each standard document being written by these agencies is not as comprehensive as AS/NZS 4399. For example, BS 7914, AATCC TM 183, and CEN/TC248WG 14 are standard documents presenting a method for taking fabric UV transmittance measurements and formulas for converting that data into UPF and/or percent block information. ASTM D 6544 is a standard document presenting a procedure for exposing fabric to simulated sunlight and to repeated laundering before transmittance measurements are done. Standard Scientific Units for UV Protection Ultraviolet protection factor (UPF) is the scientific unit used to indicate the amount of UV protection provided to skin by fabric. It is like the sun protection factor (SPF), used on sunscreen lotion bottles in its interpretation. The higher the value (UPF or SPF), the longer a person can stay in the sun until the area of skin under the product (sunscreen lotion or fabric) becomes red. A person who can stay in the sun 10 minutes until his/her skin just starts to get red can stay in the sun 30 times longer wearing a fabric with a UPF of 30 or a sunscreen lotion of SPF 30. At the end of the 300 minutes, the amount of UV exposure is the same. It just took longer under the protection of fabric or sunscreen lotion. UPF and SPF are measures of sunburn protection because skin redness is the end point in determining the value. Several reasons have been given for using UPF rather than SPF as the scientific unit for designating UV protection provided by fabric. The first of these is to make a distinction in the data collection method. Fabric can be placed into a spectrophotometer and that instrument can provide data about how much of each wavelength of UV passes through the fabric. This is not the case for testing sunscreen lotions. The protection they provide to UV radiation is usually determined by applying sunscreen to a person’s skin and then directing simulated sunlight at that skin area. A second reason for using UPF is to emphasize that the protection is from ultraviolet radiation, not to the entire sunlight spectrum of radiation. Percent block is another scientific unit to express amount of UV protection. Actually, it is a unit that expresses a fabric property, the ability of the fabric to block UV from passing through it. The higher the percent of block, the better the fabric is at keeping UV radiation from reaching the skin. In many cases, UV block is expressed as UVA block and as UVB block. United States Standards In the United States, three standard documents have been developed to spell out how fabric is to be prepared prior to submission to UV transmittance testing, how UV transmittance data is to be obtained and then used to calculate UV protection for each specimen tested, and how this information in turn is to be combined to determine the protection value to be placed on a consumer product label. Two national standard setting organizations (AATCC and ASTM) have been involved. The titles of the standards presented in the order in which they would be used are: • ASTM D 6544, Preparation of Textiles Prior to UV Transmittance
Testing; The first document, ASTM D 6544, is unique among the world’s UV textile documents in that it requires manufacturers or retailers to launder garment fabric they want to claim is UV protective 40 times, to expose it to 100 AATCC Fading Units of simulated sunlight under conditions described in 8.2 a in AATCC 16E, and if it is to be made into swimwear, to expose it to chlorinated pool water as instructed in AATCC 162 section 8.3. The rationale is that the UV protection factor to be placed on the label should be the lowest protection expected during the use-life of the article. A unique inclusion in ASTM D 6544 is reference to ASTM sampling documents to help ensure that label information is specific to a production lot. The AATCC 183 document does not differ in any significant way from the method outlined by the Australians, from the BS 7914 (Method of test for penetration of erythemally weighted solar ultraviolet radiation through clothing fabrics; 1988), or CEN/TC 248WG14 (Apparel fabrics, Solar UV protective properties – Method of test, 1998) or in the AS/NZS 4399. The approach in all documents is to use a spectrophotometer to collect the transmittance data. Many values are collected as a transmittance value is taken at five-nanometre increments along the UV spectrum (UVA and UVB). In each document, the same formula is then used to calculate the UPF and percent of blocking (UVA and UVB) from the transmittance data. In the formula, those wavelengths that are known to make a greater contribution to skin burning than others are given greater weight in determining the sunburning protection ability of the fabric. ASTM D 6603 instructs that a label in a UV protective textile must contain: a) A UPF value; Like AS/NZS, fabrics with calculated label UPF values of 40 to 50+ are classed in the Excellent UV protection category, those with UPF values greater than 25 but less than 40 in the Very Good UV protection category, and those with calculated label UPF values higher than 15 but less than 25 in the Good UV protection category. Other standard setting organizations have not published documents pertaining to labeling. Textiles with calculated UPFs of less than 15 are not to be called nor labeled as UV protective. A claim can be made that the area of skin covered by the UV protective fabric is protected against sunburn. No claims are permitted about prevention of cancer or reduced aging of the skin. Claims cannot be made that people with skin sensitized to solar radiation as a result of taking prescribed drugs are protected against skin flare-ups. The Federal Trade Commission (FTC) and the Consumer Product Safety Commission (CPSC) have assisted in the development of the three U.S. standards. The standards are voluntary but could become mandatory if the emerging and rapidly growing UV protective clothing industry does not use the voluntary standards for preparing specimens, for testing, and for proper labeling. Certifiers An interesting aspect of the emerging industry is the trend to have product certifiers. Certifiers include the American Sun Protection Association, the Skin Cancer Foundation, the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA), the International Test Association for Applied UV Protection, and Cancer Society of South Africa. Certifiers may use the standards of national standard setting organizations, as the first three listed above do, or may develop their own, as is the case with the latter two certifiers. In all cases, certifiers have developed distinctive labels that are given or sold to producers of UV-protective textiles. These labels make the product readily identifiable as UV protective in the consumer marketplace. Further Information Those currently involved in or thinking about being involved in the manufacture of UV protective fabric, UV protective clothing, UV protective shade devices, or the distribution of such products can obtain assistance with understanding of the U.S. standards by using the Internet addresses used throughout this document, contacting the author, the AATCC , or the director of the American Sun Protection Association, Mary K. Buller. // Copyright 2001, ASTM |
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For centuries, people have known that fabric prevented one’s skin
from tanning and/or burning. Sahara desert dwellers, for example,
covered themselves from head to foot and continue to do so today.
Eighteenth century European and American upper-class women understood
that wearing long dresses with long sleeves, carrying parasols,
and wearing gloves prevented even the slightest coloration of
their skin. One motivation for preventing such tanning was the
desire not to be identified as a member of the working class who
often labored out-of-doors.| Kathryn L. Hatch is professor of textiles at the University of Arizona, College of Agriculture and Life Sciences, Tucson, Ariz. She is the chair of ASTM Subcommittee D13.65 on UV-Protective Textiles. |