Sun protective clothing
Sun protective clothing is clothing specifically designed for sun protection and is produced from a fabric rated for its level of ultraviolet (UV) protection. A novel weave structure and denier (related to thread count per inch) may produce sun protective properties. In addition, some textiles and fabrics employed in the use of sun protective clothing may be pre-treated with UV inhibiting ingredients during manufacture to enhance their UV blocking capacity.
Not only limited to UV-inhibiting textile use, sun protective clothing may also adhere to specific design parameters – including styling appropriate to full coverage of the skin most susceptible to UV damage. Long sleeves, full collars, and full-length trousers and skirts are common styles for clothing as a sun protective measure.
A number of fabrics and textiles in common use today need no further UV-blocking enhancement based on their inherent fiber structure, density of weave, and dye components – especially darker colors and indigo dyes. Good examples of these fabrics contain full percentages or blends of heavy weight natural fibers like cotton, linen and hemp or light-weight synthetics such as polyester, nylon, spandex and polypropylene. Natural or synthetic indigo dyed denim, twill weaves and canvas are also good examples. However, a significant disadvantage is the heat retention caused by heavier weight and darker colored fabrics.
As sun protective clothing is usually meant to be worn during warm and humid temperatures, some UV-blocking textiles and clothing may be designed with ventilated weaves, moisture wicking and antibacterial properties to assist in cooling and breathability.
Although clothing has been used for protection against solar exposure for thousands of years, in modern times sun protective clothing was popularized (but not exclusively used) in Australia as an option or adjunct to sunscreen lotions and sunblock creams. Sun protective clothing and UV protective fabrics in Australia now follow a lab-testing procedure regulated by a federal agency: ARPANSA. This standard was established in 1996 after work by Australian swimwear companies. The British standard was established in 1998. The NRPB (National Radiological Protection Board) forms the basis of the British Standards Institute standard. Using the Australian method as a model, the USA standard was formally established in 2001, and now employs a more stringent testing protocol: This method includes fabric longevity, abrasion/wear and washability. UPF testing is now very widely used on clothing used for outdoor activities.
The original UPF rating system was enhanced in the United States by the ASTM (American Standards and Testing Methods) Committee D13:65 at the behest of the U.S. Federal Trade Commission (FTC) to qualify and standardize the emerging sun protective clothing and textile industry. When the FDA discontinued regulating sun-protective clothing, the Solar Protective Factory took the lead in developing performance and durability testing standards by working with the American Society for Testing and Materials (ASTM). The CEO of the Solar Protective Factory served as the chairman of the ASTM committee (D13.65) working with the Federal Trade Commission (FTC) and the Consumer Product Safety Commission (CPSC), to establish the UPF testing protocols and labeling standards which are presently used in the United States.
The FDA had reviewed clothing making sun protection claims (SPF, % UV blockage, or skin cancer prevention claims) in 1992. Only one brand of sun protective clothing, Solumbra, was reviewed and cleared under medical device regulations. The FDA initially regulated sun protective clothing as a medical device, but later transferred oversight for general sun protective clothing to the FTC. The UPF rating system may eventually be adopted by interested apparel and domestic textile/fabric manufacturers in the industry at large as a "value added" program strategic to complement consumer safety and consumer awareness. Before UPF standards were in place, SPF ratings were used for clothing, this has since been disregarded as a means of measuring a fabrics ability to block UV rays, since SPF is a rating that is used for skin applications, it measures how much longer a person's skin takes to redden when the application was applied. UPF ratings clearly rate a fabrics ability to block UV radiation.
Factors that affect the level of sun protection provided by a fabric, in approximate order of importance, include weave, color, weight, stretch, and wetness. In addition, UV absorbers may be added at various points in the manufacturing process to enhance UV protection levels. The more open/less dense the fabric, the worse the protection(weave weight stretch).The darker the color, the more dye, the better the protection. Getting a fabric wet reduces the protection as much as half except for silk and viscose which can get more protective when wet. Polyester contains a benzene ring that absorbs UV light.
There is some indication that washing fabrics in detergents containing fabric brighteners, which absorb UV radiation, might increase their protective capability. Studies at the University of Alberta also suggest that darker colored fabrics can offer more protection than lighter colored fabrics.
Provide better protection:
- Specially manufactured fabrics
- ZnO Cotton Viscose fabrics
- black or dark blue denim jeans
- wool garments
- Satin finished silk of any weight
- Shiny polyester blends
- tightly woven fabrics
- unbleached cotton(most cotton sold is bleached)
Provide low protection:
- polyester crepe
- bleached cotton
- undyed/white jeans
- worn/old fabric
A relatively new rating designation for sun protective textiles and clothing is UPF (Ultraviolet Protection Factor). Unlike SPF (Sun Protection Factor) that traditionally uses human sunburn testing in a laboratory environment, UPF measures both UV radiation transmittance using a laboratory instrument (spectroradiometer) and an artificial light source and translates these results using a mathematical expression based upon the sunburn action spectrum (erythema action spectrum) integrated over the relevant UV spectrum. Theroretically, both human SPF testing and in vitro laboratory instrument testing measure a product's relative ability to protect against minimal sunburn compared to skin that is not protected.
Developed in 1998 by Committee RA106, the testing standard for sun protective fabrics in the United States is the American Association of Textile Chemists and Colorists (AATCC) Test Method 183. This method is based on the original guidelines established in Australia in 1994. Below is the ASTM Standard for Sun Protective Clothing and Swimwear which is considered the industry standard in rating such sun protective clothing:
UPF Ratings and Protection Categories
|UPF Rating||Protection Category||% UV radiation Blocked|
|UPF 15 - 24||Good||93.3 - 95.9|
|UPF 25 - 39||Very Good||96.0 - 97.4|
|UPF 40 - 50+||Excellent||97.5 - 99+|
Summary UPF Testing Protocol
AATCC 183 method defines the UPF rating for a fabric/textile as the ratio of UV measured without the protection of the fabric (compared to) with protection of the fabric. For example, a fabric rated UPF 30 means that if 30 units of UV fall on the fabric only 1 unit will pass through. A UPF 30 fabric that blocks or absorbs 29 out of 30 units of UV is therefore blocking 96.7% UV. UPF tests are normally conducted in a laboratory with a spectrophotometer or a spectroradiometer.
AATCC 183 should be used in conjunction with other related standards including American Society for Testing and Materials (ASTM) D 6544 and ASTM D 6603. ASTM D 6544 specifies simulating the life cycle of a fabric so that a UPF test can be done at the end of a fabric's life cycle – which is when most fabrics provide the most reduced level of UV protection. ASTM D 6603 is a consumer format recommended for visible hangtag and care labelling of sun protective clothing and textiles. A manufacturer may publish a test result to a maximum of UPF 50+.
While there is some correlation between the amount of visible light that passes through a fabric and the amount of UV that passes the same fabric, it is not a strong relationship. Based on some of the new-technology fibers and textiles designed for the sole purpose of UV blocking, it is not always possible to gain a good understanding of the UV protection level of a fabric simply by holding it up and examining how much visible light passes through the fabric.
Sun protective clothing and textile/fabric manufacturers are currently a self-regulating industry in North America, prescribed by the AATCC and ASTM methods of testing.
- Gies, H.P., Roy, C.R., Elliot, G., & Zongli, W. (1994). "Ultraviolet Radiation Protection Factors for Clothing". Health Physics 67 (2): 131–139. doi:10.1097/00004032-199408000-00003. PMID 8026966.
- Gambichler, T., Rotterdam, Altmeyer, P., & Hoffmann, K. (2001). "Protection against ultraviolet radiation by commercial summer clothing: need for standardized testing and labelling". BMC (BioMed Central) Dermatology I: 6–9. doi:10.1186/1471-5945-1-6.
- American Association of Textile Chemists and Colorists (AATCC) Test Method 183
- American Society for Testing and Materials (ASTM) Standard D 6544
- American Society for Testing and Materials (ASTM) Standard D 6603
- Stanford, Duncan G., Georgouras, Katherine E. & Pailthorpe, Michael T. (1997). "Rating clothing for sun protection: current status in Australia". Journal of the European Academy of Dermatology & Venereology 8 (1): 12–17. doi:10.1016/S0926-9959(96)00101-8.