In vitro and in vivo determination of the UV protection factor for lightweight cotton and viscose summer fabrics: A preliminary study

Abstract

Background: One of the most important elements in the prevention of skin cancer is the use of comfortable UV-protective clothing. Owing to their low weight, cotton fabrics, and especially viscose fabrics made from filament yarns, are ideal for summer clothing and in fact enjoy a high degree of acceptance among consumers. Two methods are available for determining the UV protection factor (UPF) of textiles: the in vitro method is based on the spectrophotometric determination of the transmission of UV radiation through these fabrics; the in vivo method is based on the determination of the minimal erythema dose for a test subject with and without textiles. Objective: This study was performed to assess the UPF of lightweight cotton and viscose fabrics and whether the use of these two methods to determine the UPF of viscose fabrics and cotton fabrics produces congruent results. Methods: We tested 7 different viscose fabrics and 7 different cotton fabrics. Three of the viscose fabrics (ENKA SUN) had been specially treated, by depositing pigments in the fibers, to confer UV-protective properties. The determination of the in vitro and in vivo UPF was performed with a spectrophotometer and sun simulator, respectively. Results: The in vivo measurements on the untreated viscose fabrics produced UPF values lower than those obtained from the in vitro measurements. For one of these untreated viscose fabrics, the difference between the in vivo UPF and the in vitro UPF was statistically significant (P < .05). In contrast, the in vivo measurements on the specially treated viscose textiles and on the cotton fabrics resulted in UPF values higher than the in vitro UPF values. For one specially treated viscose fabric and 4 cotton fabrics, this difference was statistically significant (P < .05). Conclusion: Our results suggest, however, that—depending on the type of fabric—determination of the UPF by the in vitro method is not in agreement with the in vivo method. In vivo measurements made with lightweight specially treated UV-protective clothing showed in contrast to the untreated viscose fabrics that these garments offer very good protection against UV radiation. These results underscore the importance of developing and refining such UV-protective materials. (J Am Acad Dermatol 2000;43:1009-16.)