Effect of stretch on the ultraviolet spectral transmission of one type of commonly used clothing.

The spectral ultraviolet (UV) transmission through stockings was measured in field and laboratory based trials using a spectroradiometer. From these spectral UV measurements, the ultraviolet protection factor (UPF) was calculated. The UPF of stockings measured in the field was generally higher than that measured in the laboratory when using a quartz tungsten halogen light as the UV source. The UPF of 50 denier stockings decreased 868% when stretched 30% from their original size. Doctors recommending and patients using high denier stockings for patient photoprotection should be aware of the dramatic decrease in UPF when the stocking is in a stretched position, such as over a human leg.