Pre-vitamin D3 effective ultraviolet transmission through clothing during simulated wear

Background/purpose: Clothing is an important protective layer used to reduce ultraviolet (UV) exposures to the skin surface. However, not all UV exposure is linked to detrimental health effects with some exposure to UVB wavelengths below 316 nm required for the synthesis of pre-vitamin D-3. The aim of the current research was to investigate the effect of fabric type, color, fit, and wetness on the transmission of pre-vitamin D-3 effective UV through garments during simulated wear, in a high UV exposure environment. Methods: Dosimeters fabricated from polysulfone film were positioned at eight selected body sites on the skin surface and clothing surface of identically designed, loose and fitted, black and white T-shirts made up in two knitted fabric types and tested when both dry and when drying after initial wetting (n=3 replicates). The T-shirts were placed on manikins set to simulate humans in the sun between 09:30 and 12:30 Eastern Standard Time during the Southern Hemisphere summer period. The post-exposure absorbance was measured and the dosimeters were calibrated for biologically effective UV for pre-vitamin D-3 synthesis with a UV spectroradiometer. The effect of fit, fabric type, color, and wetness on pre-vitamin D-3 effective UV transmission during simulated wear was assessed. Results: Irradiances varied among body sites with the highest erythemal exposures to a horizontal plane over the 3 h period reaching approximately 14.5 minimal erythema dose (MED) while the highest exposure under the garment was 0.22 MED which may not be above the threshold for pre-vitamin D-3 synthesis for the time period investigated. Fabric and fit were the main variables affecting transmission of pre-vitamin D-3 effective UV. Some interactions were identified between the fabric color and wetness and between fabric type and color; however, while significantly modifying transmission these effects were small. Conclusion: Transmission of pre-vitamin D-3 effective UV occurred through the high UPF knitted fabrics investigated. However, the length of exposure will influence whether the irradiances are sufficient to be above the threshold for pre-vitamin D-3 synthesis. The main effect on transmission of pre-vitamin D-3 effective UV was the fit of the T-shirt and its fabric type (probably structure) rather than color or degree of wetness.