![Ultraviolet protection factor (UPF) is primarily a measure of UVB protection whereas critical wavelength (CW) is a measure of the degree of broad-spectrum protection. (A) UPF is a mathematical function designed to recapitulate sun protection factor (SPF) from a laboratory measurement of transmittance and is weighted toward the UVB portion of the spectrum. Left: Plots of the erythemal effectiveness function (Eλ) and the solar spectral irradiance (Sλ) over the UVR spectral range. Right: The product of Eλ and Sλ has a peak that lies predominantly (75%) within the UVB range (280–315 nm). Very little of the UPF function comes from wavelengths longer than 360 nm, where the UVR intensity is highest but the erythemal effectiveness is near zero [48]. (B) Visual representation of the CW as the wavelength below which 90% of the total absorbance (area under the curve) in the UVR region is contained. Left: Hypothetical sunscreen that primarily blocks UVB radiation has a critical wavelength below the 370 nm threshold required by the FDA to be labeled broad-spectrum. Right: Hypothetical sunscreen with improved UVA blocking performance meets the broad-spectrum criterion. A sunscreen could meet the CW criterion of 370 nm without comprehensively blocking UVA radiation.](https://www.researchgate.net/publication/358048960/figure/fig1/AS:11431281210550167@1702052767119/Ultraviolet-protection-factor-UPF-is-primarily-a-measure-of-UVB-protection-whereas_Q320.jpg)
![Transmittance of organic sunscreen filters (tested in this study) and inorganic sunscreen filters (ZnO and TiO2). Data were obtained from the BASF sunscreen simulator [59] where the maximum concentration allowable by the FDA [46] was used to generate each curve.](https://www.researchgate.net/publication/358048960/figure/fig4/AS:11431281210550171@1702052769003/Transmittance-of-organic-sunscreen-filters-tested-in-this-study-and-inorganic-sunscreen_Q320.jpg)
![Transmittance spectra of the four fabrics designed for UV protection tested in this study (orange and purple lines) compared to “normal” clothing items tested by Coyne, et al. (gray lines). The data from Coyne, et al. were digitized, converted to transmittance and represent the average of the 16 measurements as reported in the original study. White cotton and dark grey cotton were GAP, Inc. 100% cotton shirts. The denim was 69% cotton, 30% polyester, 1% spandex GAP jeans. Polyester refers to a 84% polyester, 16% spandex Coolibar rash guard [71].](https://www.researchgate.net/publication/358048960/figure/fig5/AS:11431281210550172@1702052769407/Transmittance-spectra-of-the-four-fabrics-designed-for-UV-protection-tested-in-this-study_Q320.jpg)
January 2022
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Simple Summary Photoprotection reduces invasive melanoma incidence and mortality, but not all sun protection modalities are created equal. Dermatologists have long debated the pros and cons of photoprotective clothing and sunscreen, but few studies compare the effectiveness of these two modalities head-to-head. This study uses both in vitro and in vivo techniques to compare the ultraviolet radiation (UVR) protective capacity of four modern textiles and two commercially available, broad-spectrum sunscreens. Abstract Ultraviolet radiation (UVR) exposure is the most important modifiable risk factor for skin cancer development. Although sunscreen and sun-protective clothing are essential tools to minimize UVR exposure, few studies have compared the two modalities head-to-head. This study evaluates the UV-protective capacity of four modern, sun-protective textiles and two broad-spectrum, organic sunscreens (SPF 30 and 50). Sun Protection Factor (SPF), Ultraviolet Protection Factor (UPF), Critical Wavelength (CW), and % UVA- and % UVB-blocking were measured for each fabric. UPF, CW, % UVA- and % UVB-blocking were measured for each sunscreen at 2 mg/cm² (recommended areal density) and 1 mg/cm² (simulating real-world consumer application). The four textiles provided superior UVR protection when compared to the two sunscreens tested. All fabrics blocked erythemogenic UVR better than the sunscreens, as measured by SPF, UPF, and % UVB-blocking. Each fabric was superior to the sunscreens in blocking full-spectrum UVR, as measured by CW and % UVA-blocking. Our data demonstrate the limitations of sunscreen and UV-protective clothing labeling and suggest the combination of SPF or UPF with % UVA-blocking may provide more suitable measures for broad-spectrum protection. While sunscreen remains an important photoprotective modality (especially for sites where clothing is impractical), these data suggest that clothing should be considered the cornerstone of UV protection.