Jose Aguilera ^1* Daniel Cárdenas-Gónzalez ¹ Cristina Sánchez Roldán ¹ Salvador Gonzalez ² Ricardo Bosch García ¹ Enrique Herrera Ceballos ¹ María Victoria De Gálvez ¹

• ¹ University of Malaga, Málaga, Spain
• ² University of Alcalá, Alcalá de Henares, Madrid, Spain

Background and objective: We are exposed to solar radiation from early childhood, so learning different photoprotection strategies is fundamental. As a primary prevention tool, knowledge of the solar ultraviolet radiation to which we are exposed is fundamental. There are devices based on the color change of photochromic substances when exposed to UV radiation, which are widely used as a tool for children's play. The aim was to assess both quantitatively and qualitatively the effectiveness of the use of these devices under different conditions of simulated sun exposure.Materials and methods: 10 commercial UV-indicating photochromic devices plus 3 pure photochromic substances were used. Photochromic devices belong to spirooxazines family of molecules. They were exposed to different rates of UV radiation under solar UV-visible simulator and the velocity, degree of response and color reversal time were analysed both visually and objectively by using a colorimeter based on three-dimensional CIE L*a*b* color space values. Activation response was also evaluated under different UV-high energy visible light wavelengths by use of different cutoff filters. Finally, devices were exposed under a high UV irradiance interposing sunscreens of different solar protection factors in order to evaluate their potentials as indicators for sunscreen reapplication.. Results: All the devices and pure substances offered color change almost immediately under sun simulated radiation. From very low irradiances (UVI >3) they saturated color and it was not possible to observe and measure color change. The time to color reversal take longer time than activation (from 60 seconds to get initial values). When devices were exposed to UVI of 10 with topical sunscreen overlay, color was observed after 1 min irradiation even under sunscreen with SPF of 50+. Photochromic devices were activated both under UVA and high energy visible light. Conclusion: UV radiation indicators using photochromic substances, although they could be an awareness-raising element, are of limited use as indicators of UV radiation intensity and dosimetry. They are useful elements for detecting presence/absence of UV radiation and do not distinguish between different UV radiation spectral bands. Moreover, their incorporation as photoprotection elements used by minors could lead to exposures that are not objectively controlled.