Background: The irradiance of standard ultraviolet daylight (UV-DL) is representative of most frequently encountered UV exposure conditions and simulators of UV-DL can now be used to properly investigate the biological effects of a non-extreme UV radiation. One of the characteristics of the simulated UV-DL used in this study is its dUVA to dUVB irradiance ratio, which amounts to 24, instead of close to 10, for the simulated zenithal UV radiation (UV-SSR).
Purpose/methods: The aim of our study was to compare photobiological effects induced, in human skin, by acute and semi-chronic exposure to simulated UV-DL with those induced by UV-SSR.
Results: Differences between UV doses needed to induce given biological effects after exposure to simulated UV-DL compared with UV-SSR indicate that the spectral distribution of the UV spectrum is of primary importance with regard to biological endpoints in the epidermis (SBC, p53, thymine dimers, Langerhans cells, and melanocyte alterations, etc.) and in the dermis (collagen, tenascin, etc.). Significant biological damage was noticed after 19 cumulative exposures to 0.5 minimum erythemal dose (MED) of UV-DL over 4 weeks. 0.5 MED of UV-DL corresponds to 1/9 of the daily typical dose received in Paris in April, emphasizing the need for an efficient daily UV protection.
Conclusion: Simulated UV daylight is a relevant new tool for daily photoprotection studies.