The impact of trace amounts of long wavelength UVA1 on visible light induced effects

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Conference Proceeding

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Journal of Investigative Dermatology


Our skin is exposed to visible light (VL) and long wavelength ultraviolet A1 (UVA1) radiation (370-400 nm) present in sunlight even after application of organic broad spectrum sunscreens. The effects of these wavelengths on pigmentation and erythema have been demonstrated. However, a dose response has not been investigated which can provide insight on how skin responses can vary based on the duration of sun exposure. Ten subjects with Fitzpatrick skin phototype IV-VI were enrolled. On day 0, subjects were irradiated with two light source; one comprising pure VL and the other VL with less than 0.5% UVA1 (VL+UVA1) at a dose of 80 J/cm2, 160 J/cm2, 320 J/cm2 and 480 J/cm2. The irradiance was set at 175 mW/cm2. Skin responses were evaluated immediately, at 24 hours, 7 days, and 14 days after irradiation. Assessment methods included investigator’s global assessment (IGA), diffuse reflectance spectroscopy (DRS), and colorimetry. Clinical IGA scores suggest that 3/10 subjects for the 320 J/cm2 site, and 5/10 subjects for the 480 J/cm2 site had clinical erythema immediately after irradiation on the VL+UVA1 side only. No erythema was observed for the corresponding pure VL sites. Only the highest dose, 480 J/cm2,resulted in pigmentation response that was statistically significantly different at all time points between the two light sources (p<0.05). Pigmentation response from VL+UVA1 site was two times more intense than that of pure VL at the day 14 time point. Spectroscopy and histology data analysis are under progress. Wavelengths not covered by current broad spectrum sunscreens have implications on pigmentation and erythema. There appears to be a threshold dose of UVA1 which in combination with VL results in immediate erythema followed by darker and persistent pigmentation. The effects can be noticed at approximately two hours of outdoor sun exposure.





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