ABSTRACT
I. INTRODUCTION The sun provides energy necessary for life on earth, and its electromagnetic spectrum covers γ - and x-ray, ultraviolet (UV) and visible light, as well as infrared (IR) and microwave radiation. Relative to photooxidative stress and diseases related to sun exposure, UV and visible radiation play a particularly important role. This includes the spectrum from 280 to 750 nm, that comprises UVB (280-315 nm), UVA (315-380 nm), and visible light (380-750 nm). Most of the UV light is absorbed by the ozone layer of the atmosphere, and less than 4% of the UVB intensity reaches the surface of earth. However, the thickness of the shielding ozone layer is decreasing; therefore, exposure to UV light increases. UV light is directly damaging to living organisms by inducing chemical reactions with relevant biomolecules. Visible light drives photosynthesis, which is essential for converting radiation energy. However, visible light may also cause damage resulting from physicochemical processes, reactive oxygen species being formed in light-exposed tissues. The modification of biologically important molecules in photooxidative reactions has been associated with pathological processes in the development of several diseases of light-exposed tissue, including cataract, age-related macular degeneration, skin cancer, skin aging, or skin erythema formation. There is increasing evidence that dietary antioxidants such as carotenoids, tocopherols, or ascorbate protect against photooxidative reactions.
