Fig. 1

Depths of ultraviolet (UV) radiation (UVR). UVC, with the shortest wavelength (100–290 nm) and highest energy, is mostly blocked by the ozone layer and rarely reaches human skin. Contrastingly, both UVB and UVA can penetrate the ozone layer. UVA, with the longest wavelength (320–400 nm) and lowest energy, can reach deep into the dermis, whereas UVB (wavelength: 290–320 nm) mostly reaches the surface of the dermis