Non-solar sources of ultraviolet radiation and cutaneous malignant melanoma: a review of the evidence

Abstract

Ultraviolet radiation (UVR) is non-ionizing radiation with shorter wavelengths than visible light. The primary source of human exposure to UVR is the sun, although there are a variety of non-solar sources which also emit UVR. UVR encompasses wavelengths between 100 nm and 400 nm, and has been divided into three broad ranges on the basis of biologic activity: UVC comprises the shortest wavelengths, usually 100-280 nm; UVB includes 280 to 315 or 320 nm; and UVA consists of the longer wavelengths. UVC is the most dangerous to life, but is relatively unimportant because no solar UVC reaches the earth. UVB is called the erythemal range because of its ability to cause the redness of skin which is called “erythema” and which can end up as sunburn. UVA has generally been considered to be relatively safe because obvious injurious effects are minimal. There is, however, heterogeneity of effect within each range depending on the intensity of the specific wavelengths present. All UVR below 290–295 nm is absorbed by the earth’s atmosphere, thereby limiting the range of wavelengths comprising solar exposure. This is not true for non-solar sources where wavelengths in any of the ranges may be present; however, UVC of wavelengths shorter than 200 nm is heavily attenuated by air so that virtually no exposure in this range occurs.