Sunlight is composed of a continuous electromagnetic spectrum divided into UV (100 nm–390 nm), visible (400 nm–700 nm) and infrared (>700 nm). The UV section of the spectrum is subdivided into UVA (320 nm–390 nm), UVB (290 nm–320 nm) and UVC (<290 nm).1 UVC is strongly absorbed by stratospheric ozone and is practically absent at sea level, although accidental exposure still can occur. UVA comprises 90–95% of the remaining incident UV radiation.2 The interaction of UV radiation with human skin is a complex and controversial subject, although the general principles are becoming clear and well-accepted within the scientific community.
UVA Skin Protection: Issues and New Developments
Jan 2nd, 2014