Understanding Ultraviolet Radiation and the UPF Rating System Sunlight fuels life, but its invisible ultraviolet (UV) component is a relentless aggressor against human skin and textile fibers alike. Ultraviolet radiation is divided into three bands: UVA (315–400 nm), which penetrates deep into the dermis and accelerates photoaging; UVB (280–315 nm), the primary cause of sunburn…