ultraviolet light exposure (UV)

Introduction

ultraviolet light spectrum, in increasing energy and thus increasing biologic harmful effects, consists of:
- UV-A (400 to 315 nm)
- UV-B (315 to 280 nm)
- UV-C (280 to 100 nm)
UV rays are easily absorbed by nucleic acids, proteins, lipids, and other molecules present within cells
UV ray exposure may cause point mutations in DNA, DNA damage, denaturation of proteins, and can induce apoptosis and cellular senescence
some UV light skin exposure is needed for vitamin D synthesis and insufficient exposure may lead to vitamin D deficiency and rickets
excessive short term exposure may cause:
- welder flash burns - UV keratopathy (photo keratitis)
- retinal damage
- sunburn to skin
excessive long term exposure may cause:
- hastened skin and eye aging
- cataracts
- skin cancer, especially melanoma
UV-A light therapy has also been used to help treat some skin conditions such as psoriasis using PUVA where psoralens are combined with UV-A light

UV-C light has the highest energy of the UV spectrum and is the most damaging biologically
fortunately, most natural UV-C light is blocked by the atmosphere from reaching the earth's surface
UV-C light is often used as a germicidal agent to decontaminate surfaces and air and there are concerns that even these exposures may cause irreversibly harm to skin and retinal cells in particular - see Aging 2024 Germicidal lamps using UV-C radiation may pose health safety issues: a biomolecular analysis of their effects on apoptosis and senescence