Optical radiation refers to the spectrum of electromagnetic radiation that ranges in wavelengths of 100 nanometers (nm) to 1 millimeter (mm) comprising of infrared radiation, visible light, and ultraviolet radiation. Radiation with wavelengths on the lower end, between 100 nm and 400 nm, are categorized as ultraviolet radiation, while those between 400 nm and 800 nm refer to visible light, which can be seen with the human eye. Wavelengths of light above this level, from 800 nm to 1 mm, are said to belong to the the infrared radiation band. While being invisible to the human eye, both ultraviolet and infrared radiation affect it, depending upon the length of exposure, which makes it important to understand optical radiation thoroughly when creating artificial lighting devices.
Even man-made light is a source of optical radiation whether it emits visible or invisible light. Television and computer displays, concert lights, welding lights, and tanning lamps are just a few of the devices that people use on a constant basis. Knowing the kind of light emitted and the duration of exposure is critical in determining if there are any optical risks in using those devices. In 2002, the European Parliament and Council set forth an Artificial Optical Radiation Directive defining optical radiation and highlighting the minimum safety and health requirements for people working with this type of radiation in their work environments. Certain types of radiation, like light from the sun, microwaves, radio waves, and X-rays, are not covered within this directive.
Different types of radiation are beneficial or detrimental to a person's health depending on the duration of exposure. For instance, sun lamps that emit ultraviolet radiation are used by many to acquire tans within set times. Too much exposure to ultraviolet radiation, though, whether due to artificial light or natural sunlight can result in skin damage and premature aging of the skin; prolonged exposure to infrared radiation is also harmful. Though most of the light sources used in work environments do not present any optical radiation risk to the workers, it is important for those designing these environments to be aware of the risks and keep exposure limit values in mind.
Some of the industries where specialized light sources are used include industrial lasers, welding and metalworking, and television studio lighting. Other areas include ultraviolet curing lamps, stage lighting, and tanning lights. While the directive was primarily created to prevent workers from being exposed to excessive radiation as well as detecting any undesirable effects on health in a timely fashion, it also seeks to prevent any long-term health risks due to regular exposure. Employers need to carry out risk assessments that comply with the directive and utilize action plans that include various measures to ensure that exposure limit values are not exceeded.