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Optical radiation is the term applied collectively to ultraviolet (UV), visible, and infrared (IR) radiation, encompassing the portion of the electromagnetic spectrum between X‐rays and radiowaves. The common term “light” may be considered synonymous with visible radiation, that is, with the portion of the optical radiation spectrum that can be visually perceived by humans. However, “light” and related terms are sometimes used colloquially to include UV radiation and IR radiation as well as visible radiation.

Common sources of potentially harmful levels of optical radiation include the sun, welding and plasma arcs, xenon lamps, mercury lamps, “black lights”, sunlamps, germicidal lamps, excimer lamps, light‐emitting diodes (LEDs), incandescent lamps, heat lamps, industrial ovens and furnaces, and very hot or molten glass and metal. All of these sources may be considered broadband optical radiation sources because they produce radiation of multiple wavelengths, in most cases over a continuum. In contrast to broadband sources, lasers produce optical radiation that is monochromatic and coherent. Laser hazards are addressed in Nonionizing Radiation: Lasers of this volume.

The main target organs for optical radiation are the eye and skin. The potential short‐term adverse effects of overexposure to UV radiation are burning of the skin (erythema) and painful inflammation of the cornea of the eye (photokeratitis). UV radiation is the only type of nonionizing electromagnetic radiation that is a known human carcinogen, causing several types of skin cancer (1). Chronic overexposure to UV radiation may also result in cataract (clouding of the lens of the eye), premature aging of the skin, and immunosuppression. Acute overexposure of the eye to visible and near‐IR radiation may cause temporary or permanent retinal injury resulting in loss of visual acuity. The retina may be somewhat protected from acute overexposure to visible radiation by constriction of the pupil and by the aversion response, which causes the viewer to blink and look away within about 0.25 seconds of seeing an intense light. However, not all people exhibit an aversion response (2); moreover, the aversion response may be voluntarily overridden during viewing tasks. Chronic overexposure to blue light is associated with age‐related macular degeneration, a condition that can cause loss of central vision. Absorption of IR radiation causes heating of tissue. If the rate of radiant heat absorption by the tissue exceeds the rate that heat is dissipated from the tissue through blood circulation and other means, overheating or burning of the irradiated area of the skin or eyes can result. Radiant heat absorption from IR sources may also contribute to whole‐body heat stress. Chronic exposure to IR radiation may contribute to lens opacities, the so‐called “glassblowers' cataract.” A thorough review of the biological effects of optical radiation can be found in Infrared, Visible, and Ultraviolet Radiation (3).

Optical radiation exposure is as old as life under the sun, but new sources of exposure arise from new technologies. Recognition, evaluation, and control of any optical radiation exposure in the workplace begin with the characterization of the broadband radiation sources. Section 2 reviews the basic science of optical radiation and introduces the specialized terms and units used to characterize radiation sources and radiation exposures; this is the necessary background for applying exposure standards and interpreting measurements. Section 3 discusses the characteristics of common optical radiation sources. Section 4 addresses the quantitative assessment of optical radiation hazards and Section 5 describes the basic principles for control of these hazards. Section 6 provides some practical discussion of hazard recognition and control for specific processes or sources.