Health & Performance
Last Update: November 7, 2010
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Optical Radiation

When up and about, either indoors or outdoors, people are illuminated by daylight or electric light and, consequently, are bathed in electromagnetic radiation in the visible, ultraviolet and infrared wavelengths. A figure of the electromagnetic spectrum is provided below. This radiation can have effects on human health simply as radiation, regardless of whether or not it stimulates the visual system or the circadian system. The effects can be both positive and negative. The possible effects of electromagnetic radiation outside of the ultraviolet, visible and infrared, e.g., the x-ray, microwave and radio wave regions, are not considered here.

The Electromagnetic Spectrum. 
Optical Radiation Figure 1.
Illustration of the electromagnetic spectrum. 
+ Click image to enlarge.

Negative Effects On The Eye
Optical radiation in the visible, ultraviolet and infrared wavelengths can cause tissue damage to the eye. Where the damage occurs depends on where in the eye the energy contained in each photon is absorbed. This varies with wavelength. The tissue damage can be caused by two mechanisms, thermal and photochemical.
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Negative Effects On The Skin
The skin is the largest organ in the human body. It provides mechanical protection, environmental sensing and a means of thermal regulation. It is also susceptible to damage from optical radiation.
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Threshold Limit Values
Recommended limits for exposure to ultraviolet, visible and infrared radiation have been published by a number of organizations. Probably the best known are those of the American Conference of Governmental Industrial Hygienists (ACGIH). These recommendations take the form of threshold limit values.
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Limiting Risk
Overall, the risk of skin or eye damage, burns, electrical shock or other hazards from electric lighting is extremely small.
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Positive Effects
Exposure to optical radiation can benefit health, directly and indirectly. The best-known positive effect of optical radiation is the synthesis of vitamin D. Ultraviolet radiation and short-wavelength visible light are also used in certain medical treatments. Very short wavelength ultra-violet radiation (UV-C) has an increasing role in disinfection of both air and water and thus in disease prevention.
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