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Light Right for Sight: Health and Efficiency in Lighting Practice Arnold Wilkins MRC Applied Psychology Unit, UK Abstract There are several aspects of electric lighting that may affect health, including low-frequency magnetic fields, ultra-violet emissions, glare, and variation in luminous intensity, both variation that can be seen as flicker and that which is too rapid to be seen. These aspects are considered in relation to energy efficiency. For most there are no clear trade-offs between health and efficiency; indeed, improvements in efficiency are, if anything, beneficial to health. There is, however, one important exception and it concerns rapid (100-Hz) variation. Some high-efficiency sources (such as high-pressure discharge lamps) vary rapidly in brightness to a greater extent than the less efficient lamps they often replace. Other high-efficiency sources (such as compact fluorescent lamps with high-frequency ballast) exhibit less variation. The 100-Hz variation is too rapid to be seen but affects visual neurones and has been linked to headaches, eye-strain and anxiety. The variation may be one reason for the improvements in health that result from daylighting. The move towards energy efficiency can therefore be a move towards or away from visual comfort and improved health, depending on the way the energy savings are achieved. There are many aspects of lighting design and practice that many be of relevance to health. This paper does not provide a comprehensive review but concentrates instead on those aspects that relate to energy efficiency and the specific circumstances where improvements in efficiency may be detrimental to health.
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