Actinic Effects of Light and Biological Implications*

Abstract— Illumination is not the only, nor even the most important, benefit of the earth's complement of solar optical radiation; life itself is physically and chemically balanced between effects of too much and too little of it. Chemically, the effects range from the synthesis of ozone in the stratosphere and biochemicals in the biosphere, to the influence or control of complete living organisms, including humans. This actinism depends upon the spectrum, irradiancc and modulation, or SIAM. of the natural optical radiation environment. By manipulating the SIAM of artificially produced actinic optical radiation, profound effects are now routinely induced in people, animals and plants. The next logical application for this SIAM technology is in the environments where people themselves live and work. Meanwhile, it should be recognized that artificial illumination, as presently prescribed for these environments, is actinic.