In fact,a human system is exposed to a variety of xenobiotics,particularaly drugs in its life span more over animal kingdom and aquatic life is also exposed to such xenobiotics as a result of usage by human. A rationale of interaction of light and the photochemical effect with the biological system and environment as neccasiated the extended and indepth knowledge of the subject of photobiology and environmental photochemistry.

The subject is also of interest to social scientists who can motivate the society for preventing the misusage of light for a better living.........