Most of the literature concerning chlorine deals with continuous exposure, and is not readily applicable to this intermittent release of chlorine. Brungs(1973) reported that very little work has been done on the effects of intermittent exposure on fish, and that temperature has little or no effect on chlorine toxicity.

Since many steam-electric generating plants are on streams with predominantly warmwater fish, it was important to determine the effects of the intermittent release of chlorine on a fish of this type. The toxicity of intermittent chlorination, and the possible interaction with temperature to a warmwater fish, bluegill (Lepomis macrochirus) was investigated with the support of the American Electric Power Corporation. Because relatively little is known about the physiological effects of intermittent chlorination on fish, a study of this problem was performed using the rainbow trout (Salmo irdneri).This species was chosen because of the availability of large mature specimens. the ease of handling- and the considerable amount of physiological background data in the literature.

Another part of this study was to investigate the histological changes occurring in the bluegill and rainbow trout that resulted from intermittent chlorination. The data obtained were used to construct an hypothesis concerning the toxic mode of action of chlorine to freshwater fish.