Some researchers have related the toxicity of chlorinated seawater to the residual chlorine contents of the water. This has resulted in the establishment of guidelines for reducing the chlorine levels in the discharged water. However, when chlorine is added to seawater, a great proportion of it is consumed in the oxidation of the naturally occurring organic and inorganic materials of the water. Therefore, the harmful effects of the chlorinated discharges can most probably be attributed to the reaction by-products. Very little information is available about these by-products.