The Toxicity of Pollutants to Aquatic Organisms

There are many circumstances in which the need to measure toxicity may arise. Many thousands of chemical substances are used for industrial, agricultural and domestic purposes, and their numbers increase annually. The toxicity of these chemicals and of their by-products and degradation products to aquatic animals needs to be determined, since any compound manufactured and used in substantial quantities is likely to become a contaminant of watercourses. In the case of novel compounds or formulations, toxicity testing may precede large-scale manufacture and form part of the research into the feasibility of its commercial application. Toxicity tests may be incorporated into effluent monitoring schemes. Identification of the more toxic components of complex effluents may be a prerequisite for the development and improvement of effective treatment processes. The measurement of toxicity is essential in the formulation of quality standards for receiving waters. Finally, compliance with a toxicity standard may be a legal requirement for consent to discharge an effluent. In this chapter we shall consider the basic principles of toxicology in relation to water pollutants and aquatic organisms, and the methods by which the toxicity and toxic effects of pollutants to aquatic life may be studied. The application of toxicological data in water pollution control, and their use in the formulation of water quality standards will also be considered, both in this chapter and in Chapter 6.