SECTION 11 



TOXIC ORGANIC RESIDUES IN FISH 



Howard E. Johnson 



INTRODUCTION 



The distribution of synthetic organic chemicals in the environment has 

 emerged as a major problem of industrialized nations throughout the world. 

 The discovery of widespread environmental contamination by DDT and dieldrin 

 has led to the recognition of many other environmental contaminants includ- 

 ing such industrial chemicals as polychlorinated biphenyls (PCB), pthalate 

 esters, and hexachlorobenzene. 



The development of sophisticated analytical techniques and intensified 

 chemical monitoring efforts has shown that a wide variety of synthetic or- 

 ganic chemicals or their degradation products is present in the aquatic en- 

 vironment. As many as 40 potentially hazardous chemicals have been identi- 

 fied in some rivers that receive domestic and industrial effluents 

 (Kleopfer and Fairless, 1972; Hites, 1973). Significant contamination may 

 also be occurring in some regions because of chemical fallout from the 

 atmosphere. The ecological and public health hazard of these contaminants 

 is largely unknown, but the potential effect is considerable. 



PRODUCTION AND DISTRIBUTION 



The problem of environmental contamination is increased because of the 

 magnitude of commercial chemical production. The United States has in- 

 creased its production of chemicals by nearly 10% a year with present pro- 

 duction exceeding 140 billion pounds. As many as 500 new chemicals are 

 produced each year with little or no knowledge of the potential hazard of 

 their behavior in the environment (Lee, 1964). Some compounds have highly 

 toxic, carcinogenic, or mutagenic properties that may be especially 

 damaging if they are accumulated in aquatic systems. In some instances the 

 degradation products or metabolites may be of equal or greater consequences, 



Aquatic ecosystems are especially vulnerable to the effects of chemical 

 pollutants. Acutely toxic concentrations resulting from accidental spills 

 or direct application have caused extensive fish kills over broad areas of 

 the environment, but many chemicals occur in the environment at concentra- 

 tions that are not directly lethal to fish. These compounds are distri- 

 buted as microcontaminants, i.e., concentrations of a few parts per million 



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