35 



Sublethal Toxicity of Chlorinated Catechols 



When discussing mechanism of toxic action it v/as sut,-gested that 

 chlorinated catechols may uncouple oxidative phosphorylation at 

 acute and sublethal concentrations, as does pentachlorophenol, A 

 symptom of imcoupling is increased rate of respiration or oxygen 

 utilisation (Negherbon, 1959> Goodnight, 1942) and the present 

 experiments inaicated that respiration was increased by di- and 

 tetrachlorocatechol. Due to similarity of symptoms and chemical 

 structure to pentachlorophenol it is reasonable to assume that 

 chlorinated catechols are uncouplers. Similarly, it would be 

 logical to assuEie that di- and tetrachlcrophenol are also 

 uncouplers. 



Chronic exposure to chlorinated catechols or phenols at 

 sublethal concentrations which cause abnormally high oxygen 

 consumption may be to a fish's disadvantage. Since the chlorinated 

 catechols and phenols apparently disrupt or reduce, by vmcoupling 

 oxidative phosphorylation, the flow of energy required for 

 maintenance and growth, the fish would use its food less 

 efficiently. Inefficient utilization of fooa over a long period 

 would probably result in development of a smaller fish with less 

 likelihooQ of successfully completing its life cycle. 



It was shown that nearly lethal concentrations of di- and 

 tetrachlorocatechol caused increased oxygen uptake, up to 1.5 to 1.6 

 times the control rate. On the other hand precise determination of 

 a threshold concentration for respiration increase was not obtained, 

 R threshold concentration is one at which a response is at the 

 point of occurring and would become detectable following a slight 

 increase in concentration of the toxicant. However, the data 

 indicated concentrations at which a small response was detected and 

 above which greater response was likely. These concentrations will 

 be referred to as minimal and will be compared with 96-hr TL^'s in 

 the following paragraphs. 



