value, and residues. The transfer of residues through food chains of which 

 the exposed vegetation is a part is also being investigated 



CLINICAL (DIAGNOSTIC) TESTS 



The use of diagnostic tests in hazard assessment procedures can decrease 

 the time required for safety evaluation of chemicals, define no-effect ex- 

 posure concentrations more adequately, and provide a better understanding of 

 the mode of action of chemicals. Routine diagnostic tests are frequently 

 not available to aquatic toxicologists because biochemical and physiological 

 research has been minimal in aquatic toxicology, which is a relatively new 

 field of science, as compared to such fields as human medicine (Mehrle and 

 Mayer 1979). The "state of the art" of physiological, biochemical, and his- 

 tological tests in aquatic toxicology held at Pellston, Michigan (Macek et 

 a1 . 1978). The participants rated the relative utility of eleven toxicity 

 tests, using the criteria of ecological significance of effects, scientific 

 and legal defensibility, availability of acceptable methods, utility of test 

 results in predicting effects in aquatic environments, the general applica- 

 bility to all classes of chemicals, and the simplicity and cost of the test. 

 In terms of present utility for use in assessing the hazard to aquatic envi- 

 ronments, acute lethality tests were rated highest, followed by embryo- 

 larval tests, chronic toxicity tests measuring reproductive effects, and 

 residue accumulation studies. Histological tests ranked ninth, and physio- 

 logical and biochemical tests tenth in overall and present relative utility 

 because of the inability to relate the results of these tests to adverse 

 environmental impacts. 



Physiological and biochemical tests are generally not conducted for two 

 reasons: (1) it is felt that they are mainly useful in evaluating the mode 

 of action of chemicals (Brungs and Mount 1978); or (2) there is not enough 

 basic information known about fish physiology and biochemistry to ascertain 

 the ultimate effects, since alterations in these processes do not neces- 

 sarily indicate a disadvantage to the survival and success of the organisms. 



The analytical techniques and instrumentation are well developed for 

 performing clinical analyses, and considerable research on physiological and 

 biochemical responses induced by chemical toxicants has been conducted, but 

 useful biological or diagnostic indicators have not been developed. In our 

 opinion, the main reason for this lack of progress has been the lack of a 

 comprehensive, integrated approach in toxicological studies with fish. To 

 overcome this problem, researchers must conduct biochemical, physiological, 

 and histopathological investigations in conjunction with toxicity studies 

 that measure important whole-animal responses. Establishing the relation- 

 ship of organism to sub-organism responses will help insure development of 

 pertinent diagnostic indicators of fish health. The choice of whole-animal 

 responses to evaluate in toxicity studies with fish depends on the purpose 

 of the toxicology program, but in most aquatic toxicology programs, emphasis 

 is given to toxicant effects on survival, growth and development, reproduc- 

 tion, and adaptability. 



48 



