with a continuum of response in which no such threshold is apparent. The need for "a 

 number" caused the U.S. Environmental Protection Agency (EPA) to abandon the 

 expert judgment approach used in the book entitled Water Quality Criteria— 1912,'' 

 and to adopt (for the EPA — Natural Resources Defense Council Consent Decree) a 

 much more rigid but reproducible method of picking a point value for use as a 

 threshold concentration. 



The decade closed before the wisdom or acceptance of that approach had become 

 clear. While only known by a very few scientists at the time of this writing, the 

 development of such methodology demanded an unprecedented and objective 

 examination of the existing aquatic toxicity data base. That examination shattered 

 many perceptions held so long that they had become accepted as axioms. Only at the 

 time of this writing are these perceptions being set forth for the profession to 

 examine. We feel certain that as they are studied and their meaning understood, they 

 will bring about a reversal in the priority of information needs as we saw them during 

 the 1970s. For example, the difference in sensitivity among aquatic species has been 

 known to be large. That that difference is frequently 100 to 1,000 times greater than 

 the difference between acute and chronic effect levels for many chemicals has not 

 been generally recognized. The suggestion is that relatively more resources should be 

 expended on studying acute toxicity on more species rather than on chronic toxicity 

 for a few species for a given amount of testing. This will not be readily accepted by 

 many toxicologists. 



Applications 



The progress on methods and data generation made during the 1970s decade was 

 applied as it became available in environmental regulation, principally for water 

 pollution regulation. 



Under the pesticide registration requirements, impact testing of aquatic species 

 was initiated. No longer were human health effects the only major concern in 

 approval. Many water quality standards were adopted by the states. These standards 

 were intended to define an acceptable maximum level of contamination of water that 

 would not jeopardize water uses, including propagation of aquatic life. Such 

 standards were based almost exclusively on single species toxicity tests. 



More recently, the Toxic Substances Control Act (among other things) requires 

 manufacturers to obtain approval to produce new chemicals. Test standards 

 describing useful tests to perform for obtaining necessary data are currently being 

 finalized for the Federal Register. These standards, by and large, are single species 

 tests developed during the seventies. Decisions based on single species tests will have 

 a profound effect on the economy as well as the environment. 



An increased interest has also been expressed recently in limiting the toxicity of 

 effluents as well as requiring some minimum level of treatment technology. Again, 

 single species tests are being viewed as the best and most practical way to measure and 

 limit toxicity emissions. 



While the limitations of single species tests are many, they do have marked 

 advantages of cost and brevity as compared to our currently available, more complex 

 tests such as microcosms. During a decade when gross pollution was being cleaned up 

 and public support was strong, single species tests served us well. The trend now is 

 towards fine tuning our regulatory efforts and eliminating more subtle effects. Many 

 are seriously asking whether we have overregulated. The 1980s may be a time when 

 the precise use and limitation of single species tests is more clearly delineated and we 

 become more aware of exactly how they should be used. 



FUTURE RESEARCH 



The 1980s begin with a lessening of the fervor that was so much a part of Earth Day 

 and the years following. The public's sentiment will have much to do with the course 

 of scientific investigation because much of the research not required by regulations is 



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