theoretical data. However, even in experimental determinations there may be 

 a diversity in repetitions, as well as deviations caused by the toxicologi- 

 cal experiment itself, especially when the test concentrations utilized 

 differ by orders of magnitude. 



The reported results were derived for in experiments on Daphnia , but 

 this approach is applicable for other aquatic organisms as well. This ap- 

 proach has been shown to be particularly effective in experiments with long- 

 lived species (Parina et al_. 1979). It is assumed that these regularities 

 are applicable for other indices of the effects of toxic substances on 

 aquatic organisms. 



In summary, it may be concluded that of all newly developing methods of 

 quick screening of toxic effects of pollutants on the aquatic organisms 

 using forecasting techniques, the most effective method, is still the use of 

 mathematical extrapolation of data from acute experiments. The dynamics of 

 the results of toxic influence for aquatic organisms (mortality) can be 

 shown as a combination of simpler processes. The connection of mortality 

 with time, and the onset of given effects with concentration can best be 

 described by power function equations. For evaluation of regression equa- 

 tions describing these statistically reliable relationships, 3 to 4 experi- 

 mental points are necessary. These equations can be used for determination 

 of the effects of the pollutant on the organisms for a period that exceeds 

 the duration of observation, and for concentrations, that have not been 

 experimentally investigated, including an approximation acceptable concen- 

 trations of the pollutant in the aquatic environment. It is particularly 

 advisable to use this approach for work under field conditions, or with 

 long-lived organisms, when the possibility of long-term observations does 

 not exist. This approach may also be used for investigations into a wide 

 spectrum of concentrations of a given pollutant. 



REFERENCES 



Filenko, O.F. and O.V. Parina. 1979. The distribution in organ systems, 

 as factor in determining the toxicity of tri-alkyl tin chlorides for 

 carp. In press. 



Filov, V.A. and E.I. Liublina. 1965. The connection of toxic activity of 

 volatile organic compounds with their physico-chemical properties. 

 Biophysica, 10: N 4, pp. 602-608. 



Jackim, E. 1973. Influence of lead and other metals on fish 8-aminolevuli- 

 nate dehydrase activity. J. Fish. Res. Board Can. 30: 560. 



Parina, O.V., O.F. Filenko and O.P. Siutkina. 1979. The connection of 

 toxicity with some physico-chemical properties of organic tin compounds 

 in carp. D^ The Reaction of Aquatic Organic Tin Compounds. Ed. by N.S. 

 Stroganov. Moscow State University, pp. 147-155. 



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