blished, i.e., the calculated quantity of any polluting substances, both as 

 to concentration and as to total volume, which can be discharged without 

 disrupting the MPC at the measurement line. 



Sanitary-hygienic MPC's are not the subject of the present report, but 

 we note that, as they are developed, both short-term and long-term effects 

 of substances on the sanitary condition of bodies of water are considered 

 (the oxygen regime, content of substances capable of decomposition, capacity 

 of the water for stagnation and self-purification, number of microorganisms, 

 etc.), on the organoleptic properties of water, on the health of the local 

 population (toxicity, pathogenic organisms, etc.) (Cherkinskiy, 1971). In 

 the past decade, the stability of the pollutants and their cumulative pro- 

 perties have also come to be considered. 



The fishing MPC's require study of: the stability of the pollutant, its 

 influence on the sanitary status of the reservoir (transparency, color of 

 water, pH, oxygen regime, BOD, etc.); the organisms of phytoplankton, 

 aquatic microorganisms, zooplankton, zoobenthos, spawn, larvae and mature 

 fish; cumulation of the substance by fish; and the influence on the quality 

 of fish flesh. Approximate times of experiments were presented by us in our 

 previous report (Lesnikov, 1976). 



In analyzing the materials which we have received from our American col- 

 leagues, we at first thought to compare all available materials, but then 

 decided to concentrate our attention on research on fresh-water organisms, 

 since water toxicologic studies on marine organisms have not yet been suffi- 

 ciently developed in the USSR (Patin, 1977) to speak of the relative toxi- 

 city resistance of species. Therefore, the results of USA studies on marine 

 organisms shall be included only as is convenient. 



In the USA, the degree of danger of a substance for fish and other 

 aquatic organisms, as determined experimentally, is summed up in the inte- 

 gral indicator "water quality criterion". According to McKee and Wolf 

 (1963), this indicator is considered in the establishment of "water quality 

 standards" for specific areas of bodies of water. The specifics of use of 

 the body of water and relative toxicity resistance of the species which in- 

 habit it are considered. 



In order for one nation to use data obtained by another nation, it is 



necessary to gain some idea concerning the relative toxicity resistance of 



test organisms. Naturally, representatives of local aquatic fauna are used 



both in the USSR and in the USA. 



In our country it is the usual practice to divide organisms into four 

 groups in terms of their relative toxicity resistance (oligotoxobes, beta- 

 mesotoxobes, alphamesotoxobes and polytoxobes) (Lesnikov, 1976). We shall 

 attempt to classify the test organisms used for toxicologic research in both 

 the USSR and USA from this standpoint. It must be considered that this 

 classification is somewhat arbitrary, since the toxicity resistance of or- 

 ganisms varies for various toxic substances. It is more correct to speak 

 only of trends. The relationship of sensitivity also varies as a function 

 of the duration of exposure. We shall present here data obtained by the 



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