Cholinesterase has been inhibited more in the first case (Kozlovskaya 

 and Novichikova 1979). Organophosphorus pesticides on continued chronical 

 exposure prove no less dangerous than with acute intoxication. 



CONCLUSIONS 



Organochlorine pesticides have been replaced with organophosphorus on 

 the assumption that as a result of lower persistf^nce in the aquatic environ- 

 ment those compounds will be of little danger to aquatic organisms. Organo- 

 phosphorus pesticides have proven to be highly toxic to the majority of 

 species of aquatic invertebrates. The data provided in this study demon- 

 strates that there are concentrations in reservoirs, which greatly exceed 

 lethal levels for sensitive species. 



The intensive application of organophosphorus pesticides as a part of 

 agricultural practices results in a periodic influx of these pesticides into 

 water bodies. In natural waters, pollution levels are produced which cause 

 chronic effects upon aquatic animals. This is especially dangerous because 

 organophosphorus compounds possess an additive effect, and are poorly 

 avoided by aquatic animals. 



An indicator of the effects of organophosphorus pesticides in an inhibi- 

 tion of cholinesterase in both acute and chronic intoxication. In patholog- 

 ical processes, the inhibition of cholinesterase as a target enzyme un- 

 doubtedly plays a leading role, although death occurs when the inhibition of 

 enzymes is still incomplete. 



REFERENCES 



Bilikova, A. 1973. Pesticides in Slovene surface water. In: Water 

 Management, 21, No. 10, pp. 261-263. 



Boiko, I.B. and B.A. Pulatov. 1977. Materials on the hygienic reasoning 

 behind the maximum acceptable concentrations in waste water. Gigiena i 

 Sanitariya, No. 8, pp. 106-107 



Drevenkar, V., K. Fink, M. Stipcevic, and B. Stengl. 1975. The fate of 

 pesticides in aquatic environment. 1. The persistence of some organo- 

 phosphorus pesticides in river water. Archives of Council on Hygiene 

 and Toxicology, 26:4, pp. 275-266. 



Flerov, B.A. and L.N. Lapkina. 1976. The avoidance of certain toxic solu- 

 tions by the medical leech. Informational Bulletin, 30, pp. 48-52. 



Flerov, B.A. and V.B. Tagunov. 1978. Analyzing the response to avoid 



toxic substances in the Branchipod Streptocephalis tovicorni. Informa- 

 tion Bulletin, 40, pp. 68-71. 



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