Method of analysis is extremely important. The 

 organic and inorganic contents of water influence 

 the presence of pesticides and because these 

 compounds are biologically active, they tend to 

 accumulate in certain phases of the aquatic en- 

 vironment. As the result of alteration of the 

 environment, altered levels of pesticides may ap- 

 pear in an active biological role. Biological accu- 

 mulations represent the greatest variabilities which 

 affect the method of analysis. 



The Agricultural Research Service of the De- 

 partment of Agriculture seeks to develop morbidity 

 and mortality records of livestock losses. Criteria 

 for waterborne diseases are dependent upon mass 

 statistics for losses which relate the incidence of 

 disease to the water environment. Laboratory 

 studies provide evidence on which to base criteria. 

 The occurrence of disease as the result of ecologi- 

 cal situations which involve water serve to prove 

 the validity of the laboratory observations. Without 

 this mass of epidemiological information, concepts 

 which are not applicable or unnecessarily expen- 

 sive may be perpetuated in relation to water man- 

 agement. In reference to the diseases (virus, para- 

 sitic, bacterial, or fungal) transmitted by water, 

 reliance should be placed upon epidemiological 

 studies to define the source of contamination and 

 to develop the remedial measures for control. 



irrigation 

 water supplies 



143 



