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and sensitive tests and, even then, the presence of some highly 

 dangerous materials or conditions can only be inferred by indirect 

 evidence. 



Materials and Conditions which Degrade the Environment 



One of the major constituents of municipal and many industrial 

 wastes is decomposable organic material . Such materials consist 

 primarily of carbohydrates from plants and paper, proteins from 

 animal matter, and miscellaneous fats and oils. The decomposable 

 organics are not necessarily detrimental by themselves but exert 

 a secondary effect by reducing dissolved oxygen in the water. The 

 level of dissolved oxygen is one direct index of the healthiness of 

 the system. High levels are generally indicative of a healthy 

 system which will support a diverse biota and multiple use. The 

 lower the concentration of dissolved oxygen becomes, the sicker the 

 system is, and the less desirable it is for habitat or use. 



Another class of materials, primarily organic, that can have 

 considerable impact on the estuarine ecosystem are the flesh-tainting 

 substances. Generally these materials are contained in industrial 

 waste effluents and they result in offensive tastes, odors and 

 colors of fish and shellfish. 



The salts of heavy metals are fairly soluble and stable in solution. 

 Consequently, they will persist for extended lengths of time. Many 

 of these are highly toxic to the aquatic biota, and since many marine 

 organisms exhibit the ability to accumulate and concentrate substances 



