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symptoms. Note for example, some marine food organism for man such as mus- 
sels and oysters have natural proclivities to store relatively high levels 
of metals in some of their tissues. Mussels normally store relatively high 
levels of cadmium and oysters store high concentrations of copper. Neither 
appears to suffer nor does man upon consuming them. 
The subject of whether or not marine organisms take up significant quanti- 
ties of many toxicants, such as cadmium or PCBs, from marine sediments is 
complex and subject to debate but present indications are that the iain 
route of entrance is via water. Again, it is the purpose of the special 
care measures of disposal submitted here to sequester toxic materials away 
from interstitial waters in the sediment bed. 
Persistence. As used in environmental management, persistence refers 
to the property of toxic substances to resist degradation by the activity 
of such organisms as bacteria or fungi or by natural physico-chemical fac- 
tors for substantial periods of time. In other words, the material by 
remaining intact persists in its original toxic state. For the most part 
persistence is concerned with compounds, not elements, and with organics, 
not with inorganics. Certainly it is the chlorinated hydrocarbons that are 
of principal concern. 
There is no doubt that thé chlorinated hydrocarbons, including such insec- 
ticides as DDT, endrin, aldrin, and other chlorinated compounds such as the 
PCBs, are relatively persistent when released into the marine environment. 
Nevertheless, there is a common misconception that once these compounds get 
into water or sediments they will remain there forever. This, of course, 
is not so. Persistence is a time-related function which is of significance 
only in a comparative sense. All components of the marine ecosystem are 
dynamic, which means that residues of chlorinated hydrocarbons are removed 
from (1) aquatic environments by codistillation, metabolism, etc., (2) from 
sediments by microbiological activities and chemical degradation, and (3) 
from organisms by various metabolic processes in liver and/or kidney 
cells (Buescher et al., 1964; Bridges, 1961). 
