Factors That Determine Toxicity and Persistence

Sites of action. When a chemical interacts with one or more of these, there will be a toxic effect on the organism if the concentration exceeds a certain threshold. The chemical has an effect on the organism. 

Sites of metabolism. When a chemical reaches one of these, it is metabolized. Usually this means detoxication, but sometimes (most importantly) the consequence is activation. The organism acts upon the chemical. 

Sites of storage. When located in one of these, the chemical has no toxic effect, is not metabolized, and is not available for excretion. However, after release from storage, it may travel to sites of action and sites of metabolism. 

Organic Pollutants An Ecotoxicological Perspective, Second Edition 

Furthermore, any particular type of site belonging to any one of these categories may exist in a number of different cellular or tissue locations. For example, acetylcholinesterase is located in a number of different mammalian tissues (e.g., brain, peripheral nervous system, and red blood cells), and all of these may be inhibited by 

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