Biomagnification refers to the tendency of some chemicals to concentrate in living organisms and to pass up the food chain as they are consumed. Especially pernicious are those chemicals that are easily absorbed, not easily metabolized or excreted, have long half-lives, and an affinity for fat. These include methyl mercury; polychlorinated biphenyls (PCBs); and the chlorinated hydrocarbon pesticides such as DDT, aldrin, dieldrin, lindane, and heptachlor. Substances that are water-soluble and biodegradable are not generally subject to biomagnification.

The loads of these chemicals increase in small, ostensibly harmless increments, but are concentrated in higher trophic levels, as organisms eat and in turn are eaten. Over time, the repeated consumption of contaminated prey ultimately results in the accumulation of high and possibly toxic levels within the ...

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