Movement of Pollutants along Food Chains

Organic Pollutants An Ecotoxicological Perspective, Second Edition 

Biomagnification along terrestrial food chains is principally due to bioaccumulation from food, the principal source of most pollutants (Walker 1990b). In a few instances, the major route of uptake may be from air, from contact with contaminated surfaces, or from drinking water. The bioaccumulation factor (BAF) of a chemical is given by the following equation  

Biomagnification along aquatic food chains may be the consequence of bioconcentration as well as bioaccumulation. Aquatic vertebrates and invertebrates can absorb pollutants from ambient water bottom feeders can take up pollutants from sediments. The bioconcentration factor (BCF) of a chemical absorbed directly from water is defined as 

BCFs and BAFs measured before the steady state is reached have little value because they are dependent on the period of exposure of the organism to the chemical, and thus may greatly underestimate the degree of biomagnification that is possible. This statement should be qualified by the reservation that there may be situations in which the duration of exposure cannot be long enough for the steady state to be reached, for example, where the life span of an insect is very short. The principal processes of uptake and loss by different types of organisms are indicated in Table 4.1 (see also Box 4.2). 

A rough indication of the relative importance of different mechanisms of uptake and loss is given by a scoring system on the scale -t- Within each category of organ- 

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PCB mixtures were once used for a variety of purposes, and came to cause widespread environmental pollution. Over 100 different congeners are present in commercial products such as Aroclor 1248 and Aroclor 1254. PCBs are lipophilic, stable, and of low vapor pressure. Many of the more highly chlorinated PCBs are refractory, showing very strong biomagnification with movement along food chains. 

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