At this point, it is perhaps necessary to make a distinction among the following three terms that have been referenced throughout either explicitly or implicitly: bioconcentration factor (BCF), bioaccumulation factor (BAF), and biomagnification factor (BMF).

A BCF is defined as the ratio of a test chemical’s concentration in the tissues of an organism, to the chemical’s concentration in the surrounding medium (e.g., usually water), when the chemical uptake is supposedly from this medium only.

A BAF is defined as the ratio of a test chemical’s concentration in the tissues of an organism, to the chemical’s concentration in the surrounding medium (e.g., usually water), when all potential uptake mechanisms (e.g., from the organism’s prey as food) are included.

A BMF is defined as the ratio of a test chemical’s concentration in the tissues of an organism, to the tissue concentration in the organism’s prey in the food chain.

The above definitions (Code of Federal Regulations, 2003) assert that BCF and BAF can be used interchangeably, if the chemical uptake from all other potential routes is inconsequential when compared to that from the surrounding medium. It is based on this assumption or speculation that BCF and BAF are almost used interchangeably in this lecture and in much of the open literature. In any case, there are also a fair number of food-chain models available for assessing quantitatively the uptake of chemicals by fish, shellfish, and the kind, for which a more recent framework can be found in the paper by DePinto and Narayanan (1997).