Bioaccumulation

Bioaccumulation is generic term for various processes that lead to an increase in the concentration of a substance in a living organism in one way or another.

Bioaccumulation can be reversible or irreversible. In case of reversible accumulation the substance can be secreted again. In case of irreversible accumulation, the substance is permanently bound to the tissue of the organism.

Storage of a substance in the fatty tissue of an organism may not immediately lead to acute effects. However, when the fat is used for energy, the substance is released again, causing acute toxicity.

In the GESAMP hazard profile, category A1 gives information about the bioaccumulation of a substance. The rating is either based on the log Pow or the BCF.

Log Pow is a value that describes how the substance naturally distributes between water and n-octanol. The n-octanol is representative for the organism’s tissue (fatty acid). A high log Pow value means that a substance easily moves from water to the fatty tissue. A low log Pow value means that the substance rather stays in the water.

Log Pow measurements, however, only apply to inorganic chemicals.

As the log Pow only accounts for the tendency of a substance to move to fatty tissue, the BCF (Bio Concentration Factor) also accounts for other processes in the metabolism of an organism, which may enhance the secretion of the substance.