The limits of bioaccumulation of organic pigments in fish: their relation to the partition coefficient and the solubility in water and octanol.

A reliable experimental determination of the partition coefficient Pow of organic pigments is met with serious difficulties due to the extremely low water solubilities of these compounds. Therefore, the Pow values and the water solubilities were calculated for 11 typical organic pigments and some disperse dyes as well. The calculated Pow values of the pigments were very high predicting bioaccumulation factors (BF) several orders of magnitude above 100. Based on recent studies confirming that n-octanol simulates lipids in their solubilizing effect on organic chemicals, the solubilities of these organic pigments in n-octanol were measured in order to estimate their potential for lipid storage. The very low solubility values indicate that in spite of the very high predicted BF such pigments cannot build up concentrations in lipids (hence in fish) which could be of concern considering their generally low toxicity and the extremely small amounts entering the environment. Therefore, there should be no need to perform a fish bioaccumulation test for assessing the bioaccumulation potential of such compounds, provided they show comparable solubility characteristics as the pigments investigated in this study.