Bioconcentration Factor (BCF)

The bioconcentration factor (BCF) is the ratio of a chemical’s concentration in an organism to its concentration in surrounding water at steady state, expressed in L/kg. It measures uptake from water alone, through gills and skin, excluding dietary intake (which bioaccumulation and biomagnification add). BCF rises with lipophilicity: substances with a log octanol-water partition coefficient between 4 and 6 concentrate most strongly. Under EU REACH a BCF at or above 2,000 L/kg flags a substance as bioaccumulative and at or above 5,000 L/kg as very bioaccumulative, feeding the PBT and vPvB assessment that can list a substance of very high concern.