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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

In general, BCF and BAF data for Cd show an inverse relationship to exposure concentrations.
BCF's for cadmium are highest in algae and lowest in fish. In algae, external adsorption of Cd is one of the reasons for high BCF. Hardness and Cd concentration in the water are inversely related to BCF.
Median BCF (per dry weight) reported in the EU risk assessment (ECB 2008) are: 115116 (algae), 5000 (invertebrates), 233 (vertebrates)
The risk assessment mentions a median BAF for vertebrates of 167. Highest BAF is observed for the invertebrate Hyalella (170000), at a very low Cd concentration.

Key value for chemical safety assessment

Additional information

BCF's for cadmium are highest in algae and lowest in fish; High BCF in algae does not necessarily reflect high bioconcentration, because a significant part of the Cd is absorbed to the outer side of the organisms, and not taken up. Another factor of error is the lack of gut clearance in invertebrates. Organs (kidney, liver) contain most Cd.

Main influencing factors for Cd BCF are hardness and Cd concentration in the water. Increasing water hardness reduces Cd uptake. BCF is also inversely related to Cd concentration in water.

McGeer et al (2003) recently extensively the reviewed evidence on bioconcentration and bioaccumulation of cadmium as a function of exposure concentration in a number of taxonomic groups (algae, molluscs, arthropods, annelids, salmonid fish, cyprinid fish, and other fish). The data clearly illustrated that there is a significant degree of control on internal cadmium content. In general, BCF data showed an inverse relationship to exposure concentrations. In all cases, the relationship of BCF to exposure was significant and negative. The slopes of the BCF/BAF – exposure relations were: algae: -0.72, insects: -0.32, arthropods: -0.61, molluscs: -0.50, salmonids: -0.87, Centrarchids: -0.47, Killifish: -0.05, other fish: -0.72. Overall, species mean slope was -0.49 +/- 0.04 (McGeer et al 2003. Environm. Toxicology & Chemistry, vol 22, nr 5, 1017 -1037).

Considering the weight of evidence and mainly because of this well documented inverse relationship between BCF and exposure, it is concluded that Cd and its compounds are not to be considered as bioaccumulative. It has also been demonstrated that Cd is not biomagnifying in the lower parts of the foodchain.