Cadmium

Endpoint summary

Additional information

stability

Waived: Inorganic substance: According to Annex IX of REACH Regulation, information on hydrolysis is not required for inorganics.

Also the other endpoints under 5.1. e.g; phototransformation in air, water and soil, are not applicable to Cadmium metal

biodegradation

Biodegradation is not applicable to metals/inorganic substances. Tests are not to be conducted if the substance is inorganic (Annex VII of REACH regulation)

bioaccumulation water/sediment

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).

bioaccumulation soil

The EU Risk assessment (ECB 2008) presents BAF values that were calculated from the soil:biota concentration ratio’s. Most organisms are earthworms and the Cd levels were expressed on dry or wet weight basis. All the data on earthworms were obtained from specimens with guts voided prior to analysis.

Cadmium is concentrated from the soil into earthworms organisms (BAF values are all higher than 1). Most important factors affecting the bioaccumulation of Cd by earthworms are the Cd concentration of the soil, soil type, pH, soil organic matter and CEC.

The influence of the Cd content of the soil on the bioaccumulation of Cd is illustrated in most of the studies. Cadmium concentrations in earthworms increase with increasing Cd levels in a non-proportional way. As a result, the BAF observed in Cd-contaminated or Cd-enriched soils is lower than the BAF observed in control soils.

transport and distribution

For metals, the transport and distribution over the different environmental compartments e.g. the water (dissolved fraction, fraction bound to suspended matter), soil (fraction bound or complexed to the soil particles, fraction in the soil pore water,...) is described and quantified by the metal partition coefficients between these different fractions. The information on these partition coefficients is given under 5.6.

Partition coefficients for cadmium in freshwater have been reviewed in the EU risk assessment report (ECB 2008). Based on this experimental evidence, a partition coefficient for the distribution between solid particulate matter and water (Kpsusp) of 130 x 10³l/kg has been defined for EU waters and was used throughout the RAR..

The Kp for the distribution between sediment and water (Kp_sed) was estimated in the RAR from the ratio of the average sediment (1.32mg/kgDW)to average water Cd concentrations (0.14µg/l). This "best fit" Kd yields 10000L/kgDW (ECB 2008).

These partition coefficients have been used since then in other legislative processes in the EU (e.g. the water framework directive) and will also be used for REACH.

For the marine water, a partition coefficient water/suspended matter of 617 l/kg has been derived.