Cadmium carbonate

Endpoint summary

Additional information

Aquatic bioaccumulation

There is a number of data available on the possible accumulation of cadmium in aquatic organisms.

BCF in fish are generally below the criterion for considering a substance bioaccumulative.

Higher BCF /BAF factors are observed in the lower levels of the food chain (algae notably). However, there are some uncertainties with the data: the high BCF/BAF factors observed in the algae are (at least partly) due to external absorption, not to uptake. In general, algae data are not considered in a context of bioaccumulation. The higher levels in invertebrates may be related to lack of gut clearance of the organisms studied.

In terms of hazard identification/classification, several considerations speak further against considering Cd as bioaccumulative substance:

-the BCF/BAF values observed with Cd consistently decrease with increasing exposure, which clearly shows some level of physiological regulation of uptake. One of the key theoretical conditions of the BCF model in terms of its relevance for chronic toxicity and applicability to the hazard identification/classification of chemicals is that the BCF/BAF should be independent of exposure. BCF/BAF values should in other words remain fairly constant over a range of exposures, which is clearly not the case for Cd.

-Evidence related to biomagnification in the aquatic food chain consistently shows that Cd is not biomagnifying.

Based on an extensive review of evidence on a wide variability of taxonomic groups, McGeer et al (2003) concluded that the BCF/BAF criteria, as conceived for organic substances, are inappropriate for the hazard identification and classification of metals, including Cd. They highlighted the inconsistency between BCF/BAF values and toxicological data, as BCF values are highest (suggesting hazard) at low exposure concentrations and are lowest (indicating no hazard) at the highest exposure concentrations, were toxicity is likely.

The following information is taken into account for any hazard / risk / bioaccumulation assessment:

In general, BCF and BAF data show an inverse relationship to exposure concentrations.

BCF in fish are generally below the criterion for considering a substance bioaccumulative. The risk assessment mentions a median BAF for vertebrates of 167.

Terrestrial bioaccumulation

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.

The following information is taken into account for any hazard / risk / bioaccumulation assessment:

Median BAF observed on earthworms is 15 (expressed on a dry weight basis). For arthropoda, the median BAF is 1.4 (summary from the EU risk assessment, ECB 2008). The BAF observed in Cd-contaminated or Cd-enriched soils is lower than the BAF observed in control soils. In a field study, the BAF observed under contaminated conditions on Lumbricus rubellus was 12-123, under control conditions it was 190.

General conclusion

Considering the elements mentioned above, cadmium and its compounds are not considered as bioaccumulative.

In the aquatic compartment, BCF in fish are generally below the criterion for considering a substance bioaccumulative. Cadmium is clearly not bioaccumulative in terrestrial organisms.

In terms of hazard identification/classification, several considerations further confirm this conclusion: substance:

-the BCF/BAF values observed with Cd consistently decrease with increasing exposure, which clearly shows some level of physiological regulation of uptake. One of the key theoretical conditions of the BCF model in terms of its relevance for chronic toxicity and applicability to the hazard identification/classification of chemicals is that the BCF/BAF should be independent of exposure. BCF/BAF values should in other words remain fairly constant over a range of exposures, which is clearly not the case for Cd.

-Evidence related to biomagnification in the aquatic food chain consistently shows that Cd is not biomagnifying.

Based on an extensive review of evidence on a wide variability of taxonomic groups, McGeer et al (2003) concluded that the BCF/BAF criteria, as conceived for organic substances, are inappropriate for the hazard identification and classification of metals, including Cd. They highlighted the inconsistency between BCF/BAF values and toxicological data, as BCF values are highest (suggesting hazard) at low exposure concentrations and are lowest (indicating no hazard) at the highest exposure concentrations, were toxicity is likely.