Cobalt(2+) hydrogen citrate

Endpoint summary

Additional information

For cobalt citrate, short-term toxicity tests with fish, aquatic invertebrates and algae are available.

Besides, there are reliable data available on other ecotoxicological endpoints for different analogue substances.

The environmental fate pathways and ecotoxicity effects assessments for cobalt metal and cobalt compounds is based on the observation that adverse effects to aquatic, soil- and sediment-dwelling organisms are a consequence of exposure to the bioavailable ion, released by the parent compound. The result of this assumption is that the ecotoxicology will be similar for all soluble cobalt substances used in the ecotoxicity tests. Therefore, data from soluble cobalt substances are used in the derivation of ecotoxicological and environmental fate endpoints, based on the cobalt ion.

Cobalt

Information taken from WHO CICAD (2006):

A 96-h EC50 for cobalt based on growth of the freshwater green alga Chlorella vulgaris was reported as 0.56 mg/L, whereas EC50s for aquatic vascular plants were 0.14 and 0.24 mg/L. The 5-day EC50 for cobalt based on growth of the marine diatom Ditylum brightwellii was 0.3 mg/L. For freshwater invertebrates, acute LC50s (24–96 h) range from 1.1 to 239 mg/L. Several studies on Daphnia magna reproduction were reported, with a 21-day EC50 at 0.01 mg/L and a 28-day NOEC of 0.003 mg/L; however, later studies found 21-day NOECs ranging from 0.03 to 0.05 mg/L for varying levels of calcium carbonate.

The lowest reported NOEC for aquatic organisms was for the water flea Ceriodaphnia dubia in a 7-day test, at <0.003 mg/L. The most sensitive marine invertebrates were lobster larvae, with 96-h LC50s ranging from 4.5 to 22.7 mg/L. 96-hour LC50s for freshwater fish range from 1.4 to 333 mg/L. A 16-day NOEC based on survival was reported at 0.06 mg/L. Test results for marine fish suggest that at least the species tested are relatively insensitive to cobalt, with 96-h LC50s ranging from 52.5 to >1000 mg/L.Ca2+ competition and dissolved organic matter complexation were the most important factors preventing Co2+ from binding at the gills in natural water tests. However, the effect of Ca2+ ions on the uptake and potential toxicity of cobalt occurs at very low Ca2+ concentrations, probably lower than those used in any of the reported toxicity tests.

Under most environmental conditions, including both fresh water and marine water, much of cobalt is dissolved either as cobalt carbonate or as Co2+ ions. However, the actual bioavailability appears to depend on the water chemistry and particularly the concentration of Ca2+ ions and dissolved organic matter complexation. It is suggested that there might be an effect of water hardness on aquatic toxicity (WHO CICAD, 2006).

References: World Health Organization (2006). Concise International Chemical Assessment Document 69. COBALT AND INORGANIC COBALT COMPOUNDS.