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Ecotoxicological information

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Cobalt di(acetate) readily dissociates in aqueous solution into free cobalt ions and acetic acid. The pKa of 7.75 indicates that at pH values below, cobalt(di)acetate is almost completely dissociated, wherease the percentage decreases at higher pH values. Therefore an ecotoxicological risk assessment for the aquatic compartment by means of the dissociation products of cobalt di(acetate) is appropiate. There are sufficient data available for both dissociation products. The main conclusions are given below.

a) The inorganic component (cobalt) is acute and chronic toxic to aquatic organisms: Fish LC50 (96h) = 1.4 mg/L cobalt; Daphnia LC50 (48h) = 1.1 mg/L cobalt; Algae (96h) EC50 = 0.56 mg/L cobalt; Fish NOEC (16d) = 0.06 mg/L cobalt (survival); Daphnia NOEC (21d) = 0.005 mg/L cobalt.

b) The organic component (acetic acid CAS: 64-19-7) is not toxic to aquatic organisms: Fish LC50 (48h) = 410 mg/L; Daphnia LC50 (24h) = 6000 mg/L; Algae EC10 (8d) = 4000 mg/L.

These data markedly show, that the toxic component of cobalt(acetate) is cobalt. It is generally accepted, that the principal toxic component of various cobalt salts is cobalt (dependent on the corresponding anion) (see also: CICAD 69). Therefore toxicity values for cobalt compounds (such as: cobalt salts), where the major toxic component is cobalt, can be considered as equivalent. Consequently, data from other cobalt salts or- compounds have been used to fill data gaps within this dossier.