Registration Dossier
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EC number: 242-538-0 | CAS number: 18727-04-3
Long-term toxicity to aquatic invertebrates
Administrative data
Link to relevant study record(s)
Description of key information
EC50 (28d) = 0.012 mg cobalt hydrogencitrate/L for Hyalella azteca (growth) (read-across from cobalt chloride hexahydrate)
NOEC (28d) = 0.012 mg cobalt hydrogencitrate/L for Daphnia magna (reproduction) (read-across from cobalt sulfate)
Key value for chemical safety assessment
Additional information
No data on long-term toxicity to aquatic invertebrates are available for cobalt hydrogen citrate. However, there are reliable data available 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.
Data on chronic single-species toxicity tests resulting in high quality NOEC/L(E)C10 values (expressed as Co) for freshwater invertebrates (n=4) are summarised in Table 2 of the WHO CICAD document, 2006 (see attached document).Chronic data for two different species were extracted and used in the effects assessment. The 21-day LC50 values (mortality) for Daphnia magna range from 21 μg Co/L, tested as cobalt chloride hexahydrate (Biesinger & Christensen, 1972) to 30 μg Co/L, tested as cobalt sulfate (WHO CICAS, 2006), resulting in recalculated values from 88.7 to 126.8 µg cobalt hydrogencitrate/L.
More sensitive values were available as NOECs (reproduction) for Daphnia magna (21d and 28d) and Ceriodaphnia dubia (7d), and ranged from <3 to 13 for C. dubia (unknown cobalt compound) and 30 to 50 µg for D. magna (unknown cobalt compound), respectively, with the most reliable NOEC(28d) of 3 µg Co/L, tested as cobalt sulfate with D. magna (WHO CICAD, 2006). The latter NOEC would result in a value of 12.7 µg cobalt hydrogencitrate/L.
In the key study conducted according to methods comparable to guidelines, the effects of cobalt chloride hexahydrate on Hyalella azteca were investigated and resulted in an EC50 (28d) of 2.9 µg Co/L for growth (Norwood, 2007), equivalent to 12.3 µg cobalt hydrogencitrate/L.
Further results for other aquatic invertebrates are available and comprised in the attached table.
References: World Health Organization (2006). Concise International Chemical Assessment Document 69. COBALT AND INORGANIC COBALT COMPOUNDS.
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