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EC number: 242-538-0 | CAS number: 18727-04-3
Toxicity to aquatic algae and cyanobacteria
Administrative data
Link to relevant study record(s)
Description of key information
ErC50 (72 h) = 1.6 mg cobalt citrate/L (Desmodesmus subspicatus) (equivalent to 2.15 mg cobalt hydrogencitrate/L )
NOECr (72 h) = 0.11 mg cobalt citrate/L (Desmodesmus subspicatus) (equivalent to 0.15 mg cobalt hydrogencitrate/L)
LC50 (96h) = 2.52 mg cobalt hydrogencitrate/L (Chlorella vulgaris) (read-across from cobalt chloride)
LC50 (96h) = 1.26 mg cobalt hydrogencitrate/L (Ditylum brightwellii) (read-across from cobalt chloride)
NOEC (21d) = 2.52 mg cobalt hydrogencitrate/L (Chlorella vulgaris) (read-across from cobalt nitrate)
Key value for chemical safety assessment
Additional information
One study on the toxicity to algae is available for cobalt citrate (CAS 866-81-9). Within this key study conducted according to OECD 201 and GLP, Desmodesmus subspicatus was exposed to 0.1, 0.22, 0.46, 1.0 and 2.2 mg/L test substance (nominal) for 72 h under static exposure (Muckle, 2012). As a result, an EC50 of 1.6 mg/L, equivalent to 2.15 mg cobalt hydrogencitrate/L and a NOEC of 0.11 mg/L, equivalent to 0.15 mg cobalt hydrogencitrate/L were reported for growth rate. Analytical measurements showed recoveries of 35 to 92%, thus the results were based on measured concentrations (geometric mean).
Additionally, there are reliable data available for different analogue cobalt compounds.
Data on algae toxicity tests resulting in high quality EC50 values (expressed as Co) for freshwater algae and protozoans (n=10) are summarised in Table 2 of the WHO CICAD document, 2006 (see attached document).Acute and chronic data for different algae species in fresh- and saltwater were extracted and used in the effects assessment.
The EC50 values for freshwater algae range from 0.56 mg Co/L for Chlorella vulgaris (Rachlin and Grosso, 1993) to 10.8 mg Co/L for Spirulina platensis (WHO CICAD, 2006). Two EC50 values were available for marine species with a similar spectrum of 0.3 mg Co/L for Ditylum brightwellii and 10.2 mg Co/L for Nitzschia closterium. The 21-day NOECs and LOECs for freshwater algae ranged from 0.6 to 1.6 mg Co/L (WHO CICAD, 2006).
These findings result in recalculated values from 2.37 to 45.6 mg cobalt hydrogencitrate/L for acute freshwater endpoints, from 1.27 to 43.1 mg cobalt hydrogencitrate/L for acute marine endpoints and from 2.5 to 6.8 mg cobalt hydrogencitrate/L for chronic freshwater endpoints.
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