Cobalt molybdate

Short-term toxicity to fish

Description of key information

LC50 (96h) = 5.22 mg cobalt molybdenum oxide/L (Oncorhynchus mykiss) (read-across from cobalt chloride)

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

5.22 mg/L

Additional information

One study on the short-term toxicity to fish is available for cobalt molybdenum oxide. Within this study, conducted according to national guidelines and OECD 203, Chinese rare minnows were exposed to 100 mg/L test substance (nominal) for 96 h under static exposure in a limit test. As a result, no mortality or any other effects were observed in any of the treatments, hence an LC50 of > 100 mg/L was reported, equivalent to 22.16 mg/L (measured concentrations as derived from analytical measurements).

Additionally, there are reliable data available for different structurally analogue substances.

The environmental fate pathways and ecotoxicity effects assessments for cobalt metal and cobalt compounds as well as for molybdenum metal and molybdenum 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 and molybdenum substances used in the ecotoxicity tests. Therefore, data from soluble cobalt and molybdenum substances are used in the derivation of ecotoxicological and environmental fate endpoints, based on the cobalt ion and molybdenum ion, respectively.

Cobalt

Data on acute single-species toxicity tests resulting in high quality NOEC/L(E)C10 values (expressed as Co) for freshwater and marine fish (n= 12) are summarised in the WHO CICAD, 2006 (see attached table).

A short-term toxicity test on the effects of cobalt chloride to Oncorhynchus mykiss conducted according to methods comparable to guidelines was chosen here as a representative test yielding the lowest effect concentration (Marr et al., 1998), resulting in a LC50 (96h) value of 1.406 mg/L, equivalent to 5.22 mg cobalt molybdenum oxide/L. Further results for other freshwater and marine fish are available and comprised in the attached table (range of 96h LC50 values: 1.4 - 333 mg Co/L for freshwater fish and 52.5 - >1000 mg Co/L for marine fish).

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

Molybdenum

Freshwater:

Two studies on the acute toxicity to freshwater fish are available. A publication of Kimball (1978) reports on an 8-day test with Pimephales promelas and a resulting 96h-LC50 range from 577 to 678 mg Mo/L. The Huntingdon Research Centre (1994) tested Oncorhynchus mykiss for 96 h which resulted in a LC50 of 420 mg diammonium dimolybdate/L, corresponding to 237 mg Mo/L.

In addition, three studies conducted with sodium molybdate dihydrate are listed in the CSR on diammonium dimolybdate (CAS 27546-07-2), which are not reported in detail here, but presented in a table. The 96h-LC50 values range from 609.1 to 3014 mg Mo/L for Oncorhynchus mykiss and Pimephales promelas, respectively.

Author, year	Species	Test duration	LC50 [mg Mo/L]
Canton et al., 2009	Pimephales promelas	96 h	609.1 - 681.4 (m)
Huntingdon Research centre, 1994	Oncorhynchus mykiss	96 h	3014 (n)
McConnell, 1977	Oncorhynchus mykiss	96 h	800 -1320 (n), 781 -1339 (est)

Thus, the 96h-LC50 values for freshwater fish range from 237 to 3014 mg Mo/L.

 

Marine:

No data for acute toxicity to marine fish are available.

Conclusion
As the effect values derived from analogue cobalt compounds are considerably lower than those derived from analogue molybdenum substances, it can be reasoned that the cobalt ion will account for the effects in ecotoxicological testing. Hence, it was concluded to put forward the most sensitive and reliable results derived from analogue cobalt compounds for assessment purposes, and recalculate them for CoMoO4.