Cobalt molybdate

Short-term toxicity to aquatic invertebrates

Description of key information

EC50 (48h) = 5.53 mg cobalt molybdenum oxide/L (Daphnia magna) (read-across from cobalt chloride hexahydrate)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

5.53 mg/L

Additional information

No data on short-term toxicity to aquatic invertebrates are available for cobalt molybdenum oxide. However, 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 L(E)C50 values (expressed as Co) for freshwater invertebrates (n=11) are summarised in the WHO CICAD, 2006 (see attached table).

Acute data for Daphnia magna were extracted and used in the effects assessment. The LC50(48h) values ranged from 1.1 mg Co/L, tested as cobalt chloride hexahydrate to 6 mg Co/L, tested as cobalt sulfate, resulting in recalculated values from 4.08 to 22.3 mg cobalt molybdenum oxide/L. The key study (Khangarot and Ray, 1989) showed an acute toxicity resulting in an EC50(48h) of 1.49 mg Co/L, tested as cobalt chloride hexahydrate (equivalent to 5.53 mg cobalt molybdenum oxide/L).

Studies on other invertebrate species such as rotifers, different copepod species and crayfish showed a range of EC50 values from 3.4 to 27.8 mg Co/L, tested as cobalt chloride hexahydrate, equivalent to 12.6 to 103.2 mg cobalt molybdenum oxide/L (WHO CICAD, 2006). These data are comprised in the attached table.

 

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 invertebrates are available. A study conducted by the Huntington Research Centre (1994) on Daphnia magna with ammonium molybdate resulted in a 48h-EC50 of 79 mg Mo/L. In a publication of Kimball (1978) on molybdenum trioxide, a 48h-EC50 of 206.8 mg Mo/L is reported for Daphnia magna.

In addition, six studies conducted with sodium molybdate dihydrate/disodium molybdate are listed in the CSR on diammonium dimolybdate (CAS 27546-07-2), which are not reported in detail here, but listed in a table. Five of them report 48h results on Daphnia magna, leading to an EC50 range of 130.9 - 2847.5 mg Mo/L. An EC50 of 1005.5 mg Mo/L is determined in a 48h-test on Ceriodaphnia dubia. Also the aquatic worm Girardia dorotocephala was investigated and obtained an EC50 of 1226 mg Mo/L.

Author, year	Species	Test duration	EC50 [mg Mo/L]
GEI, 2006	Ceriodaphnia dubia	48 h	1005.5 - 1024.6
GEI, 2006	Daphnia magna	48 h	1680.4 - 1776.6
Rodriguez, 2007	Daphnia magna	48 h	2729 4
Diamantino et al., 2000	Daphnia magna	48 h	2847.5
Huntingdon Research Centre, 1994	Daphnia magna	48 h	130.9
Canton et al., 2006	Girardia dorotocephala	48 h	1226

Thus, the EC50 for freshwater invertebrates ranges from 79 - 2847.5 mg Mo/L.

 

Marine:

No data for acute toxicity to marine invertebrates 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.