Cobalt molybdate

Endpoint summary

Additional information

One study is available on the short-term toxicity of cobalt molybdenum oxide to soil macroorganisms. In this study, earthworms (Eisenia fetida) were exposed to the substance in artificial soil at 1000 mg/kg soil dw in a limit test (He, 2012). The test was conducted according to national guidelines and OECD 207. No effects were observed in any of the treatments and as a result, an LC50 (14 d) of > 1000 mg/kg soil dw was obtained.

No data on chronic terrestrial toxicity 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

Information taken from WHO CICAD (2006):

There is little evidence of cobalt toxicity to plants due to elevated concentrations in soil. Cobalt tolerance, along with tolerance to other metals, has been found in plant populations growing on soils high in particular metals. Exclusion of the metal has been demonstrated in the cobalt tolerance of some species, whereas others growing on cobalt-rich copper clearings are hyperaccumulators of cobalt. Adverse effects on earthworm growth and springtail reproduction have been reported at 300–400 mg/kg dry weight. Data regarding the toxicity of cobalt to soil microorganisms are limited. In the terrestrial environment, adverse effects of cobalt on birds and wild mammals would appear unlikely, with cobalt deficiency in ruminants more likely than cobalt toxicosis (WHO CICAD, 2006).

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

Molybdenum

16 studies on the terrestrial toxicity of molybdenum are available. The selected data cover different trophic levels and numerous families (see table).

Taxonomic group	Species
soil macroorganisms	Eisenia Enchytraeus
terrestrial arthropods	Folsomia
terrestrial plants	Lolium Hordeum Zea Brassica Trifolium Lycopersicon Daucus Pisum
birds	Gallus Meleagris

The soil macroorganisms (including terrestrial arthropods) show EC10 values ranging from 7.88 - > 2843 mg Mo/ kg soil dw. In 21 d tests on different mono- and dicotyledonous plants a wide range of EC10 of 0.4 - 2844 mg Mo/ kg soil dw is observed. While 3 month- and 6 month tests on 2 different dicotyledonae have EC10 values of >= 114 mg Mo/kg soil dw as well as microorganism tests (EC10 from 10 - 10000 mg Mo/kg soil dw). In publications, tests on the toxicity to birds are found. While a test with Gallus domesticus had a NOEC of 400 and >= 3 mg Mo/kg diet, another test with Meleagris gallopavo had a NOEC of >= 1 mg Mo/ kg diet.

In the IMOA soils project, a total of 10 topsoils with contrasting properties that may affect the toxicity of Mo in soil were collected and on each of these soils a series of 11 toxicity tests was performed after spiking with Na₂MoO₄ (5 plant assays: root elongation for barley and shoot yield for Oilseed rape, Red clover, Ryegrass and Tomato; 3 invertebrate assays: reproduction for Enchytraeus crypticus, Eisenia andrei and Folsomia candida; and 3 microbial assays: nitrification, glucose induced respiration and mineralisation of plant residues). For the invertebrates, ecotoxicity tests were also conducted on an OECD artificial soil.

Additionally, 3 soils were aged outdoors after spiking with sodium molybdate. After 6 and 11 months, subsamples were collected and the 10 ecotoxicity tests (same as above, without barley root elongation assay) were conducted on these soils.

The total number of 113 dose-response curves (i.e. 10 soils * 11 assays + 3 invertebrate assays in OECD control soil) yielded in total 82 useful EC10 and 4 NOEC data (when no reliable EC10 was available because the EC10 was below the lowest tested concentration). For the other 27 dose-response-curves, no reliable EC10 or NOEC could be derived because there was either already an effect at the smallest dose tested (unbounded LOEC, in 5 plant dose-response curves) or no effect at the largest dose tested (unbounded NOEC, in 12 microbial and 10 invertebrate dose-response curves).

All data were based on added mg Mo/kg dw soil.