Cobalt molybdate

Toxicity to birds

Description of key information

EC10 (14d) = 431 mg cobalt molybdenum oxide/kg feed (Gallus gallus) for pathology (read-across from cobalt chloride hexahydrate)

Additional information

No data on toxicity to birds 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 birds resulting in high quality information (expressed as Co) on several bird species (n=3) are summarized in the WHO CICAD (2006).

Dietary levels of 251 mg Co/kg feed, tested as cobalt chloride hexahydrate, caused a mortality of 10% in 14 day old broiler chickens, while concentrations of 116 mg Co/kg feed and higher decreased body weight and food intake significantly, the resulting concentrations of cobalt molybdenum oxide are 932 and 431 mg cobalt molybdenum oxide/kg feed respectively (Diaz et al., 1994). Another study on 2-week old chickens showed significant adverse effects on growth at 100 mg Co/kg diet, tested as cobalt chloride, and significant mortality at 200 mg Co/kg diet, tested as cobalt chloride, after 5 weeks (with corresponding concentrations of 371 and 743 mg cobalt molybdenum oxide/kg diet). The latter study showed similar results at 200 mg Co/kg feed causing lesions and significant mortality at 500 mg Co/kg feed after 28 days in white peking ducklings, resulting in concentrations of 743 and 1,857 mg cobalt molybdenum oxide/kg feed respectively

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

Molybdenum

Only one reliable NOEC value was found for birds (Davies et al., 1960) with a value of 400 mg /kg dry weight. The other study by Reid et al. (1956) resulted in unbounded NOECs.

In terms of secondary poisoning, an assessment can be made considering, in combination, the BAF values with the toxicity in birds. the modest BAF in combination with the low toxicity in birds would suggest that the soil-earthworm-bird pathway is unlikely to pose any risk to wildlife and that the generic PNECsoil will drive the risk assessment.

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.