Aluminum cobalt oxide

Short-term toxicity to fish

Description of key information

LC50 (96 h) = 1.406 mg Co/L (Oncorhynchus mykiss) (read-across from cobalt chloride)

Additional information

No data on the short-term toxicity to fish are available for the test substance cobalt aluminium 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 aluminium metal and aluminium 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 ecotoxicological behaviour will be similar for all soluble cobalt and aluminium substances used in the ecotoxicity tests.

As cobalt aluminium oxide has shown to be highly insoluble with regard to the results of the transformation/dissolution test protocol (pH 6, 28 d), it can be assumed that under environmental conditions in aqueous media, the components of the substance will be present in a bioavailable form only in minor amounts, if at all. Within this dossier all available data from cobalt and aluminium substances are pooled and used for the derivation of ecotoxicological and environmental fate endpoints, based on the cobalt ion and aluminium ion. For cobalt, only data from soluble substances were available and for aluminium, both soluble and insoluble substance data were available. All data were pooled and considered as a worst-case assumption for the environment. However, it should be noted that this represents an unrealistic worst-case scenario, as under environmental conditions the concentration of soluble Co2+ and Al3+ ions released is negligible.

 

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 (96 h) value of 1.406 mg/L. Further results for other freshwater and marine fish are available and comprised in the attached table (range of 96 h 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.

Aluminium

Many “acute” toxicity studies (i.e. <12 days) have been conducted with fish in acidic soft waters due to concern about aluminium leaching in environments sensitive to acid rain. Many of these experiments were conducted in flow-through systems to mimic the effects of mixing zones where some type of substance (i.e. lime) is added to increase the system pH. In the cases where effects due to transient forms of aluminium were investigated (i.e. Teien et al. 2004, 2006), fish were maintained in certain sections of a raceway, with a specified time of equilibration, or time after mixing. Most of the existing literature for fish focused on effects to Salmo salar since it is among the most sensitive fish species. Roy and Campbell (1997) showed that DOM had a protective effect against aluminium toxicity to S. salar. Gundersen et al. 1994 suggested just a minor effect of HA on aluminium toxicity with Oncorhynchus mykiss. It is possible that in some of the flow-through studies, aluminium toxicity is due to transient forms of aluminium, because transient forms may be present for the first several minutes after mixing in the flow-through diluter mixing chambers.

 

While there are many studies that have investigated the toxicity of aluminium to fish, relatively few evaluated aluminium toxicity over a range of pH values. Roy and Campbell (1995) demonstrated that aluminium toxicity, on the basis of monomeric aluminium, decreased (less toxic) as pH decreased from 5.3 to 4.4. At weakly alkaline pH (i.e. pH 7.58 to 8.14), Gundersen et al. (1994) demonstrated very little effect of pH or hardness on aluminium toxicity to O. mykiss over higher pH ranges. Studies conducted at Norwegian Institute for Water Research (

NIVA) (Figure 7.1.1.1.1-1) show the effect of pH and other characteristics on survival at 190 hours; the results also demonstrate the effect of mixing time on mortality. From the literature, there were minimal studies that investigated the effect of water hardness on aluminium toxicity to fish. 

Thirteen acute toxicity studies to fish are prepared for informational purposes with a total of seven fish species, and are presented for demonstrating the completeness of the literature review. The available 96-h LC50s varied from 0.078 to > 218.6 mg Al/L, and 16-d LC50s ranged from 0.43 to 3.91 mg Al/L. The NOECs (96 h) varied from > 0.07 to > 50 mg Al/L.

Literary studies investigating the effects of aluminum in the aquatic environment have extensively used test solutions with aluminum concentrations above that of its solubility limit. Results of these studies are therefore limited for the investigation of intrinsic toxicity.

Conclusion
As the effect values derived from analogue cobalt compounds are considerably lower than those derived from analogue aluminium substances, it can be reasoned that the cobalt ion will mainly account for ecotoxicological effects of the substance. Hence, it was concluded to put forward the most sensitive and reliable results derived from analogue cobalt compounds for assessment purposes. Still, it should be noted that this represents an unrealistic worst-case scenario as under environmental conditions in aqueous media, the components of the highly insoluble substance will be present in a bioavailable form only in minor amounts, if at all, and hence, the concentration of soluble Co2+ and Al3+ ions released is negligible.