Cobalt aluminate blue spinel

Bioaccumulation: aquatic / sediment

Administrative data

Endpoint:

bioaccumulation in aquatic species: fish

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance has a low potential to cross biological membranes

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
According to Column 2 of Information Requirement 9.3.2., Annex IX, Commission Regulation (EU) 1907/2006, ”The study need not be conducted if: the substance has a low potential for bioaccumulation (for instance a log Kow ≤ 3) and/or a low potential to cross biological membranes.”

Cobalt aluminate blue spinel can be considered environmentally and biologically inert due to the characteristics of the synthetic process (calcination at a high temperature of approximately 1000°C), rendering the substance to be of a unique, stable crystalline structure in which all atoms are tightly bound and not prone to dissolution in environmental and physiological media. This assumption is supported by available transformation/dissolution data (Pardo Martinez, 2013) that indicate a very low release of pigment components at pH 8, the pH that maximises dissolution. Transformation/dissolution tests at a loading of 1 mg/L and pH 8 resulted in dissolved cobalt concentrations that remained below the LOD (i.e. < 0.5 µg Co/L) during the 28-d test. Dissolved aluminium concentrations after 7 and 28 days amount to 1.9 and 2 µg Al/L, respectively. Thus, the rate and extent to which Cobalt aluminate blue spinel produces soluble (bio)available ionic and other aluminium-and cobalt-bearing species in environmental media is limited. Hence, the pigment can be considered as environmentally and biologically inert during short- and long-term exposure. The poor solubility of Cobalt aluminate blue spinel is expected to determine its behaviour and fate in the environment, including its low potential for bioaccumulation.

Further, “for naturally occurring substances such as metals, bioaccumulation is more complex, and many processes are available to modulate both accumulation and potential toxic impact. Many biota for example, tend to regulate internal concentrations of metals through (1) active regulation, (2) storage, or (3) a combination of active regulation and storage over a wide range of environmental exposure conditions. Although these homeostatic control mechanisms have evolved largely for essential metals, it should be noted that non-essential metals are also often regulated to varying degrees because the mechanisms for regulating essential metals are not entirely metal-specific (ECHA, 2008).”

As the most abundant metal in the lithosphere, aluminium is ubiquitous in the environment. The speciation of aluminium in the environment is determined by pH, mineralogical composition, and the abundance of organic complexing agents. Under most environmental conditions, aluminium has a low mobility. However, decreasing pH (below pH 5.5) increases the mobility of aluminium ions. Estimated steady-state bioaccumulation factors (BAFs) of Brook trout (Salvelinus fontinal) range from 36 to 215 (WHO 1997 and references therein). There does not appear to be evidence to biomagnify. Since according to the CLP Regulation (EU) No 1272/2008, Section 4.1.2.8.1, “A BCF in fish of ≥ 500 is indicative of a potential to bioconcentrate for classification purposes”, the potential for the bioaccumulation of aluminium in fish seems low.

Cobalt is an essential trace element, acts as catalytic or structural components of larger molecules and occupy key roles in essential metabolic pathways of microorganisms, plants, and animals.

Cobalt is ubiquitous with an average abundance of 17 mg Co/kg in the upper continental crust and found in several rock-forming minerals. Cobalt ions are most mobile in the surface environment under acidic and reducing conditions (Salminen et al. 2005 and references therein). Cobalt is e.g. required in the nitrogen fixation processes of bacteria, algae and plants. In animals cobalt is the key element of Vitamin B12, which is required i.e., as co-factor for methionine synthase, in the synthesis of the citric acid cycle intermediate, succinyl-CoA and for a proper function of neurons. It can be assumed that the cellular uptake of cobalt is actively regulated by a strict control system as already known for other trace elements, which suggest a low potential for cobalt bioaccumulation. Furthermore, cobalt does not biomagnify (WHO, 2006 and references therein).

In sum, the potential of Cobalt aluminate blue spinel for bioaccumulation can safely be expected to be low. Thus, the study on bioaccumulation does not need to be conducted based on low solubility, bioavailability and a corresponding low bioaccumulation potential of Cobalt aluminate blue spinel in accordance with Column 2 of Information Requirement 9.3.2., Annex IX, Commission Regulation (EU) 1907/2006.

References:

ECHA (2008) Guidance on IR & CSA, Appendix R.7.13-2: Environmental risk assessment for metals and metal compounds. July 2008.

WHO (1997) Environmental Health Criteria 194 – Aluminum

WHO (2006) Concise International Chemical Assessment Document 69 - Cobalt and inorganic cobalt compounds