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Ecotoxicological information

Short-term toxicity to aquatic invertebrates

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Description of key information

On the basis of the physico-chemical hazards associated with the substance, this study is omitted in accordance with REACH Annex XI, section 2. The substance reacts spontaneously with air and water therefore testing is not technically feasible. 

Key value for chemical safety assessment

Additional information

Trimethylaluminium is classified as Pyr. Liquid 1, Water React. Flam. Gas 1 and Skin Corr. 1B. Therefore, the substance ignites upon exposure to air, reacts violently with water and causes severe burns to the skin and eyes. Consequently, it is not technically feasible to conduct ecotoxicological or environmental fate studies with this substance.

Trimethylaluminium reacts spontaneously with water to produce aluminium hydroxide and methane or methanol and also reacts spontaneously with air; the products of complete combustion being aluminium oxide, carbon dioxide and water. Therefore, the ecotoxicological effects of aluminium oxide and aluminium hydroxide need to be considered when evaluating the effects of long-term exposure to trimethylaluminium.

Aluminium oxide and aluminium hydroxide are not classified for effects on the environment. For inorganic substances like aluminium oxide and aluminium hydroxide, the environmental fate assessment is based on the elemental concentration (i.e., pooling all inorganic speciation forms together). Biotic degradation and abiotic degradation are irrelevant processes, irrespective of the environmental compartment that is under consideration: these processes may alter the speciation form of an element, but it will not eliminate the element from the aquatic compartment by degradation or transformation. This elemental-based assessment (pooling all speciation forms together) can be considered as the worst-case. Available data indicate that aluminium salts are of low toxicity in most waters with circumneutral pH (pH 5.5 to 7.4). Insoluble salts such as aluminium oxide and aluminium hydroxide are considered not to be hazardous to the environment. Aluminium ions released to waters rapidly form insoluble aluminium hydroxides in mixing zones, which may sorb to fish gills resulting rarely in asphyxiation and mortality. These conditions however are not typical and are more likely to occur in specific mixing zones. In the majority of cases, the dissolved natural background concentrations of aluminium are in equilibrium and therefore any addition of aluminium causes the precipitation of aluminium compounds from solution without resulting in effects to aquatic life. The relative contribution of aluminium added by humans to the existing natural pools of aluminium in soils and sediments is very small and therefore not considered to be relevant either in terms in terms of toxicity.