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Environmental fate & pathways

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In general, (abiotic) degradation is an irrelevant process for inorganic substances that are assessed on an elemental basis. Aluminum zirconium chloride hydroxide is an inorganic substance which will rapidly dissociate into aluminum, zirconium, chloride and hydroxide ions upon dissolution in the environment. However, zirconium ions will not remain as such in solution.Thus, regarding the environmental fate and toxicity of aluminum zirconium chloride hydroxide (if any), it can be assumed that it will not be driven by zirconium.Therefore, full read-across to other aluminum substances considering a typical aluminum content of ca. 19.4% isjustified.

The following information is taken into account for any hazard / risk / persistency assessment: Aluminium is the most abundant metal in the lithosphere, and is characterized by a complex biogeochemical cycle (Driscoll and Postek 1996; Exley, 2003). Aluminium can participate in hydrolysis reactions, thereby forming a number of monomeric and polymeric Al-hydroxides and this process is highly dependent on pH. Under REACH (ECHA 2008, Chapter R.7B – Endpoint Specific Guidance), the term ‘Hydrolysis’ refers to the “Decomposition or degradation of a chemical by reaction with water”, and this is a function of pH (i. e., abiotic degradation). Aluminium persists in the environment irrespective of whatever chemical species form as a result of hydrolysis, although it may form insoluble aluminium hydroxides that precipitate out of solution. Characterization of aluminium in environmental media is typically based on total aluminium concentrations inclusive of all specific chemical forms or species. Since hydrolysis changes the chemical form but does not decompose aluminium and since characterization of total aluminium considers all chemical forms, the concept of degradation of aluminium by hydrolysis is not relevant in the consideration of its environmental fate.

References:

Driscoll C.T., Postek K.M. (1996) The chemistry of aluminium in surface waters. In: Sposito G., editor, The environmental chenistry of aluminium. 2nd edition.(FL): CRC Press. p: 363-418.

Exley C. (2003) A biogeochemical cycle for aluminium. Journal of Inorganic Biochemistry 97:17.