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Environmental fate & pathways

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Read across approach

In the assessment of the environmental fate and pathways of fatty acids, C6-19-branched, zinc salts (CAS 68551-44-0), a read-across approach from data for the metal cation and the organic anion is followed. This read-across strategy is based upon the assumption that upon release to the environment and dissolution in aqueous media, fatty acids, C6-19-branched, zinc salts will completely dissociate and only be present in its dissociated form, i.e. as zinc cation and C6-19-branched carboxylate anions.

Upon dissolution in water, it is indeed predicted that metal carboxylates dissociate completely into the metal cation and the organic anion at environmentally relevant conditions. No information is available on the stability constants of fatty acids, C6-19-branched, zinc salts, but predictions of stability of other zinc carboxylates (Zn propionate, Zn valerate, Zn isovalerate and Zn benzoate) in a standard ISO 6341 medium (2 mMCaCl2, 0.5 mM MgSO4, 0.77 mM NaHCO3 and 0.077 mM KCl, pH 6 and 8) clearly show that monodentate ligands such as carboxylic acids have no potential for complexing zinc ions in solution (Visual minteq. Version 3.0, update of 18 October 2012.

Upon dissolution and dissociation of fatty acids, C6-19-branched, zinc salts into Zn2+ and C6-19-branched carboxylate anions, both constituent ions will each show its proper (bio)degradation, bioaccumulation and partitioning behaviour in the environment, as reported for the corresponding metal ion and carboxylic acid (Zn2+ and fatty acids, C6-19-branched). The environmental fate and behaviour for the metal and organic moieties is predicted to be clearly different from each other, resulting in a different relative distribution over the environmental compartments (water, air, sediment and soil).

Only few data on environmental fate are available for fatty acids, C6-19-branched or its salts. Based on the similarities in structure, physical-chemical properties, environmental fate and toxicity between fatty acids C6-19-branched and neodecanoic acid (C10-neo acid; CAS 26896-20-8), data for neodecanoic acid were therefore selected for the read-across approach. This is consistent with the grouping approach followed by the US EPA HPV programme for even a wider range of neo acids (C5-C28;