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In cases where no data are available for tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate, a read-across approach with the corresponding parent acid 2-phosphonobutane-1,2,4-tricarboxylic acid is proposed.


In aqueous media, tetrasodium hydrogen 2-phosphonatobutane-tricarboxylate and 2-phosphonobutane-1,2,4-tricarboxylic acid dissociate into the corresponding anion (2-phosphonatobutane-tricarboxylate ion) and the sodium ion and hydrogen ion (proton), respectively. Fate, behavior and the ecotoxicological properties of 2-phosphonobutane-1,2,4-tricarboxylic acid and its tetrasodium salt are thought to be an effect of the phosphonato-carboxylate ion rather than of the sodium ion or the hydrogen ion (proton), which are normal constituents in environmental systems and have no relevant ecotoxic properties in low concentrations.


Therefore a read-across between tetrasodium hydrogen 2-phosphonatobutane-tricarboxylate and 2-phosphonobutane-1,2,4-tricarboxylic acid is justified.


 


Hydrolysis


With regard to its chemical structure tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate does not contain hydrolysable functional groups and is therefore not expected to hydrolyses under environmental conditions.


In line with this, no indication for a hydrolysis after 5 days at 50 °C can be found and no half-life times and hydrolysis rates were determined for tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate (Holzaht-Grimme, 2021). 


 


Phototransformation in water


As there is no data available for tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate, results of the parent acid, 2-phosphonobutane-1,2,4-tricarboxylic acid are taken into account for this endpoint. The results of modelling based on the irradiation of 2-phosphonobutane-1,2,4-tricarboxylic acid, the parent acid of tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate, in buffer pH 9 and in presence of FeCl3 indicated that the mean photolysis half-life should range from 2-3 days in summer to 15-65 days in winter. The results of modelling based on the irradiation of 2-phosphonobutane-1,2,4-tricarboxylic acid in pure water and stored in brown glass prior to irradiation indicated that the mean photolysis half-lives should range from 0.2-0.3 days in summer to 1-10 days in winter.