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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

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.
A 50.4% solution of 2-phosphonobutane-1,2,4-tricarboxylic acid showed 4.3 % respiration inhibition of activated sludge at a test item concentration of 1000 mg/L. As the effect value related to nominal concentration of the water solution, the effect concentration is converted based upon the water content of the test item, resulting in an EC10 and EC50 of 504 mg/l.

Key value for chemical safety assessment

EC50 for microorganisms:
504 mg/L

Additional information

As there is no data 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-phosphono-butane-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.

To assess the toxicity of 2-phosphonobutane-1,2,4-tricarboxylic acid to microorganisms, a study was conducted in accordance with Council Regulation (EC) No 440/2008, Method C.11 "Activated sludge respiration inhibition" (2008) - equivalent to OECD Guideline 209 (1984). The activated sludge was exposed to a 50.4% water solution of 2-phosphonobutane-1,2,4-tricarboxylic acid at different concentrations. The respiration rate of each mixture was determined after aeration periods of 3 hours. 2-phosphonobutane-1,2,4-tricarboxylic acid solution showed 4.3 % respiration inhibition of activated sludge at a test item concentration of 1000 mg/L. The EC50 is higher than 1000 mg/L. The effect value related to nominal concentration of the water solution, since no analytical monitoring was performed. Therefore the effect concentration is converted based upon the water content of the test item, resulting in an EC10 and EC50 of 504 mg/l.