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Long-term toxicity to aquatic invertebrates

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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.
Prolonged toxicity with Daphnia magna was performed according to "Effects on Reproduction" (proposal for an update of OECD guideline 202, Part II; Draft 6/5/1991 and the following results were obtained:
EC 50 (immobilisation, 21d): > 1071 mg/L
EC 50 (reproduction, 21d): > 329 - < 1071 mg/L
NOEC (reproduction, 21d): 104 mg/L
LOEC (reproduction, 21d): 329 mg/L

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater invertebrates:
104 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.

A study was performed to assess the effects of 2-phosphonobutane-1,2,4-tricarboxylic acid on the reproductive output of parthenogenetic Daphnia magna STRAUS under semi static conditions. The study was conducted in accordance with the proposal for an update of OECD guideline 202, Part II; Draft 6/5/1991: “Prolonged Toxicity Study with Daphnia magna: Effects on Reproduction" After a 21d-exposure period, the total number of living offspring produced per parent animal alive at the end of the test was assessed. The reproductive output of the Daphnia exposed to the test substance was compared to that of the control in order to determine the Lowest Observed Effect Concentration (LOEC) and the No Observed Effect Concentration (NOEC) according to the Dunnett-Test Procedure. A NOEC of 104 mg/l and a LOEC of 329 mg/l for the endpoint reproduction were obtained. The results relate to the arithmetic mean of measured concentrations. The stability of the substance during the experiment was confirmed by analytical monitoring. The recovery rate was between 98.1% and 115.9%.

This toxicity study is classified as acceptable and satisfies the guideline requirements for the chronic toxicity study to aquatic invertebrates (Daphnia magna).