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No substance-specific data are available for tris[(2-hydroxyethyl)ammonium] citrate, however read-across from monoethanolamine and citric acid is used for the assessment to meet the majority of the standard REACH information requirements. Tris[(2-hydroxyethyl)ammonium] citrate is the neutral salt of monoethanolamine and citric acid. Monoethanolamine and citric acid are the starting materials for the synthesis of tris[(2-hydroxyethyl)ammonium] citrate, and the only difference is that in tris[(2-hydroxyethyl)ammonium] citrate the substances are present in their ionic forms as a monoethanolamine cation and a citrate anion. It is expected that the ecotoxicological properties of tris[(2-hydroxyethyl)ammonium] citrate shall be governed by the properties of monoethanolamine and citric acid (for more details see reporting format for the analogue approach in Appendix A.2).

There is a complete set of data available for monoethanolamine. Besides short-term tests on fish, invertebrates and algae also long-term studies are available. For citric acid the base set data are available, including a microorganism toxicity study.

Guideline studies for short-term toxicity are available for freshwater fish. The critical acute effect concentration for monoethanolamine is a 96-h LC50 value of 349 mg/L in carp (Cyprinus carpio) (Huels, 1997a), the critical effect concentration for citric acid is a 48-h LC50 value of 440 mg/L in golden orfe (Leuciscus idus melanotus) (Juhnke and Lüdemann, 1978). For monoethanolamine a guideline study for long-term toxicity is available, the critical chronic effect concentration is a 30-d NOEC of 1.2 mg/L in Japanese killifish (Oryzias latipes) (NITE, 2006). After correction for molecular weight, the effect concentrations for tris[(2-hydroxyethyl)ammonium] citrate of 860 mg/L for short-term toxicity and 7.37 mg/L for long-term toxicity in fish will be used in the assessment.

For invertebrates short-term toxicity guideline studies are available for Daphnia magna. The critical effect concentrations for monoethanolamine is a 48-h EC50 value of 65 mg/L (Huels, 1997b), the critical effect concentration for citric acid is a 24-h EC50 value of 1,535 mg/L (Bringmann and Kühn, 1982). For monoethanolamine a guideline study for long-term toxicity is available, the critical chronic effect concentration is a 21-d NOEC 0.85 mg/L (NITE, 1996). After correction for molecular weight, the effect concentrations for tris[(2-hydroxyethyl)ammonium] citrate of 399 mg/L for short-term toxicity and 5.22 mg/L for long-term toxicity in daphnids will be used in the assessment.

A growth inhibition guideline study is available for freshwater algae. The critical effect concentrations for monoethanolamine are a 72-h EC50 value of 2.5 mg/L and a 72-h NOEC of 1 mg/L in Pseudokirchneriella subcapitata (NITE, 1996), the critical effect concentration for citric acid is a 8-d toxicity threshold (which is equivalent to an EC3) value of 640 mg/L in Scenedesmus quadricauda (Bringmann and Kuhn, 1977). After correction for molecular weight, the effect concentrations for tris[(2-hydroxyethyl)ammonium] citrate of 15.4 mg/L for short-term toxicity and 6.15 mg/L for long-term toxicity in algae will be used in the assessment.

For the toxicity of microorganisms a respiration inhibition guideline study with domestic activated sludge is available (BASF, 1991) for monoethanolamine. The 30-min EC10 is >1,000 mg/L. For citric acid a growth inhibition test with Pseudomonas putida is available, the 16-h toxicity threshold (which is equivalent to an EC3) is >10,000 mg/L. After correction for molecular weight, an effect concentration for tris[(2-hydroxyethyl)ammonium] citrate of >6,146 mg/L for STP microorganism toxicity will be used in the assessment.