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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

The 72-h EC50 value and the 72-h NOEC for monoethanolamine in Pseudokirchneriella subcapitata are 2.5 and 1 mg/L respectively. The 3-h toxicity threshold (equivalent to an EC3) for citric acid in Scenedesmus quadricauda is 640 mg/L.
After correction for molecular weight the effect concentrations for tris[(2-hydroxyethyl)ammonium] citrate are 15.4, 6.15 and 1,250 mg/L respectively. The values of 10.4 and 4.14 mg/Lwill be used in the assessment.

Key value for chemical safety assessment

EC50 for freshwater algae:
15.4 mg/L
EC10 or NOEC for freshwater algae:
6.15 mg/L

Additional information

No studies with algae are available for tris[(2-hydroxyethyl)ammonium] citrate. 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).

A GLP-compliant OECD 201 test with Pseudokirchneriella subcapitata is available for monoethanolamine (NITE, 1996b). The72-h EC50 value and the 72-h NOEC for monoethanolamine are 2.5 and 1 mg/L respectively, a safety factor need not to be applied to these values. Instead, the effect concentration will be corrected for molecular weight. The effect concentrations for tris[(2-hydroxyethyl)ammonium] citrate are 15.4 and 6.15 mg/L.

For citric acid a non-GLP growth inhibition study with Scenedesmus quadricauda is available (Bringmann and Kühn, 1977). The 8-d toxicity threshold (equivalent to an EC3 value) is 640 mg/L, a safety factor need not to be applied to this value. Instead, the effect concentration will be corrected for molecular weight. The effect concentration for tris[(2-hydroxyethyl)ammonium] citrate is 1,250 mg/L.

The effect concentrations of 10.4 and 4.14 mg/L will be used in the assessment.