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Short-term toxicity to aquatic invertebrates

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Description of key information

EC50,48h >100 mg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
100 mg/L

Additional information

The 48 hour acute toxicity of succinic acid to Daphnia magna was determined in two semi-static tests according to the OECD 202 and EC C2 guideline.

#1: In the first test Daphnia were exposed over a 48 hour period to succinic acid at nominal concentrations of 0 (control), 6.25, 12.5, 25, 50 and 100 mg/L. pH ranged from 4.7 in the 100 mg/L treatment to 7.4 in the 6.25 mg/L treatment in a dose related response.  Concentrations of succinic acid were verified analytically at test initiation, after 24 hours in both new and old test media and test termination.  Geometric mean measured concentrations was 5.27, 10.62, 25.43, 49.58 and 99.79 mg/L. The 48-hour EC50 was determined to be 63 mg/L with 95% confidence limits of 55 to 71 mg/L. The corresponding no-observed effect concentration (NOEC) was determined to be 25 mg/L.

#2: Key Study:

In the second test Daphnia were exposed over a 48 hour period to succinic acid at nominal concentrations of 0 (control), 6.25, 12.5, 25, 50 and 100 mg/L. As recommended by the guideline, the pHs of the stock solutions used to prepare the test media were adjusted to that of the dilution water before addition of the test substance.  Concentrations of succinic acid were verified analytically at test initiation, after 24 hours in both new and old test media and test termination.  Geometric mean measured concentrations were 5.28, 10.53, 23.47, 49.87 and 102.07 mg/L. Based on the geometric mean concentrations the 48-hour EC50was determined to be >102 mg/L. The corresponding no-observed effect concentration (NOEC) was determined to be 23 mg/L.

Based on the fact that the effects seen in the first experiment were influenced by the pH change the most appropriate endpoint to use for the assessment of succinic acid toxicity is the 48 hour EC50value of >100 mg/L obtained in the study with pH adjustment. 

Supporting study:

Randall reports that the 48 hour acute toxicity of succinic acid to Daphnia magna is ("based on some earlier work") 374.2 mg/L.

Taking into account all studies the 48 h EC 50 value for succinic acid is >100 mg/L.