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Aquatic toxicity of succinic anhydride was assessed in a read-across approach using the hydrolysis product of succinic anhydride, succinic acid (DT50 = approx. 5 min). Due to the fast hydrolysis of succinic anhydride in aqueous solutions, succinic acid is suitable to assess the aquatic toxicity of succinic acid.

Short-term fish

In a 96-h acute toxicity study according to test guideline OECD 203, juvenile D. rerio were exposed to a single succinic acid concentration of 100 mg/L under semi-static conditions.  The 96-h LC50 was > 100 mg /L (nominal concentration).  The NOEC value, based on mortality, was 100 mg/L.  Both values correpond to 85 mg/L succinic anhydride. No sublethal effects were observed. 

Short term invertebrates

The 48h acute toxicity of succinic acid to Daphnia magna was determined in two semi-static tests according to the OECD 202 guideline. Test species were exposed at nominal concentration of 6.5, 12.5, 25, 50, and 100 mg/L for 48 h. Based on the fact that the effects seen in the first experiments were influenced by pH changes, the most appropriate endpoint to use for the assessment of succinic acid toxicity is the 48-h EC50 value of > 102 mg/L, corresponding to 86 mg/L succinic anhydride, obtained in the study with pH adjustment.

Aquatic algae and cyanobacteria

In a 72-h toxicity study, cultures of Pseudokirchneriella subcapitata were exposed to succinic acid at nominal concentrations of 0 (control), 0.39, 0.78, 1.56, 3.13, 6.25, 12.5, 25, 50, and 100 mg/L under static conditions in accordance with the OECD guideline 201. This test was conducted twice as effects were seen in the first experiment, likely related to drastic pH changes. Therefore, results from the second study with pH control measures are more reliable. The NOEC and EC50 values for biomass and growth rate were 100 mg/L and > 100 mg/L, respectively, corresponding to 85 mg/L succinic anhydride.

Activated sludge

Activated sludge obtained from a sewage treatment plant was exposed in a 3-hour respiration inhibition test to nominal concentrations of 0 (control), 7.7, 19.3, 48.2, 120.6 and 301.5 mg succinic acid/L. The test design included duplicate samples and followed OECD guideline 209. The 3-hour EC50 based on respiration inhibition was > 300 mg succinic acid/L, corresponding to 254 mg/L succinic anhydride.

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