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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Test results with pH adjustment: Based on the nominal concentrations of the test item 4,4‘-Sulfonyldiphthalic acid dianhydride (DSDA), the 72 hour-ErC50 for Pseudokirchneriella subcapitata was >100 mg/L. The 72 hour-ErC10 for Pseudokirchneriella subcapitata was >100 mg/L.
The NOEC after 72 hours was 100 mg/L. The LOEC after 72 hours was >100 mg/L.

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Additional information

At the pH-adjusted nominal test item concentration of 100 mg/L ofthe test item4,4‘-Sulfonyldiphthalic acid dianhydride (DSDA) and the other concentration levels of 6.25 to 25 mg/L, which remained in a pH range (pH 7.40 – 8.78), effects could not be observed on growth inhibition ofPseudokirchneriella subcapitataafter 72 hours. At the concentration level of 100 mg/L and 50 mg/L in test media without pH adjustment with a resulting solution pH of 4.34 – 5.82, a 100 % and 7%, respectively growth inhibition was observed after 72 hours. The test item remained in solution in pH-adjusted and pH–unadjusted solutions as recoveries of ≥ 96%, i.e., the hydrolysis product, after 72 hours range from 96 to 109%. Thus,Pseudokirchneriella subcapitatawere exposed to the hydrolysis product in solutions with and without pH adjustment. Therefore, observed effects are assumed to be pH-related and are not assumed to be toxic effects of 4,4‘-Sulfonyldiphthalic acid dianhydride (DSDA). The absence of observed toxic effects at 100 mg/L in pH adjusted solutions indicates the lack of a hazardous potential since the pH of aquatic systems is typically well buffered.