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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

Algal growth inhibition: ErC50= 90.5 mg/L; EyC50 = 70.3 mg/L; NOEC = 46.9 mg/L

Key value for chemical safety assessment

EC50 for freshwater algae:
90.5 mg/L
EC10 or NOEC for freshwater algae:
46.9 mg/L

Additional information

Algal growth inhibitionto the unicellular freshwater green alga Pseudokirchneriella subcapitata has been investigated according to OECD/EU test methods. Hexahydrophthalic anhydridewas found to inhibit the growth after 72 hours exposure, the EbC50, ErC50 and EyC50 in non-adjusted media were 72.9 mg/L, 90.5 mg/L and 70.3 mg/L, respectively. In pH-adjusted media, no inhibition occurred during the test, so the EC50 value for all parameters was >91.9 mg/L. The “no observed effect concentration” (NOEC) for area under the growth curve, growth rate and yield was 46.9 mg/L in non-adjusted media and 91.9 mg/L in pH-adjusted media. These results suggest that the pH of the test media, decreased by the presence of the test substance following its degradation, was responsible for the toxicity observed in the non- adjusted media.

In accordance with ECHA guidance oninformation requirements and chemical safety assessment,Chapter R.7b: Endpoint specific guidance, theErC50 endpoint is used in DNEL derivation. This is because use of values based on biomass cannot be applied to an analysis of results from a system in exponential growth without logarithmic transformation.