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Ecotoxicological information

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Acute immobilisation to Daphnia magna has been investigated according to OECD/EU test methods. The effects of a limit concentration of 100 mg/L were determined, with and without adjustment of pH. The LC50 was in excess of 100 mg/L and the NOEC was 100 mg/L.

Algal growth inhibition to the unicellular freshwater green alga Pseudokirchneriella subcapitata has been investigated according to OECD/EU test methods. Hexahydrophthalic anhydride was 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.

Acute toxicity to fish has been investigated using a freshwater species in accordance with OECD test methods. The determined LC50 was > 1000 mg/L and the NOEC was 1000 mg/L based on mortality.

Toxicity to microorganisms has been investigated in a respiration inhibition test conducted according to OECD test methods. Nominal concentrations of 1000.2, 460.1, 220, 100 and 46 mg/L were examined with the highest concentration also examined with pH adjusted to 7.5 ± 0.5 to differentiate between pH effects and effects of the test substance. Hexahydrophthalic anhydride showed inhibition of the respiration rate of activated sludge in concentrations above 100 mg/L. The highest concentrated treatment (1000 mg/L) showed a mean inhibition value of 95 % and a pH of 4.6 at the end of the test. Two replicates at this concentration with pH adjusted to pH 7.5 ± 0.5 showed a mean inhibition value of only 17 % leading to the conclusion that inhibition was mostly caused by the acidic character of the hydrolysed test substance. The IC50 was 370 mg/L and the no observed effect concentration (NOEC) was 100 mg/L.