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Short-term toxicity to aquatic invertebrates

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Description of key information

1) WoE: Short-term toxicity to invertebrates (Daphnia magna); K2; 1977; no guideline (Eastman's internal method); predates GLP; EC50 (immobility, 96h) > 97 mg/L (nominal concentrations)
2) WoE: Short-term toxicity to invertebrates (Daphnia magna); K2; 1989; EU Method C2 or 84/449/EEC; GLP; EC50 (immobility, 48h) = 38.7 mg/L (nominal concentrations based on TOC content)
3) WoE: Short-term toxicity to invertebrates (Mysidopsis bahia); K2; 1998; EPA/600/4-90/027; not GLP; LC50 (mortality, 48h) > 1.8 mg/L (nominal concentration)

Key value for chemical safety assessment

Additional information

For this endpoint 3 studies are available. Two describing the acute toxicity towards the freshwater invertebrate Daphnia magna and one describing the toxicity towards the saltwater invertebrate Mysidopsis bahia. The first study (by Hirsch, 1977) was not performed according to any specific guideline and predates GLP. The results of this limit test indicate that there is an EC50 (immobility, 96h) > 97 mg/L (nominal concentrations). The second study (Scholz, 1989) was performed according to the EU Method C2 (acute toxicity for Daphnia) and evaluated a concentration range. After 48h, the EC50 (immobility) was 38.7 mg/L, while the NOEC (immobility, 48h) was determined at 14.5 mg/L (nominal concentration based on TOC content). The third study with Mysidopsis bahia (Moser, 1998) was performed according to the EPA/600/4 -90/027 guideline, but not in a GLP compliant laboratory. The toxicity was evaluated over a certain concentration range and after 48h of exposure no mortality was observed up to 1.8 mg/L. Therefore the LC50 (48h) was described to be above the water solubility (>1.5 mg/L).

The toxicity reported in both Daphnia studies differed (EC50 96h > 97 mg/L (solvent used) versus EC50 48h = 38.7 mg/L (no solvent used)) substantially. A reason for this discrepancy might be located in the purity of the test substance. In the study by Scholz (1989) the purity of the substance was only 92.1% while a substantial amount of monoester was present. Due to the lack of data on the purity of the substance in the study by Hirsch (1977) comparison between both studies (and test results) is therefore difficult. Nevertheless, both studies are indicative of the absence of severe acute aquatic toxicity towards aquatic invertebrates.

Although all three tests have certain restrictions, they provide sufficient information to assess the lack of acute toxicity and therefore it is believed that a weight of evidence approach is most appropriate. All tests lack information on actually measured test concentrations (only nominal concentrations are reported) and only two tests evaluated multiple concentrations. Additionally, only the test performed with Mysidopsis bahia evaluated concentrations below water solubility. Therefore, the tests reporting test concentrations well above the water solubility need to be treated with caution.