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Toxicity to aquatic algae and cyanobacteria

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Description of key information

A study was performed to assess the acute toxicity of the test material to algae, Scenedesmus subspicatus CCAP 276/20. The method followed the EU Method C.3 (Algal Inhibition test).
Algae was exposed to Water Accommodated Fractions of the test material at 0 and 1000 mg/L for 72 hours at a temperature of 24±1 degrees C under static test conditions. 6 replicates were done at 1000 mg/L.
The 72 hour EL50 for the test material to algae based on nominal loading rates was >1000 mg/L WAF (growth rate and biomass). The 72 hour No Observed Effect loading rate was 1000 mg/L loading rate WAF.

Key value for chemical safety assessment

Additional information

Value for CSA: >1000 mg/L WAF.

- In the key study (Vryenhoef, 2004; SPL project number: 1666/057) for the acute toxicity to algae, Scenedesmus subspicatus CCAP 276/20, the study was conducted according to the EU Method C.3 (Algal Inhibition test).

This study is presented as the key information as the reliability rating for this study is 2, according to the criteria of Klimisch, 1997 as analytical measurements on the test material were not conducted. This is the most recent and robust study available and has been used for classification purposes.

- The Ward et al, 1994 study was conducted to recognised OECD guidelines and GLP, however a WAF method was used to disperse the test material in solution. It was noted in the study that undissolved insoluble test material was seen at the highest concentrations and no attempt was made to removed the undissolved test material, hence trapping or fouling of test organisms may occur which are physical affects rather than toxic effects. A reliability rating of 3 was assigned according to the criteria of Klimisch, 1997.

Results: Based on the number of cells/ml, the 72 hour EC50 (reported as EL50) is 6.5 mg/L and the 96 hour EC50 is 5.8 mg/L. Based on the average specific growth rate, the 72 hour EC50 (reported as EL50) is 8.4 mg/L and the 96 hour EC50 is 8.7 mg/L.

Regrowth of inhibited cultures from the 50 mg/L test level revealed that the effect at this concentration of the test material was algistatic

rather than algicidal.