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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Toxicity to aquatic alge reveals an EC50 of 22 mg/L and an EC10 of 9.4 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
22 mg/L
EC10 or NOEC for marine water algae:
9.4 mg/L

Additional information

Toxicity of Diethyl oxalate to aquatic algae was tested according to OECD test guideline 201 and GLP (BorsodChem 2011). However, the test report lacks information on preparation or stirring time of the stock solution. The obvious fluctuations show that the hydrolysis of Diethyl oxalate already started well before the test organisms were introduced and proceeded during the study period. No information can be obtained from the study to which concentrations of Diethyl oxalate and/or Oxalic acid the algae were exposed to during the course of the study. However, as outlined above, it is very likely that Oxalic acid is the relevant compound when Diethyl oxalate comes into contact with water. Though no adverse effects on Algae have been observed in the study, it therefore appears reasonable to disregard the study due to its methodological limitations. Instead, using a worst-case approach, the information available for Oxalic acid (and the second hydrolysis product, ethanol), should be used to assess the aquatic hazard of Diethyl oxalate (for more detailed information on the approach taken, please see the read-across justification attached to chapter 13 of this dossier).

Toxicity of Oxalic acid (CAS 144-62-7) to aquatic algae according to a OECD 201 guideline test reveals an ErC50 (72h) of 22.0 mg/L and NOErC (72h) of 9.4 mg/L (NITE 1998). Supportingly, Bringmann & Kuhn tested Oxalic acid in a cell multiplication inhibition test on algae during 8 d. Under this method, the onset of the inhibition of cell multiplication under the influence of hazardous water pollutants is determined and a Toxicity threshold of 80 mg/L was estimated (Bringmann & Kuhn 1978). These results are in line with the results depicted on ECHA disseminated dossier, which shows a toxicity to aquatic algae in a OECD 201 guideline test: EC50 (72h) = 20.58 mg/L and EC10 = 7.55 mg/L (ECHA disseminated dossier, accessed 13 July 2018).