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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Three toxicity tests with algae were performed. These tests were well described and performed according OECD guideline 201 applying GLP conditions and all three should have a high Klimisch score. The studies in standard OECD media Gancet (2009) and Kean (2014) however, gave results which are typical for testing with long alkyl diethanol amines. The results of the chemical analyses of these tests show that the test subsubstance concentration did not remain constant in the test system due to sorption to algae and also for a faction (<20% Kean) to glassware. According to the OECD 201 guideline (point 40) this doesn't have to be an issue as long as there is no reduction in growth inhibition, i.e. the substance is only sorbed to algae and not degraded or for a large fraction sorbed to glassware. For the test from Kean the dose response was therefore according to the guideline based on measured initial test concentrations. This was not done for the study from Gancet and the result of Gancet is therefore not considered to be suitable for risk assessment or C&L.

Results of the study from Kean (to be used for C&L): Significant effect (growth rate) was observed on growth rate at 0.008 mg/L. The NOEC is therefore 0.008 mg/L and LOEC is 0.016 mg/L. The ErC10 is 0.016 mg/L and the ErC50 is 0.054 mg/L. The EbC50 was found to be 0.022 mg/L.

The third algae test from Scheerbaum (2009) was performed in river water and resulted in a 72 hr ErC10 of 34.1 ug/L  and 72 hr ErC50 of 86.7 ug/L. This result is considered to better suitable for risk assessment following the bulkapproach i.e. comparing exposure and effects using the total concentration.

Key value for chemical safety assessment

EC50 for freshwater algae:
86.7 µg/L
EC10 or NOEC for freshwater algae:
34.1 µg/L

Additional information

Three toxicity tests with algae were performed. These tests were well described and performed according OECD guideline 201 applying GLP conditions and all three should have a high Klimisch score. The studies in standard OECD media from Gancet (2009) and Kean (2014) however, gave results which are typical for testing with long alkyl diethanol amines. The results of the chemical analyses of these tests show that the test subsubstance concentration did not remain constant in the test system due to sorption to algae and also for a faction (<20% Kean) to glassware. According to the OECD 201 guideline (point 40) this doesn't have to be an issue as long as there is no reduction in growth inhibition, i.e. the substance is mainly sorbed to algae and not degraded or for a large fraction sorbed to glassware. For the test from Kean the dose response was therefore according to the guideline based on nominal test concentrations which deviated less than 20% from the measured initial test concentrations. This was not done for the study from Gancet and the result of this study is therefore not considered to be suitable for risk assessment or C&L.

Results of the study from Kean (to be used for C&L) which was performed in standard OECD test media resulted in a 72 hr ErC10 of 0.016 mg/L and a 72 hr ErC50 of 0.054 mg/L. The 72 hr EbC50 was found to be 0.022 mg/L.

The third algae test from Scheerbaum (2009) was performed in river water and resulted in a 72 hr ErC10 of 34.1 ug/L and 72 hr ErC50 of 86.7 ug/L. This result is considered to better suitable for risk assessment following the bulkapproach i.e. comparing exposure and effects using the total concentration.