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Toxicity to aquatic algae and cyanobacteria

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Description of key information

The loading rate of test item causing a 10 and 50 % reduction in growth rate (EL10/50) were estimated to be 8.82 and 20.94 mg/L, respectively. 

Key value for chemical safety assessment

EC50 for freshwater algae:
20.94 mg/L
EC10 or NOEC for freshwater algae:
8.82 mg/L

Additional information

A study was designed to determine the effects of the test item on the growth of Pseudokirchneriella subcapitata over a 72h period, according to the OECD 201 Guideline.

Due to high viscosity of the test item, pre-experiments were performed in order to determine appropriate procedures to design the definitive test conditions: from results obtained, it was decided to use prepare independent test solutions with slow-stirring conditions.

The stability of the substance was not confirmed over the definitive test period; however, as this substance is UVCB, results were expressed as Loading Rate (mg/L).

The loading rate of test item causing a 10 and 50 % reduction in growth rate (EL10/50) were estimated to be 8.82 and 20.94 mg/L, respectively.

The loading rate of test item causing a 10 and 50 % reduction in yield (EL10/50) were estimated to be 2.39 and 8.38 mg/L, respectively.

Another study was performed to determinate the growth inhibition of the freshwater algae Pseudokirchneriella subcapitata (previously known as Raphidocelis subcapitata and Selenastrum capricornutum) exposed to the test item for a duration of 72 hours according to the OECD Guideline 201. This study was not considered as reliable, significant deficiencies being observed in the study protocol. The test item was not prepared as a Water Accommodated Fraction (WAF) as recommended for complex multi-component substances with some highly insoluble components in the OECD Guidance Document No 23. The chemical analyses performed detected the most soluble part of the test substances and were thus not representative of the concentrations of all the test substance.