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Toxicity to aquatic algae and cyanobacteria

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Description of key information

The 72 hour ErC50 was greater than 100 % v/v saturated solution. The No Observed Effect Concentration was superior or equal to 100 % v/v saturated solution.

Key value for chemical safety assessment

Additional information

In the key study, the toxicity of the test material to aquatic algae was investigated in a GLP study which was conducted in accordance with standardised guidelines OECD 201 and EU Method C.3. The study was assigned a reliability score of 1 in line with the criteria set forth by Klimisch (1997).

Information indicating the test material was insoluble in water instigated pre-study solubility work. The solubility work conducted indicated that it was not possible to obtain a testable solution of the test material using traditional methods of preparation. Given the low water solubility and high purity of the test material, the use of a saturated solution method of preparation was considered most appropriate.

Following preliminary range-finding tests the algae, Pseudokirchneriella subcapitata was exposed to a solution of the test material at a concentration of 100 % v/v saturated solution (six replicate flasks) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1°C. The test material solution was prepared by stirring an excess (50 mg/L) of test material in culture medium using a propeller stirrer at approximately 1500 rpm for 24 hours. After the stirring period any undissolved test material was removed by filtration (0.2 μm Sartorius Sartopore filter, first approximate 1 litre discarded in order to pre-condition the filter) to produce a 100 % v/v saturated solution of the test material. Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group, using a Coulter® Multisizer Particle Counter.

Analysis of the test preparations at 0 and 72 hours showed measured erbium concentrations of 0.0053 and 0.0052 mg/L respectively were obtained, equivalent to a test material concentration of 0.0060 mg/L.

Under the conditions of the study, exposure of Pseudokirchneriella subcapitata to the test material gave an ErC50 value of greater than 100 % v/v saturated solution and a NOEC of 100% v/v saturated solution. Similar results were seen for both growth rate and yield. In conclusion no toxic effects were seen in freshwater algae as a result of exposure to the test material.