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Toxicity to aquatic algae and cyanobacteria

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Description of key information

The effect of the test item on the growth of Pseudokirchneriella subcapitata has been investigated and gave EC50 values of greater than 100% v/v saturated solution. The No Observed Effect Concentration was 100% v/v saturated solution.
This study showed that there were no toxic effects at saturation.

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Additional information

Introduction

A study was performed to assess the effect of the test item on the growth of the green alga Pseudokirchneriella subcapitata. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (2006) No 201, "Freshwater Alga and Cyanobacteria, Growth Inhibition Test" referenced as Method C.3 of Commission Regulation (EC) No 761/2009.

Methods

Pre-study solubility work conducted indicated that it was not possible to obtain a testable solution of the test item using traditional methods of preparation e.g. ultrasonication and high shear mixing. It was therefore considered that the use of a saturated solution method of preparation was most appropriate for this test item.

Following a preliminary range-finding test, Pseudokirchneriella subcapitata was exposed to a solution of the test item 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 item solution was prepared by stirring an excess (50 mg/L) of test item in culture medium using a propeller stirrer at approximately 1500 rpm for 24 hours. After the stirring period any undissolved test item was removed by filtration (0.2 µm Gelman Acrocap filter, first approximate 500 mL discarded in order to pre-condition the filter) to produce a saturated solution of the test item.

Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group, using a Coulter® Multisizer Particle Counter.

Results

Exposure of Pseudokirchneriella subcapitata to the test item gave EC50values of greater than 100% v/v saturated solution. The No Observed Effect Concentration was determined to be 100% v/v saturated solution.

Chemical analysis of the test preparations at 0 and 72 hours showed measured test concentrations of less than the limit of quantitation (LOQ) of the analytical method employed were obtained which was determined to be 0.0051 mg titanium/L. This does not infer that no test item was in solution, just that any which was present was at a concentration of less than the LOQ.

This study showed that there were no toxic effects at saturation.

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