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Short-term toxicity to aquatic invertebrates

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Description of key information

The test item was assessed for short term toxicity to Daphnia according to OECD Guidelines for Testing of Chemicals (April 2004) No 202, "Daphniasp., Acute Immobilisation Test" referenced as Method C.2 of Commission Regulation (EC) No. 440/2008.  Based on the time-weighted mean measured test concentrations, the 48 hour EC50 was 11 mg/L with 95 % confidence limits of 9.2 - 12 mg/L.  The NOEC was 4.6 mg/L and the LOEC was 8.7 mg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
11 mg/L

Additional information

The test item was assessed for short term toxicity to Daphnia according to OECD Guidelines for Testing of Chemicals (April 2004) No 202, "Daphniasp., Acute Immobilisation Test" referenced as Method C.2 of Commission Regulation (EC) No. 440/2008.

Preliminary 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.

 

A preliminary media preparation trial indicated that a dissolved test item concentration of approximately 85 mg/L was obtained from a saturated solution method of preparation indicating this to be the limit of water solubility of this item under test conditions.

 

Following a preliminary range-finding test, twenty daphnids (4 replicates of 5 animals) were exposed to an aqueous solution of the test item at nominal concentrations of 10, 18, 32, 56 and 100% v/v saturated solution for 48 hours at a temperature of approximately 20°C under semi-static test conditions. The test item solutions were prepared by stirring an excess (100mg/L) of test item in test water using a propeller stirrer at approximately 1500 rpm for24hours. 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
100% v/v saturated solution of the test item. This saturated solution was then further diluted as necessary, to provide the required test concentrations. Immobilization and any adverse reactions to exposure were recorded after 24 and 48 hours.

 

Analysis of the freshly prepared test media at 0 and 24 hours showed measured test concentrations to range from 3.9 to 64 mg/L. A decline in measured test concentration was observed in the old or expired test media at 24 and 48 hours to between 2.0 and 50 mg/L and hence it was considered appropriate to calculate the results based on the time-weighted mean measured test concentration only in order to give a “worst case” analysis of the data.

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Analysis of the immobilization data by the maximum-likelihood probit method at 24 hours and trimmed Spearman-Karber method (Hamilton et al, 1977) at 48 hours based on the time-weighted mean measured test concentrations gave the following results:

The 24 h EC50 was 12 mg/L with 95 % confidence limits of 9.9 - 14 mg/L.

The 48 h EC50 was 11 mg/L with 95 % confidence limits of 9.2 - 12 mg/L.

The No Observed Effect Concentration after 24 and 48 hours exposure was 4.6 mg/L. The Lowest Observed Effect Concentration after 24 and 48 hours exposure was 8.7 mg/L.

The slopes and their standard errors of the response curves at 24 hours were 8.6 (SE = 1.7). Due to the nature of the data it was not possible to calculate the slope and error of response curve at 48 hours.