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EC number: 202-297-4
CAS number: 94-04-2
IntroductionA study was performed to assess the effects of the test item on the early life stages of the fathead minnow (Pimephales promelas). The method followed that described in the OECD Guidelines for Testing of Chemicals (2013) No 210, "Fish, Early-Life Stage Toxicity Test”.
MethodsPreliminary 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.A preliminary media preparation trial indicated that a dissolved test item concentration of approximately 18 mg/L was obtained from a saturated solution method of preparation.Based on the results of a preliminary range-finding test, newly fertilized fathead minnow eggs (4 replicates of 20 eggs per group) were exposed to solutions of the test item at nominal concentrations of 0.56, 1.8, 5.7, 18 and 58% v/v saturated solution for a period of 33 days at a temperature of approximately 24 to 25 °C under semi-static test conditions. The test solutions were renewed daily throughout the test with the exception of Day 3 where there was no water change to avoid causing premature hatching of the eggs. The test item solution was prepared by stirring an excess (100 mg/L) of test item in test water using a magnetic stirrer for approximately 48 hours (the test vessel used was completely filled and sealed with a bung to try and reduce losses of the test item). After the stirring period any undissolved test item was removed by filtration (0.2 μm Sartorius Sartopore filter, first approximate 2 L used to pre-condition the filter was discarded) 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 groups of 0.56, 1.8, 5.7, 18 and 58% v/v saturated solution.The number of mortalities and any sub-lethal effects of exposure in each test and control vessel were recorded daily until termination of the test (28 days post-hatch). At test termination the length and wet weight of the surviving fish were measured.
ResultsAnalysis of the fresh test preparations on Days 0, 6, 13, 20, 27 and 32 showed measured test concentrations to range from 0.017 to 2.3 mg/L. A decline in measured test concentration of the aged test preparations on Day 1 showed measured test concentrations to range from 0.011 to 1.05 mg/L, all other aged preparations did not show any test item present (non-detected) and hence it was considered appropriate to calculate the results based on the geometric mean measured test concentrations in order to give a “worst case” analysis of the data. The geometric mean measured concentrations were determined to be 0.0095, 0.020, 0.047, 0.47 and 1.6 mg/L. The Day 0 and Day 1 control samples showed signs of test item present (0.0052 and 0.0055 mg/L respectively)*.
* = Considered to be due to post sample contamination as no reduction in the test item concentration wasapparent from Day 0 to Day 1 as per all other test groups and as such it is highly unlikely that this contamination came directly from within the control tank.
Exposure of fathead minnow (Pimephales promelas) to the test item gave the following results based on the nominal test concentrations:
Hatching Concentration 95% confidence limits (mg/L) (mg/L)EC10 0.030 0.021 to 0.039EC20 0.050 0.038 to 0.064EC50 0.11 0.083 to 0.15
Post-hatch Survival Concentration 95% confidence limits(mg/L) (mg/L)*LC10 >0.047 Not DeterminedLC20 >0.047 Not DeterminedLC50 >0.047 Not Determined
Length Concentration 95% confidence limits(mg/L) (mg/L)*EC10 >0.047 Not DeterminedEC20 >0.047 Not DeterminedEC50 >0.047 Not Determined
Weight Concentration 95% confidence limits(mg/L) (mg/L)*EC10 0.041 0.022 to 0.075EC20 >0.047 Not DeterminedEC50 >0.047 Not Determined* = It was not possible to calculate 95% confidence limits for the LCx values as the data generated did not fit the models available for the calculation of confidence limits.
† = It was not possible to calculate 95% confidence limits for the ECx/LCx values as the data generated did not fit the models available for the calculation of confidence limits.
The EC10 of freshwater fish is 0.020 mg.L.
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