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Short-term toxicity to fish

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Description of key information

Key study performed according to GLP and OECD Guideline 203:
The acute toxicity of the test item to the freshwater fish fathead minnow (Pimephales promelas) has been investigated. Given the decline in measured test concentrations it was considered justifiable to base the results on the time-weighted mean measured test concentrations. The 72-Hour LC50 based on the time-weighted mean measured test concentrations was >0.17 mg/L. The No Observed Effect Concentration was 0.17 mg/L.
 

Key value for chemical safety assessment

Additional information

Introduction

A study was performed to assess the acute toxicity of 9-dodecenoic acid, methyl ester (9DDAME) (CAS No. 39202-17-0) to fathead minnow (Pimephales promelas). The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (1992) No 203, "Fish, Acute Toxicity Test" referenced as Method C.1 of Commission Regulation (EC) No. 440/2008 and US EPA Draft Ecological Effects Test Guidelines OPPTS 850.1075 "Fish Acute Toxicity Test, Freshwater and Marine".

 

Methods

Following a preliminary range-finding test, ten fish were exposed to an aqueous solution of the test item, at a single concentration of 100% v/v saturated solution (0.17 mg/L based on time-weighted mean measured test concentrations) at a temperature of 20 ºC to 21°C under semistatic test conditions. The test period was 96 hours, however during the last 24 hours of the test no dissolved test item was detected in the exposure vessels and hence the results have been calculated using a 72-hour exposure to the test item. The test item solution was prepared by stirring an excess (50 mg/L) of test item in dechlorinated tap water 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 100% v/v saturated solution of the test item. The number of mortalities and any sub-lethal effects of exposure in each test and control vessel were determined 3 and 6 hours after the start of exposure and then daily throughout the test until termination after 96 hours.

 

Results

The study showed no toxic effects at saturation.

Analysis of the freshly prepared test preparation at 0, 24, and 48 hours showed measured concentrations to range from 0.836 to 0.933 mg/L. Analysis of the corresponding old media at 24, 48 and 72 hours showed measured concentrations of less than the limit of quantitation (LOQ) of the analytical method (assessed as 0.011 mg/L).

 

Analysis of the freshly prepared test media at 72 hours and the corresponding old test media at 96 hours showed no detectable test item. It was therefore considered that the test organisms had not been exposed to the test item over the final 24 hours of the test period and therefore all results have been based on a 72-Hour exposure period.

 

Given the decline in measured test concentrations over each 24-Hour period, it was considered justifiable to base the results on the time-weighted mean measured test concentrations. The time-weighted mean measured concentration was calculated to be 0.17 mg/L.

 

The 72-Hour LC50 based on the time-weighted mean measured test concentrations was greater than 0.17 mg/L. The No Observed Effect Concentration was 0.17 mg/L.

 

Given that the test item showed no toxic effects over a 72-Hour period at a time-weighted mean measured test concentration of 0.17 mg/L, and given the consistency of the measured test item concentrations over the first 72 hours of the exposure period, it is considered likely that the 96-Hour LC50would also be greater than 0.17 mg/L.

The decline in test item within relatively brief periods means that a stable concentration was not attained. Therefore the test should not be regarded reliable without restriction. The repeated observation of virtually complete disappearance suggests that this reflects an inherent property of the test item, although the cause of this is currently unknown.