9-Octadecenoic acid (Z)-, zinc salt, basic

Short-term toxicity to fish

Description of key information

Exposure of Rainbow trout (Oncorhynchus mykiss) to the test item gave an LC50 value based on the average initial measured test concentration of greater than 1.6 mg/L. This study showed that there were no toxic effects at saturation.

Additional information

Fish

The key study was performed to OECD Guideline No. 203 and EC Method C1. 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 and high shear mixing. A pre-study media preparation trial indicated that a dissolved test item concentration of approximately 3.8 mL (calculated from analysis of dissolved zinc determined as 0.54 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, seven fish were exposed to an aqueous solution of test item, at a single concentration of 1.6 mg/L (calculated from analysis of dissolved zinc determined as 0.23 mg/L) for a period of 96 hours at a temperature of approximately 15°C under semi-static test conditions. The test item solution was prepared by stirring an excess (50 mg/L) of test item in test water using a propeller stirrer at approximately 1500 rpm for 24 hours. After the stirring period any undissolved test item was removed by filtration (0.2µm Sartorius Sartpore filter, first approximate 2 litres discarded in order to pre-condition the filter) to produce a 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.

There were no mortalities in 7 fish exposed to test concentrations of 1.6 mg/L for a period of 96 hours.

There were no sub-lethal effects of exposure observed in the test.

The test concentration of 1.6 mg/L was the highest attainable test concentration that could be prepared due to the limited solubility of the test item in water.

Analysis of the freshly prepared test preparations at 0 and 72 hours showed measured test concentrations to range from 1.27 to 1.90 mg/L (calculated from analysis of dissolved zinc determined to range from 0.18 to 0.27 mg/L). There was no significant change in the measured concentrations at 24 and 96 hours and so the results are based on the average initial measured test concentration only.

The test was considered to be valid given that none of the control fish died or showed signs of stress during the test and the oxygen concentration at the end of the test was ≥60% of ASV (6.1 mg O₂/L) in the control and test vessels.

Exposure of Rainbow trout (Oncorhynchus mykiss) to the test item gave an LC50 value based on the average initial measured test concentration of greater than 1.6 mg/L. This study showed that there were no toxic effects at saturation.