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Short-term toxicity to fish

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Description of key information

In a key read-acros Guideline (OECD 203) fish toxicity study, the 96-hour LC50 of Hexylcinnamaldehyde (CAS# 101-86-0) on the fathead minnow (Pimephales promelas) was determined to be 1.7 mg/L, with 95% confidence limits of 0.93 and 2.3 mg/L. When adjusted for the molecular weight of the test material, an LC50 of 1.2mg/L is achieved. The no-mortality concentration and the NOEC were both determined to be 0.93 mg/L.

Key value for chemical safety assessment

LC50 for freshwater fish:
1.2 mg/L

Additional information

In a key read-acros Guideline (OECD 203) fish toxicity study (Wildlife International Ltd., 2010a), the acute effects of the test material (Hexylcinnamaldehyde; CAS# 101-86-0) on the fathead minnow (Pimephales promelas) were evaluated during a 96-hour exposure period under flow-through test conditions.

 

Fathead minnows were exposed to a geometric series of five test concentrations, a negativecontrol (dilution water), a solvent control (0.1 mL/L dimethylformamide) and a stabilizer control(0.01 mg/L stabilizer mix) for 96 hours under flow-through conditions. Two replicate test chambers were maintained in each treatment and control group, with 10 fish in each test chamber, for a total of 20 fish per concentration. Nominal test concentrations selected were 0.19, 0.38, 0.75, 1.5 and 3.0 mg/L. The concentration of the stabilizer mixture in the stabilizer control was equal to the concentration of stabilizer mixture in the highest treatment concentration. Mean measured test concentrations were determined from samples of test water collected from each treatment and control group at the beginning, the approximate mid-point and the end of the test.Delivery of the test substance to the test chambers was initiated four days prior to the introductionof the fathead minnows to the test water in order to achieve equilibrium of the test substance in the test chambers. The fish were impartially assigned to exposure chambers at test initiation. Observations of mortality and other signs of toxicity were made approximately 1, 24, 48, 72 and 96 hours after test initiation. Cumulative percent mortality observed in the treatment groups was used to determine LC50 values at 24, 48, 72 and 96 hours. The no-mortality concentration and the no-observed-effect concentration (NOEC) were determined by visual interpretation of the mortality and biological observation data.

 

When measured concentrations of the samples collected during the test were averaged, the mean measured test concentrations for this study were 0.12, 0.27, 0.61, 0.93 and 2.3 mg/L, representing 63, 71, 81, 62 and 77% of nominal concentrations, respectively.

 

All fish in the negative, solvent and stabilizer control groups appeared normal throughout the test. All fathead minnows in the 0.12, 0.27, 0.61 and 0.93 mg/L treatment groups also appeared normalthroughout the test, with no mortalities or overt signs of toxicity observed. Percent mortality in the2.3 mg/L treatment group at test termination was 80%. Signs of toxicity observed among fish in the2.3 mg/L treatment group were lethargy and lying on the bottom of the test chamber.

 

Based on the results observed, the 96-hour LC50 was determined to be 1.7 mg/L, with 95% confidence limits of 0.93 and 2.3 mg/L. When adjusted for the molecular weight of the test material, an LC50 of 1.2mg/L is achieved. The no-mortality concentration and the NOEC were both determined to be 0.93 mg/L.