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Long-term toxicity to fish

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Under semi-static conditions of 72 hour renewal with WAFs, the effect on growth rates and other observed effects in juvenile fish (Danio rerio) exposed to the test substance for 28 days was conducted according to OECD Test Guideline 215.

During the entire test period, the pH values of the control and Test Media were between 7.3 and 7.6, and the Dissolved Oxygen (DO) values varied from 93% to 102% of the air saturation at the test temperature, and the temperature of the Test Media was maintained in the range of 22°C to 23 °C. All fishes in the control group were normal. The mean weight of fish in the controls increased more than 50%. So the study met the acceptability criteria prescribed by the protocol (dissolved oxygen concentration: no less than 60% of the air saturation value; temperature: (23±2) °C and not different by more than ± 1 °C between test chambers; the increasing rate of the mean wet-weight of fish: no less than 50% of the initial weight). Therefore the test was considered valid.

In order to confirm the stability of the test substance in the test medium (renewed WAF), concentrations of the test samples during the test were analyzed by HPLC-DAD. The results show that linearity for the concentration range of 0.50 mg/L to 20.0 mg/L is good (r^2 = 0.999). The minimum detection concentration for water sample is 0.50 mg/L.

It was not possible to verify the concentration stability of the test substance in the WAF solutions, due to the extremely low aqueous solubility of the test substance. The aqueous solubility of the test substance is approximately 2.4E-5 mg/L based on QSAR estimates, and this estimate is further confirmed by measurement data which indicate that the aqueous solubility is below <0.001 mg/L. The aqueous solubility of the test substance thus falls well below the the HPLC-DAD minimum detection concentration of 0.50 mg/L. Therefore, concentration stability in the WAF solution was ensured by way of applying high loading rates (up to 150 mg/L), long WAF equilibration time (24 hr), and regular WAF renewals (every 72 hr) throughout the duration of the test.

The results showed that under valid semi-static test conditions (72 h-renewal), the LOELR is >150 mg/L, which substantially exceeds the water solubility of the substance. Therefore no effect was observed at the aqueous solubility limit, based on a loading rate of 150 mg/L (analysed concentration in water <0.50 mg/L).

Other supporting data indicate that the test substance is not acutely toxic to fish, aquatic invertebrates and algae at its maximum water solubility limits, and the test substance does not cause chronic toxicity to an aquatic invertebrate (Daphnia magna) at its maximum water solubility limit.

Furthermore, the test substance is not bioaccumulative (Section 5.3). In a dietary exposure study on fish with a mean feed concentration of 630 ppm, a 12 -day uptake phase, and a 21 -day depuration phase (section 5.3.1), no mortality, abnormal behavior, or discoloration in the fish were observed in the test group relative to the control group.

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