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Ecotoxicological information

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For the assessment of aquatic toxicity of the substance short-term toxicity data with fish, aquatic invertebrates, algae and microorganisms are available. Long term aquatic toxicity studies were carried out with fish and daphnia.

Short term toxicity to fish

The toxicity of the substance to carp was assessed in a study according to OECD Guideline 203 (Fish, Acute Toxicity Test, 1992). A limit test was performed consisting of a blank control and a maximum soluble fraction of the substance in test medium. The total test period was 96 hours and samples for analytical confirmation of actual exposure concentrations were taken at the start, after 24 hours and at the end of the test period.

Analyses of samples taken from the glass-wool filtered solution of 100 mg/L showed that the measured concentration varied between 1.3 and 2.1 mg/L during the test period. These concentrations were at or slightly above the expected concentrations based on the solubility in pure water.

Under the conditions of the test the substance induced no visible or lethal effects in carp up to the limit of solubility in test medium. The 96 h LC50 exceeded the water soluble fraction of the test substance obtained after glass-wool filtration of a loading rate prepared at 100 mg/l, with an actual concentration ranging between 1.3 and 2.1 mg/L.

The toxicity of the substance towards zebrafish was assessed in a 96 h test according to OECD Guideline 203. Ten fish were exposed to a test solution containing 102.4 mg/L (nominal concentration) of the test substance and 103.5 mg/L Tween-20 as a vehicle. There were no higher concentrations employed as the test substance was not soluble in water. Using the vehicle could help to dispers the substance, but it was not helpful to keep the substance stay steadily in the water for a long period of time. In a control experiment fish were exposed to a solution that contained the vehicle only. The measured concentration of the substance in the water was 97.2 mg/L at the beginning of the test and 87.8 mg/L after 24 hours. Semi-static mode of exposure was chosen with a renewal of the test solution every 24 hours. No poisoning symptoms were observed in the treatment and in the control group throughout the treatment period.

Average mortality of fish at the test concentration of 102.4 mg/L was found to be 6.67 %. The average mortality of fish in the control group was found to be 6.67 %.

In conclusion, the 96 h LC50 in zebrafish exceeded 102.4 mg/L in this test.

Long term Toxicity to fish

In an early life satage study according to OECD Guideline 210 and OPPTS Draft Guideline 850.1400 fertilized eggs of Fathead Minnow (Pimephales promelas) were exposed to the test substance at nominal concentrations of 4.1, 8.1, 16, 33 and 65 µg/L (measured concentrations: 4.1, 8.1, 16, 33 and 59 µg/L) under flow through conditions. Dimethylformamide was used as a vehicle in a concentration of 0.025 mL/L. After completion of hatch at test day 4 the larvae were exposed for another 28 days to the test substance. The embryo hatching success was assessed and at termination of the test the development of normal larvae, larval survival, length and dry weight of larvae were assessed. No adverse effects were observed. Therefore a NOEC of 59 µg/L and a LOEC of > 59 µg/L were derived.

Short-term toxicity to aquatic invertebrates

The toxicity of the substance to daphnia magna was determined according to OECD Guideline 202. A static test design was used. The daphnids were exposed to a water accomodated fractions of the test substance for 48 hours. Under the conditions of the study with Daphnia magna exposed to the substance no significant acute immobilisation of Daphnia magna was observed up to the limit of solubility in test medium. The 48h-EC50 exceeded the water soluble fraction of the substance obtained after glass or glass-wool filtration of a loading rate prepared at 100 mg/l, with an average measured concentration of 0.1 mg/l.

Long-term toxicity to aquatic invertebrates

In a full life cycle test (exposure time: 21 days) the toxicity of the test substance towards daphnia magna was assessed in test according to OPPTS Draft Guideline under static renewal conditions. Dimethylformamide was used as a solvent in a concentration of 0.1 mL/L. Test concentrations employed were 1, 2.6, 6.4, 16, 40, 100 µg/L (nominal concentrations) or 0.46, 1.1, 3.7, 9.8, 26, 82 µg/L (measured concentrations; geometrical mean). The endpoints assessed were immobilisation, abnormial behaviour, numbers of offspring, immobilised offspring and time to first brood release and growth.

Based on the most sensitive indicator of toxicity (i.e., survival), the 21-day NOEC for the substance and D. magna was determined to be 26 μg/L. The 21-day LOEC was determined to be 82 μg/L.

The 21-day NOEC for reproduction and growth was 26 μg/L. The 21-day LOEC for reproduction and growth was > 26 μg/L, the highest geometric mean measured concentration statistically analyzed.

The 21-day EC50 value for immobilisation was determined to be 54 μg/L, with 95 % confidence intervals of 53 to 54 μg/L. Since no concentration tested resulted in ≥ 50 % reduction in reproduction or growth (total body length and dry weight), the EC50 values for reproduction and growth were empirically estimated to be > 26 μg/L, the highest geometric mean measured concentration statistically analyzed.

Toxicity to aquatic algae

The toxicity of the substance to algae was determined according to OECD Guideline 201 using a static test design for 72 hours. The water accomodated fraction of the substance was used. Under the conditions of the present study with Pseudokirchneriella subcapitata, no significant reduction of growth rate or inhibition of yield was recorded at any of the concentrations of the substance tested. The study included a highest concentration prepared at a loading rate of 100 mg/l, with an initial measured concentration of 0.8 mg/l that equalled the limit of solubility (NOEC).

Toxicity to microorganisms

The toxicity of the substance towards waste water bacteria was assessed in an assay according to OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test, 1984). Since the substance was hardly soluble in water test concentrations were prepared separately in Milli-RO water. Two 1 litre test bottles were filled with 250 ml of test substance mixtures with initial loading rates of 200 mg/L. These mixtures were stirred in dark glass closed bottles for 24 hours. Subsequently, 16 ml synthetic sewage feed, 200 ml activated sludge and Milli-RO water up to 500 ml were added resulting in a loading rate of 100 mg/L. This loading rate was tested in duplicate. Optimal contact between the test substance and test medium was ensured applying continuous aeration and stirring. Thereafter oxygen consumption was measured and recorded for approximately 10 minutes.

No significant inhibition of respiration rate of the sludge was recorded at a loading rate of 100 mg/L. The duplicate measurement confirmed the results of the first measurement. Therefore no further testing was necessary.

The EC50 of the substance exceeded a loading rate of 100 mg/L (based on nominal concentrations).