Teflubenzuron

Long-term toxicity to aquatic invertebrates

Description of key information

In a semi-static test with Daphnia magna following to OECD TG 211 the 21-day NOEC of the test item was determined to be 0.062 µg a.s./L. In a flow-through life-cycle test with the seasalt mysid Mysidopsis bahia the 27-day NOEC of the test item was determined to be 0.043 µg a.s./L (mean measured).

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

NOEC

Effect concentration:

0.062 µg/L

Marine water invertebrates

Marine water invertebrates

Dose descriptor:

NOEC

Effect concentration:

0.043 µg/L

Additional information

Two studies on the long-term toxicity of test item to aquatic invertebrates are available. All presented studies were peer-reviewed during the assessment of teflubenzuron according to Council Directive 91/414/EEC.

 

Key information

ECT (2003): A Study on the Chronic Toxicity of BAS 309 I to Daphnia magna. Unpublished report, report No. G3FQ, according to Draft Assessment Report (2007) according to Council Directive 91/414/EEC, crossreference: MCA 8.2.2/01

The long-term toxicity of test item to Daphnia magna was assessed in a 21-day Daphnia Reproduction study according to OECD TG 211. In this study 12 daphnia per treatment (12 vessels containing 1 daphnid for each test concentration and control and solvent control) were used.

One day before starting the test all young daphnids were removed from selected holding vessels. The stock solution was prepared once per week by dissolving 50 mg of the test item in 500 mL acetone, afterwards the stock solution was diluted in Medium M4 to prepare a second stock solution. The test concentrations were prepared by diluting the second stock solution with Medium M4 to achieve nominal concentrations of 0, 0.021, 0.062, 0.185, 0.556, 1.667 and 5.0 µg a.s./L. On day 2, 5, 9, 12, 16 and 19 samples for chemical analysis were taken from the test vessels of control, C1, C3 and C6 from freshly (0 h) and aged solutions (72 h). Samples were analysed by HPLC/UV with a quantification limit of 0.10 µg/L.

The analytical verification determined mean measured concentrations of 0, 0.020, 0.167 and 4.26 µg a.s./L, which corresponds to a mean recovery of 86% of nominal and based on time-weighted average 92% of nominal. Therefore, all biological results were reported based on nominal concentrations.

To determine the highest concentration tested which was not statistically significant different to the solvent control (NOEC) the One-way Analysis of Variance (ANOVA) test and Dunnett`s multiple t-tests procedure were used for homogeneous variances, Bonferroni t-test after Holm was performed for heterogeneous variances. In the treatments groups, mortality was corrected by solvent control mortality using Abbott`s formula.

In the test vessels, pH varied between 7.5 and 8.3 (SD 0.16), temperature ranged from 19.2 to 20.3 °C (SD 0.21) and oxygen concentration (% dissolved oxygen) varied from 9.8 to 112.1 % (SD 13.3; minimum 7.56 mg/L. Immobilised parent animals in the controls were below 20% (12.5%) and average cumulative numbers of offspring per mobile parent daphnid in the controls were above 91 (limit ≥ 60 after 21 d). Water hardness (limit > 140 mg/L), pH (required 6-9) and dissolved oxygen (limit ≥ 3.0 mg/L) were within the required range. Thus, all validity criteria for the test were fulfilled.

EC50 for survival parent daphnids was 0.317 µg a.s./L, while an EC50 for reproduction was not determined. The NOEC was determined to be 0.185 µg a.s./L for reproduction and survival. Based on the effect parameter length of parent daphnids a NOEC of 0.062 µg a.s./L was determined, which is the key value.

The study was regarded acceptable for the hazard and risk assessment under Regulation (EC) No 1907/2006. 

 

Wildlife International Ltd. (1996): Teflubenzuron: A flow-through life-cycle toxicity test with the saltwater mysid (Mysidopsis bahia). Unpublished report No. 243A-101, according to Draft Assessment Report (2007) according to Council Directive 91/414/EEC, crossreference:  MCA 8.2.5/03

In a life-cycle study with the saltwater mysid M. bahia according to the US EPA Guideline 540/9-82-024 (1982) the long-term toxicity of test item was assessed over an exposure duration of 27 d in a flow-through system.

A primary stock was prepared by dissolving test item in acetone. Then aliquots were diluted with acetone to prepare 4 additional stock solutions. The five stock solutions were mixed with dilution water to achieve the nominal test concentrations of 0.0077, 0.017, 0.037, 0.082 and 0.18 µg a.s./L, based on the results of an 7-day range-finding test. Additionally, the mysids were exposed to a control and a solvent control. The concentration of acetone in the solvent control and in all treatment groups was 0.05 mL/L. Juvenile mysids less than 24 hours old were used as test animals. During the 14-day holding, water temperature was 24.5 to 25.1 °C, the pH ranged from 8.0 to 8.1, the salinity ranged from 20 to 21 ‰ and dissolved oxy­gen was between 6.8 and 7.3 mg/L. Dilution water was natural seawater, diluted to a salinity of 20 ‰ with well water. Prior to delivery to the diluter system, the seawater was filtered two times and was aerated. Salinity and pH were measured during the test period. A continuous-flow diluter and syringe pumps were used to deliver the solutions. The flow of dilution water was controlled by rotameters. Each test chamber received approximately 14 volume additions of test water every day.

Two replicate test chambers, each containing three compartments with 10 mysids were maintained for each treatment and control group. At test initiation, the juvenile mysids were transferred among glass beakers and then to the test chambers. Prior to sexual maturity, the compartments were 500 mL glass beak­ers (days 0 – 8) and 12 cm glass culture dishes (days 9 – 15). On day 15, female and male adults were paired in reproductive compartments (5 cm glass Petri dishes). The test compartments were placed in 19-L glass aquaria. The volume of test solution in the test chambers was between 5.5 and 9.0 L. The test chambers were placed in an environmental chamber at 27 ± 1 °C. Fluorescent tubes at a photoperiod of 16 hours light and 8 hours dark provided the lighting. Light intensity was 542 lx at the surface. Observations of the survival and behaviour auf each first generation mysid were made daily throughout the test. Prior to pairing, sex and maturity were deter­mined microscopically. After pairing, the number of second-generation mysids were counted, recorded and observed for abnormal development and behaviour, daily. At the end of the test, the sex of each surviving first-generation mysid was confirmed, the length and the dry weight was measured.

Temperatures were within 27 ± 1 °C throughout the test. On day 10, dissolved oxygen had dropped to 51% of saturation (3.6 mg/L) and therefore all test chambers were aerated until dissolved oxygen reached 79% of saturation. No resulting effects on survival could be detected. Measurements of pH ranged from 8.0 to 8.2. Salinity in the control remained at 20‰ throughout the test.

The mean measured concentrations were 0.009, 0.019, 0.043, 0.091 and 0.22 µg a.s./L, which represented 111 to 122% of nominal concentrations. Therefore, the results were based on mean measured concentrations.

Negative and solvent controls were compared using 2 x 2 contingency tables and the Chi-square test or Student's t-test. Since no difference between the controls were determined, the data were pooled In the pooled control group mortality was 13% (day 0-15) and 9.8% (day 15-27). Mysids exposed to the test item at concentrations ≤ 0.043 µg a.s./L showed no effects on mortality, reproduction and growth. Consequently, the LOEC, based on mortality, was 0.091 µg a.s./L and the NOEC was 0.043 µg a.s./L.

The study was regarded acceptable for the hazard and risk assessment under Regulation (EC) No 1907/2006. 

 

Conclusion

Based on information of a valid Daphnia magna reproduction according to OECD TG 211 the 21-day NOEC (mortality) is determined to be 0.062 µg a.s./L based on nominal concentrations. In a life-cycle study with the saltwater mysid M. bahia the 27-day NOEC (mortality) was determined to be 0.043 µg a.s./L.