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Toxicity to soil macroorganisms except arthropods

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Description of key information

The LC50 for adult mortality on Day 21 was 871 mg/kg dry soil (95 % confidence interval 783 mg/kg dry soil to 978 mg/kg dry soil). The NOEC was 560 mg/kg dry soil. The EC50 for the number of juveniles on Day 42 was 278.4 mg/kg dry soil (95 % confidence interval 164.9 to 470.0 mg/kg dry soil). The NOEC was 100 mg/kg dry soil (OECD 220).

Key value for chemical safety assessment

Short-term EC50 or LC50 for soil macroorganisms:
278.4 mg/kg soil dw
Long-term EC10, LC10 or NOEC for soil macroorganisms:
100 mg/kg soil dw

Additional information

GUIDELINE

 

A study was performed to assess the effects of the test item on the reproductive output of the enchytraeid wom Enchytraeus albidus in an artificial soil under laboratory conditions. The method followed was that described in OECD Guideline for the testing of Chemicals (2004) No 220, Enchytraeid Reproductive Test.

 

METHOD

 

Eleven groups of worms were allocated to the study and eight groups of 40 worms were treated with test item at 20, 35, 60, 100, 175, 315, 560 and 1000 mg/kg dry soil. The three groups of 80 worms were water control, solvent control and a positive control group treated with Mascot Systemic (active ingredient carbendazim) at 1.2 mg/kg dry soil. Adult worms were removed from the soil on Day 21 and the juvenile worms were reared until Day 42.

 

RESULTS

 

Adult mortality was reported as 0 % (20, 35, 60, 100, 175 and 315 mg/kg dry soil), 10 % (560 mg/kg dry soil) and 67.5 % (1000 mg/kg dry soil) compared to 2.5 % in the solvent and water control groups and 23.8 % in the positive control group. The mean number of juveniles produced was 144.0 (20 mg/kg dry soil), 121.8 (350 mg/kg dry soil), 99.8 (60 mg/kg dry soil), 92.3 (100 mg/kg dry soil), 86.5 (175 mg/kg dry soil), 80.3 (315 mg/kg dry soil), 43.5 560 mg/kg dry soil) and 25.0 (1000 mg/kg dry soil). The mean number of juveniles produced was 136.0 in the solvent control group and 153.4 in the water control group. A mean of 3.8 juveniles was produced in the positive control group.

 

Reduction in the number of juveniles was calculated as 0, 10.4, 26.6, 32.1, 36.4, 41.0, 68.0 and 81.6 % at test item treatment rates of 20, 35, 60, 100, 175, 315, 560 and 1000 mg/kg dry soil compared to the solvent control. Statistically significant reductions were observed at 175 and 315 mg/kg dry soil (0.004**) and 560 and 1000 mg/kg dry soil (p < 0.001***).

 

The study was considered valid as there was ≤ 20 % adult mortality at Day 21 and ≥ 25 juveniles had been produced in each control replicate by the end of the test with the coefficient of variation of reproduction ≤ 50 %. In addition, application of the toxic reference (carbendazim applied at 1.2 mg/kg dry soil) resulted in substantial and unequivocal toxic effects.

 

CONCLUSION

 

The LC50 for adult mortality on Day 21 was 871 mg/kg dry soil (95 % confidence interval 783 mg/kg dry soil to 978 mg/kg dry soil). The NOEC was 560 mg/kg dry soil. The EC50 for the number of juveniles on Day 42 was 278.4 mg/kg dry soil (95 % confidence interval 164.9 to 470.0 mg/kg dry soil). The NOEC was 100 mg/kg dry soil.