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Toxicity to soil microorganisms

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Description of key information

Cyclacet's long term toxicity to soil micro-organism is 110 mg/kg soil dw, based on read-across from Verdox. The value is converted for molecular weight and log Kow.

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:
110 mg/kg soil dw

Additional information

The read across to Cyclacet is presented in the Terrestrial toxicity Overall Endpoint summary. The executive summary of the Verdox study is presented below.

Verdox and its long-term toxicity to soil micro-organisms.

The toxicity of the test substance for soil microflora was tested according to OECD TG 216 using nitrogen transformation in soil. The concentrations tested were 0, 10, 32, 100, 320 and 1000 mg/kg dw soil. The reference substance was sodium chloride. The soil used was abiologically active agricultural soil: Silty sand. The effect parameter was NO3-nitrogen production after 28 days exposure (soil nitrogen transformation). Nominal concentrations were used. No statistical significant effects of the test item on nitrate content in soil were observed at day 28 up to a concentration of 100 mg Verdox/kg soil dw by Williams Multiple t-test Procedure. For concentrations of 320 mg and 1000 mg test substance/kg soil dw, the deviations to control were significant (Williams Multiple t-test Procedure). At day 28 differences in nitrogen production to the control were -30.25 %, 36.26%, 35.90% for 10-100 mg/kg soil, not significantly and not concentration related. At 320 and 1000 mg/kg dw the reduction was -99.64% and -73.94% for 320 mg and 1000 mg test substance/kg soil dw significantly though no clear dose relation. An EC10 could not be derived. The NOEC was determined to be 100 mg/kg soil dw based on nominal values.